[hurd, commited] hurd: alterations to MSG_EXAMINE interface (intr-msg.h)

[Samuel Thibault]

From: Mike Kelly <mike@weatherwax.co.uk>

MSG_EXAMINE has been broadened to allow the signal thread (for
example) to access additional arguments that are passed to
interruptible RPCs in other threads. All architecture specific
variants of intr-msg.h now comply with the revised interface and the
single user of MSG_EXAMINE (report-wait.c) adjusted accordingly.
Message-ID: <20260401194948.90428-2-mike@weatherwax.co.uk>
---
 hurd/report-wait.c                  | 15 ++++++++++++-
 sysdeps/mach/hurd/i386/intr-msg.h   | 35 ++++++++++++++---------------
 sysdeps/mach/hurd/x86_64/intr-msg.h | 19 +++++++---------
 3 files changed, 39 insertions(+), 30 deletions(-)

diff --git a/hurd/report-wait.c b/hurd/report-wait.c
index 3f141345f4..703482c6cc 100644
--- a/hurd/report-wait.c
+++ b/hurd/report-wait.c
@@ -155,16 +155,29 @@ _S_msg_report_wait (mach_port_t msgport, thread_t thread,
 	  assert (count == MACHINE_THREAD_STATE_COUNT);
 	  if (SYSCALL_EXAMINE (&state, msgid))
 	    {
+	      mach_msg_header_t* msghdr;
 	      mach_port_t send_port, rcv_port;
+	      mach_msg_size_t rcv_sz;
 	      mach_msg_option_t option;
 	      mach_msg_timeout_t timeout;
 
 	      /* Blocked in a system call.  */
 	      if (*msgid == -25
 		  /* mach_msg system call.  Examine its parameters.  */
-		  && MSG_EXAMINE (&state, msgid, &rcv_port, &send_port,
+		  && MSG_EXAMINE (&state, &msghdr, &rcv_port, &rcv_sz,
 				  &option, &timeout) == 0)
 		{
+		  if (msghdr != NULL)
+		    {
+		      send_port = msghdr->msgh_remote_port;
+		      *msgid = msghdr->msgh_id;
+		    }
+		  else
+		    {
+		      send_port = MACH_PORT_NULL;
+		      *msgid = 0;
+		    }
+
 		  if (send_port != MACH_PORT_NULL && *msgid != 0)
 		    {
 		      /* For the normal case of RPCs, we consider the
diff --git a/sysdeps/mach/hurd/i386/intr-msg.h b/sysdeps/mach/hurd/i386/intr-msg.h
index e8acf63bd0..5b9a35d526 100644
--- a/sysdeps/mach/hurd/i386/intr-msg.h
+++ b/sysdeps/mach/hurd/i386/intr-msg.h
@@ -106,30 +106,29 @@ struct mach_msg_trap_args
 
 
 /* This cannot be an inline function because it calls setjmp.  */
-#define MSG_EXAMINE(state, msgid, rcvname, send_name, opt, tmout)	      \
+#define MSG_EXAMINE(state, msghdr, rcvname, rcvsz, opt, tmout)		      \
 ({									      \
   const struct mach_msg_trap_args *args = (const void *) (state)->uesp;	      \
-  mach_msg_header_t *msg;						      \
-  _hurdsig_catch_memory_fault (args) ? -1 :				      \
-    ({									      \
-      msg = args->msg;							      \
+  int ret = _hurdsig_catch_memory_fault (args) ? -1 : 0;		      \
+  if (ret == 0)								      \
+    {									      \
+      mach_msg_header_t *msg = args->msg;				      \
+      *(msghdr) = msg;							      \
       *(opt) = args->option;						      \
       *(tmout) = args->timeout;						      \
       *(rcvname) = args->rcv_name;					      \
+      *(rcvsz) = args->rcv_size;					      \
       _hurdsig_end_catch_fault ();					      \
-      if (msg == 0)							      \
+      if (msg != NULL)							      \
 	{								      \
-	  *(send_name) = MACH_PORT_NULL;				      \
-	  *(msgid) = 0;							      \
+	  ret = _hurdsig_catch_memory_fault (msg) ? -1 : 0;		      \
+	  if (ret == 0)							      \
+	    {								      \
+	      /* Access memory at msg to ensure validity */		      \
+	      *((volatile mach_msg_id_t *) &msg->msgh_id) = msg->msgh_id;     \
+	      _hurdsig_end_catch_fault ();				      \
+	    }								      \
 	}								      \
-      else								      \
-	{								      \
-	  if (_hurdsig_catch_memory_fault (msg))			      \
-	    return -1;							      \
-	  *(send_name) = msg->msgh_remote_port;				      \
-	  *(msgid) = msg->msgh_id;					      \
-	  _hurdsig_end_catch_fault ();					      \
-	}								      \
-      0;								      \
-    });									      \
+    }									      \
+    ret;								      \
 })
diff --git a/sysdeps/mach/hurd/x86_64/intr-msg.h b/sysdeps/mach/hurd/x86_64/intr-msg.h
index 82cc78eeb5..6f0ea90ded 100644
--- a/sysdeps/mach/hurd/x86_64/intr-msg.h
+++ b/sysdeps/mach/hurd/x86_64/intr-msg.h
@@ -92,27 +92,24 @@
 
 
 /* This cannot be an inline function because it calls setjmp.  */
-#define MSG_EXAMINE(state, msgid, rcvname, send_name, opt, tmout)	      \
+#define MSG_EXAMINE(state, msghdr, rcvname, rcvsz, opt, tmout)  	      \
 ({									      \
   int ret = 0;								      \
   const struct machine_thread_state *s = (state);			      \
-  const mach_msg_header_t *msg = (const void *) s->rdi;			      \
+  mach_msg_header_t *msg = (void *) s->rdi;				      \
+  *(msghdr) = msg;   							      \
   *(rcvname) = s->r8;							      \
   *(opt) = s->rsi;							      \
   *(tmout) = s->r9;							      \
-  if (msg == 0)								      \
-    {									      \
-      *(send_name) = MACH_PORT_NULL;					      \
-      *(msgid) = 0;							      \
-    }									      \
-  else									      \
+  *(rcvsz) = s->r10;							      \
+  if (msg != NULL)							      \
     {									      \
       ret = _hurdsig_catch_memory_fault (msg) ? -1 : 0;			      \
       if (ret == 0)							      \
         {								      \
-          *(send_name) = msg->msgh_remote_port;				      \
-          *(msgid) = msg->msgh_id;					      \
-          _hurdsig_end_catch_fault ();					      \
+	    /* Access memory at msg to ensure validity */		      \
+	    *((volatile mach_msg_id_t *) &msg->msgh_id) = msg->msgh_id;       \
+	    _hurdsig_end_catch_fault ();				      \
 	}								      \
     }									      \
   ret;									      \
-- 
2.53.0