Some notes in using crash this summer

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Hello Dave,

Here are some “notes” i have done in using crash this summer.

Thanks.

 

================================================================================

PROBLEM TO START CRASH

================================================================================

 

PB to start crash with this version :

[root@fedora4 crash-4.0-2.33]# cat /proc/version

Linux version 2.6.16.1 (root@xxxxxxxxxxxxxxxxxx) (version gcc 4.0.0 20050519 (Red Hat 4.0.0-8)) #2 SMP PREEMPT Tue Apr 11 12:38:29 CEST 2006

 

 

 

crash 4.0-2.33

Copyright (C) 2002, 2003, 2004, 2005, 2006  Red Hat, Inc.

Copyright (C) 2004, 2005, 2006  IBM Corporation

Copyright (C) 1999-2006  Hewlett-Packard Co

Copyright (C) 2005  Fujitsu Limited

Copyright (C) 2005  NEC Corporation

Copyright (C) 1999, 2002  Silicon Graphics, Inc.

Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.

This program is free software, covered by the GNU General Public License,

and you are welcome to change it and/or distribute copies of it under

certain conditions.  Enter "help copying" to see the conditions.

This program has absolutely no warranty.  Enter "help warranty" for details.

 

GNU gdb 6.1

Copyright 2004 Free Software Foundation, Inc.

GDB is free software, covered by the GNU General Public License, and you are

welcome to change it and/or distribute copies of it under certain conditions.

Type "show copying" to see the conditions.

There is absolutely no warranty for GDB.  Type "show warranty" for details.

This GDB was configured as "i686-pc-linux-gnu"...

 

crash: invalid size request: 0  type: "hardirq_ctx"

 

=================================================================

MAY BE A PROBLEM WITH STRUCT AND ARRAYS

=================================================================

May be a problem with struct ?

 

crash> struct kmem_cache_s f7ffdc80 

struct kmem_cache_s {

  array = {0xf7ffb980, 0xc1ddf500, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,

    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,

    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},

  batchcount = 12,

  limit = 24,

  lists = {

    slabs_partial = {

      next = 0xf7bdd000,

      prev = 0xf701a000

    },

    slabs_full = {

      next = 0xc1f3a000,

      prev = 0xf7e8c000

    },

[...]

  name = 0xc0322190 "task_struct",

  next = {

    next = 0xf7ffde78,

    prev = 0xf7ffdc78

  }

}

 

 

crash> struct kmem_cache_s.array f7ffdc80 <--- OTHER FIELDS ARE COMMING WITH ARRAY

  array = {0xf7ffb980, 0xc1ddf500, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,

    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,

    0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},

  batchcount = 12,

  limit = 24,

  lists = {

    slabs_partial = {

      next = 0xf7828000,

      prev = 0xf7bdd000

    },

    slabs_full = {

      next = 0xc1eb3000,

      prev = 0xf7e8c000

    },

    slabs_free = {

      next = 0xf7ffdd18,

      prev = 0xf7ffdd18

    },

    free_objects = 13,

    free_touched = 0,

    next_reap = 11377353,

    shared = 0xf7ff5000

  },

crash>

 

 

=================================================================

I THINK THERE IS A POINTER PROBLEM WITH SIG

=================================================================

It seems there is a pointer problem with sig.

(Also, currently, sig -l and sig -s do not support RT signals).

 

I use the very simple programme (procsig.c) which block and send a signal using tkill()

 

 

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <linux/unistd.h>

 

#ifndef GETTID

pid_t gettid(void) {return syscall(__NR_gettid);}

#endif

#ifndef TKILL

int tkill(pid_t tid, int sig) {return syscall (__NR_tkill,tid,sig); }

#endif

 

void sigusr2(int sig, siginfo_t *sp, void *uc)

{

}

 

void sigcatch()

{

        struct sigaction sa;

        sigemptyset(&sa.sa_mask);

        sa.sa_flags = SA_SIGINFO;

        sa.sa_sigaction = sigusr2;

        if (sigaction(SIGUSR2, &sa, NULL)==-1) {

                perror("sigaction() - SIGUSR2"); exit(1);

        }

}

void sig_block()

{

        sigset_t set;

        sigemptyset(&set);

        sigaddset(&set, SIGUSR2);

        if (sigprocmask(SIG_SETMASK, &set,NULL) == -1) {

                perror("sigprocmask()"); exit(1);

        }

        if(tkill(gettid(), SIGUSR2)==-1){

                perror("tkill()"); exit(1);

        }

}

 

 

main(int argc)

{

    sig_block();

    sigcatch();

   

    pause();

}

 

 

[root@fedora4 ~]# ./procsig &

[1] 4985

[root@fedora4 ~]# crash -s

crash> set 4985

    PID: 4985

COMMAND: "procsig"

   TASK: f7e19020  [THREAD_INFO: f4a97000]

    CPU: 0

  STATE: TASK_INTERRUPTIBLE

crash> sig >/tmp/res  <----------- NETHER FINISH, I MUST KILL THE TASK

 

 

This is what i get in the file /tmp/res

 

 

PID: 4985   TASK: f7e19020  CPU: 0   COMMAND: "procsig"

SIGPENDING: no

    SIGNAL: 0000000000000800

   BLOCKED: 0000000000000800

SIGNAL_STRUCT: c1e57980  COUNT: 1

 SIG SIGACTION  HANDLER       MASK       FLAGS  

 [1]  c1f3e604  SIG_DFL 0000000000000000 0

 [2]  c1f3e618  SIG_DFL 0000000000000000 0

 [3]  c1f3e62c  SIG_DFL 0000000000000000 0

[...]

[60]  c1f3eaa0  SIG_DFL 0000000000000000 0

[61]  c1f3eab4  SIG_DFL 0000000000000000 0

[62]  c1f3eac8  SIG_DFL 0000000000000000 0

[63]  c1f3eadc  SIG_DFL 0000000000000000 0

SIGQUEUE:  SIG  SIGINFO

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

             0  f7e194a4

            12  f7ac1344

            .....

            .....

=================================================================

IS CRASH ABLE TO READ per_cpu__xxxxxx STRUCTURES ?

================================================================

Strange results with per_cpu__xxxxxxx

May be, i do something which is not correct. The "problem" exists only with SMP.

 

 

crash> sys

      KERNEL: /boot/vmlinux-2.6.11-prep

    DUMPFILE: /dev/crash

        CPUS: 2

        DATE: Fri Jul 21 16:30:51 2006

      UPTIME: 00:09:11

LOAD AVERAGE: 0.01, 0.11, 0.08

       TASKS: 105

    NODENAME: fedora4.domain.com

     RELEASE: 2.6.11-prep

     VERSION: #6 SMP Fri Jul 21 10:13:20 CEST 2006

     MACHINE: i686  (2399 Mhz)

      MEMORY: 1.5 GB

 

crash> per_cpu__loopback_stats

per_cpu__loopback_stats = $6 = {

  rx_packets = 3435973836,

  tx_packets = 3435973836,

  rx_bytes = 3435973836,

  tx_bytes = 3435973836,

  rx_errors = 3435973836,

  tx_errors = 3435973836,

  rx_dropped = 3435973836,

  tx_dropped = 3435973836,

  multicast = 3435973836,

  collisions = 3435973836,

  rx_length_errors = 3435973836,

  rx_over_errors = 3435973836,

  rx_crc_errors = 3435973836,

  rx_frame_errors = 3435973836,

  rx_fifo_errors = 3435973836,

  rx_missed_errors = 3435973836,

  tx_aborted_errors = 3435973836,

  tx_carrier_errors = 3435973836,

  tx_fifo_errors = 3435973836,

  tx_heartbeat_errors = 3435973836,

  tx_window_errors = 3435973836,

  rx_compressed = 3435973836,

  tx_compressed = 3435973836

}

crash> rd per_cpu__loopback_stats 10

c040c320:  cccccccc cccccccc cccccccc cccccccc   ................

c040c330:  cccccccc cccccccc cccccccc cccccccc   ................

c040c340:  cccccccc cccccccc                     ........

 

An other one :

crash> per_cpu__irq_stat

per_cpu__irq_stat = $1 = {

  __softirq_pending = 1954047342,    /* ???? */

  idle_timestamp = 1668312320,

  __nmi_count = 1835364191,

  apic_timer_irqs = 1702521203

}

crash> rd per_cpu__irq_stat 4

c0407380:  7478656e 63706d00 6d656f5f 657a6973   next.mpc_oemsize

 

 

=================================================================

A SMALL DETAIL with ps

=================================================================

In using prothread - the very first time when i do ps procthread, i see VSZ and RSS with 0

 

FIRS TIME

crash> ps procthread

   PID    PPID  CPU   TASK    ST  %MEM     VSZ    RSS  COMM

   4844      1   1  f6646020  IN   0.0       0      0  procthread

   4845      1   0  f6646560  IN   0.0   22108    552  procthread

>  4846      1   1  f78f5560  RU   0.0   22108    552  procthread

 

SECOND TIME is OK

crash> ps procthread

   PID    PPID  CPU   TASK    ST  %MEM     VSZ    RSS  COMM

   4844      1   1  f6646020  IN   0.0   22108    552  procthread

   4845      1   0  f6646560  IN   0.0   22108    552  procthread

>  4846      1   1  f78f5560  RU   0.0   22108    552  procthread

 

Here is procthread.c

 

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <assert.h>

#include <pthread.h>

 

#ifndef GETTID

#include <linux/unistd.h>

_syscall0(pid_t,gettid);

#endif

 

#define NBR_THREADS 2

pthread_t tid[NBR_THREADS];

 

void *lwp_pr(void *lwp_num)

{

    int ret;

    pid_t tid = gettid();

    printf("PPID %d TGID %d TID %d\n",

        getppid(), getpid(), tid);

    while(1)

        if (tid % 2)

            sleep(1);

}

 

main(int argc)

{

    int i, ret;

    printf("main PPID %d TGID %d TID %d\n",

       getppid(), getpid(), gettid());

    for (i=0 ; i <NBR_THREADS ; i++) {

        ret = pthread_create( &tid[i],NULL, lwp_pr, NULL);

        assert(ret == 0);

    }

    pause();

}

 

 

=================================================================

A SMALL DETAIL WITH SYS -c

=================================================================

A small detail with sys -c

Many obsolete or not implemented system calls map (#define) on sys_ni_syscall.

 

[root@fedora4 boot]# grep sys_ni_syscall System.map-2.6.11-prep

c0136278 T sys_ni_syscall

[root@fedora4 boot]# grep c0136278 System.map-2.6.11-prep

c0136278 W compat_sys_futex

c0136278 W compat_sys_get_mempolicy

c0136278 W compat_sys_keyctl

c0136278 W compat_sys_mbind

c0136278 W compat_sys_mq_getsetattr

c0136278 W compat_sys_mq_notify

c0136278 W compat_sys_mq_open

c0136278 W compat_sys_mq_timedreceive

c0136278 W compat_sys_mq_timedsend

c0136278 W compat_sys_set_mempolicy

c0136278 W compat_sys_socketcall

c0136278 W ppc_rtas

c0136278 W sys32_ipc

c0136278 W sys32_sysctl

c0136278 W sys_get_mempolicy

c0136278 W sys_mbind

c0136278 T sys_ni_syscall

c0136278 W sys_pciconfig_iobase

c0136278 W sys_pciconfig_read

c0136278 W sys_pciconfig_write

c0136278 W sys_set_mempolicy

 

crash> sys -c

NUM  SYSTEM CALL                FILE AND LINE NUMBER

  0  sys_restart_syscall        ../kernel/signal.c: 2037

  1  sys_exit                   ../kernel/exit.c: 870

  2  sys_fork                   ../arch/i386/kernel/process.c: 650

  3  sys_read                   ../fs/read_write.c: 313

  4  sys_write                  ../fs/read_write.c: 331

  5  sys_open                   ../fs/open.c: 938

  6  sys_close                  ../fs/open.c: 1018

  7  sys_waitpid                ../kernel/exit.c: 1533

  8  sys_creat                  ../fs/open.c: 974

  9  sys_link                   ../fs/namei.c: 2015

 10  sys_unlink                 ../fs/namei.c: 1863

 11  sys_execve                 ../arch/i386/kernel/process.c: 688

 12  sys_chdir                  ../fs/open.c: 519

 13  sys_time                   ../kernel/time.c: 59

 14  sys_mknod                  ../fs/namei.c: 1620

 15  sys_chmod                  ../fs/open.c: 635

 16  sys_lchown16               ../kernel/uid16.c: 26

 17  sys_set_mempolicy          ../kernel/sys_ni.c: 13 <--- in fact, "it is" sys_ni_syscall

 

crash> sys -c mempolicy

NUM  SYSTEM CALL                FILE AND LINE NUMBER

 17  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 31  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 32  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 35  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 44  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 53  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 56  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 58  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 98  sys_set_mempolicy          ../kernel/sys_ni.c: 13

112  sys_set_mempolicy          ../kernel/sys_ni.c: 13

127  sys_set_mempolicy          ../kernel/sys_ni.c: 13

130  sys_set_mempolicy          ../kernel/sys_ni.c: 13

137  sys_set_mempolicy          ../kernel/sys_ni.c: 13

167  sys_set_mempolicy          ../kernel/sys_ni.c: 13

188  sys_set_mempolicy          ../kernel/sys_ni.c: 13

189  sys_set_mempolicy          ../kernel/sys_ni.c: 13

223  sys_set_mempolicy          ../kernel/sys_ni.c: 13

251  sys_set_mempolicy          ../kernel/sys_ni.c: 13

273  sys_set_mempolicy          ../kernel/sys_ni.c: 13

274  sys_set_mempolicy          ../kernel/sys_ni.c: 13

275  sys_set_mempolicy          ../kernel/sys_ni.c: 13

276  sys_set_mempolicy          ../kernel/sys_ni.c: 13

283  sys_set_mempolicy          ../kernel/sys_ni.c: 13

285  sys_set_mempolicy          ../kernel/sys_ni.c: 13

 

Il would be more clear, il we could "force" sys_ni_syscall (of course we have the reference to sys_ni.c).

 

==============================================================================

Command irq x should be extended for recent systems

==============================================================================

irq only allowed between 0 and 15 (old PICs)

 

==============================================================================

repeat is not abortable in case of a mistake ?

==============================================================================

If i do repeat 2 xxxxxxx (instead of repeat -2 xxxxxx), i must kill crash

 

 

============================================================================================

MOUNT DOES NOT SHOW NAMESPACE

=============================================================================================

About mount : an option -n would be very interesting to show namespaces (when supported)

 

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