linux-stable.git/arch/powerpc/kernel/process.c, branch v6.17

powerpc: Don't use --- in kernel logs

2025-04-29T06:11:38+00:00

When a kernel log containing --- at the start of a line is copied into
a patch message, 'git am' drops everything located after that ---.

Replace --- by ---- to avoid that.

Signed-off-by: Christophe Leroy 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/54a1f8d2c3fb5b95434039724c8c141052ae5cc0.1739346038.git.christophe.leroy@csgroup.eu

powerpc/64: Use get_user() in start_thread()

2024-12-18T08:11:57+00:00

For ELFv1 binaries (big endian), the ELF entry point isn't the address
of the first instruction, instead it points to the function descriptor
for the entry point. The address of the first instruction is in the
function descriptor.

That means the kernel has to fetch the address of the first instruction
from user memory.

Because start_thread() uses __get_user(), which has no access_ok()
checks, it looks like a malicious ELF binary could be crafted to point
the entry point address at kernel memory. The kernel would load 8 bytes
from kernel memory into the NIP and then start the process, it would
typically crash, but a debugger could observe the NIP value which would
be the result of reading from kernel memory.

However that's NOT possible, because there is a check in
load_elf_binary() that ensures the ELF entry point is < TASK_SIZE
(look for BAD_ADDR(elf_entry)).

However it's fragile for start_thread() to rely on a check elsewhere,
even if the ELF parser is unlikely to ever drop the check that elf_entry
is a user address.

Make it more robust by using get_user(), which checks that the address
points at userspace before doing the load. If the address doesn't point
at userspace it will just set the result to zero, and the userspace
program will crash at zero (which is fine because it's self-inflicted).

Note that it's also possible for a malicious binary to have a valid
ELF entry address, but with the first instruction address pointing into
the kernel. However that's OK, because it is blocked by the MMU, just
like any other attempt to jump into the kernel from userspace.

Reported-by: Linus Torvalds 
Signed-off-by: Michael Ellerman 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20241216121706.26790-1-mpe@ellerman.id.au

asm-generic: introduce text-patching.h

2024-11-07T22:25:15+00:00

Several architectures support text patching, but they name the header
files that declare patching functions differently.

Make all such headers consistently named text-patching.h and add an empty
header in asm-generic for architectures that do not support text patching.

Link: https://lkml.kernel.org/r/20241023162711.2579610-4-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) 
Reviewed-by: Christoph Hellwig 
Acked-by: Geert Uytterhoeven  # m68k
Acked-by: Arnd Bergmann 
Reviewed-by: Luis Chamberlain 
Tested-by: kdevops 
Cc: Andreas Larsson 
Cc: Andy Lutomirski 
Cc: Ard Biesheuvel 
Cc: Borislav Petkov (AMD) 
Cc: Brian Cain 
Cc: Catalin Marinas 
Cc: Christophe Leroy 
Cc: Dave Hansen 
Cc: Dinh Nguyen 
Cc: Guo Ren 
Cc: Helge Deller 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: Johannes Berg 
Cc: John Paul Adrian Glaubitz 
Cc: Kent Overstreet 
Cc: Liam R. Howlett 
Cc: Mark Rutland 
Cc: Masami Hiramatsu (Google) 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Oleg Nesterov 
Cc: Palmer Dabbelt 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Cc: Russell King 
Cc: Song Liu 
Cc: Stafford Horne 
Cc: Steven Rostedt (Google) 
Cc: Suren Baghdasaryan 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Uladzislau Rezki (Sony) 
Cc: Vineet Gupta 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

powerpc/32: Implement validation of emergency stack

2024-08-30T11:30:20+00:00

VMAP stack added an emergency stack on powerpc/32 for when there is
a stack overflow, but failed to add stack validation for that
emergency stack. That validation is required for show stack.

Implement it.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/2439d50b019f758db4a6d7b238b06441ab109799.1724156805.git.christophe.leroy@csgroup.eu

powerpc: Remove obsoleted declaration for _get_SP

2024-08-30T11:01:01+00:00

The implementation of _get_SP() was removed in commit f4db196717c6
("[POWERPC] Remove  _get_SP"), remove the now obsolete declaration.

Signed-off-by: Gaosheng Cui 
Reviewed-by: Christophe Leroy 
[mpe: Update change log to refer to correct commit per Christophe]
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240822130609.786431-2-cuigaosheng1@huawei.com

powerpc: Replace CONFIG_4xx with CONFIG_44x

2024-06-28T12:28:48+00:00

Replace 4xx usage with 44x, and replace 4xx_SOC with 44x.

Also, as pointed out by Christophe, if 44x || BOOKE can be simplified to
just test BOOKE, because 44x always selects BOOKE.

Retain the CONFIG_4xx symbol, as there are drivers that use it to mean
4xx || 44x, those will need updating before CONFIG_4xx can be removed.

Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240628121201.130802-6-mpe@ellerman.id.au

powerpc/4xx: Remove CONFIG_BOOKE_OR_40x

2024-06-28T12:28:48+00:00

Now that 40x is gone, replace CONFIG_BOOKE_OR_40x by CONFIG_BOOKE.

Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240628121201.130802-5-mpe@ellerman.id.au

powerpc: Fix typos

2024-05-07T14:21:30+00:00

Fix typos, most reported by "codespell arch/powerpc".  Only touches
comments, no code changes.

Signed-off-by: Bjorn Helgaas 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240103231605.1801364-8-helgaas@kernel.org

powerpc/dexcr: Reset DEXCR value across exec

2024-05-03T10:46:51+00:00

Inheriting the DEXCR across exec can have security and usability
concerns. If a program is compiled with hash instructions it generally
expects to run with NPHIE enabled. But if the parent process disables
NPHIE then if it's not careful it will be disabled for any children too
and the protection offered by hash checks is basically worthless.

This patch introduces a per-process reset value that new execs in a
particular process tree are initialized with. This enables fine grained
control over what DEXCR value child processes run with by default.
For example, containers running legacy binaries that expect hash
instructions to act as NOPs could configure the reset value of the
container root to control the default reset value for all members of
the container.

Signed-off-by: Benjamin Gray 
[mpe: Add missing SPDX tag on dexcr.c]
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240417112325.728010-4-bgray@linux.ibm.com

powerpc/dexcr: Track the DEXCR per-process

2024-05-03T10:46:51+00:00

Add capability to make the DEXCR act as a per-process SPR.

We do not yet have an interface for changing the values per task. We
also expect the kernel to use a single DEXCR value across all tasks
while in privileged state, so there is no need to synchronize after
changing it (the userspace aspects will synchronize upon returning to
userspace).

Signed-off-by: Benjamin Gray 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240417112325.728010-3-bgray@linux.ibm.com