[PATCH v8 19/20] aarch64: Use __alloc_gcs in makecontext

[Adhemerval Zanella Netto]

LGTM, thanks.

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

On 14/01/25 13:03, Yury Khrustalev wrote:
> From: Szabolcs Nagy <szabolcs.nagy@arm.com>
> 
> ---
>  sysdeps/unix/sysv/linux/aarch64/makecontext.c | 38 ++++---------------
>  1 file changed, 8 insertions(+), 30 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/aarch64/makecontext.c b/sysdeps/unix/sysv/linux/aarch64/makecontext.c
> index 815a604556..a18160d990 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/makecontext.c
> +++ b/sysdeps/unix/sysv/linux/aarch64/makecontext.c
> @@ -22,6 +22,8 @@
>  #include <stdint.h>
>  #include <ucontext.h>
>  
> +#include "aarch64-gcs.h"
> +
>  #define GCS_MAGIC 0x47435300
>  
>  /* Reserved for future use.  */
> @@ -32,41 +34,17 @@ static struct _aarch64_ctx *extension (void *p)
>    return p;
>  }
>  
> -#ifndef SHADOW_STACK_SET_TOKEN
> -# define SHADOW_STACK_SET_TOKEN (1UL << 0)
> -# define SHADOW_STACK_SET_MARKER (1UL << 1)
> -#endif
> -
> -static void *
> -map_shadow_stack (void *addr, size_t size, unsigned long flags)
> -{
> -  return (void *) INLINE_SYSCALL_CALL (map_shadow_stack, addr, size, flags);
> -}
> -
> -#define GCS_MAX_SIZE (1UL << 31)
> -#define GCS_ALTSTACK_RESERVE 160
> -
> +/* Allocate GCS stack and record it in the context.  */
>  static void *
>  alloc_makecontext_gcs (size_t stack_size)
>  {
> -  size_t size = (stack_size / 2 + GCS_ALTSTACK_RESERVE) & -8UL;
> -  if (size > GCS_MAX_SIZE)
> -    size = GCS_MAX_SIZE;
> -
> -  unsigned long flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN;
> -  void *base = map_shadow_stack (NULL, size, flags);
> -  if (base == (void *) -1)
> +  void *base;
> +  size_t size;
> +  void *gcsp = __alloc_gcs (stack_size, &base, &size);
> +  if (gcsp == NULL)
>      /* ENOSYS, bad size or OOM.  */
>      abort ();
> -  uint64_t *gcsp = (uint64_t *) ((char *) base + size);
> -  /* Skip end of GCS token.  */
> -  gcsp--;
> -  /* Verify GCS cap token.  */
> -  gcsp--;
> -  if (((uint64_t)gcsp & 0xfffffffffffff000) + 1 != *gcsp)
> -    abort ();
> -  /* Return the target GCS pointer for context switch.  */
> -  return gcsp + 1;
> +  return gcsp;
>  }
>  
>  /* makecontext sets up a stack and the registers for the