Re: [PATCH 3/3 v2] Process record support for PowerPC

[Wei-cheng Wang <cole945 at gmail dot com>]

On 2014/12/9 äå 03:13, Ulrich Weigand wrote:
> Wei-cheng Wang wrote:
> > 	* ppc-linux-tdep.c (powerpc_linux_in_dynsym_resolve_code):
> > 	Scan PLT stub backward for reverse debugging.
> > 	(ppc_linux_init_abi): set powerpc_linux_in_dynsym_resolve_code
> > 	for both 32-bit and 64-bit.
>
> As I said in the reply to the 0/3 mail, I really think it would be
> better to handle this within the PPC skip_trampoline_code implementation,
> instead of having in_dynsym_resolve_code suddenly also cover the
> trampolines ...

  Hi,

  See the new patch, I moved the for-loop into skip_trampoline_code,
  and removed in_dynsym_resolve_code.

> It seems odd to have in_dynsym_resolve_code call into
> skip_trampoline_code.  Is there a reason why the skip_trampoline_code
> implementation cannot accept a PC in the middle of the sequence?

  I thought skip-trampoline is used to find the target address for
  inserting step-resume breakpoint, so it doesn't make sense for
  reverse-stepping, because we are just stepping from the target address.
  And for forward-stepping, when we reach the very first instruction of
  trampoline code, we can just skip the resolving code by inserting
  a step-resume breakpoint, so we don't have to step through the resolving
  code and check whether we are in the middle of trampoline code.

  in_dynsym_resolve_code is used to check whether we are in (the middle of)
  the resolving code, so we can keep going to step though the resolving code.
  Therefor I thought in_dynsym_resolve_code is the proper place to implement.

  Since skip-trampoline-code had implemented the plt-stub pattern-match code
  we need, by calling it in in-dynsym-resolve-code, we don't need to have
  duplicate pattern-match code in both functions.

Wei-cheng,
Thanks

--

2014-12-06  Wei-cheng Wang  <cole945@gmail.com>

	* ppc-linux-tdep.c (ppc_skip_trampoline_code):
	Scan PLT stub backward for reverse debugging.
	* ppc64-tdep.c (ppc64_skip_trampoline_code): Likewise.


---
 gdb/ppc-linux-tdep.c | 58 ++++++++++++++++++++++------------
 gdb/ppc64-tdep.c     | 88 +++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 99 insertions(+), 47 deletions(-)

diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index fa41d34..b57f41d 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -51,6 +51,7 @@
 #include "linux-tdep.h"
 #include "linux-record.h"
 #include "record-full.h"
+#include "infrun.h"

 #include "stap-probe.h"
 #include "ax.h"
@@ -314,31 +315,50 @@ ppc_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   CORE_ADDR target = 0;
+  int scan_limit, i;

-  if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub, insnbuf))
-    {
-      /* Insn pattern is
-		lis   r11, xxxx
-		lwz   r11, xxxx(r11)
-	 Branch target is in r11.  */
-
-      target = (ppc_insn_d_field (insnbuf[0]) << 16)
-	| ppc_insn_d_field (insnbuf[1]);
-      target = read_memory_unsigned_integer (target, 4, byte_order);
-    }
+  scan_limit = 1;
+  /* When reverse-debugging, scan backward to check whether we are
+     in the middle of trampoline code.  */
+  if (execution_direction == EXEC_REVERSE)
+    scan_limit = 4;	/* At more 4 instructions.  */

-  if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub_so, insnbuf))
+  for (i = 0; i < scan_limit; i++)
     {
-      /* Insn pattern is
-		lwz   r11, xxxx(r30)
-	 Branch target is in r11.  */
+      if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub, insnbuf))
+	{
+	  /* Insn pattern is
+	     lis   r11, xxxx
+	     lwz   r11, xxxx(r11)
+	     Branch target is in r11.  */
+
+	  target = (ppc_insn_d_field (insnbuf[0]) << 16)
+		   | ppc_insn_d_field (insnbuf[1]);
+	  target = read_memory_unsigned_integer (target, 4, byte_order);
+	}
+      else if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub_so,
+					insnbuf))
+	{
+	  /* Insn pattern is
+	     lwz   r11, xxxx(r30)
+	     Branch target is in r11.  */
+
+	  target = get_frame_register_unsigned (frame,
+						tdep->ppc_gp0_regnum + 30)
+		   + ppc_insn_d_field (insnbuf[0]);
+	  target = read_memory_unsigned_integer (target, 4, byte_order);
+	}
+      else
+	{
+	  /* Scan backward one more instructions if doesn't match.  */
+	  pc -= 4;
+	  continue;
+	}

-      target = get_frame_register_unsigned (frame, tdep->ppc_gp0_regnum + 30)
-	       + ppc_insn_d_field (insnbuf[0]);
-      target = read_memory_unsigned_integer (target, 4, byte_order);
+      return target;
     }

-  return target;
+  return 0;
 }

 /* Wrappers to handle Linux-only registers.  */
diff --git a/gdb/ppc64-tdep.c b/gdb/ppc64-tdep.c
index 8acd754..25a0816 100644
--- a/gdb/ppc64-tdep.c
+++ b/gdb/ppc64-tdep.c
@@ -20,6 +20,7 @@
 #include "defs.h"
 #include "frame.h"
 #include "gdbcore.h"
+#include "infrun.h"
 #include "ppc-tdep.h"
 #include "ppc64-tdep.h"
 #include "elf-bfd.h"
@@ -464,35 +465,66 @@ ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
 				    ARRAY_SIZE (ppc64_standard_linkage8))))
 		     - 1];
   CORE_ADDR target;
+  int scan_limit, i;

-  if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage8, insns))
-    pc = ppc64_standard_linkage4_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage7, insns))
-    pc = ppc64_standard_linkage3_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage6, insns))
-    pc = ppc64_standard_linkage4_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage5, insns)
-	   && (insns[8] != 0 || insns[9] != 0))
-    pc = ppc64_standard_linkage3_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage4, insns)
-	   && (insns[9] != 0 || insns[10] != 0))
-    pc = ppc64_standard_linkage4_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage3, insns)
-	   && (insns[8] != 0 || insns[9] != 0))
-    pc = ppc64_standard_linkage3_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage2, insns)
-	   && (insns[10] != 0 || insns[11] != 0))
-    pc = ppc64_standard_linkage2_target (frame, pc, insns);
-  else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage1, insns))
-    pc = ppc64_standard_linkage1_target (frame, pc, insns);
-  else
-    return 0;
-
-  /* The PLT descriptor will either point to the already resolved target
-     address, or else to a glink stub.  As the latter carry synthetic @plt
-     symbols, find_solib_trampoline_target should be able to resolve them.  */
-  target = find_solib_trampoline_target (frame, pc);
-  return target ? target : pc;
+  scan_limit = 1;
+  /* When reverse-debugging, scan backward to check whether we are
+     in the middle of trampoline code.  */
+  if (execution_direction == EXEC_REVERSE)
+    scan_limit = ARRAY_SIZE (insns) - 1;
+
+  for (i = 0; i < scan_limit; i++)
+    {
+      if (i < ARRAY_SIZE (ppc64_standard_linkage8) - 1
+	  && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage8, insns))
+	pc = ppc64_standard_linkage4_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage7) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage7,
+					   insns))
+	pc = ppc64_standard_linkage3_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage6) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage6,
+					   insns))
+	pc = ppc64_standard_linkage4_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage5) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage5,
+					   insns)
+	       && (insns[8] != 0 || insns[9] != 0))
+	pc = ppc64_standard_linkage3_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage4) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage4,
+					   insns)
+	       && (insns[9] != 0 || insns[10] != 0))
+	pc = ppc64_standard_linkage4_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage3) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage3,
+					   insns)
+	       && (insns[8] != 0 || insns[9] != 0))
+	pc = ppc64_standard_linkage3_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage2) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage2,
+					   insns)
+	       && (insns[10] != 0 || insns[11] != 0))
+	pc = ppc64_standard_linkage2_target (frame, pc, insns);
+      else if (i < ARRAY_SIZE (ppc64_standard_linkage1) - 1
+	       && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage1,
+					   insns))
+	pc = ppc64_standard_linkage1_target (frame, pc, insns);
+      else
+	{
+	  /* Scan backward one more instructions if doesn't match.  */
+	  pc -= 4;
+	  continue;
+	}
+
+      /* The PLT descriptor will either point to the already resolved target
+         address, or else to a glink stub.  As the latter carry synthetic @plt
+         symbols, find_solib_trampoline_target should be able to resolve them.  */
+      target = find_solib_trampoline_target (frame, pc);
+      return target ? target : pc;
+  }
+
+  return 0;
 }

 /* Support for convert_from_func_ptr_addr (ARCH, ADDR, TARG) on PPC64
--
1.9.1