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SubjectRe: [PATCH v10 37/38] compiler-gcc.h: Introduce __nostackp function attribute

* Tom Lendacky <thomas.lendacky@amd.com> wrote:

> Create a new function attribute, __nostackp, that can used to turn off
> stack protection on a per function basis.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> include/linux/compiler-gcc.h | 2 ++
> include/linux/compiler.h | 4 ++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index cd4bbe8..682063b 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -166,6 +166,8 @@
>
> #if GCC_VERSION >= 40100
> # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
> +
> +#define __nostackp __attribute__((__optimize__("no-stack-protector")))
> #endif
>
> #if GCC_VERSION >= 40300
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 219f82f..63cbca1 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -470,6 +470,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
> #define __visible
> #endif
>
> +#ifndef __nostackp
> +#define __nostackp
> +#endif

So I changed this from the hard to read and ambiguous "__nostackp" abbreviation
(does it mean 'no stack pointer?') to "__nostackprotector", plus added this detail
to the changelog:

| ( This is needed by the SME in-place kernel memory encryption feature,
| which activates encryption in its sme_enable() function and thus changes the
| visible value of the stack protection cookie on function return. )

Agreed?

Thanks,

Ingo

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