Re: [PATCH v4] Add dll trampoline code handling for windows 64bit

[Pedro Alves <palves at redhat dot com>]

Hi Kai,

On 07/25/2012 06:57 PM, Kai Tietz wrote:
> Hello,
> 
> I have now this patch for a while on my radar.  I contacted Roland
> Schwingel about the status of his paperwork with FSF, and he told me
> that he completed it.  

Thanks.

> So I want to ping this patch for him, as he
> isn't able to ping on that patch himself for the next week(s).

A patch with the comments addressed would have been better than just a ping.  ;-)

>>> 2012-04-02  Roland Schwingel <roland.schwingel@onevision.com>
>>
>> Should be two spaces after your name.
>>

>>> +/* Check win64 DLL jmp trampolines and find jump destination.  */
>>
>> The correct spelling is "Win64" capitalized.

>>>  static void
>>>  amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>>>  {
>>>    struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
>>>
>>> +  /* Register trampoline handling code.  */
>>> +  set_gdbarch_skip_trampoline_code (gdbarch, amd64_windows_skip_trampoline_code);
>>
>> A nit, but it'd be cleaner/clearer to put this after the amd64_init_abi call, or
>> better, near the end of the function, after set_gdbarch_skip_main_prologue.  The current
>> code reads "initialize the base arch, then install overrides.".  This new call
>> here breaks that flow.
>>
>>> +
>>>    amd64_init_abi (info, gdbarch);

I confirm his paperwork is okay.  I've done the changes mentioned above, and
also a few other formatting fixes.  I've checked it in, as below.

2012-07-27  Roland Schwingel  <roland.schwingel@onevision.com>

	* amd64-windows-tdep.c: Include "frame.h".
	(amd64_windows_skip_trampoline_code): New function.
	(amd64_windows_init_abi): Add trampoline registration.

---

 gdb/amd64-windows-tdep.c |   37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/gdb/amd64-windows-tdep.c b/gdb/amd64-windows-tdep.c
index 41e0efa..528fbb6 100644
--- a/gdb/amd64-windows-tdep.c
+++ b/gdb/amd64-windows-tdep.c
@@ -24,6 +24,7 @@
 #include "gdbcore.h"
 #include "regcache.h"
 #include "windows-tdep.h"
+#include "frame.h"

 /* The registers used to pass integer arguments during a function call.  */
 static int amd64_windows_dummy_call_integer_regs[] =
@@ -154,6 +155,40 @@ amd64_skip_main_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
   return pc;
 }

+/* Check Win64 DLL jmp trampolines and find jump destination.  */
+
+static CORE_ADDR
+amd64_windows_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
+{
+  CORE_ADDR destination = 0;
+  struct gdbarch *gdbarch = get_frame_arch (frame);
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+
+  /* Check for jmp *<offset>(%rip) (jump near, absolute indirect (/4)).  */
+  if (pc && read_memory_unsigned_integer (pc, 2, byte_order) == 0x25ff)
+    {
+      /* Get opcode offset and see if we can find a reference in our data.  */
+      ULONGEST offset
+	= read_memory_unsigned_integer (pc + 2, 4, byte_order);
+
+      /* Get address of function pointer at end of pc.  */
+      CORE_ADDR indirect_addr = pc + offset + 6;
+
+      struct minimal_symbol *indsym
+	= indirect_addr ? lookup_minimal_symbol_by_pc (indirect_addr) : NULL;
+      const char *symname = indsym ? SYMBOL_LINKAGE_NAME (indsym) : NULL;
+
+      if (symname)
+	{
+	  if (strncmp (symname, "__imp_", 6) == 0
+	      || strncmp (symname, "_imp_", 5) == 0)
+	    destination
+	      = read_memory_unsigned_integer (indirect_addr, 8, byte_order);
+	}
+    }
+
+  return destination;
+}

 static void
 amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
@@ -174,6 +209,8 @@ amd64_windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   tdep->integer_param_regs_saved_in_caller_frame = 1;
   set_gdbarch_return_value (gdbarch, amd64_windows_return_value);
   set_gdbarch_skip_main_prologue (gdbarch, amd64_skip_main_prologue);
+  set_gdbarch_skip_trampoline_code (gdbarch,
+				    amd64_windows_skip_trampoline_code);

   set_gdbarch_iterate_over_objfiles_in_search_order
     (gdbarch, windows_iterate_over_objfiles_in_search_order);