Index: gdb/amd64-obsd-tdep.c
--- gdb/amd64-obsd-tdep.c.orig
+++ gdb/amd64-obsd-tdep.c
@@ -39,8 +39,40 @@
 /* Support for signal handlers.  */
 
 /* Default page size.  */
-static const int amd64obsd_page_size = 4096;
+static const CORE_ADDR amd64obsd_page_size = 4096;
 
+/* Offset & instructions for sigreturn(2).  */
+
+#define SIGRETURN_INSN_LEN 9
+
+struct amd64obsd_sigreturn_info_t {
+  int offset;
+  gdb_byte sigreturn[SIGRETURN_INSN_LEN];
+}; 
+
+static const amd64obsd_sigreturn_info_t
+  amd64obsd_sigreturn_info[] = {
+  /* OpenBSD 6.4 */
+  { 9, { 0x48, 0xc7, 0xc0,
+         0x67, 0x00, 0x00, 0x00, /* movq $SYS_sigreturn, %rax */
+         0x0f, 0x05 } },         /* syscall */
+  /* OpenBSD 5.1 */
+  { 6, { 0x48, 0xc7, 0xc0,
+         0x67, 0x00, 0x00, 0x00, /* movq $SYS_sigreturn, %rax */
+         0x0f, 0x05 } },         /* syscall */
+  { 7, { 0x48, 0xc7, 0xc0,
+         0x67, 0x00, 0x00, 0x00, /* movq $SYS_sigreturn, %rax */
+         0x0f, 0x05 } },         /* syscall */
+  /* OpenBSD 5.0 */
+  { 6, { 0x48, 0xc7, 0xc0,
+         0x67, 0x00, 0x00, 0x00, /* movq $SYS_sigreturn, %rax */
+         0xcd, 0x80 } },         /* int $0x80 */
+  { 7, { 0x48, 0xc7, 0xc0,
+         0x67, 0x00, 0x00, 0x00, /* movq $SYS_sigreturn, %rax */
+         0xcd, 0x80 } },         /* int $0x80 */
+  { -1, {} }
+};
+
 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
    routine.  */
 
@@ -49,20 +81,8 @@ amd64obsd_sigtramp_p (struct frame_info *this_frame)
 {
   CORE_ADDR pc = get_frame_pc (this_frame);
   CORE_ADDR start_pc = (pc & ~(amd64obsd_page_size - 1));
-  const gdb_byte osigreturn[] =
-  {
-    0x48, 0xc7, 0xc0,
-    0x67, 0x00, 0x00, 0x00,	/* movq $SYS_sigreturn, %rax */
-    0xcd, 0x80			/* int $0x80 */
-  };
-  const gdb_byte sigreturn[] =
-  {
-    0x48, 0xc7, 0xc0,
-    0x67, 0x00, 0x00, 0x00,	/* movq $SYS_sigreturn, %rax */
-    0x0f, 0x05			/* syscall */
-  };
-  size_t buflen = (sizeof sigreturn) + 1;
-  gdb_byte *buf;
+  const amd64obsd_sigreturn_info_t *info;
+  gdb_byte buf[SIGRETURN_INSN_LEN];
   const char *name;
 
   /* If the function has a valid symbol name, it isn't a
@@ -76,22 +96,22 @@ amd64obsd_sigtramp_p (struct frame_info *this_frame)
   if (find_pc_section (pc) != NULL)
     return 0;
 
-  /* If we can't read the instructions at START_PC, return zero.  */
-  buf = (gdb_byte *) alloca ((sizeof sigreturn) + 1);
-  if (!safe_frame_unwind_memory (this_frame, start_pc + 6, buf, buflen))
-    return 0;
+  for (info = amd64obsd_sigreturn_info; info->offset != -1; info++)
+    {
 
-  /* Check for sigreturn(2).  Depending on how the assembler encoded
-     the `movq %rsp, %rdi' instruction, the code starts at offset 6 or
-     7.  OpenBSD 5.0 and later use the `syscall' instruction.  Older
-     versions use `int $0x80'.  Check for both.  */
-  if (memcmp (buf, sigreturn, sizeof sigreturn)
-      && memcmp (buf + 1, sigreturn, sizeof sigreturn)
-      && memcmp (buf, osigreturn, sizeof osigreturn)
-      && memcmp (buf + 1, osigreturn, sizeof osigreturn))
-    return 0;
+      /* If we can't read the instructions at return zero.  */
+      if (!safe_frame_unwind_memory (this_frame,
+        start_pc + info->offset, buf, sizeof buf))
+        continue;
 
-  return 1;
+      /* Check for sigreturn(2).  */
+      if (memcmp (buf, info->sigreturn, sizeof buf))
+        continue;
+
+      return 1;
+    }
+
+  return 0;
 }
 
 /* Assuming THIS_FRAME is for a BSD sigtramp routine, return the