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 but
the problem exist with kernel 2.6.30 also. 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 .data0xc0745e20 -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.
Regards,
Suresh
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