Re: [RFA] Add epilogue unwinder for AMD64

[Hui Zhu <teawater@gmail.com>]

With this patch and amd64-1.txt, all the reverse testsuite pass.
It's so great!

Thanks for you keep work in this part.  Thank you very much.

Hui

On Mon, Aug 17, 2009 at 08:18, Michael Snyder<msnyder@vmware.com> wrote:
> This patch corresponds to the similar one in i386-tdep.c, and
> corrects for a gcc issue with elf/dwarf debug info in function
> epilogues.  It is needed in order to make reverse-step and next
> work properly for stepping backward through a return.
>
> No testsuite regressions.
>
> OK to commit?
>
>
> 2009-08-16  Michael Snyder  <msnyder@vmware.com>
>
>        * amd64-tdep.c: Add a frame unwinder for function epilogues.
>        (amd64_in_function_epilogue_p): New function.
>        (amd64_epilogue_frame_sniffer): New function.
>        (amd64_epilogue_frame_cache): New function.
>        (amd64_epilogue_frame_this_id): New function.
>        (amd64_epilogue_frame_unwind): New struct frame_unwind.
>        (amd64_init_abi): Hook the new unwinder.
>
> Index: amd64-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/amd64-tdep.c,v
> retrieving revision 1.64
> diff -u -p -r1.64 amd64-tdep.c
> --- amd64-tdep.c        10 Aug 2009 03:02:39 -0000      1.64
> +++ amd64-tdep.c        16 Aug 2009 23:12:25 -0000
> @@ -1887,6 +1887,89 @@ static const struct frame_base amd64_fra
>   amd64_frame_base_address
>  };
>
> +/* Normal frames, but in a function epilogue.  */
> +
> +/* The epilogue is defined here as the 'ret' instruction, which will
> +   follow any instruction such as 'leave' or 'pop %ebp' that destroys
> +   the function's stack frame.  */
> +
> +static int
> +amd64_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
> +{
> +  gdb_byte insn;
> +
> +  if (target_read_memory (pc, &insn, 1))
> +    return 0;   /* Can't read memory at pc.  */
> +
> +  if (insn != 0xc3)     /* 'ret' instruction.  */
> +    return 0;
> +
> +  return 1;
> +}
> +
> +static int
> +amd64_epilogue_frame_sniffer (const struct frame_unwind *self,
> +                             struct frame_info *this_frame,
> +                             void **this_prologue_cache)
> +{
> +  if (frame_relative_level (this_frame) == 0)
> +    return amd64_in_function_epilogue_p (get_frame_arch (this_frame),
> +                                        get_frame_pc (this_frame));
> +  else
> +    return 0;
> +}
> +
> +static struct amd64_frame_cache *
> +amd64_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);
> +  struct amd64_frame_cache *cache;
> +  gdb_byte buf[4];
> +
> +  if (*this_cache)
> +    return *this_cache;
> +
> +  cache = amd64_alloc_frame_cache ();
> +  *this_cache = cache;
> +
> +  /* Cache base will be %esp plus cache->sp_offset (-8).  */
> +  get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
> +  cache->base = extract_unsigned_integer (buf, 8,
> +                                         byte_order) + cache->sp_offset;
> +
> +  /* Cache pc will be the frame func.  */
> +  cache->pc = get_frame_pc (this_frame);
> +
> +  /* The saved %esp will be at cache->base plus 16.  */
> +  cache->saved_sp = cache->base + 16;
> +
> +  /* The saved %eip will be at cache->base plus 8.  */
> +  cache->saved_regs[AMD64_RIP_REGNUM] = cache->base + 8;
> +
> +  return cache;
> +}
> +
> +static void
> +amd64_epilogue_frame_this_id (struct frame_info *this_frame,
> +                             void **this_cache,
> +                             struct frame_id *this_id)
> +{
> +  struct amd64_frame_cache *cache = amd64_epilogue_frame_cache (this_frame,
> +                                                              this_cache);
> +
> +  (*this_id) = frame_id_build (cache->base + 8, cache->pc);
> +}
> +
> +static const struct frame_unwind amd64_epilogue_frame_unwind =
> +{
> +  NORMAL_FRAME,
> +  amd64_epilogue_frame_this_id,
> +  amd64_frame_prev_register,
> +  NULL,
> +  amd64_epilogue_frame_sniffer
> +};
> +
>  static struct frame_id
>  amd64_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame)
>  {
> @@ -2065,6 +2148,12 @@ amd64_init_abi (struct gdbarch_info info
>
>   set_gdbarch_dummy_id (gdbarch, amd64_dummy_id);
>
> +  /* Hook the function epilogue frame unwinder.  This unwinder is
> +     appended to the list first, so that it supercedes the other
> +     unwinders in function epilogues.  */
> +  frame_unwind_prepend_unwinder (gdbarch, &amd64_epilogue_frame_unwind);
> +
> +  /* Hook the prologue-based frame unwinders.  */
>   frame_unwind_append_unwinder (gdbarch, &amd64_sigtramp_frame_unwind);
>   frame_unwind_append_unwinder (gdbarch, &amd64_frame_unwind);
>   frame_base_set_default (gdbarch, &amd64_frame_base);
>
>