Hi Thomson,
It seems that your problem is the CONFIG_DEBUG_RODATA option was
enabled, It is recommend to turn CONFIG_DEBUG_RODATA off when using kgdb.
From the kgdb document(DocBook/kgdb.tmpl):
If the architecture that you are using supports the kernel option
CONFIG_DEBUG_RODATA, you should consider turning it off. This
option will prevent the use of software breakpoints because it
marks certain regions of the kernel's memory space as read-only.
If kgdb supports it for the architecture you are using, you can
use hardware breakpoints if you desire to run with the
CONFIG_DEBUG_RODATA option turned on, else you need to turn off
this option.
Thanks,
Dongdong
Thomson, Patrick S wrote:
> Hi Folks,
>
> I'm wondering if anyone has had issues with setting breakpoints. I'm
> able to break into the kernel, access data, do a backtrace, etc, but
> when I attempt to set a breakpoint, then continue, I get the following error:
>
> Cannot insert breakpoint 1.
> Error accessing memory address 0xffffffff81310931: Unknown error 4294967295.
>
> I'm attaching a sample session, I had set remote debug to 1
>
> Thanks!
> Pat Thomson
>
> [pstho...@psthomso-desk2 linux-2.6.36-rc6-kgdb]$ gdb ./vmlinux
> GNU gdb (GDB) Fedora (7.0.1-45.fc12)
> Copyright (C) 2009 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "i686-redhat-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from
> /home/psthomso/Kernels/linux-2.6.36-rc6-kgdb/vmlinux...done.
> (gdb) show architecture
> The target architecture is set automatically (currently i386:x86-64)
> (gdb) set debug remote 1
> (gdb) target remote /dev/ttyS1
> Remote debugging using /dev/ttyS1
> Sending packet: $qSupported#37...Sending packet: $qSupported#37...Sending
> packet: $qSupported#37...Sending packet: $qSupported#37...Timed out.
> Timed out.
> Timed out.
> Ignoring packet error, continuing...
> Packet qSupported (supported-packets) is supported
> warning: unrecognized item "timeout" in "qSupported" response
> Sending packet: $Hg0#df...Sending packet: $Hg0#df...Sending packet:
> $Hg0#df...Sending packet: $Hg0#df...Ack
> Packet received: OK
> Sending packet: $?#3f...Ack
> Packet received: S05
> Sending packet: $Hc-1#09...Ack
> Packet received: OK
> Sending packet: $qC#b4...Ack
> Packet received: QC00000000fffffffd
> Sending packet: $qAttached#8f...Ack
> Packet received:
> Packet qAttached (query-attached) is NOT supported
> Sending packet: $qOffsets#4b...Ack
> Packet received:
> Sending packet: $g#67...Ack
> Packet received:
> 140000000000000067000000000000000af00000000000000000e4010088ffff46000000000000004600000000000000c839e4010088ffffc839e4010088ffff0000000000000000730000000000000000dcca3f0288ffffc844c081ffffffff0030ef3f0288ffff7019a281ffffffff04000000000000009600000000000000cba40881ffffffff020000001000000018000000
> kgdb_breakpoint (key=70, tty=0x46) at kernel/kgdb.c:1749
> 1749 wmb(); /* Sync point after breakpoint */
> Sending packet: $qSymbol::#5b...Ack
> Packet received:
> Packet qSymbol (symbol-lookup) is NOT supported
> (gdb) bt
> Sending packet: $mffff880001e439c0,40#5e...Ack
> Packet received:
> c0a40881ffffffff183ae4010088fffffe972b81ffffffff82000000000000000100000000000000f839e4010088ffff220000000000000000dcca3f0288ffff
> Sending packet: $mffff880001e43a00,40#53...Ack
> Packet received:
> 01000000000000000030ef3f0288ffff0100000000000000283ae4010088ffff1c992b81ffffffff983ae4010088ffff391f2b81ffffffff983ae4010088ffff
> Sending packet: $mffff880001e43a80,40#5b...Ack
> Packet received:
> 220000000000000001000000000000000100000000000000e83ae4010088ffff80413681ffffffff010000000000000090b93a3f0288ffff2200000000000000
> Sending packet: $mffff880001e43ac0,40#86...Ack
> Packet received:
> 00b03a3f0288ffff2200000000000000010000000000000001000000000000000100000000000000383be4010088ffff51613681ffffffff2ece17c964080000
> Sending packet: $mffff880001e43b40,40#58...Ack
> Packet received:
> 53623681ffffffff883be4010088ffff0200000000000000883be4010088ffff1081383f0288ffff00b03a3f0288ffff01000000000000000080383f0288ffff
> Sending packet: $mffff880001e43b00,40#54...Ack
> Packet received:
> 0100000001000000310000000288ffff00b03a3f0288ffff0100000000000000f8b73a3f0288ffff22000000000000000100000000000000883be4010088ffff
> Sending packet: $mffff880001e43b80,40#5c...Ack
> Packet received:
> 0080383f0288ffffb83be4010088ffffe70c3a81ffffffff0080f83f0288ffff1081383f0288ffff0100000000000000204fa681ffffffff083ce4010088ffff
> Sending packet: $mffff880001e43bc0,40#87...Ack
> Packet received:
> b2f53981ffffffffd83be4010088ffff4600000001000000083ce4010088ffff0080383f0288ffff603cf3430288ffff0080f83f0288ffff0400000000000000
> Sending packet: $mffff880001e43c00,40#55...Ack
> Packet received:
> 0000000000000000b83ce4010088ffff0dfa3981ffffffff0f2110ff0200ffff503ce4010088ffff8000000000ffffff0058753f0288ffff18c9cd4f0288ffff
> Sending packet: $mffff880001e43cc0,40#88...Ack
> Packet received:
> adfc3981ffffffffcc8d0181ffffffff07f081370088ffff0100000000000000204fa681ffffffff2d4e0681ffffffff00c0713f0288ffff80c4483f0288ffff
> Sending packet: $mffff880001e43c80,40#5d...Ack
> Packet received:
> 0100000000000000b83ce4010088ffff0080f83f0288ffff0058753f0288ffff00a8fb3f0288ffff00f081370088ffff0800000000000000183de4010088ffff
> Sending packet: $mffff880001e43d00,40#56...Ack
> Packet received:
> 0080f83f0288ffff0004e83f0288ffff0000000000000000583de4010088ffff05a63a81ffffffff383de4010088ffff80c4483f0288ffff0000000000000000
> Sending packet: $mffff880001e43d40,40#5a...Ack
> Packet received:
> 0004e83f0288ffff0004e83f0288ffff30a680370088ffff883de4010088ffff75f13381ffffffff883de4010088ffff00a680370088ffff8005e83f0288ffff
> Sending packet: $mffff880001e43d80,40#5e...Ack
> Packet received:
> 80c4483f0288ffff083ee4010088ffff5acd3581ffffffffe83de4010088ffff2ea70d81ffffffff401da281ffffffff40030000fffffffff500000000000000
> Sending packet: $mffff880001e43e00,40#57...Ack
> Packet received:
> 80c4483f0288ffff883ee4010088ffff65d73581ffffffff401da281ffffffffe04ee3460288ffffe84ee3460288ffff009380370088ffff00a680370088ffff
> Sending packet: $mffff880001e43e80,40#5f...Ack
> Packet received:
> 0000000000000000b83ee4010088ffff7ff63581ffffffff0004e83f0288ffff460200000000000000000000000000000000000000000000d83ee4010088ffff
> Sending packet: $mffff880001e43ec0,40#8a...Ack
> Packet received:
> 0ce83381ffffffffc09ccc3f0288ffff1500000000000000283fe4010088ffff1fc40881ffffffff489ed04f0288ffff0000000000000000083fe4010088ffff
> Sending packet: $mffff880001e43f00,40#58...Ack
> Packet received:
> 0073d53f0288ffff15000000000000006473d53f0288ffff489ed04f0288ffff0000000000000000583fe4010088ffff68e30881ffffffff0000000000000000
> Sending packet: $mffff880001e43f40,40#5c...Ack
> Packet received:
> 150000000000000099000000000000001500000000000000783fe4010088ffff73520081ffffffff783fe4010088ffff0000000000000000a83fe4010088ffff
> Sending packet: $mffff880001e43f80,40#60...Ack
> Packet received:
> 84480081ffffffffd89fd04f0288ffffd89fd04f0288ffff00000000000000000000000000000000709ed04f0288ffff53a24581ffffffff709ed04f0288ffff
> Sending packet: $mffffffff8145a253,9#cf...Ack
> Packet received: fa0f1f800000000065
> Sending packet: $mffffffff8145a239,1a#2c...Ack
> Packet received: 1f84000000000048830424804883ec50e80287baffe8d5a5baff
> Sending packet: $mffff88024fd09e70,9#6f...Ack
> Packet received: 089fd04f0288ffff48
> Sending packet: $mffff88024fd09e56,1a#cc...Ack
> Packet received: 0000989ed04f0288ffffe0ede4010088ffff4ea24581ffffffff
> Sending packet: $mffff880001e43fc0,40#8b...Ack
> Packet received:
> 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
> Sending packet: $m0,9#02...Ack
> Packet received: E14
> #0 kgdb_breakpoint (key=70, tty=0x46) at kernel/kgdb.c:1749
> #1 sysrq_handle_gdb (key=70, tty=0x46) at kernel/kgdb.c:1609
> #2 0xffffffff812b97fe in __handle_sysrq (key=103, tty=0xffff88023fef3000,
> check_mask=<value optimized out>) at drivers/char/sysrq.c:522
> #3 0xffffffff812b991c in handle_sysrq (key=70, tty=0x46)
> at drivers/char/sysrq.c:554
> #4 0xffffffff812b1f39 in kbd_keycode (handle=<value optimized out>,
> event_type=<value optimized out>, event_code=34, value=1)
> at drivers/char/keyboard.c:1204
> #5 kbd_event (handle=<value optimized out>, event_type=<value optimized
> out>,
> event_code=34, value=1) at drivers/char/keyboard.c:1317
> #6 0xffffffff81364180 in input_pass_event (dev=<value optimized out>,
> type=1,
> code=34, value=1) at drivers/input/input.c:118
> #7 0xffffffff81366151 in input_handle_event (dev=0xffff88023f3ab000, type=1,
> code=34, value=1) at drivers/input/input.c:307
> #8 0xffffffff81366253 in input_event (dev=0xffff88023f3ab000, type=1,
> code=34, value=1) at drivers/input/input.c:336
> #9 0xffffffff813a0ce7 in hidinput_hid_event (hid=<value optimized out>,
> field=0xffff88023f388000, usage=0xffff88023f388110, value=1)
> at drivers/hid/hid-input.c:646
> #10 0xffffffff8139f5b2 in hid_process_event (hid=0xffff88023ff88000,
> field=0xffff88023f388000, usage=0xffff88023f388110, value=1,
> interrupt=<value optimized out>) at drivers/hid/hid-core.c:875
> ---Type <return> to continue, or q <return> to quit---q
> Quit
> (gdb) l
> 1744 void kgdb_breakpoint(void)
> 1745 {
> 1746 atomic_inc(&kgdb_setting_breakpoint);
> 1747 wmb(); /* Sync point before breakpoint */
> 1748 arch_kgdb_breakpoint();
> 1749 wmb(); /* Sync point after breakpoint */
> 1750 atomic_dec(&kgdb_setting_breakpoint);
> 1751 }
> 1752 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
> 1753
> (gdb) p kgdb_setting_breakpoint
> Sending packet: $mffffffff81bbe694,4#32...Ack
> Packet received: 01000000
> $1 = {counter = 1}
> (gdb) show breakpoint
> (gdb) b ata_xfer_mask2mode
> Sending packet: $mffffffff81310928,12#cc...Ack
> Packet received: 554889e50f1f44000083c8ff0fbdd70f44d0
> Sending packet: $mffffffff81310928,1#9a...Ack
> Packet received: 55
> Sending packet: $mffffffff81310929,3#9d...Ack
> Packet received: 4889e5
> Sending packet: $mffffffff81310931,1#94...Ack
> Packet received: 83
> Breakpoint 1 at 0xffffffff81310931: file drivers/ata/libata-core.c, line 918.
> (gdb) c
> Continuing.
> Sending packet: $Z0,ffffffff81310931,1#dd...Ack
> Packet received: E14
> Packet Z0 (software-breakpoint) is supported
> Warning:
> Cannot insert breakpoint 1.
> Error accessing memory address 0xffffffff81310931: Unknown error 4294967295.
>
> (gdb) d 1
> (gdb) c
> Continuing.
> Sending packet: $vCont?#49...Ack
> Packet received:
> Packet vCont (verbose-resume) is NOT supported
> Sending packet: $Hc0#db...Ack
> Packet received: OK
> Sending packet: $c#63...Ack
>
>
> ------------------------------------------------------------------------------
>
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> Kgdb-bugreport@lists.sourceforge.net
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>
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