This is the mail archive of the
gdb-patches@sources.redhat.com
mailing list for the GDB project.
[rfa/ppc] prologue parser tweaks
- From: Andrew Cagney <cagney at gnu dot org>
- To: gdb-patches at sources dot redhat dot com
- Date: Tue, 16 Mar 2004 17:28:54 -0500
- Subject: [rfa/ppc] prologue parser tweaks
Hello,
Attached are two tweaks to the PPC skip_prologue method so that it works
better with glibc:
- handle glibc syscall
Without this an unwinder won't be able to find its way out of a system
call - it needs to figure out the location of a local label, see comment
for details.
- handle PIC code where the LR appears to be saved twice
It appears that skip_prologue code tried to handle this but missed an
edge case. Without this the wrong LR gets used when trying to unwind
out of GLIBC.
Ok for mainline?
Andrew
2004-03-07 Andrew Cagney <cagney@redhat.com>
* rs6000-tdep.c: Add field "func_start".
(skip_prologue): New variable num_skip_syscall_insn, use to skip
over first half of a GNU/Linux syscall and update "func_start".
Record only the first LR save, use to skip over PIC code.
Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/rs6000-tdep.c,v
retrieving revision 1.183
diff -u -r1.183 rs6000-tdep.c
--- rs6000-tdep.c 2 Mar 2004 02:20:25 -0000 1.183
+++ rs6000-tdep.c 16 Mar 2004 22:08:24 -0000
@@ -65,6 +65,7 @@
struct rs6000_framedata
{
+ CORE_ADDR func_start; /* true function start */
int offset; /* total size of frame --- the distance
by which we decrement sp to allocate
the frame */
@@ -502,6 +503,7 @@
int minimal_toc_loaded = 0;
int prev_insn_was_prologue_insn = 1;
int num_skip_non_prologue_insns = 0;
+ int num_skip_syscall_insn = 0;
const struct bfd_arch_info *arch_info = gdbarch_bfd_arch_info (current_gdbarch);
struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
@@ -521,6 +523,7 @@
lim_pc = refine_prologue_limit (pc, lim_pc);
memset (fdata, 0, sizeof (struct rs6000_framedata));
+ fdata->func_start = pc;
fdata->saved_gpr = -1;
fdata->saved_fpr = -1;
fdata->saved_vr = -1;
@@ -548,6 +551,70 @@
if (target_read_memory (pc, buf, 4))
break;
op = extract_signed_integer (buf, 4);
+
+ /* A PPC64 GNU/Linux system call function starts with a
+ non-threaded fast-path, only when that fails is a stack frame
+ created, treat it as several functions:
+ nptl/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep-cancel.h
+
+ *INDENT-OFF*
+ NAME:
+ SINGLE_THREAD_P
+ bne- .Lpseudo_cancel
+ __NAME_nocancel:
+ li r0,162
+ sc
+ bnslr+
+ b 0x7fe014ef64 <.__syscall_error>
+ Lpseudo_cancel:
+ stdu r1,-128(r1)
+ ...
+ *INDENT-ON* */
+
+ if (((op & 0xffff0000) == 0x38000000 /* li r0,N */
+ && pc == fdata->func_start + 0)
+ || (op == 0x44000002 /* sc */
+ && pc == fdata->func_start + 4
+ && num_skip_syscall_insn == 1)
+ || (op == 0x4ca30020 /* bnslr+ */
+ && pc == fdata->func_start + 8
+ && num_skip_syscall_insn == 2))
+ {
+ num_skip_syscall_insn++;
+ continue;
+ }
+ else if ((op & 0xfc000003) == 0x48000000 /* b __syscall_error */
+ && pc == fdata->func_start + 12
+ && num_skip_syscall_insn == 3)
+ {
+ num_skip_syscall_insn++;
+ fdata->func_start = pc;
+ continue;
+ }
+
+ if ((op & 0xfc1fffff) == 0x7c0802a6)
+ { /* mflr Rx */
+ /* Since shared library / PIC code, which needs to get its
+ address at runtime, can appear to save more than one link
+ register vis:
+
+ *INDENT-OFF*
+ stwu r1,-304(r1)
+ mflr r3
+ bl 0xff570d0 (blrl)
+ stw r30,296(r1)
+ mflr r30
+ stw r31,300(r1)
+ stw r3,308(r1);
+ ...
+ *INDENT-ON*
+
+ remember just the first one, but skip over additional
+ ones. */
+ if (lr_reg < 0)
+ lr_reg = (op & 0x03e00000);
+ continue;
+ }
if ((op & 0xfc1fffff) == 0x7c0802a6)
{ /* mflr Rx */