[Bug breakpoints/13346] Multiple breakpoints/losing symbol tableissue

["j.vimal at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13346

--- Comment #6 from Vimal <j.vimal at gmail dot com> 2011-10-26 15:50:27 UTC ---
(In reply to comment #5)

Thanks for the offset explanation.  It cleared things up.

> > guest# cat /sys/module/openvswitch_mod/sections/.text
> > 0xffffffffa00ca000
> 
> Not sure why they call it `.text' but there is only a probability of 1:4095
> that this is really a .text address.  Most probably you need to add the .text
> section address above (from readelf -WS ./openvswitch_mod.ko | grep '\.text').

I see this info for .text:

    Name              Type            Address          Off
    .text             PROGBITS        0000000000000000 000064

    Size   ES Flg Lk Inf Al
    017518 00  AX  0   0  4

So, I did:

cat /proc/modules/.../.text
0xffffffffa00f9000

(gdb) add-symbol-file ~/vm/openvswitch_mod.ko 0xffffffffa00f9064
add symbol table from file "/home/jvimal/vm/openvswitch_mod.ko" at
        .text_addr = 0xffffffffa00f9064
                                     ^^ added offset 64

(y or n) y
Reading symbols from /home/jvimal/vm/openvswitch_mod.ko...done.
(gdb) break dp_process_received_packet
Breakpoint 1 at 0xffffffffa00fc42c: file
/home/nikhilh/openvswitch/datapath/linux/datapath.c, line 262. (2 locations)


(gdb) info br
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   <MULTIPLE>
1.1                         y     0xffffffffa00fc42c
/home/nikhilh/openvswitch/datapath/linux/datapath.c:262
1.2                         y     0xffffffffa00fc44b
/home/nikhilh/openvswitch/datapath/linux/datapath.c:262

There are still two breakpoints.   Which seems weird.

If I hit the breakpoint, the line numbers and locals information is still
missing.

So I tried another approach:

guest# cat /proc/kallsyms | grep dp_process
ffffffffa00d63c8 t dp_process_received_packet   [openvswitch_mod]

(gdb) break *0xffffffffa00d63c8
Breakpoint 1 at 0xffffffffa00d63c8

(gdb) c
Continuing.

Breakpoint 1, 0xffffffffa00d63c8 in dp_detach_port ()
(Which is a completely different function altogether!  Does this suggest that
the 0x64 offset could be wrong?)


If I do not add the offset 0x64, I see this:
(gdb) add-symbol-file ~/vm/openvswitch_mod.ko 0xffffffffa00bf000
add symbol table from file "/home/jvimal/vm/openvswitch_mod.ko" at
        .text_addr = 0xffffffffa00bf000
(y or n) y
Reading symbols from /home/jvimal/vm/openvswitch_mod.ko...done.


(gdb) break *0xffffffffa00c23c8
Breakpoint 1 at 0xffffffffa00c23c8
(gdb) info br
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0xffffffffa00c23c8 <dp_process_received_packet>
                                                    ^^^^^^^^ This seems correct

(gdb) c
Continuing.

Breakpoint 1, 0xffffffffa00c23c8 in dp_process_received_packet ()
(gdb) info args
No symbol table info available.

Here is the line number info from the kernel module.

# readelf -wil openvswitch_mod.ko

 <1><3f4e4>: Abbrev Number: 89 (DW_TAG_subprogram)
    <3f4e5>   DW_AT_external    : 1
    <3f4e6>   DW_AT_name        : (indirect string, offset: 0x1aeb8):
dp_process_received_packet
    <3f4ea>   DW_AT_decl_file   : 29
    <3f4eb>   DW_AT_decl_line   : 261
    <3f4ed>   DW_AT_prototyped  : 1
    <3f4ee>   DW_AT_low_pc      : 0x33c8
    <3f4f6>   DW_AT_high_pc     : 0x3690
    <3f4fe>   DW_AT_frame_base  : 0x322c        (location list)
    <3f502>   DW_AT_sibling     : <0x3f67c>

  (followed by args/locals information)

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