powerpc: Replace GPL 2.0+ README.legal boilerplate with SPDX

Upstream Linux never had a "README.legal" file, but it was present
in early source releases of Linux/m68k. It contained a simple copyright
notice and a link to a version of the "COPYING" file that predated the
addition of the "only valid GPL version is v2" clause.

Get rid of the references to non-existent files by replacing the
boilerplate with SPDX license identifiers.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/d91725ff1ed5d4b6ba42474e2ebfeebe711cba23.1695031668.git.geert@linux-m68k.org

powerpc/32: Fix overread/overwrite of thread_struct via ptrace

The ptrace PEEKUSR/POKEUSR (aka PEEKUSER/POKEUSER) API allows a process
to read/write registers of another process.

To get/set a register, the API takes an index into an imaginary address
space called the "USER area", where the registers of the process are
laid out in some fashion.

The kernel then maps that index to a particular register in its own data
structures and gets/sets the value.

The API only allows a single machine-word to be read/written at a time.
So 4 bytes on 32-bit kernels and 8 bytes on 64-bit kernels.

The way floating point registers (FPRs) are addressed is somewhat
complicated, because double precision float values are 64-bit even on
32-bit CPUs. That means on 32-bit kernels each FPR occupies two
word-sized locations in the USER area. On 64-bit kernels each FPR
occupies one word-sized location in the USER area.

Internally the kernel stores the FPRs in an array of u64s, or if VSX is
enabled, an array of pairs of u64s where one half of each pair stores
the FPR. Which half of the pair stores the FPR depends on the kernel's
endianness.

To handle the different layouts of the FPRs depending on VSX/no-VSX and
big/little endian, the TS_FPR() macro was introduced.

Unfortunately the TS_FPR() macro does not take into account the fact
that the addressing of each FPR differs between 32-bit and 64-bit
kernels. It just takes the index into the "USER area" passed from
userspace and indexes into the fp_state.fpr array.

On 32-bit there are 64 indexes that address FPRs, but only 32 entries in
the fp_state.fpr array, meaning the user can read/write 256 bytes past
the end of the array. Because the fp_state sits in the middle of the
thread_struct there are various fields than can be overwritten,
including some pointers. As such it may be exploitable.

It has also been observed to cause systems to hang or otherwise
misbehave when using gdbserver, and is probably the root cause of this
report which could not be easily reproduced:
https://lore.kernel.org/linuxppc-dev/dc38afe9-6b78-f3f5-666b-986939e40fc6@keymile.com/

Rather than trying to make the TS_FPR() macro even more complicated to
fix the bug, or add more macros, instead add a special-case for 32-bit
kernels. This is more obvious and hopefully avoids a similar bug
happening again in future.

Note that because 32-bit kernels never have VSX enabled the code doesn't
need to consider TS_FPRWIDTH/OFFSET at all. Add a BUILD_BUG_ON() to
ensure that 32-bit && VSX is never enabled.

Fixes: 87fec0514f61 ("powerpc: PTRACE_PEEKUSR/PTRACE_POKEUSER of FPR registers in little endian builds")
Cc: stable@vger.kernel.org # v3.13+
Reported-by: Ariel Miculas <ariel.miculas@belden.com>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220609133245.573565-1-mpe@ellerman.id.au

powerpc: Finalise cleanup around ABI use

Now that we have CONFIG_PPC64_ELF_ABI_V1 and CONFIG_PPC64_ELF_ABI_V2,
get rid of all indirect detection of ABI version.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/709d9d69523c14c8a9fba4486395dca0f2d675b1.1652074503.git.christophe.leroy@csgroup.eu

powerpc: Replace PPC64_ELF_ABI_v{1/2} by CONFIG_PPC64_ELF_ABI_V{1/2}

Replace all uses of PPC64_ELF_ABI_v1 and PPC64_ELF_ABI_v2 by
resp CONFIG_PPC64_ELF_ABI_V1 and CONFIG_PPC64_ELF_ABI_V2.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/ba13d59e8c50bc9aa6328f1c7f0c0d0278e0a3a7.1652074503.git.christophe.leroy@csgroup.eu

ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h

Rename tracehook_report_syscall_{entry,exit} to
ptrace_report_syscall_{entry,exit} and place them in ptrace.h

There is no longer any generic tracehook infractructure so make
these ptrace specific functions ptrace specific.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-3-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

powerpc: Move C prototypes out of asm-prototypes.h

We originally added asm-prototypes.h in commit 42f5b4cacd78 ("powerpc:
Introduce asm-prototypes.h"). It's purpose was for prototypes of C
functions that are only called from asm, in order to fix sparse
warnings about missing prototypes.

A few months later Nick added a different use case in
commit 4efca4ed05cb ("kbuild: modversions for EXPORT_SYMBOL() for asm")
for C prototypes for exported asm functions. This is basically the
inverse of our original usage.

Since then we've added various prototypes to asm-prototypes.h for both
reasons, meaning we now need to unstitch it all.

Dispatch prototypes of C functions into relevant headers and keep
only the prototypes for functions defined in assembly.

For the time being, leave prom_init() there because moving it
into asm/prom.h or asm/setup.h conflicts with
drivers/gpu/drm/nouveau/nvkm/subdev/bios/shadowrom.o
This will be fixed later by untaggling asm/pci.h and asm/prom.h
or by renaming the function in shadowrom.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/62d46904eca74042097acf4cb12c175e3067f3d1.1646413435.git.christophe.leroy@csgroup.eu

asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by a config option
named CONFIG_HAVE_FUNCTION_DESCRIPTORS and use it instead of
'dereference_function_descriptor' macro to know whether an
arch has function descriptors.

To limit churn in one of the following patches, use
an #ifdef/#else construct with empty first part
instead of an #ifndef in asm-generic/sections.h

On powerpc, make sure the config option matches the ABI used
by the compiler with a BUILD_BUG_ON() and add missing _CALL_ELF=2
when calling 'sparse' so that sparse sees the same piece of
code as GCC.

And include a helper to check whether an arch has function
descriptors or not : have_function_descriptors()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4a0f11fb0ea74a3197bc44dd7ba25e53a24fd03d.1644928018.git.christophe.leroy@csgroup.eu

powerpc: Snapshot thread flags

Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.

To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.

Convert them all to the new flag accessor helpers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-11-mark.rutland@arm.com

powerpc: Add dear as a synonym for pt_regs.dar register

Create an anonymous union for dar and dear regsiters, we can reference
dear to get the effective address when CONFIG_4xx=y or CONFIG_BOOKE=y.
Otherwise, reference dar. This makes code more clear.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
[mpe: Reword commit title]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210807010239.416055-4-sxwjean@me.com

powerpc: Add esr as a synonym for pt_regs.dsisr

Create an anonymous union for dsisr and esr regsiters, we can reference
esr to get the exception detail when CONFIG_4xx=y or CONFIG_BOOKE=y.
Otherwise, reference dsisr. This makes code more clear.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
[mpe: Reword commit title]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210807010239.416055-2-sxwjean@me.com

powerpc: remove partial register save logic

All subarchitectures always save all GPRs to pt_regs interrupt frames
now. Remove FULL_REGS and associated bits.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210316104206.407354-11-npiggin@gmail.com

powerpc/ptrace: Remove duplicate check from pt_regs_check()

"offsetof(struct pt_regs, msr) == offsetof(struct user_pt_regs, msr)"
checked in pt_regs_check() twice in a row. Remove the second check.

Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210305112807.26299-1-efremov@linux.com

powerpc/64: context tracking remove _TIF_NOHZ

Add context tracking to the system call handler explicitly, and remove
_TIF_NOHZ.

This improves system call performance when nohz_full is enabled. On a
POWER9, gettid scv system call cost on a nohz_full CPU improves from
1129 cycles to 1004 cycles and on a housekeeping CPU from 550 cycles
to 430 cycles.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210130130852.2952424-31-npiggin@gmail.com

powerpc/ptrace: Create ptrace_get_fpr() and ptrace_put_fpr()

On the same model as ptrace_get_reg() and ptrace_put_reg(),
create ptrace_get_fpr() and ptrace_put_fpr() to get/set
the floating points registers.

We move the boundary checkings in them.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/24a1baedea7f7ae7b6bf27be98bab6d01b5ca2c1.1597770847.git.christophe.leroy@csgroup.eu

powerpc/ptrace: Consolidate reg index calculation

Today we have:

#ifdef CONFIG_PPC32
index = addr >> 2;
if ((addr & 3) || child->thread.regs == NULL)
#else
index = addr >> 3;
if ((addr & 7))
#endif

sizeof(long) has value 4 for PPC32 and value 8 for PPC64.

Dividing by 4 is equivalent to >> 2 and dividing by 8 is equivalent
to >> 3.

And 3 and 7 are respectively (sizeof(long) - 1).

Use sizeof(long) to get rid of the #ifdef CONFIG_PPC32 and consolidate
the calculation and checking.

thread.regs have to be not NULL on both PPC32 and PPC64 so adding
that test on PPC64 is harmless.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/3cd1e284e93c60db981659585e18d1f6bb73ed2f.1597770847.git.christophe.leroy@csgroup.eu

powerpc/ptrace: move ptrace_triggered() into hw_breakpoint.c

ptrace_triggered() is declared in asm/hw_breakpoint.h and
only needed when CONFIG_HW_BREAKPOINT is set, so move it
into hw_breakpoint.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8402c516023da1371953a65af7df2008758ea0c4.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: create ppc_gethwdinfo()

Create ippc_gethwdinfo() to handle PPC_PTRACE_GETHWDBGINFO and
reduce ifdef mess

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/82fefcc1ec75b96cece792878217a5d85ecda0c2.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: create ptrace_get_debugreg()

Create ptrace_get_debugreg() to handle PTRACE_GET_DEBUGREG and
reduce ifdef mess

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c1482c41a39cc216f4073a51070d8680f52d5054.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: split out ADV_DEBUG_REGS related functions.

Move ADV_DEBUG_REGS functions out of ptrace.c, into
ptrace-adv.c and ptrace-noadv.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Squash in fixup patch from Christophe]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e2bd7d275bd5933d848aad4fee3ca652a14d039b.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: move register viewing functions out of ptrace.c

Create a dedicated ptrace-view.c file.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/bfd8c3ed57c9057e4a5d3816737b5ee98c6f7e43.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: split out TRANSACTIONAL_MEM related functions.

Move TRANSACTIONAL_MEM functions out of ptrace.c, into
ptrace-tm.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2d0ef3bb2610c0344bd42252c7134f429818c000.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: split out SPE related functions.

Move CONFIG_SPE functions out of ptrace.c, into
ptrace-spe.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0f17a331760310b5562fae3791cdd3cf9c64237b.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: split out ALTIVEC related functions.

Move CONFIG_ALTIVEC functions out of ptrace.c, into
ptrace-altivec.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/35dae891d01c817fca0fd6ab406a3a2c7bf07f60.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: split out VSX related functions.

Move CONFIG_VSX functions out of ptrace.c, into
ptrace-vsx.c and ptrace-novsx.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/dc8e20c8c95b7e83add0c6dd48f9470628896c5c.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: drop PARAMETER_SAVE_AREA_OFFSET

PARAMETER_SAVE_AREA_OFFSET is not used, drop it.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6dac2b49207647f75cbf0e6771a545e691f0fd93.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: drop unnecessary #ifdefs CONFIG_PPC64

Drop a bunch of #ifdefs CONFIG_PPC64 that are not vital.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/af38b87a7e1e3efe4f9b664eaeb029e6e7d69fdb.1582848567.git.christophe.leroy@c-s.fr

powerpc/ptrace: remove unused header includes

Remove unused header includes in ptrace.c and ptrace32.c

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6276df0be87a4329c2bb46b3b0f02059ae9e70e6.1582848567.git.christophe.leroy@c-s.fr

powerpc: Move ptrace into a subdirectory.

In order to allow splitting of ptrace depending on the different
CONFIG_ options, create a subdirectory dedicated to ptrace and move
ptrace.c and ptrace32.c into it.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/9ebcbe37834e9d447dd97f4381084795a673260c.1582848567.git.christophe.leroy@c-s.fr