[PATCH] add support for -fcf-protection

[Niels Möller]

Jakub Martisko <jamartis at redhat.com> writes:

> Hello,
>
> attached patch modifies the x86_64 assembly files, to support
> -fcf-protection/intel CET [1,2] controls. Modifications are done via the
> m4 macros, so it should be quite easy to modify the patch to use the
> changes only conditionaly druing the compilation.
> --- a/mpn/x86_64/coreibwl/addmul_1.asm
> +++ b/mpn/x86_64/coreibwl/addmul_1.asm
> @@ -107,33 +107,39 @@ L(tab):	JMPENT(	L(f0), L(tab))
>  	JMPENT(	L(f7), L(tab))
>  	TEXT
>  
> -L(f0):	mulx(	(up), %r10, %r8)
> +L(f0):	CFPROT_ENDBR
> +	mulx(	(up), %r10, %r8)

This looks a bit intrusive. Maybe better to split the L macro into two,
one for code labels and one for data labels, and have the expansion of
the former include an endbr instructin, when appropriate?

> diff --git a/mpn/x86_64/coreihwl/mul_basecase.asm b/mpn/x86_64/coreihwl/mul_basecase.asm
> index b2656c8..e4a8381 100644
> --- a/mpn/x86_64/coreihwl/mul_basecase.asm
> +++ b/mpn/x86_64/coreihwl/mul_basecase.asm
> @@ -439,3 +439,4 @@ L(ret2):pop	%rbp
>  	FUNC_EXIT()
>  	ret
>  EPILOGUE()
> +CF_PROT

Adn this should perhaps go into ASM_END. Not sure how consistently
ASM_END is used, though. Another alternative is to use m4 divert to get the
note added at the end of each assembly file.

Regards,
/Niels

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