Bug 126913

Note, this is hard to diagnose, need bug 126095 fixed to be able to
examine the code.  However, as the example illustrates, there's a problem:

cagney@tonic$ gcc -o tonic nothing.c -g
cagney@tonic$ gdb tonic
GNU gdb Red Hat Linux (6.0post-0.20040223.21rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and
you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "ia64-redhat-linux-gnu"...Using host
libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) run
Starting program: /home/cagney/tmp/tonic 

Program received signal SIGINT, Interrupt.
0x200000000019b282 in getpid () from /lib/tls/libc.so.6.1
(gdb) display/i $pc
1: x/i $pc  0x200000000019b282 <getpid+2>:                  nop.i 0x0
(gdb) disassemble 
Dump of assembler code for function getpid:
0x200000000019b280 <getpid+0>:  [MII]       mov r15=1041
0x200000000019b281 <getpid+1>:              break.i 0x100000;;
0x200000000019b282 <getpid+2>:              nop.i 0x0
0x200000000019b290 <getpid+16>: [MFB]       nop.m 0x0
0x200000000019b291 <getpid+17>:             nop.f 0x0
0x200000000019b292 <getpid+18>:             br.ret.sptk.few b0;;
End of assembler dump.
(gdb) The program is running.  Exit anyway? (y or n) y
cagney@tonic$ gcc -g -o sigbpt sigbpt.c
cagney@tonic$ gdb sigbpt
GNU gdb Red Hat Linux (6.0post-0.20040223.21rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and
you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "ia64-redhat-linux-gnu"...Using host
libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) break keeper
Breakpoint 1 at 0x40000000000006a2: file sigbpt.c, line 27.
(gdb) handle SIGSEGV print pass nostop
Signal        Stop      Print   Pass to program Description
SIGSEGV       No        Yes     Yes             Segmentation fault
(gdb) run
Starting program: /home/cagney/tmp/sigbpt 

Program received signal SIGSEGV, Segmentation fault.

Breakpoint 1, keeper (sig=11) at sigbpt.c:27
27      }
(gdb) disassemble 
Dump of assembler code for function keeper:
0x40000000000006a0 <keeper+0>:  [MMI]       mov r2=r12;;
0x40000000000006a1 <keeper+1>:              st4 [r2]=r32
0x40000000000006a2 <keeper+2>:              mov r12=r2
0x40000000000006b0 <keeper+16>: [MFB]       nop.m 0x0
0x40000000000006b1 <keeper+17>:             nop.f 0x0
0x40000000000006b2 <keeper+18>:             br.ret.sptk.many b0;;
End of assembler dump.
(gdb) stepi
0x40000000000006b0      27      }
(gdb) 
0x40000000000006b1      27      }
(gdb) 
27      }
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) stepi
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) 
<signal handler called>
(gdb) stepi
<signal handler called>
(gdb) 

Program received signal SIGSEGV, Segmentation fault.
<signal handler called>
(gdb) 

The code should have eventually stepi'ed back to the faulted
instruction.  It appears to have instead also executed that faulting
instruction.

What's extra weird is that it didn't end up back in keeper.