[PATCH glibc] Update hurd/intr-msg.c to be more portable

[PATCH glibc] Update hurd/intr-msg.c to be more portable

[Flavio Cruz]

Summary of the changes:
- Introduce BAD_TYPECHECK from MiG to make it simpler to do type
  checking.
- Replace int type with mach_msg_type_t. This assumes that
  mach_msg_type_t is always the same size as int which is not true for
  x86_64.
- Calculate the size and align using PTR_ALIGN_UP, which is a bit
  cleaner and similar to what we do elsewhere.
- Define mach_msg_type_t to check using designated initializers.
---
 hurd/intr-msg.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/hurd/intr-msg.c b/hurd/intr-msg.c
index 716d87ab6a..a8e4d04041 100644
--- a/hurd/intr-msg.c
+++ b/hurd/intr-msg.c
@@ -28,6 +28,11 @@
 # define mig_reply_header_t	mig_reply_error_t
 #endif
 
+/* Macro used by MIG to cleanly check the type.  */
+#define BAD_TYPECHECK(type, check) __glibc_unlikely (({	\
+  union { mach_msg_type_t t; uint32_t w; } _t, _c;	\
+  _t.t = *(type); _c.t = *(check);_t.w != _c.w; }))
+
 error_t
 _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 			 mach_msg_option_t option,
@@ -61,7 +66,7 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 #ifdef NDR_CHAR_ASCII
       NDR_record_t ndr;
 #else
-      int type;
+      mach_msg_type_t type;
 #endif
       int code;
     } check;
@@ -222,11 +227,12 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 
 	      if (ty->msgtl_header.msgt_inline)
 		{
+		  /* Calculate length of data in bytes.  */
+		  const vm_size_t length = ((number * size) + 7) >> 3;
 		  clean_ports ((void *) ty, 0);
-		  /* calculate length of data in bytes, rounding up */
-		  ty = (void *) ty + (((((number * size) + 7) >> 3)
-				       + sizeof (mach_msg_type_t) - 1)
-				      &~ (sizeof (mach_msg_type_t) - 1));
+		  /* Move to the next argument.  */
+		  ty = (void *) PTR_ALIGN_UP ((char *) ty + length,
+		      __alignof__ (uintptr_t));
 		}
 	      else
 		{
@@ -354,19 +360,21 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
       {
 	/* We got a reply.  Was it EINTR?  */
 #ifdef MACH_MSG_TYPE_BIT
-	const union
-	{
-	  mach_msg_type_t t;
-	  int i;
-	} check =
-	  { t: { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8,
-		 1, TRUE, FALSE, FALSE, 0 } };
+	static const mach_msg_type_t type_check = {
+	  .msgt_name = MACH_MSG_TYPE_INTEGER_T,
+	  .msgt_size = sizeof (integer_t) * 8,
+	  .msgt_number = 1,
+	  .msgt_inline = TRUE,
+	  .msgt_longform = FALSE,
+	  .msgt_deallocate = FALSE,
+	  .msgt_unused = 0
+	};
 #endif
 
         if (m->reply.RetCode == EINTR
 	    && m->header.msgh_size == sizeof m->reply
 #ifdef MACH_MSG_TYPE_BIT
-	    && m->check.type == check.i
+	    && !BAD_TYPECHECK(&m->check.type, &type_check)
 #endif
 	    && !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
 	  {
-- 
2.39.2

Re: [PATCH glibc] Update hurd/intr-msg.c to be more portable

[Samuel Thibault]

Applied, thanks!

Flavio Cruz via Libc-alpha, le jeu. 04 mai 2023 00:08:12 -0400, a ecrit:
> Summary of the changes:
> - Introduce BAD_TYPECHECK from MiG to make it simpler to do type
>   checking.
> - Replace int type with mach_msg_type_t. This assumes that
>   mach_msg_type_t is always the same size as int which is not true for
>   x86_64.
> - Calculate the size and align using PTR_ALIGN_UP, which is a bit
>   cleaner and similar to what we do elsewhere.
> - Define mach_msg_type_t to check using designated initializers.
> ---
>  hurd/intr-msg.c | 34 +++++++++++++++++++++-------------
>  1 file changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/hurd/intr-msg.c b/hurd/intr-msg.c
> index 716d87ab6a..a8e4d04041 100644
> --- a/hurd/intr-msg.c
> +++ b/hurd/intr-msg.c
> @@ -28,6 +28,11 @@
>  # define mig_reply_header_t	mig_reply_error_t
>  #endif
>  
> +/* Macro used by MIG to cleanly check the type.  */
> +#define BAD_TYPECHECK(type, check) __glibc_unlikely (({	\
> +  union { mach_msg_type_t t; uint32_t w; } _t, _c;	\
> +  _t.t = *(type); _c.t = *(check);_t.w != _c.w; }))
> +
>  error_t
>  _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
>  			 mach_msg_option_t option,
> @@ -61,7 +66,7 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
>  #ifdef NDR_CHAR_ASCII
>        NDR_record_t ndr;
>  #else
> -      int type;
> +      mach_msg_type_t type;
>  #endif
>        int code;
>      } check;
> @@ -222,11 +227,12 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
>  
>  	      if (ty->msgtl_header.msgt_inline)
>  		{
> +		  /* Calculate length of data in bytes.  */
> +		  const vm_size_t length = ((number * size) + 7) >> 3;
>  		  clean_ports ((void *) ty, 0);
> -		  /* calculate length of data in bytes, rounding up */
> -		  ty = (void *) ty + (((((number * size) + 7) >> 3)
> -				       + sizeof (mach_msg_type_t) - 1)
> -				      &~ (sizeof (mach_msg_type_t) - 1));
> +		  /* Move to the next argument.  */
> +		  ty = (void *) PTR_ALIGN_UP ((char *) ty + length,
> +		      __alignof__ (uintptr_t));
>  		}
>  	      else
>  		{
> @@ -354,19 +360,21 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
>        {
>  	/* We got a reply.  Was it EINTR?  */
>  #ifdef MACH_MSG_TYPE_BIT
> -	const union
> -	{
> -	  mach_msg_type_t t;
> -	  int i;
> -	} check =
> -	  { t: { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8,
> -		 1, TRUE, FALSE, FALSE, 0 } };
> +	static const mach_msg_type_t type_check = {
> +	  .msgt_name = MACH_MSG_TYPE_INTEGER_T,
> +	  .msgt_size = sizeof (integer_t) * 8,
> +	  .msgt_number = 1,
> +	  .msgt_inline = TRUE,
> +	  .msgt_longform = FALSE,
> +	  .msgt_deallocate = FALSE,
> +	  .msgt_unused = 0
> +	};
>  #endif
>  
>          if (m->reply.RetCode == EINTR
>  	    && m->header.msgh_size == sizeof m->reply
>  #ifdef MACH_MSG_TYPE_BIT
> -	    && m->check.type == check.i
> +	    && !BAD_TYPECHECK(&m->check.type, &type_check)
>  #endif
>  	    && !(m->header.msgh_bits & MACH_MSGH_BITS_COMPLEX))
>  	  {
> -- 
> 2.39.2
> 

-- 
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.