Re: [PATCH v5 08/16] x86/stackprotector/64: Convert to normal percpu variable

[Borislav Petkov]

On Tue, Nov 05, 2024 at 10:57:53AM -0500, Brian Gerst wrote:
> 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, allowng it to
> become a normal percpu variable instead of at a fixed location.  This
> removes the contraint that the percpu section must be zero-based.

Unknown word [contraint] in commit message.
Suggestions: ['constraint',...

Use a spellchecker for your commit messages please.

> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 5b773b34768d..88a1705366f9 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -140,14 +140,7 @@ ifeq ($(CONFIG_X86_32),y)
>          # temporary until string.h is fixed
>          KBUILD_CFLAGS += -ffreestanding
>  
> -    ifeq ($(CONFIG_STACKPROTECTOR),y)
> -        ifeq ($(CONFIG_SMP),y)
> -            KBUILD_CFLAGS += -mstack-protector-guard-reg=fs \
> -                             -mstack-protector-guard-symbol=__ref_stack_chk_guard
> -        else
> -            KBUILD_CFLAGS += -mstack-protector-guard=global
> -        endif
> -    endif
> +        percpu_seg := fs

Any particular reason this var is not in all caps like the rest of the vars in
this file?

	PERCPU_SEG := fs

...

Thx.

-- 
Regards/Gruss,
    Boris.

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