Re: [PATCH v3 13/13] aarch64: fix _mcount for pac-ret

[Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>]

On 15/05/2020 11:40, Szabolcs Nagy wrote:
> gcc -pg with -mbranch-protection=pac-ret passes signed return address
> to _mcount, so _mcount now has to always strip pac from the frompc
> since that's from user code that may be built with pac-ret.
> 
> This is a backward incompatible _mcount abi change introduced by
> return address signing support in gcc-7.

Which change are you referring about specifically?

Besides it, LGTM.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

> 
> TODO: fix -pg on the gcc side?
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94791
> ---
>  sysdeps/aarch64/machine-gmon.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/aarch64/machine-gmon.h b/sysdeps/aarch64/machine-gmon.h
> index 730a23b781..328cbdda16 100644
> --- a/sysdeps/aarch64/machine-gmon.h
> +++ b/sysdeps/aarch64/machine-gmon.h
> @@ -30,5 +30,5 @@ static inline void mcount_internal (u_long frompc, u_long selfpc)
>  #define MCOUNT                                                    \
>  void __mcount (void *frompc)                                      \
>  {                                                                 \
> -  mcount_internal ((u_long) frompc, (u_long) RETURN_ADDRESS (0)); \
> +  mcount_internal ((u_long) strip_pac (frompc), (u_long) RETURN_ADDRESS (0)); \
>  }
>