samples/hw_breakpoint: mark sample_hbp as static

There is a sparse warning shown as below:

samples/hw_breakpoint/data_breakpoint.c:24:19: warning:
symbol 'sample_hbp' was not declared. Should it be static?

Since 'sample_hbp' is only called within data_breakpoint.c,
mark it as static to fix the warning.

Fixes: 44ee63587dce ("percpu: Add __percpu sparse annotations to hw_breakpoint")
Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

samples/hw_breakpoint: fix building without module unloading

__symbol_put() is really meant as an internal helper and is not available
when module unloading is disabled, unlike the previously used symbol_put():

samples/hw_breakpoint/data_breakpoint.c: In function 'hw_break_module_exit':
samples/hw_breakpoint/data_breakpoint.c:73:9: error: implicit declaration of function '__symbol_put'; did you mean '__symbol_get'? [-Werror=implicit-function-declaration]

The hw_break_module_exit() function is not actually used when module
unloading is disabled, but it still causes the build failure for an
undefined identifier. Enclose this one call in an appropriate #ifdef to
clarify what the requirement is. Leaving out the entire exit function
would also work but feels less clar in this case.

Fixes: 910e230d5f1bb ("samples/hw_breakpoint: Fix kernel BUG 'invalid opcode: 0000'")
Fixes: d8a84d33a4954 ("samples/hw_breakpoint: drop use of kallsyms_lookup_name()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

samples/hw_breakpoint: Fix kernel BUG 'invalid opcode: 0000'

Macro symbol_put() is defined as __symbol_put(__stringify(x))

ksym_name = "jiffies"
symbol_put(ksym_name)

will be resolved as

__symbol_put("ksym_name")

which is clearly wrong. So symbol_put must be replaced with __symbol_put.

When we uninstall hw_breakpoint.ko (rmmod), a kernel bug occurs with the
following error:

[11381.854152] kernel BUG at kernel/module/main.c:779!
[11381.854159] invalid opcode: 0000 [#2] PREEMPT SMP PTI
[11381.854163] CPU: 8 PID: 59623 Comm: rmmod Tainted: G D OE 6.2.9-200.fc37.x86_64 #1
[11381.854167] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./B360M-HDV, BIOS P3.20 10/23/2018
[11381.854169] RIP: 0010:__symbol_put+0xa2/0xb0
[11381.854175] Code: 00 e8 92 d2 f7 ff 65 8b 05 c3 2f e6 78 85 c0 74 1b 48 8b 44 24 30 65 48 2b 04 25 28 00 00 00 75 12 48 83 c4 38 c3 cc cc cc cc <0f> 0b 0f 1f 44 00 00 eb de e8 c0 df d8 00 90 90 90 90 90 90 90 90
[11381.854178] RSP: 0018:ffffad8ec6ae7dd0 EFLAGS: 00010246
[11381.854181] RAX: 0000000000000000 RBX: ffffffffc1fd1240 RCX: 000000000000000c
[11381.854184] RDX: 000000000000006b RSI: ffffffffc02bf7c7 RDI: ffffffffc1fd001c
[11381.854186] RBP: 000055a38b76e7c8 R08: ffffffff871ccfe0 R09: 0000000000000000
[11381.854188] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[11381.854190] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[11381.854192] FS: 00007fbf7c62c740(0000) GS:ffff8c5badc00000(0000) knlGS:0000000000000000
[11381.854195] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[11381.854197] CR2: 000055a38b7793f8 CR3: 0000000363e1e001 CR4: 00000000003726e0
[11381.854200] DR0: ffffffffb3407980 DR1: 0000000000000000 DR2: 0000000000000000
[11381.854202] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[11381.854204] Call Trace:
[11381.854207] <TASK>
[11381.854212] s_module_exit+0xc/0xff0 [symbol_getput]
[11381.854219] __do_sys_delete_module.constprop.0+0x198/0x2f0
[11381.854225] do_syscall_64+0x58/0x80
[11381.854231] ? exit_to_user_mode_prepare+0x180/0x1f0
[11381.854237] ? syscall_exit_to_user_mode+0x17/0x40
[11381.854241] ? do_syscall_64+0x67/0x80
[11381.854245] ? syscall_exit_to_user_mode+0x17/0x40
[11381.854248] ? do_syscall_64+0x67/0x80
[11381.854252] ? exc_page_fault+0x70/0x170
[11381.854256] entry_SYSCALL_64_after_hwframe+0x72/0xdc

Signed-off-by: Rong Tao <rongtao@cestc.cn>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

samples/hw_breakpoint: drop use of kallsyms_lookup_name()

The 'data_breakpoint' test code is the only modular user of
kallsyms_lookup_name(), which was exported as part of fixing the test in
f60d24d2ad04 ("hw-breakpoints: Fix broken hw-breakpoint sample module").

In preparation for un-exporting this symbol, switch the test over to using
__symbol_get(), which can be used to place breakpoints on exported
symbols.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Link: http://lkml.kernel.org/r/20200221114404.14641-3-will@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

samples/hw_breakpoint: drop HW_BREAKPOINT_R when reporting writes

Patch series "Unexport kallsyms_lookup_name() and kallsyms_on_each_symbol()".

Despite having just a single modular in-tree user that I could spot,
kallsyms_lookup_name() is exported to modules and provides a mechanism
for out-of-tree modules to access and invoke arbitrary, non-exported
kernel symbols when kallsyms is enabled.

This patch series fixes up that one user and unexports the symbol along
with kallsyms_on_each_symbol(), since that could also be abused in a
similar manner.

I would like to avoid out-of-tree modules being easily able to call
functions that are not exported. kallsyms_lookup_name() makes this
trivial to the point that there is very little incentive to rework these
modules to either use upstream interfaces correctly or propose
functionality which may be otherwise missing upstream. Both of these
latter solutions would be pre-requisites to upstreaming these modules, and
the current state of things actively discourages that approach.

The background here is that we are aiming for Android devices to be able
to use a generic binary kernel image closely following upstream, with any
vendor extensions coming in as kernel modules. In this case, we (Google)
end up maintaining the binary module ABI within the scope of a single LTS
kernel. Monitoring and managing the ABI surface is not feasible if it
effectively includes all data and functions via kallsyms_lookup_name().
Of course, we could just carry this patch in the Android kernel tree, but
we're aiming to carry as little as possible (ideally nothing) and I think
it's a sensible change in its own right. I'm surprised you object to it,
in all honesty.

Now, you could turn around and say "that's not upstream's problem", but it
still seems highly undesirable to me to have an upstream bypass for
exported symbols that isn't even used by upstream modules. It's ripe for
abuse and encourages people to work outside of the upstream tree. The
usual rule is that we don't export symbols without a user in the tree and
that seems especially relevant in this case.

Joe Lawrence said:

: FWIW, kallsyms was historically used by the out-of-tree kpatch support
: module to resolve external symbols as well as call set_memory_r{w,o}()
: API. All of that support code has been merged upstream, so modern kpatch
: modules* no longer leverage kallsyms by default.
:
: That said, there are still some users who still use the deprecated support
: module with newer kernels, but that is not officially supported by the
: project.

This patch (of 3):

Given the name of a kernel symbol, the 'data_breakpoint' test claims to
"report any write operations on the kernel symbol". However, it creates
the breakpoint using both HW_BREAKPOINT_W and HW_BREAKPOINT_R, which menas
it also fires for read access.

Drop HW_BREAKPOINT_R from the breakpoint attributes.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Link: http://lkml.kernel.org/r/20200221114404.14641-2-will@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details you
should have received a copy of the gnu general public license along
with this program if not write to the free software foundation inc
59 temple place suite 330 boston ma 02111 1307 usa

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1334 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

perf: Add context field to perf_event

The perf_event overflow handler does not receive any caller-derived
argument, so many callers need to resort to looking up the perf_event
in their local data structure. This is ugly and doesn't scale if a
single callback services many perf_events.

Fix by adding a context parameter to perf_event_create_kernel_counter()
(and derived hardware breakpoints APIs) and storing it in the perf_event.
The field can be accessed from the callback as event->overflow_handler_context.
All callers are updated.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-2-git-send-email-avi@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

perf: Remove the nmi parameter from the swevent and overflow interface

The nmi parameter indicated if we could do wakeups from the current
context, if not, we would set some state and self-IPI and let the
resulting interrupt do the wakeup.

For the various event classes:

- hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from
the PMI-tail (ARM etc.)
- tracepoint: nmi=0; since tracepoint could be from NMI context.
- software: nmi=[0,1]; some, like the schedule thing cannot
perform wakeups, and hence need 0.

As one can see, there is very little nmi=1 usage, and the down-side of
not using it is that on some platforms some software events can have a
jiffy delay in wakeup (when arch_irq_work_raise isn't implemented).

The up-side however is that we can remove the nmi parameter and save a
bunch of conditionals in fast paths.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/n/tip-agjev8eu666tvknpb3iaj0fg@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>

percpu: Add __percpu sparse annotations to hw_breakpoint

Add __percpu sparse annotations to hw_breakpoint.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors. This patch doesn't affect normal builds.

In kernel/hw_breakpoint.c, per_cpu(nr_task_bp_pinned, cpu)'s will
trigger spurious noderef related warnings from sparse. Changing it to
&per_cpu(nr_task_bp_pinned[0], cpu) will work around the problem but
deemed to ugly by the maintainer. Leave it alone until better
solution can be found.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <4B7B4B7A.9050902@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

hw-breakpoints: Use overflow handler instead of the event callback

struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>

hw-breakpoints: Use struct perf_event_attr to define kernel breakpoints

Kernel breakpoints are created using functions in which we pass
breakpoint parameters as individual variables: address, length
and type.

Although it fits well for x86, this just does not scale across
architectures that may support this api later as these may have
more or different needs. Pass in a perf_event_attr structure
instead because it is meant to evolve as much as possible into
a generic hardware breakpoint parameter structure.

Reported-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1259294154-5197-2-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

hw-breakpoints: Simplify error handling in breakpoint creation requests

This simplifies the error handling when we create a breakpoint.
We don't need to check the NULL return value corner case anymore
since we have improved perf_event_create_kernel_counter() to
always return an error code in the failure case.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <1259210142-5714-3-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

hw-breakpoint: Attribute authorship of hw-breakpoint related files

Attribute authorship to developers of hw-breakpoint related
files.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091123154713.GA5593@in.ibm.com>
[ v2: moved it to latest -tip ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

hw-breakpoints: Fix broken hw-breakpoint sample module

The hw-breakpoint sample module has been broken during the
hw-breakpoint internals refactoring. Propagate the changes
to it.

Reported-by: "K. Prasad" <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

hw-breakpoints: sample HW breakpoint over kernel data address

This patch introduces a sample kernel module to demonstrate the use of Hardware
Breakpoint feature. It places a breakpoint over the kernel variable 'pid_max'
to monitor all write operations and emits a function-backtrace when done.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>