[PATCH 2/2] nptl: Enable MTE for stacks created for threads.

[Yury Khrustalev]

On Fri, Mar 14, 2025 at 01:21:42PM +0000, Cupertino Miranda wrote:
> This patch adds MPROT_MTE flag to newly mapped stacks for threads, if
> DT_AARCH64_MEMTAG_STACK is present in the array of dynamic tags in the
> executable.
> 
> ...
>
> diff --git a/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c b/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
> index a4bc82c99b..7ed92855ae 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
> +++ b/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
>
> ...
>
> +int
> +stack_mem_tagging_prot (void)
> +{
> +  if ((GLRO(dl_aarch64_cpu_features).mte_state & AARCH64_CPU_FEATURE_MTE_STATE_STACK) == 8
> +      && _dl_mte_mode ())
> +    return PROT_MTE;

Because we don't check the return value of prctl(PR_SET_TAGGED_ADDR_CTRL, ...), we don't
actually know if memory tagging was enabled for the process. If it wasn't, there is probably
no need to add extra mprotect flag for the threads.

Thanks,
Yury