[PATCH v4 4/6] linux: Add compatibility definitions to sys/prctl.h for MTE

[Siddhesh Poyarekar]

On 12/19/20 12:59 AM, Richard Earnshaw via Libc-alpha wrote:
> 
> Older versions of the Linux kernel headers obviously lack support for
> memory tagging, but we still want to be able to build in support when
> using those (obviously it can't be enabled on such systems).
> 
> The linux kernel extensions are made to the platform-independent
> header (linux/prctl.h), so this patch takes a similar approach.
> ---
>   sysdeps/unix/sysv/linux/sys/prctl.h | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)

Please put the additions into an architecture-specific 
sysdeps/unix/sysv/linux/aarch64/sys/prctl.h and include_next this file 
from there.

> 
> diff --git a/sysdeps/unix/sysv/linux/sys/prctl.h b/sysdeps/unix/sysv/linux/sys/prctl.h
> index 7f748ebeeb..4d01379c23 100644
> --- a/sysdeps/unix/sysv/linux/sys/prctl.h
> +++ b/sysdeps/unix/sysv/linux/sys/prctl.h
> @@ -21,6 +21,24 @@
>  #include <features.h>
>  #include <linux/prctl.h>  /*  The magic values come from here  */
>  
> +/* Recent extensions to linux which may post-date the kernel headers
> +   we're picking up...  */
> +
> +/* Memory tagging control operations (for AArch64).  */
> +#ifndef PR_TAGGED_ADDR_ENABLE
> +# define PR_TAGGED_ADDR_ENABLE	(1UL << 8)
> +#endif
> +
> +#ifndef PR_MTE_TCF_SHIFT
> +# define PR_MTE_TCF_SHIFT	1
> +# define PR_MTE_TCF_NONE	(0UL << PR_MTE_TCF_SHIFT)
> +# define PR_MTE_TCF_SYNC	(1UL << PR_MTE_TCF_SHIFT)
> +# define PR_MTE_TCF_ASYNC	(2UL << PR_MTE_TCF_SHIFT)
> +# define PR_MTE_TCF_MASK	(3UL << PR_MTE_TCF_SHIFT)
> +# define PR_MTE_TAG_SHIFT	3
> +# define PR_MTE_TAG_MASK	(0xffffUL << PR_MTE_TAG_SHIFT)
> +#endif
> +
>  __BEGIN_DECLS
>  
>  /* Control process execution.  */