[Bug gdb/10667] New: v2.6.28 KGDB/GDB problem resolving module function addresses

["sureshpc123 at yahoo dot com" <sourceware-bugzilla@sourceware.org>]

v2.6.28 of the kernel seems to have changed the way module sections are created
which prevents KGDB/GDB (v6.8) from correctly evaluating the addresses of
functions within the module. The problem does not exist with kernel v2.6.26.
Example follows:

After I load a module, I can see the module section information in the directory
/sys/module/chardev/sections as follows:

#ls -a
.                          .symtab
..                         .text
.bss                       .text.cleanup_module
.data                      .text.device_ioctl
.fixup                     .text.device_open
.gnu.linkonce.this_module  .text.device_read
.note.gnu.build-id         .text.device_release
.reginfo                   .text.device_write
.rodata.str1.4             .text.init_module
.strtab                    __ex_table
#

I then add the module symbols to gdb as follows:

(gdb) add-symbol file chardev.ko 0xc0745000 -s .data 0xc0745e20 -s .bss
0xc0746000 -s .reginfo 0xc0745534

Now when I try to get the address of a function the wrong value is returned i.e.
all functions get the same address

(gdb) p /x &device_write
$1 = 0xc0745000
(gdb) p /x &device_read
$2 = 0xc0745000
(gdb) p /x &device_open
$3 = 0xc0745000

Tried adding explicitly as follows:

(gdb) add-symbol-file ../moduletest/chardev.ko 0xc0745000 -s .reginfo
0xc0745534 -s .data 0xc0745e20 -s .bss 0xc0746000 -s .text.device_open
0xc07450a0 -s .text.device_write 0xc07450a0 -s .text.device_read 0xc07451ac add
symbol table from file "../moduletest/chardev.ko" at
     .text_addr = 0xc0745000
     .reginfo_addr = 0xc0745534
     .data_addr = 0xc0745e20
     .bss_addr = 0xc0746000
     .text.device_open_addr = 0xc07450a0
     .text.device_write_addr = 0xc07450a0
     .text.device_read_addr = 0xc07451ac (y or n) y Reading symbols from
/home/suresh/moduletest/chardev.ko...done.
(gdb) 

However, the result is still the same i.e.:

(gdb) p /x &device_write
$4 = 0xc0745000
(gdb) p /x &device_read
$5 = 0xc0745000
(gdb) p /x &device_open
$6 = 0xc0745000

Any help/explanation appreciated.

-- 
           Summary: v2.6.28 KGDB/GDB problem resolving module function
                    addresses
           Product: gdb
           Version: 6.8
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: sureshpc123 at yahoo dot com
                CC: gdb-prs at sourceware dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=10667

------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.