Cross platform GDB problem and question

[Hai Xiao]

I had host and target (our target arch is mips64octeon, and target os is
2.6.10_mvl401) version gdb both with the same
configuration --target=mips64octeon-montavista-linux.
The mips64_octeon_be-gdb is the host version gdb coming from vender's
cross-compiler toolchain, it is also configured
with --host=i686-pc-linux-gnu.

Whenever target crashed and core file generated, we can get into target os
shell later, use the target/native gdb to open the binary/executable with
the core file. In the case, target gdb works fine, it always decodes the
trace frames completely and correctly.

But question comes when we transfer the target binary (aware of its
targetted to different arch) and core file out to cross-compiling machine
(i686-pc-linux-gnu, 2.4.21-32.0.1.ELsmp i686), we find the
mips64_octeon_be-gdb can't produce a complete back trace at all.
We also tried the same test on different host machine (e.g. 2.6.9-42.7.ELsmp
i686), problem keeps the same, after the first frame decoded, it (the cross
version gdb - mips64_octeon_be-gdb) always complains with "Cannot access
memory at address 0xXYZ".

Assumption is that "mips64_octeon_be-gdb" (--host=i686-pc-linux-gnu) as a
cross-platform version gdb, it should at least be able to open up core file
with target binary properly even on host machine for offline debug (mainly
for "bt" purpose).

Any good idea on how to resolve this problem?

Thanks!


~/coredump/sci:27> mips64_octeon_be-gdb sci.bin core..181
GNU gdb 6.3 (MontaVista 6.3-20.0.88.0702529 2007-01-31)
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
"--host=i686-pc-linux-gnu --target=mips64octeon-montavista-linux"...

warning: exec file is newer than core file.
Core was generated by `/sci/sci.bin'.
Program terminated with signal 6, Aborted.
#0  0x10013388 in cache_dist_stats () at soft_util.c:627
627     soft_util.c: No such file or directory.
        in soft_util.c
(gdb) bt
#0  0x10013388 in cache_dist_stats () at soft_util.c:627
Cannot access memory at address 0x30
(gdb) info reg
                  zero               at               v0               v1
 R0   0000000000000000 0000000000000000 0000000000000000 0000000000000000
                    a0               a1               a2               a3
 R4   0000000000000000 0000000000000000 0000000000000000 ffffffff81340000
                    a4               a5               a6               a7
 R8   0000000000000005 000000000000003c 000000007ffac3c4 0000000000000001
                    t0               t1               t2               t3
 R12  0000000000000800 0000000000000000 000000001fff7944 00000000103b7630
                    s0               s1               s2               s3
 R16  0000000000000000 0000000000000000 0000000000000000 ffffffff80000010
                    s4               s5               s6               s7
 R20  ffffffff811189d8 0000000000000000 00000000103c0238 00000000103c0238
                    t8               t9               k0               k1
 R24  0000000000002000 00000000103c0000 00000000103c2000 00000000103c20f8
                    gp               sp               s8               ra
 R28  0000000000000001 000000001fff7da4 0000000000000000 0000000010013640
                    sr               lo               hi              bad
      0000000000000000 0000000000000000 00000000103b7630 000000001fff7990
                 cause               pc
      000000001fff7990 0000000010013388
(gdb)