[PATCH] Fix some i386 unwinder inconcistencies

[Mark Kettenis <mark.kettenis@xs4all.nl>]

This diff fixes a few issues with the epilogue and stack tramp unwinders.

Committed.


2011-06-12  Mark Kettenis  <kettenis@gnu.org>
 
	* i386-tdep.c (i386_epilogue_frame_cache): Simplify code.  Call
	get_frame_func instead of get_frame_pc to determine the code
	address used to construct the frame ID.
	(i386_epilogue_frame_unwind_stop_reason): Fix coding style.
	(i386_epilogue_frame_this_id): Likewise.
	(i386_epilogue_frame_prev_register): New function.
	(i386_epilogue_frame_unwind): Use i386_epilogue_frame_prev_register.
	(i386_stack_tramp_frame_sniffer): Fix coding style.
	(i386_stack_tramp_frame_unwind): Use i386_epilogue_frame_prev_register.
	(i386_gdbarch_init): Fix comments.

Index: i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.333
diff -u -p -r1.333 i386-tdep.c
--- i386-tdep.c	12 Jun 2011 18:21:55 -0000	1.333
+++ i386-tdep.c	12 Jun 2011 20:39:01 -0000
@@ -1910,11 +1910,9 @@ i386_epilogue_frame_sniffer (const struc
 static struct i386_frame_cache *
 i386_epilogue_frame_cache (struct frame_info *this_frame, void **this_cache)
 {
-  struct gdbarch *gdbarch = get_frame_arch (this_frame);
-  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   volatile struct gdb_exception ex;
   struct i386_frame_cache *cache;
-  gdb_byte buf[4];
+  CORE_ADDR sp;
 
   if (*this_cache)
     return *this_cache;
@@ -1924,18 +1922,14 @@ i386_epilogue_frame_cache (struct frame_
 
   TRY_CATCH (ex, RETURN_MASK_ERROR)
     {
-      /* Cache base will be %esp plus cache->sp_offset (-4).  */
-      get_frame_register (this_frame, I386_ESP_REGNUM, buf);
-      cache->base = extract_unsigned_integer (buf, 4,
-					      byte_order) + cache->sp_offset;
+      cache->pc = get_frame_func (this_frame);
 
-      /* Cache pc will be the frame func.  */
-      cache->pc = get_frame_pc (this_frame);
-
-      /* The saved %esp will be at cache->base plus 8.  */
+      /* At this point the stack looks as if we just entered the
+	 function, with the return address at the top of the
+	 stack.  */
+      sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);
+      cache->base = sp + cache->sp_offset;
       cache->saved_sp = cache->base + 8;
-
-      /* The saved %eip will be at cache->base plus 4.  */
       cache->saved_regs[I386_EIP_REGNUM] = cache->base + 4;
 
       cache->base_p = 1;
@@ -1950,8 +1944,8 @@ static enum unwind_stop_reason
 i386_epilogue_frame_unwind_stop_reason (struct frame_info *this_frame,
 					void **this_cache)
 {
-  struct i386_frame_cache *cache
-    = i386_epilogue_frame_cache (this_frame, this_cache);
+  struct i386_frame_cache *cache =
+    i386_epilogue_frame_cache (this_frame, this_cache);
 
   if (!cache->base_p)
     return UNWIND_UNAVAILABLE;
@@ -1964,8 +1958,8 @@ i386_epilogue_frame_this_id (struct fram
 			     void **this_cache,
 			     struct frame_id *this_id)
 {
-  struct i386_frame_cache *cache = i386_epilogue_frame_cache (this_frame,
-							      this_cache);
+  struct i386_frame_cache *cache =
+    i386_epilogue_frame_cache (this_frame, this_cache);
 
   if (!cache->base_p)
     return;
@@ -1973,12 +1967,22 @@ i386_epilogue_frame_this_id (struct fram
   (*this_id) = frame_id_build (cache->base + 8, cache->pc);
 }
 
+static struct value *
+i386_epilogue_frame_prev_register (struct frame_info *this_frame,
+				   void **this_cache, int regnum)
+{
+  /* Make sure we've initialized the cache.  */
+  i386_epilogue_frame_cache (this_frame, this_cache);
+
+  return i386_frame_prev_register (this_frame, this_cache, regnum);
+}
+
 static const struct frame_unwind i386_epilogue_frame_unwind =
 {
   NORMAL_FRAME,
   i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
-  i386_frame_prev_register,
+  i386_epilogue_frame_prev_register,
   NULL, 
   i386_epilogue_frame_sniffer
 };
@@ -2045,8 +2049,8 @@ i386_in_stack_tramp_p (struct gdbarch *g
 
 static int
 i386_stack_tramp_frame_sniffer (const struct frame_unwind *self,
-			     struct frame_info *this_frame,
-			     void **this_prologue_cache)
+				struct frame_info *this_frame,
+				void **this_cache)
 {
   if (frame_relative_level (this_frame) == 0)
     return i386_in_stack_tramp_p (get_frame_arch (this_frame),
@@ -2060,7 +2064,7 @@ static const struct frame_unwind i386_st
   NORMAL_FRAME,
   i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
-  i386_frame_prev_register,
+  i386_epilogue_frame_prev_register,
   NULL, 
   i386_stack_tramp_frame_sniffer
 };
@@ -7311,13 +7315,13 @@ i386_gdbarch_init (struct gdbarch_info i
   set_gdbarch_fetch_pointer_argument (gdbarch, i386_fetch_pointer_argument);
 
   /* Hook the function epilogue frame unwinder.  This unwinder is
-     appended to the list first, so that it supercedes the Dwarf
-     unwinder in function epilogues (where the Dwarf unwinder
+     appended to the list first, so that it supercedes the DWARF
+     unwinder in function epilogues (where the DWARF unwinder
      currently fails).  */
   frame_unwind_append_unwinder (gdbarch, &i386_epilogue_frame_unwind);
 
   /* Hook in the DWARF CFI frame unwinder.  This unwinder is appended
-     to the list before the prologue-based unwinders, so that Dwarf
+     to the list before the prologue-based unwinders, so that DWARF
      CFI info will be used if it is available.  */
   dwarf2_append_unwinders (gdbarch);