Re: [PATCH] Fix OpenBSD signal trampoline recognition

[Mark Kettenis <kettenis at chello dot nl>]

   Date: Fri, 23 Jul 2004 11:12:00 -0400
   From: Andrew Cagney <cagney@gnu.org>

   > +	  goto retry;

   We really don't need a goto, right?

Right, so I've checked in the attached.

Mark


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>

	* sparc64obsd-tdep.c (sparc64obsd_sigreturn_offset): New variable.
	(sparc64obsd_pc_in_sigtramp): Reorganize to avoid goto.

Index: sparc64obsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sparc64obsd-tdep.c,v
retrieving revision 1.7
diff -u -p -r1.7 sparc64obsd-tdep.c
--- sparc64obsd-tdep.c 23 Jul 2004 13:43:36 -0000 1.7
+++ sparc64obsd-tdep.c 30 Jul 2004 22:42:35 -0000
@@ -74,43 +74,40 @@ sparc64obsd_supply_gregset (const struct
 
    The signal trampoline will be mapped at an address that is page
    aligned.  We recognize the signal trampoline by the looking for the
-   sigreturn system call.  */
+   sigreturn system call.  The offset where we can find the code that
+   makes this system call varies from release to release.  For OpenBSD
+   3.6 and later releases we can find the code at offset 0xec.  For
+   OpenBSD 3.5 and earlier releases, we find it at offset 0xe8.  */
 
 static const int sparc64obsd_page_size = 8192;
+static const int sparc64obsd_sigreturn_offset[] = { 0xec, 0xe8, -1 };
 
 static int
 sparc64obsd_pc_in_sigtramp (CORE_ADDR pc, char *name)
 {
   CORE_ADDR start_pc = (pc & ~(sparc64obsd_page_size - 1));
   unsigned long insn;
-  int offset = 0;
+  const int *offset;
 
   if (name)
     return 0;
 
- retry:
-  /* Check for "restore %g0, SYS_sigreturn, %g1".  */
-  insn = sparc_fetch_instruction (start_pc + offset + 0xec);
-  if (insn != 0x83e82067)
+  for (offset = sparc64obsd_sigreturn_offset; *offset != -1; offset++)
     {
-      if (offset == 0)
-	{
-	  /* In OpenBSD 3.5 and earlier releases, the code
-             implementing the sigreturn system call was at a different
-             offset within the signal trampoline.  Try again.  */
-	  offset = -4;
-	  goto retry;
-	}
+      /* Check for "restore %g0, SYS_sigreturn, %g1".  */
+      insn = sparc_fetch_instruction (start_pc + *offset);
+      if (insn != 0x83e82067)
+	continue;
+
+      /* Check for "t ST_SYSCALL".  */
+      insn = sparc_fetch_instruction (start_pc + *offset + 8);
+      if (insn != 0x91d02000)
+	continue;
 
-      return 0;
-    }
-
-  /* Check for "t ST_SYSCALL".  */
-  insn = sparc_fetch_instruction (start_pc + offset + 0xf4);
-  if (insn != 0x91d02000)
-    return 0;
+      return 1;
+  }
 
-  return 1;
+  return 0;
 }
 
 static struct sparc_frame_cache *