Re: [obish?sym;rfa:doc] Wire up vsyscall

Andrew Cagney
2004-05-10T21:27:00Z

On Thu, May 06, 2004 at 04:54:55PM -0400, Andrew Cagney wrote:

>At present I know of the following problems:

4. backtrace changes:

#0 handler (sig=26, info=0xfeed7c50, context=0xfeed7cd0) at
/home/cygnus/cagney
/PENDING/2004-05-06-add-vsyscall/src/gdb/testsuite/gdb.base/siginfo.c:31
#1 0x0093e440 in __kernel_sigreturn ()
#2 0x0804848a in main () at
/home/cygnus/cagney/PENDING/2004-05-06-add-vsyscall
/src/gdb/testsuite/gdb.base/siginfo.c:66

vs

#0 handler (sig=26, info=0xfee1ea80, context=0xfee1eb00) at
/home/cygnus/cagney
/GDB/src/gdb/testsuite/gdb.base/siginfo.c:31
#1 <signal handler called>
#2 0x0804848a in main () at
/home/cygnus/cagney/GDB/src/gdb/testsuite/gdb.base/

but remember I intend changing the second to:

...
#1 0x1234 in <signal trampoline>
...

In the meantime, here's the patch from my Debian backport which should
fix this. Pending a way to indicate 'abnormal frame' status in the
CFI, we don't want to use it; frame_unwind_address_in_block will hit.
2004-01-25 Daniel Jacobowitz <drow@mvista.com>
Even with the above frame display change, this is needed. The frame
needs to identify it's type as SIGTRAMP_FRAME.

Mark?

Andrew

* i386-tdep.c (i386_gdbarch_init): Check for signal frame first.
* i386-linux-tdep.c (i386_linux_pc_in_sigtramp): Handle
__kernel_sigreturn.
Index: gdb-6.1/gdb/i386-linux-tdep.c
===================================================================
--- gdb-6.1.orig/gdb/i386-linux-tdep.c 2004-04-05 13:26:42.000000000 -0400
+++ gdb-6.1/gdb/i386-linux-tdep.c 2004-04-05 13:26:46.000000000 -0400
@@ -227,6 +227,10 @@ i386_linux_pc_in_sigtramp (CORE_ADDR pc,
exported from the shared C library, so the trampoline may appear to
be part of the preceding function. This should always be sigaction,
__sigaction, or __libc_sigaction (all aliases to the same function). */
+
+ if (name && strcmp (name, "__kernel_sigreturn") == 0)
+ return 1;
+
if (name == NULL || strstr (name, "sigaction") != NULL)
return (i386_linux_sigtramp_start (pc) != 0
|| i386_linux_rt_sigtramp_start (pc) != 0);
Index: gdb-6.1/gdb/i386-tdep.c
===================================================================
--- gdb-6.1.orig/gdb/i386-tdep.c 2004-04-05 13:26:42.000000000 -0400
+++ gdb-6.1/gdb/i386-tdep.c 2004-04-05 13:26:46.000000000 -0400
@@ -2013,6 +2013,10 @@ i386_gdbarch_init (struct gdbarch_info i
/* Helper for function argument information. */
set_gdbarch_fetch_pointer_argument (gdbarch, i386_fetch_pointer_argument);

+ /* The signal handler might have dwarf2 CFI, via the vsyscall DSO, so check
+ for this first. */
+ frame_unwind_append_sniffer (gdbarch, i386_sigtramp_frame_sniffer);
+
/* Hook in the DWARF CFI frame unwinder. */
frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);

@@ -2021,7 +2025,6 @@ i386_gdbarch_init (struct gdbarch_info i
/* Hook in ABI-specific overrides, if they have been registered. */
gdbarch_init_osabi (info, gdbarch);

- frame_unwind_append_sniffer (gdbarch, i386_sigtramp_frame_sniffer);
frame_unwind_append_sniffer (gdbarch, i386_frame_sniffer);

/* If we have a register mapping, enable the generic core file