History log of /linux-master/include/asm-generic/bug.h
Revision Date Author Comments
# 1fa568e2 25-Apr-2022 Shida Zhang <zhangshida@kylinos.cn>

bug: Have __warn() prototype defined unconditionally

The __warn() prototype is declared in CONFIG_BUG scope but the function
definition in panic.c is unconditional. The IBT enablement started using
it unconditionally but a CONFIG_X86_KERNEL_IBT=y, CONFIG_BUG=n .config
will trigger a

arch/x86/kernel/traps.c: In function ‘__exc_control_protection’:
arch/x86/kernel/traps.c:249:17: error: implicit declaration of function \
‘__warn’; did you mean ‘pr_warn’? [-Werror=implicit-function-declaration]

Pull up the declarations so that they're unconditionally visible too.

[ bp: Rewrite commit message. ]

Fixes: 991625f3dd2c ("x86/ibt: Add IBT feature, MSR and #CP handling")
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Shida Zhang <zhangshida@kylinos.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220426032007.510245-1-starzhangzsd@gmail.com


# f39650de 30-Jun-2021 Andy Shevchenko <andriy.shevchenko@linux.intel.com>

kernel.h: split out panic and oops helpers

kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out panic and
oops helpers.

There are several purposes of doing this:
- dropping dependency in bug.h
- dropping a loop by moving out panic_notifier.h
- unload kernel.h from something which has its own domain

At the same time convert users tree-wide to use new headers, although for
the time being include new header back to kernel.h to avoid twisted
indirected includes for existing users.

[akpm@linux-foundation.org: thread_info.h needs limits.h]
[andriy.shevchenko@linux.intel.com: ia64 fix]
Link: https://lkml.kernel.org/r/20210520130557.55277-1-andriy.shevchenko@linux.intel.com

Link: https://lkml.kernel.org/r/20210511074137.33666-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Co-developed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Wei Liu <wei.liu@kernel.org>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Sebastian Reichel <sre@kernel.org>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# a358f406 28-Jun-2021 Tanner Love <tannerlove@google.com>

once: implement DO_ONCE_LITE for non-fast-path "do once" functionality

Certain uses of "do once" functionality reside outside of fast path,
and so do not require jump label patching via static keys, making
existing DO_ONCE undesirable in such cases.

Replace uses of __section(".data.once") with DO_ONCE_LITE(_IF)?

This patch changes the return values of xfs_printk_once, printk_once,
and printk_deferred_once. Before, they returned whether the print was
performed, but now, they always return true. This is okay because the
return values of the following macros are entirely ignored throughout
the kernel:
- xfs_printk_once
- xfs_warn_once
- xfs_notice_once
- xfs_info_once
- printk_once
- pr_emerg_once
- pr_alert_once
- pr_crit_once
- pr_err_once
- pr_warn_once
- pr_notice_once
- pr_info_once
- pr_devel_once
- pr_debug_once
- printk_deferred_once
- orc_warn

Changes
v3:
- Expand commit message to explain why changing return values of
xfs_printk_once, printk_once, printk_deferred_once is benign
v2:
- Fix i386 build warnings

Signed-off-by: Tanner Love <tannerlove@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Mahesh Bandewar <maheshb@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: David S. Miller <davem@davemloft.net>


# cf68fffb 08-Apr-2021 Sami Tolvanen <samitolvanen@google.com>

add support for Clang CFI

This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:

https://clang.llvm.org/docs/ControlFlowIntegrity.html

Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.

With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.

Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.

Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.

CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.

By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com


# 33def849 21-Oct-2020 Joe Perches <joe@perches.com>

treewide: Convert macro and uses of __section(foo) to __section("foo")

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@gooogle.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# d19e789f 24-Jul-2020 Ingo Molnar <mingo@kernel.org>

compiler.h: Move instrumentation_begin()/end() to new <linux/instrumentation.h> header

Linus pointed out that compiler.h - which is a key header that gets included in every
single one of the 28,000+ kernel files during a kernel build - was bloated in:

655389666643: ("vmlinux.lds.h: Create section for protection against instrumentation")

Linus noted:

> I have pulled this, but do we really want to add this to a header file
> that is _so_ core that it gets included for basically every single
> file built?
>
> I don't even see those instrumentation_begin/end() things used
> anywhere right now.
>
> It seems excessive. That 53 lines is maybe not a lot, but it pushed
> that header file to over 12kB, and while it's mostly comments, it's
> extra IO and parsing basically for _every_ single file compiled in the
> kernel.
>
> For what appears to be absolutely zero upside right now, and I really
> don't see why this should be in such a core header file!

Move these primitives into a new header: <linux/instrumentation.h>, and include that
header in the headers that make use of it.

Unfortunately one of these headers is asm-generic/bug.h, which does get included
in a lot of places, similarly to compiler.h. So the de-bloating effect isn't as
good as we'd like it to be - but at least the interfaces are defined separately.

No change to functionality intended.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200604071921.GA1361070@gmail.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>


# 5916d5f9 13-Mar-2020 Thomas Gleixner <tglx@linutronix.de>

bug: Annotate WARN/BUG/stackfail as noinstr safe

Warnings, bugs and stack protection fails from noinstr sections, e.g. low
level and early entry code, are likely to be fatal.

Mark them as "safe" to be invoked from noinstr protected code to avoid
annotating all usage sites. Getting the information out is important.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134100.376598577@linutronix.de


# a44f71a9 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: move WARN_ON() "cut here" into exception handler

The original clean up of "cut here" missed the WARN_ON() case (that does
not have a printk message), which was fixed recently by adding an explicit
printk of "cut here". This had the downside of adding a printk() to every
WARN_ON() caller, which reduces the utility of using an instruction
exception to streamline the resulting code. By making this a new BUGFLAG,
all of these can be removed and "cut here" can be handled by the exception
handler.

This was very pronounced on PowerPC, but the effect can be seen on x86 as
well. The resulting text size of a defconfig build shows some small
savings from this patch:

text data bss dec hex filename
19691167 5134320 1646664 26472151 193eed7 vmlinux.before
19676362 5134260 1663048 26473670 193f4c6 vmlinux.after

This change also opens the door for creating something like BUG_MSG(),
where a custom printk() before issuing BUG(), without confusing the "cut
here" line.

Link: http://lkml.kernel.org/r/201908200943.601DD59DCE@keescook
Fixes: 6b15f678fb7d ("include/asm-generic/bug.h: fix "cut here" for WARN_ON for __WARN_TAINT architectures")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 2da1ead4 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: consolidate __WARN_FLAGS usage

Instead of having separate tests for __WARN_FLAGS, merge the two #ifdef
blocks and replace the synonym WANT_WARN_ON_SLOWPATH macro.

Link: http://lkml.kernel.org/r/20190819234111.9019-7-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# d4bce140 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: clean up helper macros to remove __WARN_TAINT()

In preparation for cleaning up "cut here" even more, this removes the
__WARN_*TAINT() helpers, as they limit the ability to add new BUGFLAG_*
flags to call sites. They are removed by expanding them into full
__WARN_FLAGS() calls.

Link: http://lkml.kernel.org/r/20190819234111.9019-6-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# f2f84b05 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: consolidate warn_slowpath_fmt() usage

Instead of having a separate helper for no printk output, just consolidate
the logic into warn_slowpath_fmt().

Link: http://lkml.kernel.org/r/20190819234111.9019-4-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 89348fc3 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: rename __WARN_printf_taint() to __WARN_printf()

This just renames the helper to improve readability.

Link: http://lkml.kernel.org/r/20190819234111.9019-3-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# ee871133 25-Sep-2019 Kees Cook <keescook@chromium.org>

bug: refactor away warn_slowpath_fmt_taint()

Patch series "Clean up WARN() "cut here" handling", v2.

Christophe Leroy noticed that the fix for missing "cut here" in the WARN()
case was adding explicit printk() calls instead of teaching the exception
handler to add it. This refactors the bug/warn infrastructure to pass
this information as a new BUGFLAG.

Longer details repeated from the last patch in the series:

bug: move WARN_ON() "cut here" into exception handler

The original cleanup of "cut here" missed the WARN_ON() case (that does
not have a printk message), which was fixed recently by adding an explicit
printk of "cut here". This had the downside of adding a printk() to every
WARN_ON() caller, which reduces the utility of using an instruction
exception to streamline the resulting code. By making this a new BUGFLAG,
all of these can be removed and "cut here" can be handled by the exception
handler.

This was very pronounced on PowerPC, but the effect can be seen on x86 as
well. The resulting text size of a defconfig build shows some small
savings from this patch:

text data bss dec hex filename
19691167 5134320 1646664 26472151 193eed7 vmlinux.before
19676362 5134260 1663048 26473670 193f4c6 vmlinux.after

This change also opens the door for creating something like BUG_MSG(),
where a custom printk() before issuing BUG(), without confusing the "cut
here" line.

This patch (of 7):

There's no reason to have specialized helpers for passing the warn taint
down to __warn(). Consolidate and refactor helper macros, removing
__WARN_printf() and warn_slowpath_fmt_taint().

Link: http://lkml.kernel.org/r/20190819234111.9019-2-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 9b87647c 28-Aug-2019 Denis Efremov <efremov@linux.com>

asm-generic: add unlikely to default BUG_ON(x)

Add unlikely to default BUG_ON(x) in !CONFIG_BUG. It makes
the define consistent with BUG_ON(x) in CONFIG_BUG.

Signed-off-by: Denis Efremov <efremov@linux.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>


# 6b15f678 16-Jul-2019 Drew Davenport <ddavenport@chromium.org>

include/asm-generic/bug.h: fix "cut here" for WARN_ON for __WARN_TAINT architectures

For architectures using __WARN_TAINT, the WARN_ON macro did not print
out the "cut here" string. The other WARN_XXX macros would print "cut
here" inside __warn_printk, which is not called for WARN_ON since it
doesn't have a message to print.

Link: http://lkml.kernel.org/r/20190624154831.163888-1-ddavenport@chromium.org
Fixes: a7bed27af194 ("bug: fix "cut here" location for __WARN_TAINT architectures")
Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 728e3e61 08-Jan-2019 Paul E. McKenney <paulmck@kernel.org>

include/asm-generic: Remove spin_is_locked() comment

The WARN_ON_SMP() comment header suggests using spin_is_locked() to
check for locks being held. But these days we prefer lockdep_assert_held(),
so this commit removes that suggestion.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arch@vger.kernel.org>


# ffb61c63 19-Dec-2018 Ingo Molnar <mingo@kernel.org>

Revert "x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs"

This reverts commit f81f8ad56fd1c7b99b2ed1c314527f7d9ac447c6.

See this commit for details about the revert:

e769742d3584 ("Revert "x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs"")

Reported-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Borislav Petkov <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Juergen Gross <jgross@suse.com>
Cc: Richard Biener <rguenther@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>


# f81f8ad5 03-Oct-2018 Nadav Amit <namit@vmware.com>

x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs

As described in:

77b0bf55bc67: ("kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs")

GCC's inlining heuristics are broken with common asm() patterns used in
kernel code, resulting in the effective disabling of inlining.

The workaround is to set an assembly macro and call it from the inline
assembly block. As a result GCC considers the inline assembly block as
a single instruction. (Which it isn't, but that's the best we can get.)

This patch increases the kernel size:

text data bss dec hex filename
18146889 10225380 2957312 31329581 1de0d2d ./vmlinux before
18147336 10226688 2957312 31331336 1de1408 ./vmlinux after (+1755)

But enables more aggressive inlining (and probably better branch decisions).

The number of static text symbols in vmlinux is much lower:

Before: 40218
After: 40053 (-165)

The assembly code gets harder to read due to the extra macro layer.

[ mingo: Rewrote the changelog. ]

Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181003213100.189959-7-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 96c6a32c 21-Aug-2018 Dmitry Vyukov <dvyukov@google.com>

include/asm-generic/bug.h: clarify valid uses of WARN()

Explicitly state that WARN*() should be used only for recoverable kernel
issues/bugs and that it should not be used for any kind of invalid
external inputs or transient conditions.

Motivation: it's a very useful capability to be able to understand if a
particular kernel splat means a kernel bug or simply an invalid user-space
program. For the former one wants to notify kernel developers, while
notifying kernel developers for the latter is annoying. Even a kernel
developer may not know what to do with a WARNING in an unfamiliar
subsystem. This is especially critical for any automated testing systems
that may use panic_on_warn and mail kernel developers.

The clear separation also serves as an additional documentation: is it a
condition that must never occur because of additional checks/logic
elsewhere? or is it simply a check for invalid inputs or unfortunate
conditions?

Use of pr_err() for user messages also leads to better error messages.
"Something is wrong in file foo on line X" is not particularly useful
message for end user. pr_err() forces developers to write more meaningful
error messages for user.

As of now we are almost there. We are doing systematic kernel testing
with panic_on_warn and are not seeing massive amounts of false positives.
But every now and then another WARN on ENOMEM or invalid inputs pops up
and leads to a lengthy argument each time. The goal of this change is to
officially document the rules.

Link: http://lkml.kernel.org/r/20180620103716.61636-1-dvyukov@gmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 173a3efd 21-Feb-2018 Arnd Bergmann <arnd@arndb.de>

bug.h: work around GCC PR82365 in BUG()

Looking at functions with large stack frames across all architectures
led me discovering that BUG() suffers from the same problem as
fortify_panic(), which I've added a workaround for already.

In short, variables that go out of scope by calling a noreturn function
or __builtin_unreachable() keep using stack space in functions
afterwards.

A workaround that was identified is to insert an empty assembler
statement just before calling the function that doesn't return. I'm
adding a macro "barrier_before_unreachable()" to document this, and
insert calls to that in all instances of BUG() that currently suffer
from this problem.

The files that saw the largest change from this had these frame sizes
before, and much less with my patch:

fs/ext4/inode.c:82:1: warning: the frame size of 1672 bytes is larger than 800 bytes [-Wframe-larger-than=]
fs/ext4/namei.c:434:1: warning: the frame size of 904 bytes is larger than 800 bytes [-Wframe-larger-than=]
fs/ext4/super.c:2279:1: warning: the frame size of 1160 bytes is larger than 800 bytes [-Wframe-larger-than=]
fs/ext4/xattr.c:146:1: warning: the frame size of 1168 bytes is larger than 800 bytes [-Wframe-larger-than=]
fs/f2fs/inode.c:152:1: warning: the frame size of 1424 bytes is larger than 800 bytes [-Wframe-larger-than=]
net/netfilter/ipvs/ip_vs_core.c:1195:1: warning: the frame size of 1068 bytes is larger than 800 bytes [-Wframe-larger-than=]
net/netfilter/ipvs/ip_vs_core.c:395:1: warning: the frame size of 1084 bytes is larger than 800 bytes [-Wframe-larger-than=]
net/netfilter/ipvs/ip_vs_ftp.c:298:1: warning: the frame size of 928 bytes is larger than 800 bytes [-Wframe-larger-than=]
net/netfilter/ipvs/ip_vs_ftp.c:418:1: warning: the frame size of 908 bytes is larger than 800 bytes [-Wframe-larger-than=]
net/netfilter/ipvs/ip_vs_lblcr.c:718:1: warning: the frame size of 960 bytes is larger than 800 bytes [-Wframe-larger-than=]
drivers/net/xen-netback/netback.c:1500:1: warning: the frame size of 1088 bytes is larger than 800 bytes [-Wframe-larger-than=]

In case of ARC and CRIS, it turns out that the BUG() implementation
actually does return (or at least the compiler thinks it does),
resulting in lots of warnings about uninitialized variable use and
leaving noreturn functions, such as:

block/cfq-iosched.c: In function 'cfq_async_queue_prio':
block/cfq-iosched.c:3804:1: error: control reaches end of non-void function [-Werror=return-type]
include/linux/dmaengine.h: In function 'dma_maxpq':
include/linux/dmaengine.h:1123:1: error: control reaches end of non-void function [-Werror=return-type]

This makes them call __builtin_trap() instead, which should normally
dump the stack and kill the current process, like some of the other
architectures already do.

I tried adding barrier_before_unreachable() to panic() and
fortify_panic() as well, but that had very little effect, so I'm not
submitting that patch.

Vineet said:

: For ARC, it is double win.
:
: 1. Fixes 3 -Wreturn-type warnings
:
: | ../net/core/ethtool.c:311:1: warning: control reaches end of non-void function
: [-Wreturn-type]
: | ../kernel/sched/core.c:3246:1: warning: control reaches end of non-void function
: [-Wreturn-type]
: | ../include/linux/sunrpc/svc_xprt.h:180:1: warning: control reaches end of
: non-void function [-Wreturn-type]
:
: 2. bloat-o-meter reports code size improvements as gcc elides the
: generated code for stack return.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
Link: http://lkml.kernel.org/r/20171219114112.939391-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Vineet Gupta <vgupta@synopsys.com> [arch/arc]
Tested-by: Vineet Gupta <vgupta@synopsys.com> [arch/arc]
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# a7bed27a 17-Nov-2017 Kees Cook <keescook@chromium.org>

bug: fix "cut here" location for __WARN_TAINT architectures

Prior to v4.11, x86 used warn_slowpath_fmt() for handling WARN()s.
After WARN() was moved to using UD0 on x86, the warning text started
appearing _before_ the "cut here" line. This appears to have been a
long-standing bug on architectures that used __WARN_TAINT, but it didn't
get fixed.

v4.11 and earlier on x86:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 2956 at drivers/misc/lkdtm_bugs.c:65 lkdtm_WARNING+0x21/0x30
This is a warning message
Modules linked in:

v4.12 and later on x86:

This is a warning message
------------[ cut here ]------------
WARNING: CPU: 1 PID: 2982 at drivers/misc/lkdtm_bugs.c:68 lkdtm_WARNING+0x15/0x20
Modules linked in:

With this fix:

------------[ cut here ]------------
This is a warning message
WARNING: CPU: 3 PID: 3009 at drivers/misc/lkdtm_bugs.c:67 lkdtm_WARNING+0x15/0x20

Since the __FILE__ reporting happens as part of the UD0 handler, it
isn't trivial to move the message to after the WARNING line, but at
least we can fix the position of the "cut here" line so all the various
logging tools will start including the actual runtime warning message
again, when they follow the instruction and "cut here".

Link: http://lkml.kernel.org/r/1510100869-73751-4-git-send-email-keescook@chromium.org
Fixes: 9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 2a8358d8 17-Nov-2017 Kees Cook <keescook@chromium.org>

bug: define the "cut here" string in a single place

The "cut here" string is used in a few paths. Define it in a single
place.

Link: http://lkml.kernel.org/r/1510100869-73751-3-git-send-email-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# b1fca27d 17-Nov-2017 Andi Kleen <ak@linux.intel.com>

kernel debug: support resetting WARN*_ONCE

I like _ONCE warnings because it's guaranteed that they don't flood the
log.

During testing I find it useful to reset the state of the once warnings,
so that I can rerun tests and see if they trigger again, or can
guarantee that a test run always hits the same warnings.

This patch adds a debugfs interface to reset all the _ONCE warnings so
that they appear again:

echo 1 > /sys/kernel/debug/clear_warn_once

This is implemented by putting all the warning booleans into a special
section, and clearing it.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# b2441318 01-Nov-2017 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# 0b396923 10-Jul-2017 Ian Abbott <abbotti@mev.co.uk>

asm-generic/bug.h: declare struct pt_regs; before function prototype

This series of patches splits BUILD_BUG related macros out of
"include/linux/bug.h" into new file "include/linux/build_bug.h" (patch
5), and changes the pointer type checking in the `container_of()` macro
to deal with pointers of array type better (patch 6). Patches 1 to 4
are prerequisites.

Patches 2, 3, 4, and 5 have been inserted since the previous version of
this patch series. Patch 6 here corresponds to v3 and v4's patch 2.

Patch 1 was a prerequisite in v3 of this series to avoid a lot of
warnings when <linux/bug.h> was included by <linux/kernel.h>. That is
no longer relevant for v5 of the series, but I left it in because it was
acked by a Arnd Bergmann and Michal Nazarewicz.

Patches 2, 3, and 4 are some checkpatch clean-ups on
"include/linux/bug.h" before splitting out the BUILD_BUG stuff in patch
5.

Patch 5 splits the BUILD_BUG related macros out of "include/linux/bug.h"
into new file "include/linux/build_bug.h" because including
<linux/bug.h> in "include/linux/kernel.h" would result in build failures
due to circular dependencies.

Patch 6 changes the pointer type checking by `container_of()` to avoid
some incompatible pointer warnings when the dereferenced pointer has
array type.

1) asm-generic/bug.h: declare struct pt_regs; before function prototype
2) linux/bug.h: correct formatting of block comment
3) linux/bug.h: correct "(foo*)" should be "(foo *)"
4) linux/bug.h: correct "space required before that '-'"
5) bug: split BUILD_BUG stuff out into <linux/build_bug.h>
6) kernel.h: handle pointers to arrays better in container_of()

This patch (of 6):

The declaration of `__warn()` has `struct pt_regs *regs` as one of its
parameters. This can result in compiler warnings if `struct regs` is not
already declared. Add an empty declaration of `struct pt_regs` to avoid
the warnings.

Link: http://lkml.kernel.org/r/20170525120316.24473-2-abbotti@mev.co.uk
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# f26dee15 10-Apr-2017 Peter Zijlstra <peterz@infradead.org>

debug: Avoid setting BUGFLAG_WARNING twice

Dan reported that his static checking complains about BUGFLAG_WARNING
being set on both sides of the bitwise-or, it figures that that might've
been an unintentional mistake.

Since there are no architectures that implement __WARN_TAINT() (I
converted them all to implement __WARN_FLAGS()), and all __WARN_FLAGS()
implementations already set BUGFLAG_WARNING, we can remove the bit from
BUGFLAG_TAINT() and make Dan's checker happy.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170410084939.4bwhrvpmauwfzauq@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 19d43626 25-Feb-2017 Peter Zijlstra <peterz@infradead.org>

debug: Add _ONCE() logic to report_bug()

Josh suggested moving the _ONCE logic inside the trap handler, using a
bit in the bug_entry::flags field, avoiding the need for the extra
variable.

Sadly this only works for WARN_ON_ONCE(), since the others have
printk() statements prior to triggering the trap.

Still, this saves a fair amount of text and some data:

text data filename
10682460 4530992 defconfig-build/vmlinux.orig
10665111 4530096 defconfig-build/vmlinux.patched

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 2553b67a 17-Mar-2016 Josh Poimboeuf <jpoimboe@redhat.com>

lib/bug.c: use common WARN helper

The traceoff_on_warning option doesn't have any effect on s390, powerpc,
arm64, parisc, and sh because there are two different types of WARN
implementations:

1) The above mentioned architectures treat WARN() as a special case of a
BUG() exception. They handle warnings in report_bug() in lib/bug.c.

2) All other architectures just call warn_slowpath_*() directly. Their
warnings are handled in warn_slowpath_common() in kernel/panic.c.

Support traceoff_on_warning on all architectures and prevent any future
divergence by using a single common function to emit the warning.

Also remove the '()' from '%pS()', because the parentheses look funky:

[ 45.607629] WARNING: at /root/warn_mod/warn_mod.c:17 .init_dummy+0x20/0x40 [warn_mod]()

Reported-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# dfbf2897 17-Mar-2016 Steven Rostedt <rostedt@goodmis.org>

bug: set warn variable before calling WARN()

This has hit me a couple of times already. I would be debugging code
and the system would simply hang and then reboot. Finally, I found that
the problem was caused by WARN_ON_ONCE() and friends.

The macro WARN_ON_ONCE(condition) is defined as:

static bool __section(.data.unlikely) __warned;
int __ret_warn_once = !!(condition);

if (unlikely(__ret_warn_once))
if (WARN_ON(!__warned))
__warned = true;

unlikely(__ret_warn_once);

Which looks great and all. But what I have hit, is an issue when
WARN_ON() itself hits the same WARN_ON_ONCE() code. Because, the
variable __warned is not yet set. Then it too calls WARN_ON() and that
triggers the warning again. It keeps doing this until the stack is
overflowed and the system crashes.

By setting __warned first before calling WARN_ON() makes the original
WARN_ON_ONCE() really only warn once, and not an infinite amount of
times if the WARN_ON() also triggers the warning.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 3c047057 20-Nov-2015 Arnd Bergmann <arnd@arndb.de>

asm-generic: default BUG_ON(x) to if(x)BUG()

When CONFIG_BUG is disabled, BUG_ON() will only evaluate the condition,
but will not actually stop the current thread. GCC warns about a couple
of BUG_ON() users where this actually leads to further undefined
behavior:

include/linux/ceph/osdmap.h: In function 'ceph_can_shift_osds':
include/linux/ceph/osdmap.h:54:1: warning: control reaches end of non-void function
fs/ext4/inode.c: In function 'ext4_map_blocks':
fs/ext4/inode.c:548:5: warning: 'retval' may be used uninitialized in this function
drivers/mfd/db8500-prcmu.c: In function 'prcmu_config_clkout':
drivers/mfd/db8500-prcmu.c:762:10: warning: 'div_mask' may be used uninitialized in this function
drivers/mfd/db8500-prcmu.c:769:13: warning: 'mask' may be used uninitialized in this function
drivers/mfd/db8500-prcmu.c:757:7: warning: 'bits' may be used uninitialized in this function
drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq':
drivers/tty/serial/8250/8250_core.c:252:18: warning: 'i' may be used uninitialized in this function
drivers/tty/serial/8250/8250_core.c:235:19: note: 'i' was declared here

There is an obvious conflict of interest here: on the one hand, someone
who disables CONFIG_BUG() will want the kernel to be as small as possible
and doesn't care about printing error messages to a console that nobody
looks at. On the other hand, running into a BUG_ON() condition means that
something has gone wrong, and we probably want to also stop doing things
that might cause data corruption.

This patch picks the second choice, and changes the NOP to BUG(), which
normally stops the execution of the current thread in some form (endless
loop or a trap). This follows the logic we applied in a4b5d580e078 ("bug:
Make BUG() always stop the machine").

For ARM multi_v7_defconfig, the size slightly increases:

section CONFIG_BUG=y CONFIG_BUG=n CONFIG_BUG=n+patch

.text 8320248 | 8180944 | 8207688
.rodata 3633720 | 3567144 | 3570648
__bug_table 32508 | --- | ---
__modver 692 | 1584 | 2176
.init.text 558132 | 548300 | 550088
.exit.text 12380 | 12256 | 12380
.data 1016672 | 1016064 | 1016128
Total 14622556 | 14374510 | 14407326

So instead of saving 1.70% of the total image size, we only save 1.48%
by turning off CONFIG_BUG, but in return we can ensure that we don't run
into cases of uninitialized variable or return code uses when something
bad happens. Aside from that, we significantly reduce the number of
warnings in randconfig builds, which makes it easier to fix the warnings
about other problems.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>


# a4b5d580 07-Apr-2014 Josh Triplett <josh@joshtriplett.org>

bug: Make BUG() always stop the machine

When !CONFIG_BUG and !HAVE_ARCH_BUG, define the generic BUG() as an
infinite loop rather than a no-op. This avoids undefined behavior if
execution ever actually reaches BUG(), and avoids warnings about code
after BUG() (such as on non-void functions calling BUG() and then not
returning).

bloat-o-meter results:

add/remove: 0/0 grow/shrink: 43/10 up/down: 235/-98 (137)
function old new delta
umount_collect 119 138 +19
notify_change 306 324 +18
xstate_enable_boot_cpu 252 269 +17
kunmap 54 70 +16
balloon_page_dequeue 112 126 +14
mm_take_all_locks 223 233 +10
list_lru_walk_node 143 152 +9
vma_adjust 1059 1067 +8
pcpu_setup_first_chunk 1130 1138 +8
mm_drop_all_locks 143 151 +8
ns_capable 55 62 +7
anon_transport_class_unregister 8 15 +7
srcu_init_notifier_head 35 41 +6
shrink_dcache_for_umount 174 180 +6
kunmap_high 99 105 +6
end_page_writeback 43 49 +6
do_exit 1339 1345 +6
__kfifo_dma_out_prepare_r 86 92 +6
__kfifo_dma_in_prepare_r 90 96 +6
fixup_user_fault 120 125 +5
repair_env_string 73 77 +4
read_cache_pages_invalidate_page 56 60 +4
isolate_lru_pages.isra 142 146 +4
do_notify_parent_cldstop 255 259 +4
cpu_init 370 374 +4
utimes_common 270 272 +2
tasklet_hi_action 91 93 +2
tasklet_action 91 93 +2
set_pte_vaddr 46 48 +2
find_get_pages_tag 202 204 +2
early_iounmap 185 187 +2
__native_set_fixmap 36 38 +2
__get_user_pages 822 824 +2
__early_ioremap 299 301 +2
yield_task_stop 1 2 +1
tick_resume 37 38 +1
switched_to_stop 1 2 +1
switched_to_idle 1 2 +1
prio_changed_stop 1 2 +1
prio_changed_idle 1 2 +1
pm_qos_power_read 111 112 +1
arch_cpu_idle_dead 1 2 +1
__insert_vmap_area 140 141 +1
sys_renameat 614 612 -2
mm_fault_error 297 295 -2
SyS_renameat 614 612 -2
sys_linkat 416 413 -3
SyS_linkat 416 413 -3
chmod_common 129 122 -7
proc_cap_handler 240 225 -15
__schedule 849 831 -18
sys_madvise 1077 1054 -23
SyS_madvise 1077 1054 -23

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 4e50ebde 07-Apr-2014 Josh Triplett <josh@joshtriplett.org>

bug: when !CONFIG_BUG, make WARN call no_printk to check format and args

The stub version of WARN for !CONFIG_BUG completely ignored its format
string and subsequent arguments; make it check them instead, using
no_printk.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# a3f7607d 07-Apr-2014 Josh Triplett <josh@joshtriplett.org>

include/asm-generic/bug.h: style fix: s/while(0)/while (0)/

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# b607e70e 07-Apr-2014 Josh Triplett <josh@joshtriplett.org>

bug: when !CONFIG_BUG, simplify WARN_ON_ONCE and family

When !CONFIG_BUG, WARN_ON and family become simple passthroughs of their
condition argument; however, WARN_ON_ONCE and family still have conditions
and a boolean to detect one-time invocation, even though the warning
they'd emit doesn't exist. Make the existing definitions conditional on
CONFIG_BUG, and add definitions for !CONFIG_BUG that map to the
passthrough versions of WARN and WARN_ON.

This saves 4.4k on a minimized configuration (smaller than allnoconfig),
and 20.6k with defconfig plus CONFIG_BUG=n.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 09682c1d 25-Jun-2012 Paul Mundt <lethal@linux-sh.org>

bug.h: Fix up CONFIG_BUG=n implicit function declarations.

Commit 2603efa31a03 ("bug.h: Fix up powerpc build regression") corrected
the powerpc build case and extended the __ASSEMBLY__ guards, but it also
got caught in pre-processor hell accidentally matching the else case of
CONFIG_BUG resulting in the BUG disabled case tripping up on
-Werror=implicit-function-declaration.

It's not possible to __ASSEMBLY__ guard the entire file as architecture
code needs to get at the BUGFLAG_WARNING definition in the GENERIC_BUG
case, but the rest of the CONFIG_BUG=y/n case needs to be guarded.

Rather than littering endless __ASSEMBLY__ checks in each of the if/else
cases we just move the BUGFLAG definitions up under their own
GENERIC_BUG test and then shove everything else under one big
__ASSEMBLY__ guard.

Build tested on all of x86 CONFIG_BUG=y, CONFIG_BUG=n, powerpc (due to
it's dependence on BUGFLAG definitions in assembly code), and sh (due to
not bringing in linux/kernel.h to satisfy the taint flag definitions used
by the generic bug code).

Hopefully that's the end of the corner cases and I can abstain from ever
having to touch this infernal header ever again.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Tested-by: Fengguang Wu <wfg@linux.intel.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 2603efa3 17-Jun-2012 Paul Mundt <lethal@linux-sh.org>

bug.h: Fix up powerpc build regression.

The asm-generic/bug.h __ASSEMBLY__ guarding is completely bogus, which
tripped up the powerpc build when the kernel.h include was added:

In file included from include/asm-generic/bug.h:5:0,
from arch/powerpc/include/asm/bug.h:127,
from arch/powerpc/kernel/head_64.S:31:
include/linux/kernel.h:44:0: warning: "ALIGN" redefined [enabled by default]
include/linux/linkage.h:57:0: note: this is the location of the previous definition
include/linux/sysinfo.h: Assembler messages:
include/linux/sysinfo.h:7: Error: Unrecognized opcode: `struct'
include/linux/sysinfo.h:8: Error: Unrecognized opcode: `__kernel_long_t'

Moving the __ASSEMBLY__ guard up and stashing the kernel.h include under
it fixes this up, as well as covering the case the original fix was
attempting to handle.

Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 37778088 10-Jun-2012 Paul Mundt <lethal@linux-sh.org>

bug.h: need linux/kernel.h for TAINT_WARN.

asm-generic/bug.h uses taint flags that are only defined in
linux/kernel.h, resulting in build failures on platforms that
don't include linux/kernel.h some other way:

arch/sh/include/asm/thread_info.h:172:2: error: 'TAINT_WARN' undeclared (first use in this function)

Caused by commit edd63a2763bd ("set_restore_sigmask() is never called
without SIGPENDING (and never should be)").

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>


# 7ccaba53 23-Mar-2012 Jan Beulich <JBeulich@suse.com>

consolidate WARN_...ONCE() static variables

Due to the alignment of following variables, these typically consume
more than just the single byte that 'bool' requires, and as there are a
few hundred instances, the cache pollution (not so much the waste of
memory) sums up. Put these variables into their own section, outside of
any half way frequently used memory range.

Do the same also to the __warned variable of rcu_lockdep_assert().
(Don't, however, include the ones used by printk_once() and alike, as
they can potentially be hot.)

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# b9075fa9 31-Oct-2011 Joe Perches <joe@perches.com>

treewide: use __printf not __attribute__((format(printf,...)))

Standardize the style for compiler based printf format verification.
Standardized the location of __printf too.

Done via script and a little typing.

$ grep -rPl --include=*.[ch] -w "__attribute__" * | \
grep -vP "^(tools|scripts|include/linux/compiler-gcc.h)" | \
xargs perl -n -i -e 'local $/; while (<>) { s/\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf\s*,\s*(.+)\s*,\s*(.+)\s*\)\s*\)\s*\)/__printf($1, $2)/g ; print; }'

[akpm@linux-foundation.org: revert arch bits]
Signed-off-by: Joe Perches <joe@perches.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 86e4ca66 26-May-2011 David S. Miller <davem@davemloft.net>

bug.h: Move ratelimit warn interfaces to ratelimit.h

As reported by Ingo Molnar, we still have configuration combinations
where use of the WARN_RATELIMIT interfaces break the build because
dependencies don't get met.

Instead of going down the long road of trying to make it so that
ratelimit.h can get included by kernel.h or asm-generic/bug.h,
just move the interface into ratelimit.h and make users have
to include that.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>


# 6b367835 24-May-2011 David S. Miller <davem@davemloft.net>

bug.h: Fix build with CONFIG_PRINTK disabled.

Based upon an email by Joe Perches.

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>


# b3eec79b 21-May-2011 Joe Perches <joe@perches.com>

bug.h: Add WARN_RATELIMIT

Add a generic mechanism to ratelimit WARN(foo, fmt, ...) messages
using a hidden per call site static struct ratelimit_state.

Also add an __WARN_RATELIMIT variant to be able to use a specific
struct ratelimit_state.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>


# ccd0d44f 25-Mar-2011 Steven Rostedt <srostedt@redhat.com>

WARN_ON_SMP(): Add comment to explain ({0;})

The define to use ({0;}) for the !CONFIG_SMP case of WARN_ON_SMP()
can be confusing. As the WARN_ON_SMP() needs to be a nop when
CONFIG_SMP is not set, including all its parameters must not be
evaluated, and that it must work as both a stand alone statement
and inside an if condition, we define it to a funky ({0;}).

A simple "0" will not work as it causes gcc to give the warning that
the statement has no effect.

As this strange definition has raised a few eyebrows from some
major kernel developers, it is wise to document why we create such
a work of art.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>


# 2092e6be 17-Mar-2011 Steven Rostedt <srostedt@redhat.com>

WARN_ON_SMP(): Allow use in if() statements on UP

Both WARN_ON() and WARN_ON_SMP() should be able to be used in
an if statement.

if (WARN_ON_SMP(foo)) { ... }

Because WARN_ON_SMP() is defined as a do { } while (0) on UP,
it can not be used this way.

Convert it to the same form that WARN_ON() is, even when
CONFIG_SMP is off.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20110317192208.444147791@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


# b2be0527 03-Apr-2010 Ben Hutchings <ben@decadent.org.uk>

panic: Allow warnings to set different taint flags

WARN() is used in some places to report firmware or hardware bugs that
are then worked-around. These bugs do not affect the stability of the
kernel and should not set the flag for TAINT_WARN. To allow for this,
add WARN_TAINT() and WARN_TAINT_ONCE() macros that take a taint number
as argument.

Architectures that implement warnings using trap instructions instead
of calls to warn_slowpath_*() now implement __WARN_TAINT(taint)
instead of __WARN().

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Helge Deller <deller@gmx.de>
Tested-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>


# 42f247c8 14-Dec-2009 Cesar Eduardo Barros <cesarb@cesarb.net>

WARN_ONCE(): use bool for boolean flag

Commit 70867453092297be9afb2249e712a1f960ec0a09 ("printk_once(): use bool
for boolean flag") changed printk_once() to use bool instead of int for
its guard variable. Do the same change to WARN_ONCE() and WARN_ON_ONCE(),
for the same reasons.

This resulted in a reduction of 1462 bytes on a x86-64 defconfig:

text data bss dec hex filename
8101271 1207116 992764 10301151 9d2edf vmlinux.before
8100553 1207148 991988 10299689 9d2929 vmlinux.after

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Daniel Walker <dwalker@fifo99.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 57adc4d2 06-May-2009 Andi Kleen <andi@firstfloor.org>

Eliminate thousands of warnings with gcc 3.2 build

When building with gcc 3.2 I get thousands of warnings such as

include/linux/gfp.h: In function `allocflags_to_migratetype':
include/linux/gfp.h:105: warning: null format string

due to passing a NULL format string to warn_slowpath() in

#define __WARN() warn_slowpath(__FILE__, __LINE__, NULL)

Split this case out into a separate call. This also shrinks the kernel
slightly:

text data bss dec hex filename
4802274 707668 712704 6222646 5ef336 vmlinux
text data bss dec hex filename
4799027 703572 712704 6215303 5ed687 vmlinux

due to removeing one argument from the commonly-called __WARN().

[akpm@linux-foundation.org: reduce scope of `empty']
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# da60682c 15-Apr-2009 David Howells <dhowells@redhat.com>

The default CONFIG_BUG=n version of BUG() should have an empty do...while

The default CONFIG_BUG=n version of BUG() should incorporate an empty a
do...while statement to avoid compilation weirdness.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# af9379c7 06-Jan-2009 David Brownell <dbrownell@users.sourceforge.net>

documentation: when to BUG(), and when to not BUG()

Provide some basic advice about when to use BUG()/BUG_ON(): never, unless
there's really no better option.

This matches my understanding of the standard policy ... which seems not
to be written down so far, outside of LKML messages that I haven't
bookmarked.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# b93a531e 16-Dec-2008 Jan Beulich <jbeulich@novell.com>

allow bug table entries to use relative pointers (and use it on x86-64)

Impact: reduce bug table size

This allows reducing the bug table size by half. Perhaps there are
other 64-bit architectures that could also make use of this.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


# ec5679e5 28-Nov-2008 Ingo Molnar <mingo@elte.hu>

debug warnings: eliminate warn_on_slowpath()

Impact: cleanup, eliminate code

now that warn_on_slowpath() uses warn_slowpath(...,NULL), we can
eliminate warn_on_slowpath() altogether and use warn_slowpath().

Signed-off-by: Ingo Molnar <mingo@elte.hu>


# f6f286f3 20-Oct-2008 Arjan van de Ven <arjan@linux.intel.com>

fix WARN() for PPC

powerpc doesn't use the generic WARN_ON infrastructure. The newly
introduced WARN() as a result didn't print the message, this patch adds
the printk for this specific case.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# d5c003b4 15-Oct-2008 Harvey Harrison <harvey.harrison@gmail.com>

include: replace __FUNCTION__ with __func__

__FUNCTION__ is gcc-specific, use __func__

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 45e9c0de 15-Sep-2008 Arjan van de Ven <arjan@linux.intel.com>

warn: Turn the netdev timeout WARN_ON() into a WARN()

this patch turns the netdev timeout WARN_ON_ONCE() into a WARN_ONCE(),
so that the device and driver names are inside the warning message.
This helps automated tools like kerneloops.org to collect the data
and do statistics, as well as making it more likely that humans
cut-n-paste the important message as part of a bugreport.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 5337407c 08-Sep-2008 Arjan van de Ven <arjan@linux.intel.com>

warn: Turn the netdev timeout WARN_ON() into a WARN()

this patch turns the netdev timeout WARN_ON_ONCE() into a WARN_ONCE(),
so that the device and driver names are inside the warning message.
This helps automated tools like kerneloops.org to collect the data
and do statistics, as well as making it more likely that humans
cut-n-paste the important message as part of a bugreport.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>


# 717115e1 25-Jul-2008 Dave Young <hidave.darkstar@gmail.com>

printk ratelimiting rewrite

All ratelimit user use same jiffies and burst params, so some messages
(callbacks) will be lost.

For example:
a call printk_ratelimit(5 * HZ, 1)
b call printk_ratelimit(5 * HZ, 1) before the 5*HZ timeout of a, then b will
will be supressed.

- rewrite __ratelimit, and use a ratelimit_state as parameter. Thanks for
hints from andrew.

- Add WARN_ON_RATELIMIT, update rcupreempt.h

- remove __printk_ratelimit

- use __ratelimit in net_ratelimit

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# a8f18b90 25-Jul-2008 Arjan van de Ven <arjan@linux.intel.com>

Add a WARN() macro; this is WARN_ON() + printk arguments

Add a WARN() macro that acts like WARN_ON(), with the added feature that it
takes a printk like argument that is printed as part of the warning message.

[akpm@linux-foundation.org: fix printk arguments]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Greg KH <greg@kroah.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 79b4cc5e 30-Jan-2008 Arjan van de Ven <arjan@infradead.org>

debug: move WARN_ON() out of line

A quick grep shows that there are currently 1145 instances of WARN_ON
in the kernel. Currently, WARN_ON is pretty much entirely inlined,
which makes it hard to enhance it without growing the size of the kernel
(and getting Andrew unhappy).

This patch build on top of Olof's patch that introduces __WARN,
and places the slowpath out of line. It also uses Ingo's suggestion
to not use __FUNCTION__ but to use kallsyms to do the lookup;
this saves a ton of extra space since gcc doesn't need to store the function
string twice now:

3936367 833603 624736 5394706 525112 vmlinux.before
3917508 833603 624736 5375847 520767 vmlinux-slowpath

15Kb savings...

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Olof Johansson <olof@lixom.net>
Acked-by: Matt Meckall <mpm@selenic.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


# 3a6a62f9 30-Jan-2008 Olof Johansson <olof@lixom.net>

debug: introduce __WARN()

Introduce __WARN() in the generic case, so the generic WARN_ON()
can use arch-specific code for when the condition is true.

Signed-off-by: Olof Johansson <olof@lixom.net>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


# 8d4fbcfb 31-Jul-2007 Linus Torvalds <torvalds@woody.linux-foundation.org>

Fix WARN_ON() on bitfield ops

Alexey Dobriyan noticed that the new WARN_ON() semantics that were
introduced by commit 684f978347deb42d180373ac4c427f82ef963171 (to also
return the value to be warned on) didn't compile when given a bitfield,
because the typeof doesn't work for bitfields.

So instead of the typeof trick, use an "int" variable together with a
"!!(x)" expression, as suggested by Al Viro.

To make matters more interesting, Paul Mackerras points out that that is
sub-optimal on Power, but the old asm-coded comparison seems to be buggy
anyway on 32-bit Power if the conditional was 64-bit, so I think there
are more problems there.

Regardless, the new WARN_ON() semantics may have been a bad idea. But
this at least avoids the more serious complications.

Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 2a41de48 17-Jul-2007 Alexey Dobriyan <adobriyan@sw.ru>

Fix sparse false positives re BUG_ON(ptr)

sparse now warns if one compares pointers with integers. However, there are
false positives, like:

fs/filesystems.c:72:2: warning: Using plain integer as NULL pointer

Every time BUG_ON(ptr) is used, ptr is checked against integer zero. Avoid
that and save ~70 false positives from allyesconfig run.

mentioned by Al.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Josh Triplett <josh@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 8f53b6fc 24-May-2007 Linus Torvalds <torvalds@woody.linux-foundation.org>

Don't call a warnign a bug. It's a warning.

Change the default printout message for WARN_ON() to say what it is, not
something else. I'm tired of having people get all aflutter about a warning.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>


# 52e88f5d 29-Dec-2006 Ingo Molnar <mingo@elte.hu>

[PATCH] change WARN_ON back to "BUG: at ..."

WARN_ON() ever triggering is a kernel bug. Do not try to paper over this
fact by suggesting to the user that this is 'only' a warning, as the
following recent commit does:

commit 30e25b71e725b150585e17888b130e3324f8cf7c
Author: Jeremy Fitzhardinge <jeremy@goop.org>
Date: Fri Dec 8 02:36:24 2006 -0800

[PATCH] Fix generic WARN_ON message

A warning is a warning, not a BUG.

( it might make sense to rename BUG() to CRASH() and BUG_ON() to
CRASH_ON(), but that does not change the fact that WARN_ON()
signals a kernel bug. )

i and others objected to this change during lkml review:

http://marc.theaimsgroup.com/?l=linux-kernel&m=116115160710533&w=2

still the change slipped upstream - grumble :)

Also, use the standard "BUG: " format to make it easier to grep logs and
to make it easier to google for kernel bugs.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 30e25b71 08-Dec-2006 Jeremy Fitzhardinge <jeremy@goop.org>

[PATCH] Fix generic WARN_ON message

A warning is a warning, not a BUG.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 7664c5a1 08-Dec-2006 Jeremy Fitzhardinge <jeremy@goop.org>

[PATCH] Generic BUG implementation

This patch adds common handling for kernel BUGs, for use by architectures as
they wish. The code is derived from arch/powerpc.

The advantages of having common BUG handling are:
- consistent BUG reporting across architectures
- shared implementation of out-of-line file/line data
- implement CONFIG_DEBUG_BUGVERBOSE consistently

This means that in inline impact of BUG is just the illegal instruction
itself, which is an improvement for i386 and x86-64.

A BUG is represented in the instruction stream as an illegal instruction,
which has file/line information associated with it. This extra information is
stored in the __bug_table section in the ELF file.

When the kernel gets an illegal instruction, it first confirms it might
possibly be from a BUG (ie, in kernel mode, the right illegal instruction).
It then calls report_bug(). This searches __bug_table for a matching
instruction pointer, and if found, prints the corresponding file/line
information. If report_bug() determines that it wasn't a BUG which caused the
trap, it returns BUG_TRAP_TYPE_NONE.

Some architectures (powerpc) implement WARN using the same mechanism; if the
illegal instruction was the result of a WARN, then report_bug(Q) returns
CONFIG_DEBUG_BUGVERBOSE; otherwise it returns BUG_TRAP_TYPE_BUG.

lib/bug.c keeps a list of loaded modules which can be searched for __bug_table
entries. The architecture must call
module_bug_finalize()/module_bug_cleanup() from its corresponding
module_finalize/cleanup functions.

Unsetting CONFIG_DEBUG_BUGVERBOSE will reduce the kernel size by some amount.
At the very least, filename and line information will not be recorded for each
but, but architectures may decide to store no extra information per BUG at
all.

Unfortunately, gcc doesn't have a general way to mark an asm() as noreturn, so
architectures will generally have to include an infinite loop (or similar) in
the BUG code, so that gcc knows execution won't continue beyond that point.
gcc does have a __builtin_trap() operator which may be useful to achieve the
same effect, unfortunately it cannot be used to actually implement the BUG
itself, because there's no way to get the instruction's address for use in
generating the __bug_table entry.

[randy.dunlap@oracle.com: Handle BUG=n, GENERIC_BUG=n to prevent build errors]
[bunk@stusta.de: include/linux/bug.h must always #include <linux/module.h]
Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Hugh Dickens <hugh@veritas.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 8c7c7c9b 20-Oct-2006 Ralf Baechle <ralf@linux-mips.org>

[PATCH] Fix warnings for WARN_ON if CONFIG_BUG is disabled

In most cases the return value of WARN_ON() is ignored. If the generic
definition for the !CONFIG_BUG case is used this will result in a warning:

CC kernel/sched.o
In file included from include/linux/bio.h:25,
from include/linux/blkdev.h:14,
from kernel/sched.c:39:
include/linux/ioprio.h: In function ‘task_ioprio’:
include/linux/ioprio.h:50: warning: statement with no effect
kernel/sched.c: In function ‘context_switch’:
kernel/sched.c:1834: warning: statement with no effect

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# d69a8922 06-Oct-2006 Andrew Morton <akpm@osdl.org>

[PATCH] Fix WARN_ON / WARN_ON_ONCE regression

Tim and Ananiev report that the recent WARN_ON_ONCE changes cause increased
cache misses with the tbench workload. Apparently due to the access to the
newly-added static variable.

Rearrange the code so that we don't touch that variable unless the warning is
going to trigger.

Also rework the logic so that the static variable starts out at zero, so we
can move it into bss.

It would seem logical to mark the static variable as __read_mostly too. But
it would be wrong, because that would put it back into the vmlinux image, and
the kernel will never read from this variable in normal operation anyway.
Unless the compiler or hardware go and do some prefetching on us?

For some reason this patch shrinks softirq.o text by 40 bytes.

Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Ananiev, Leonid I" <leonid.i.ananiev@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 684f9783 29-Sep-2006 Herbert Xu <herbert@gondor.apana.org.au>

[PATCH] Let WARN_ON/WARN_ON_ONCE return the condition

Letting WARN_ON/WARN_ON_ONCE return the condition means that you could do

if (WARN_ON(blah)) {
handle_impossible_case
}

Rather than

if (unlikely(blah)) {
WARN_ON(1)
handle_impossible_case
}

I checked all the newly added WARN_ON_ONCE users and none of them test the
return status so we can still change it.

[akpm@osdl.org: warning fix]
[akpm@osdl.org: build fix]
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 8eb94f80 27-Jun-2006 Ingo Molnar <mingo@elte.hu>

[PATCH] pi-futex: introduce WARN_ON_SMP

Introduce a new WARN_ON variant: WARN_ON_SMP(cond).

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 74bb6a09 25-Jun-2006 Ingo Molnar <mingo@elte.hu>

[PATCH] introduce WARN_ON_ONCE(cond)

Add WARN_ON_ONCE(cond) to print once-per-bootup messages.

[rostedt@goodmis.org: improve code generation]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 62c4f0a2 25-Apr-2006 David Woodhouse <dwmw2@infradead.org>

Don't include linux/config.h from anywhere else in include/

Signed-off-by: David Woodhouse <dwmw2@infradead.org>


# 91368d73 23-Mar-2006 Ingo Molnar <mingo@elte.hu>

[PATCH] make bug messages more consistent

Consolidate all kernel bug printouts to begin with the "BUG: " string.
Makes it easier to find them in large bootup logs.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# cd7619d6 01-May-2005 Matt Mackall <mpm@selenic.com>

[PATCH] Exterminate PAGE_BUG

Remove PAGE_BUG - repalce it with BUG and BUG_ON.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# c8538a7a 01-May-2005 Matt Mackall <mpm@selenic.com>

[PATCH] remove all kernel BUGs

This patch eliminates all kernel BUGs, trims about 35k off the typical
kernel, and makes the system slightly faster.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>


# 1da177e4 16-Apr-2005 Linus Torvalds <torvalds@ppc970.osdl.org>

Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!