diff options
| author | Brian Gerst <brgerst@gmail.com> | 2025-01-23 14:07:39 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-02-18 10:15:09 +0100 |
| commit | 80d47defddc000271502057ebd7efa4fd6481542 (patch) | |
| tree | 8b352a713b9f87567eb3d3a4ac1bcc55bc9311ed /arch/x86/include/asm/processor.h | |
| parent | 78c4374ef8b842c6abf195d6f963853c7ec464d2 (diff) | |
x86/stackprotector/64: Convert to normal per-CPU variable
Older versions of GCC fixed the location of the stack protector canary
at %gs:40. This constraint forced the percpu section to be linked at
absolute address 0 so that the canary could be the first data object in
the percpu section. Supporting the zero-based percpu section requires
additional code to handle relocations for RIP-relative references to
percpu data, extra complexity to kallsyms, and workarounds for linker
bugs due to the use of absolute symbols.
GCC 8.1 supports redefining where the canary is located, allowing it to
become a normal percpu variable instead of at a fixed location. This
removes the constraint that the percpu section must be zero-based.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-8-brgerst@gmail.com
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 16 |
1 files changed, 2 insertions, 14 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c0cd10182e90..a4687122951f 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -422,16 +422,8 @@ struct irq_stack { #ifdef CONFIG_X86_64 struct fixed_percpu_data { - /* - * GCC hardcodes the stack canary as %gs:40. Since the - * irq_stack is the object at %gs:0, we reserve the bottom - * 48 bytes of the irq stack for the canary. - * - * Once we are willing to require -mstack-protector-guard-symbol= - * support for x86_64 stackprotector, we can get rid of this. - */ char gs_base[40]; - unsigned long stack_canary; + unsigned long reserved; }; DECLARE_PER_CPU_FIRST(struct fixed_percpu_data, fixed_percpu_data) __visible; @@ -446,11 +438,7 @@ extern asmlinkage void entry_SYSCALL32_ignore(void); /* Save actual FS/GS selectors and bases to current->thread */ void current_save_fsgs(void); -#else /* X86_64 */ -#ifdef CONFIG_STACKPROTECTOR -DECLARE_PER_CPU(unsigned long, __stack_chk_guard); -#endif -#endif /* !X86_64 */ +#endif /* X86_64 */ struct perf_event; |