Message-ID: <5491BE7E.2060708@gmail.com>
Date: Thu, 18 Dec 2014 01:33:50 +0800
From: Wei-cheng Wang <cole945 at gmail dot com>
To: Ulrich Weigand <uweigand at de dot ibm dot com>
CC: gdb-patches at sourceware dot org
Subject: Re: [PATCH 3/3 v2] Process record support for PowerPC
On 2014/12/9 上午 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.
commit cf90fd9a07e8998540bf74f293d348a6653ac120
Author: Wei-cheng Wang <cole945@gmail.com>
Date: Sat Jan 17 14:30:59 2015 +0800
Skip-trampoline for PowerPC reverse-stepping.
Index: gdb-7.6.1/gdb/ppc64-tdep.c
===================================================================
--- gdb-7.6.1.orig/gdb/ppc64-tdep.c
+++ gdb-7.6.1/gdb/ppc64-tdep.c
@@ -20,6 +20,7 @@
#include "defs.h"
#include "frame.h"
#include "gdbcore.h"
+#include "inferior.h"
#include "ppc-tdep.h"
#include "ppc64-tdep.h"
#include "elf-bfd.h"
@@ -464,35 +465,66 @@ ppc64_skip_trampoline_code (struct frame
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
Index: gdb-7.6.1/gdb/ppc-linux-tdep.c
===================================================================
--- gdb-7.6.1.orig/gdb/ppc-linux-tdep.c
+++ gdb-7.6.1/gdb/ppc-linux-tdep.c
@@ -52,6 +52,7 @@
#include "linux-tdep.h"
#include "linux-record.h"
#include "record-full.h"
+#include "inferior.h"
#include "stap-probe.h"
#include "ax.h"
@@ -362,31 +363,50 @@ ppc_skip_trampoline_code (struct frame_i
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. */
-
- 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);
+ 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;
+ }
+
+ return target;
}
- return target;
+ return 0;
}
/* Wrappers to handle Linux-only registers. */