[PATCH] Fix some i386 unwinder inconcistencies

Mark Kettenis
2011-06-12T20:57:49Z

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);