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

[Daniel Jacobowitz <drow@false.org>]

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.

-- 
Daniel Jacobowitz

2004-01-25  Daniel Jacobowitz  <drow@mvista.com>

	* 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