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

[Ingo Molnar]

* Tom Lendacky <thomas.lendacky@xxxxxxx> 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@xxxxxxx>
> ---
>  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