+++ This bug was initially created as a clone of Bug #231327 +++

Summary:
Gdb does not accurately output the backtrace.

Version-Release of Selected Component:
gdb-6.6-5.fc7.ppc64

Description of Problem:
A core was created by gcore command of gdb.
I tried to debug with gdb, but I found that backtrace wasn't output correctly.


Using host libthread_db library "/lib64/tls/libthread_db.so.1".
Core was generated by `./small'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /lib/tls/libc.so.6...done.
Loaded symbols for /lib/tls/libc.so.6
Reading symbols from /lib/ld.so.1...done.
Loaded symbols for /lib/ld.so.1
#0  0x0fe91038 in kill () from /lib/tls/libc.so.6

Thread 1 (process 21873):
#0  0x0fe91038 in kill () from /lib/tls/libc.so.6
#1  0x10000584 in handle_alrm (signo=14) at small.c:17
#2  <signal handler called>
#3  0x0fef5fec in __pause_nocancel () from /lib/tls/libc.so.6
#4  0x10000650 in main (argc=1, argv=0xffffe9d4) at small.c:32
RESULT of kernel core generator: Passed
Using host libthread_db library "/lib64/tls/libthread_db.so.1".
Attaching to program: /mnt/tests/kernel/syscalls/vsyscall/small, process 21887
Reading symbols from /lib/tls/libc.so.6...done.
Loaded symbols for /lib/tls/libc.so.6
Reading symbols from /lib/ld.so.1...done.
Loaded symbols for /lib/ld.so.1
0x0fef5fec in __pause_nocancel () from /lib/tls/libc.so.6
Saved corefile core.gcore
Using host libthread_db library "/lib64/tls/libthread_db.so.1".
Core was generated by `/mnt/tests/kernel/syscalls/vsyscall/small'.
Reading symbols from /lib/tls/libc.so.6...done.
Loaded symbols for /lib/tls/libc.so.6
Reading symbols from /lib/ld.so.1...done.
Loaded symbols for /lib/ld.so.1
#0  0x00000000 in ?? ()

Thread 1 (process 21887):
#0  0x00000000 in ?? ()
#1  0x00000000 in ?? ()
RESULT of kernel maps permissions: Failed
RESULT: some tests Failed


-- Additional comment from anderson on 2007-03-09 15:00 EST --
The problem seen here is with gcore-generated core files.

Using the supplied "small.c" program, and letting it kill itself
via SIGSEGV, and then having the kernel generate a core
file, gdb works OK:

# gdb small core.831
GNU gdb Red Hat Linux (6.3.0.0-1.132.EL4rh)
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 "ppc64-redhat-linux-gnu"...Using host libthread_db
library "/lib64/tls/libthread_db.so.1".

Core was generated by `./small'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /lib/tls/libc.so.6...done.
Loaded symbols for /lib/tls/libc.so.6
Reading symbols from /lib/ld.so.1...done.
Loaded symbols for /lib/ld.so.1
#0  0x0feb1038 in kill () from /lib/tls/libc.so.6
(gdb) bt
#0  0x0feb1038 in kill () from /lib/tls/libc.so.6
#1  0x10000584 in handle_alrm (signo=14) at small.c:17
#2  <signal handler called>
#3  0x0ff15fec in __pause_nocancel () from /lib/tls/libc.so.6
#4  0x10000650 in main (argc=1, argv=0xffffeae4) at small.c:32
(gdb)

But if generated by gcore, it does not:

# gdb small core.837
GNU gdb Red Hat Linux (6.3.0.0-1.132.EL4rh)
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 "ppc64-redhat-linux-gnu"...Using host libthread_db
library "/lib64/tls/libthread_db.so.1".

Core was generated by `/mnt/tests/kernel/syscalls/vsyscall/small'.
Reading symbols from /lib/tls/libc.so.6...done.
Loaded symbols for /lib/tls/libc.so.6
Reading symbols from /lib/ld.so.1...done.
Loaded symbols for /lib/ld.so.1
#0  0x00000000 in ?? ()
(gdb) bt
#0  0x00000000 in ?? ()
#1  0x00000000 in ?? ()
(gdb) 


-- Additional comment from jan.kratochvil on 2007-03-09 16:52 EST --
Confirming I also see it as a GDB.ppc bug now.
Thanks for such perfectly prepared machine, going to check it on that RHTS host
until it expires. 


-- Additional comment from jan.kratochvil on 2007-03-09 17:33 EST --
The problem exists only for 64-bit GDB (gdb.ppc64) debugging (32-bit) process (ppc).
Bug is in the gcore writing.
Registers content gets corrupted.  Memory areas look to be transferred OK.
[snip]


-- Additional comment from jan.kratochvil on 2007-03-13 11:47 EST --
[snip] 
Bug IS     present in: RawHide  gdb-6.6-5.fc7.ppc64
Bug is NOT present in: upstream gdb-6.6
Bug is NOT present in: upstream HEAD

Apparently some Red Hat patches are causing a PPC regression.