Re: Linux Kernel GDB tracepoint module 2010-8-30 release

Hui Zhu
2010-09-06T07:51:19Z

cat /sys/module/hello/sections/.bss
0xf81b92ec
add-symbol-file ~/kernel/tmp/h/hello.ko 0xf81b9000 -s .bss 0xf81b92ec

(gdb) tstart
(gdb) tstatus
Trace is running on the target.
Collected 0 trace frames.
Trace buffer has 86255744 bytes of 86255744 bytes free (0% full).
Trace will stop if GDB disconnects.
Not looking at any trace frame.
(gdb) tstop
(gdb) tfind
Found trace frame 0, tracepoint 1
#0 0xf81b9068 in test_thread (data=<value optimized out>) at
/home/teawater/kernel/tmp/h/hello.c:22
22 cnt++;
(gdb) p cnt
$1 = 106
(gdb) p tv
$2 = {tv_sec = 1283760246, tv_usec = 784020}
(gdb) p year
$3 = 2010
(gdb)

Looks I need update HOWTO now.

To get all the module message with hand is uncool.
I will make it more automated when I have time.

Thanks,
Hui

On Mon, Sep 6, 2010 at 15:21, Hui Zhu <teawater@gmail.com> wrote:
> Sep  6 15:17:06 teawater kernel: [514552.780031] gtp_kp_pre_handler:
> tracepoint 1
> Sep  6 15:17:06 teawater kernel: [514552.780034] gtp_parse_x: cmd 23
> Sep  6 15:17:06 teawater kernel: [514552.780035] gtp_parse_x: cmd 22
> Sep  6 15:17:06 teawater kernel: [514552.780037] gtp_parse_x: cmd c
> Sep  6 15:17:06 teawater kernel: [514552.780039]
> gtp_action_memory_read: id:1 0000054c 8
> Sep  6 15:17:06 teawater kernel: [514552.780043]
> gtp_action_memory_read: id:1 read 0000054c 8 get error.
> Sep  6 15:17:06 teawater kernel: [514552.780048] gtp_kp_pre_handler:
> tracepoint 1 stop.
> Sep  6 15:17:06 teawater kernel: [514552.780051] tv_sec: 1283757426 - 2010
> Sep  6 15:17:06 teawater kernel: [514552.780053] gtp_kp_pre_handler:
> tracepoint 2
> Sep  6 15:17:06 teawater kernel: [514552.780055] gtp_parse_x: cmd 23
> Sep  6 15:17:06 teawater kernel: [514552.780056] gtp_parse_x: cmd 22
> Sep  6 15:17:06 teawater kernel: [514552.780057] gtp_parse_x: cmd c
> Sep  6 15:17:06 teawater kernel: [514552.780058]
> gtp_action_memory_read: id:2 0000054c 8
> Sep  6 15:17:06 teawater kernel: [514552.780061]
> gtp_action_memory_read: id:2 read 0000054c 8 get error.
> Sep  6 15:17:06 teawater kernel: [514552.780063] gtp_kp_pre_handler:
> tracepoint 2 stop.
> Sep  6 15:17:06 teawater kernel: [514552.780068] gtp_stop: tracepoint 1
> Sep  6 15:17:06 teawater kernel: [514552.792059] gtp_stop: tracepoint 2
>
> (gdb) add-symbol-file ~/kernel/tmp/h/hello.ko 0xf81b9000
> add symbol table from file "/home/teawater/kernel/tmp/h/hello.ko" at
>        .text_addr = 0xf81b9000
> (y or n) y
> Reading symbols from /home/teawater/kernel/tmp/h/hello.ko...done.
> (gdb) p year
> Cannot access memory at address 0x554
> (gdb) p tv
> Cannot access memory at address 0x54c
>
> Looks GDB didn't get the right address of this val.
>
> Export them maybe handle this issue.
>
> Thanks,
> Hui
>
>
>
> On Sun, Sep 5, 2010 at 00:47, Steven <mqyoung@gmail.com> wrote:
>> On Sun, 2010-09-05 at 00:42 +0800, Hui Zhu wrote:
>>> Could you post the other part of this code?  Then I can try to reproduce on it.
>>
>> hello.c
>> ------------------------------------------------
>> #include <linux/kthread.h>
>> #include <linux/module.h>
>> #include <linux/init.h>
>>
>> static struct task_struct *test_task;
>> volatile struct timeval tv;
>> int year;
>>
>> int test_thread(void *data)
>> {
>>        volatile int cnt = 0;
>>        set_current_state(TASK_INTERRUPTIBLE);
>>        schedule_timeout(1 * HZ); /* wait for the terminal ready */
>>
>>        while(1){
>>                set_current_state(TASK_INTERRUPTIBLE); /* this is
>> required, or thread never sleep*/
>>                if(kthread_should_stop()) break;
>>
>>                year = 2010;
>>                do_gettimeofday (&tv);
>>                printk("\ntv_sec: %d - %d\n", (int)tv.tv_sec, cnt);
>>                cnt++;
>>
>>                do_gettimeofday (&tv);
>>                printk("tv_sec: %d - %d\n", (int)tv.tv_sec, year);
>>                cnt++;
>>
>>                //reschedule after 5 seconds(approximately)
>>                schedule_timeout(60 * HZ);
>>        }
>>
>>        return 0;
>> }
>>
>> static int __init mt_init(void)
>> {
>>        int err;
>>        test_task = kthread_create(test_thread, NULL, "test_task");
>>        if(IS_ERR(test_task)){
>>                printk("Unable to start kernel thread.\n");
>>                printk("Unable to start kernel thread.\n");
>>                err = PTR_ERR(test_task);
>>                test_task = NULL;
>>                return err;
>>        }
>>        wake_up_process(test_task);
>>        return 0;
>> }
>>
>>
>> static void __exit mt_cleanup(void)
>> {
>>        if(test_task){
>>                kthread_stop(test_task);
>>                test_task = NULL;
>>        }
>> }
>>
>> module_init(mt_init);
>> module_exit(mt_cleanup);
>>
>> MODULE_LICENSE("GPL");
>> ------------------------------------------------
>>
>>
>> Makefile
>> ------------------------------------------------
>> obj-m := hello.o
>>
>> KERNELBUILD := /lib/modules/`uname -r`/build
>>
>> default:
>>        make -C $(KERNELBUILD) M=$(shell pwd) modules
>>
>> clean:
>>        rm -rf *.o *.cmd *.ko *.mod.c .tmp-versions *.symvers
>> ------------------------------------------------
>>
>>
>>
>>> Thanks,
>>> Hui
>>>
>>> On Sun, Sep 5, 2010 at 00:01, Steven <mqyoung@gmail.com> wrote:
>>> > Dear All,
>>> >
>>> > As I mentioned before, I could collect the variables of kernel function
>>> > such as vfs_readdir(ext3 is built in kernel not module). And I tried I
>>> > could collect variables of kernel's module(such as my ethernet card
>>> > driver 3c59x.ko). I will collect these info later.
>>> >
>>> > BUT, I can not collect the value of my testing module, neither global
>>> > nor local. I think there is some thing wrong with my compile option or
>>> > Makefile, any one know it? Thanks very much.
>>> >
>>> > Program:
>>> > -------------------------------------------------
>>> >  6 volatile struct timeval tv;
>>> >  7 int year;
>>> >  8
>>> >  9 int test_thread(void *data)
>>> >  10 {
>>> >  11         volatile int cnt = 0;
>>> >  12         set_current_state(TASK_INTERRUPTIBLE);
>>> >  13         schedule_timeout(1 * HZ); /* wait for the terminal ready */
>>> >  14
>>> >  15         while(1){
>>> >  16                 set_current_state(TASK_INTERRUPTIBLE);
>>> >  17                 if(kthread_should_stop()) break;
>>> >  18
>>> >  19                 year = 2010;
>>> >  20                 do_gettimeofday (&tv);
>>> >  21                 printk("\ntv_sec: %d - %d\n", (int)tv.tv_sec, cnt);
>>> >  22                 cnt++;
>>> >  23
>>> >  24                 do_gettimeofday (&tv);
>>> >  25                 printk("tv_sec: %d - %d\n", (int)tv.tv_sec, year);
>>> >  26                 cnt++;
>>> >  27
>>> >  28                 //reschedule after 5 seconds(approximately)
>>> >  29                 schedule_timeout(60 * HZ);
>>> >  30         }
>>> >  31
>>> >  32         return 0;
>>> >  33 }
>>> > -------------------------------------------------
>>> >
>>> > Makefile
>>> > -------------------------------------------------
>>> > obj-m := hello.o
>>> >
>>> > KERNELBUILD := /lib/modules/`uname -r`/build
>>> >
>>> > default:
>>> >        make -C $(KERNELBUILD) M=$(shell pwd) modules
>>> > -------------------------------------------------
>>> >
>>> >
>>> > Screen log
>>> > -------------------------------------------------
>>> > debian:/home/linux-2.6.33.6# /usr/local/bin/gdb vmlinux
>>> > GNU gdb (GDB) 7.2
>>> > Copyright (C) 2010 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-pc-linux-gnu".
>>> > For bug reporting instructions, please see:
>>> > <http://www.gnu.org/software/gdb/bugs/>...
>>> > Reading symbols from /home/linux-2.6.33.6/vmlinux...[ 3909.310118]
>>> > [ 3909.310124] tv_sec: 1283648666 - 16
>>> > [ 3909.315385] tv_sec: 1283648666 - 2010
>>> > done.
>>> > (gdb) target remote /proc/gtp
>>> > Remote debugging using /proc/gtp
>>> > 0x00000000 in ?? ()
>>> > (gdb) add-symbol-file /home/steven/hello/hello.ko 0xc8b2b000
>>> > add symbol table from file "/home/steven/hello/hello.ko" at
>>> >        .text_addr = 0xc8b2b000
>>> > (y or n) y
>>> > Reading symbols from /home/steven/hello/hello.ko...done.
>>> > (gdb) trace /home/steven/hello/hello.c:22
>>> > Tracepoint 1 at 0xc8b2b094: file /home/steven/hello/hello.c, line 22.
>>> > (gdb) trace /home/steven/hello/hello.c:26
>>> > Tracepoint 2 at 0xc8b2b0c1: file /home/steven/hello/hello.c, line 26.
>>> > (gdb) actions 1
>>> > Enter actions for tracepoint 1, one per line.
>>> > End with a line saying just "end".
>>> >>
>>> >>collect tv, year, cnt
>>> >>end
>>> > (gdb) actions 2
>>> > Enter actions for tracepoint 2, one per line.
>>> > End with a line saying just "end".
>>> >>collect tv, year, cnt
>>> >>end
>>> > (gdb) tstart
>>> > [ 4029.328129]
>>> > [ 4029.328136] tv_sec: 1283648786 - 20
>>> > [ 4029.333456] tv_sec: 1283648786 - 2010
>>> > tstop
>>> > (gdb) tfind
>>> > Found trace frame 0, tracepoint 1
>>> > #0  0xc8b2b095 in test_thread (data=0x0)
>>> > at /home/steven/hello/hello.c:22
>>> > 22                      cnt++;
>>> > (gdb) p tv
>>> > $1 = {tv_sec = 0, tv_usec = 0}
>>> > (gdb) p cnt
>>> > $2 = 0
>>> > (gdb) p year
>>> > $3 = 0
>>> > (gdb) tfind
>>> > Found trace frame 1, tracepoint 2
>>> > 0xc8b2b0c2      26                      cnt++;
>>> > (gdb) p cnt
>>> > $4 = 0
>>> > (gdb) p tv
>>> > $5 = {tv_sec = 0, tv_usec = 0}
>>> > (gdb) p year
>>> > $6 = 0
>>> > -------------------------------------------------
>>> >
>>> > Thanks,
>>> > Steven
>>> >
>>> > On Sat, 2010-09-04 at 22:58 +0800, Hui Zhu wrote:
>>> >> On Sat, Sep 4, 2010 at 17:26, Steven <mqyoung@gmail.com> wrote:
>>> >> > On Sat, 2010-09-04 at 17:17 +0800, Hui Zhu wrote:
>>> >> >> On Sat, Sep 4, 2010 at 16:56, Steven <mqyoung@gmail.com> wrote:
>>> >> >> > On Sat, 2010-09-04 at 11:41 +0800, Hui Zhu wrote:
>>> >> >> >> BTW, looks GCC and GDB don't want handle the optimization debug
>>> >> >> >> trouble (all they want is rewrite the GCC in C++ :P).
>>> >> >> >> So I think make linux kernel can close optimization is better idea, do
>>> >> >> >> you know some way or some patch to do it?
>>> >> >> >>
>>> >> >> >
>>> >> >> > Just disable CONFIG_CC_OPTIMIZE_FOR_SIZE and modify the Makefile of
>>> >> >> > kernel:
>>> >> >> > KBUILD_CFLAGS   += -O2
>>> >> >> > to
>>> >> >> > KBUILD_CFLAGS   += -O0
>>> >> >>
>>> >> >> Cool,  :)
>>> >> >>
>>> >> >> I try just change the compile option of readdir.c to without -O2, it
>>> >> >> works OK.  I think maybe it's a GDB bug too.
>>> >> >> Could you try the second issue with gdb 7.2?
>>> >> >
>>> >> > I have covered the two issues in the previous mail that I could collect
>>> >> > both global variables and locals(-O0 kernel + gdb7.2):
>>> >> >
>>> >> >        --------
>>> >> >        (gdb) trace vfs_readdir
>>> >> >        Tracepoint 3 at 0xc11756a0: file fs/readdir.c, line 24.
>>> >> >        (gdb) actions
>>> >> >        Enter actions for tracepoint 3, one per line.
>>> >> >        End with a line saying just "end".
>>> >> >        >collect *file
>>> >> >        >end
>>> >> >        (gdb) trace fs/readdir.c:29
>>> >> >        Tracepoint 4 at 0xc11756ca: file fs/readdir.c, line 29.
>>> >> >        (gdb) actions
>>> >> >        Enter actions for tracepoint 4, one per line.
>>> >> >        End with a line saying just "end".
>>> >> >        >collect res
>>> >> >        >end
>>> >> >        (gdb) tstart
>>> >> >        (gdb) tstop
>>> >> >        (gdb) tfind
>>> >> >        Found trace frame 0, tracepoint 3
>>> >> >        #0  0xc11756a1 in vfs_readdir (file=0xc7b2cf00, filler=0,
>>> >> >        buf=0x0)
>>> >> >            at fs/readdir.c:24
>>> >> >        24              struct inode *inode =
>>> >> >        file->f_path.dentry->d_inode;
>>> >> >        (gdb) p *file
>>> >> >        $4 = {f_u = {fu_list = {next = 0xc6dca500, prev = 0xc7ade480},
>>> >> >        fu_rcuhead = {
>>> >> >              next = 0xc6dca500, func = 0xc7ade480}}, f_path = {mnt =
>>> >> >        0xc6c05300,
>>> >> >            dentry = 0xc761d440}, f_op = 0xc1709a20, f_lock = {{rlock =
>>> >> >        {raw_lock = {
>>> >> >                  slock = 0}}}}, f_count = {counter = 2}, f_flags =
>>> >> >        624640,
>>> >> >          f_mode = 29, f_pos = 0, f_owner = {lock = {raw_lock = {lock =
>>> >> >        16777216}},
>>> >> >           = 0start = 0, size = 0, async_size = 0,
>>> >> >            ra_pages = 32, mmap_miss = 0, prev_pos = -1}, f_version =
>>> >> >        0,
>>> >> >          f_security = 0xc7b30120, private_data = 0x0, f_ep_links = {
>>> >> >            next = 0xc7b2cf74, prev = 0xc7b2cf74}, f_mapping =
>>> >> >        0xc761c74c}
>>> >> >        (gdb) p res
>>> >> >        $5 = 0
>>> >> >        (gdb) tfind
>>> >> >        Found trace frame 1, tracepoint 4
>>> >> >        0xc11756cb      29              res =
>>> >> >        security_file_permission(file, MAY_READ);
>>> >> >        (gdb) p res
>>> >> >        $6 = -20
>>> >> >        --------
>>> >> >
>>> >> >
>>> >> >
>>> >>
>>> >> Great.  :)
>>> >>
>>> >> Hui
>>> >
>>> >
>>
>>
>>
>