linux.git/arch/x86/kernel/module.c, branch v7.2

x86/module: Revert "Deal with GOT based stack cookie load on Clang < 17"

2026-05-27T22:20:06+00:00

Now that the minimum supported version of LLVM for building the kernel
has been raised to 17.0.1, the workaround added by

  78c4374ef8b8 ("x86/module: Deal with GOT based stack cookie load on Clang < 17")

will never be included, as the final clause in the preprocessor
conditional is always false. Revert the change to clean up the dead
code.

Acked-by: Ard Biesheuvel 
Link: https://patch.msgid.link/20260517-bump-minimum-supported-llvm-version-to-17-v2-12-b3b8cda46bdd@kernel.org
Signed-off-by: Nathan Chancellor

x86/module: Improve relocation error messages

2025-10-14T21:45:21+00:00

Add the section number and reloc index to relocation error messages to
help find the faulty relocation.

Acked-by: Petr Mladek 
Tested-by: Joe Lawrence 
Signed-off-by: Josh Poimboeuf

Merge commit 'its-for-linus-20250509-merge' into x86/core, to resolve conflicts

2025-05-13T08:47:10+00:00

 Conflicts:
	Documentation/admin-guide/hw-vuln/index.rst
	arch/x86/include/asm/cpufeatures.h
	arch/x86/kernel/alternative.c
	arch/x86/kernel/cpu/bugs.c
	arch/x86/kernel/cpu/common.c
	drivers/base/cpu.c
	include/linux/cpu.h

Signed-off-by: Ingo Molnar

x86/its: Use dynamic thunks for indirect branches

2025-05-09T20:36:58+00:00

ITS mitigation moves the unsafe indirect branches to a safe thunk. This
could degrade the prediction accuracy as the source address of indirect
branches becomes same for different execution paths.

To improve the predictions, and hence the performance, assign a separate
thunk for each indirect callsite. This is also a defense-in-depth measure
to avoid indirect branches aliasing with each other.

As an example, 5000 dynamic thunks would utilize around 16 bits of the
address space, thereby gaining entropy. For a BTB that uses
32 bits for indexing, dynamic thunks could provide better prediction
accuracy over fixed thunks.

Have ITS thunks be variable sized and use EXECMEM_MODULE_TEXT such that
they are both more flexible (got to extend them later) and live in 2M TLBs,
just like kernel code, avoiding undue TLB pressure.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Pawan Gupta 
Signed-off-by: Dave Hansen 
Reviewed-by: Alexandre Chartre

x86/alternatives: Rename 'text_poke_sync()' to 'smp_text_poke_sync_each_cpu()'

2025-04-11T09:01:34+00:00

Unlike sync_core(), text_poke_sync() is a very heavy operation, as
it sends an IPI to every online CPU in the system and waits for
completion.

Reflect this in the name.

Signed-off-by: Ingo Molnar 
Cc: Juergen Gross 
Cc: "H . Peter Anvin" 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/r/20250411054105.2341982-41-mingo@kernel.org

Merge branch 'x86/asm' into x86/core, to pick up dependent commits

2025-03-04T19:29:35+00:00

Signed-off-by: Ingo Molnar

Merge branch 'x86/cpu' into x86/asm, to pick up dependent commits

2025-03-04T10:19:21+00:00

Signed-off-by: Ingo Molnar

x86/module: Remove unnecessary check in module_finalize()

2025-02-21T13:27:42+00:00

The "calls" pointer can no longer be NULL after the following
commit:

   ab9fea59487d ("x86/alternative: Simplify callthunk patching")

Delete this unnecessary check.

Signed-off-by: Dan Carpenter 
Signed-off-by: Ingo Molnar 
Acked-by: Song Liu 
Link: https://lore.kernel.org/r/fcbb2f57-0714-4139-b441-8817365c16a1@stanley.mountain

x86/module: Deal with GOT based stack cookie load on Clang < 17

2025-02-18T09:15:05+00:00

Clang versions before 17 will not honour -fdirect-access-external-data
for the load of the stack cookie emitted into each function's prologue
and epilogue.

This is not an issue for the core kernel, as the linker will relax these
loads into LEA instructions that take the address of __stack_chk_guard
directly. For modules, however, we need to work around this, by dealing
with R_X86_64_REX_GOTPCRELX relocations that refer to __stack_chk_guard.

In this case, given that this is a GOT load, the reference should not
refer to __stack_chk_guard directly, but to a memory location that holds
its address. So take the address of __stack_chk_guard into a static
variable, and fix up the relocations to refer to that.

[ mingo: Fix broken R_X86_64_GOTPCRELX definition. ]

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Brian Gerst 
Signed-off-by: Ingo Molnar 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/r/20250123190747.745588-7-brgerst@gmail.com

x86/alternative: Simplify callthunk patching

2025-02-14T09:32:06+00:00

Now that paravirt call patching is implemented using alternatives, it
is possible to avoid having to patch the alternative sites by
including the altinstr_replacement calls in the call_sites list.

This means we're now stacking relative adjustments like so:

  callthunks_patch_builtin_calls():
    patches all function calls to target: func() -> func()-10
    since the CALL accounting lives in the CALL_PADDING.

    This explicitly includes .altinstr_replacement

  alt_replace_call():
    patches: x86_BUG() -> target()

    this patching is done in a relative manner, and will preserve
    the above adjustment, meaning that with calldepth patching it
    will do: x86_BUG()-10 -> target()-10

  apply_relocation():
    does code relocation, and adjusts all RIP-relative instructions
    to the new location, also in a relative manner.

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Sami Tolvanen 
Link: https://lore.kernel.org/r/20250207122546.617187089@infradead.org