kdb_bt.c

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/*
 * Kernel Debugger Architecture Independent Stack Traceback
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 1999-2004 Silicon Graphics, Inc.  All Rights Reserved.
 * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
 */

#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/kdb.h>
#include <linux/nmi.h>
#include "kdb_private.h"


static void kdb_show_stack(struct task_struct *p, void *addr)
{
    int old_lvl = console_loglevel;
    console_loglevel = 15;
    kdb_trap_printk++;
    kdb_set_current_task(p);
    if (addr) {
        show_stack((struct task_struct *)p, addr);
    } else if (kdb_current_regs) {
#ifdef CONFIG_X86
        show_stack(p, &kdb_current_regs->sp);
#else
        show_stack(p, NULL);
#endif
    } else {
        show_stack(p, NULL);
    }
    console_loglevel = old_lvl;
    kdb_trap_printk--;
}

/*
 * kdb_bt
 *
 *  This function implements the 'bt' command.  Print a stack
 *  traceback.
 *
 *  bt [<address-expression>]   (addr-exp is for alternate stacks)
 *  btp <pid>           Kernel stack for <pid>
 *  btt <address-expression>    Kernel stack for task structure at
 *                  <address-expression>
 *  bta [DRSTCZEUIMA]       All useful processes, optionally
 *                  filtered by state
 *  btc [<cpu>]         The current process on one cpu,
 *                  default is all cpus
 *
 *  bt <address-expression> refers to a address on the stack, that location
 *  is assumed to contain a return address.
 *
 *  btt <address-expression> refers to the address of a struct task.
 *
 * Inputs:
 *  argc    argument count
 *  argv    argument vector
 * Outputs:
 *  None.
 * Returns:
 *  zero for success, a kdb diagnostic if error
 * Locking:
 *  none.
 * Remarks:
 *  Backtrack works best when the code uses frame pointers.  But even
 *  without frame pointers we should get a reasonable trace.
 *
 *  mds comes in handy when examining the stack to do a manual traceback or
 *  to get a starting point for bt <address-expression>.
 */

static int
kdb_bt1(struct task_struct *p, unsigned long mask,
    int argcount, int btaprompt)
{
    char buffer[2];
    if (kdb_getarea(buffer[0], (unsigned long)p) ||
        kdb_getarea(buffer[0], (unsigned long)(p+1)-1))
        return KDB_BADADDR;
    if (!kdb_task_state(p, mask))
        return 0;
    kdb_printf("Stack traceback for pid %d\n", p->pid);
    kdb_ps1(p);
    kdb_show_stack(p, NULL);
    if (btaprompt) {
        kdb_getstr(buffer, sizeof(buffer),
               "Enter <q> to end, <cr> to continue:");
        if (buffer[0] == 'q') {
            kdb_printf("\n");
            return 1;
        }
    }
    touch_nmi_watchdog();
    return 0;
}

int
kdb_bt(int argc, const char **argv)
{
    int diag;
    int argcount = 5;
    int btaprompt = 1;
    int nextarg;
    unsigned long addr;
    long offset;

    /* Prompt after each proc in bta */
    kdbgetintenv("BTAPROMPT", &btaprompt);

    if (strcmp(argv[0], "bta") == 0) {
        struct task_struct *g, *p;
        unsigned long cpu;
        unsigned long mask = kdb_task_state_string(argc ? argv[1] :
                               NULL);
        if (argc == 0)
            kdb_ps_suppressed();
        /* Run the active tasks first */
        for_each_online_cpu(cpu) {
            p = kdb_curr_task(cpu);
            if (kdb_bt1(p, mask, argcount, btaprompt))
                return 0;
        }
        /* Now the inactive tasks */
        kdb_do_each_thread(g, p) {
            if (KDB_FLAG(CMD_INTERRUPT))
                return 0;
            if (task_curr(p))
                continue;
            if (kdb_bt1(p, mask, argcount, btaprompt))
                return 0;
        } kdb_while_each_thread(g, p);
    } else if (strcmp(argv[0], "btp") == 0) {
        struct task_struct *p;
        unsigned long pid;
        if (argc != 1)
            return KDB_ARGCOUNT;
        diag = kdbgetularg((char *)argv[1], &pid);
        if (diag)
            return diag;
        p = find_task_by_pid_ns(pid, &init_pid_ns);
        if (p) {
            kdb_set_current_task(p);
            return kdb_bt1(p, ~0UL, argcount, 0);
        }
        kdb_printf("No process with pid == %ld found\n", pid);
        return 0;
    } else if (strcmp(argv[0], "btt") == 0) {
        if (argc != 1)
            return KDB_ARGCOUNT;
        diag = kdbgetularg((char *)argv[1], &addr);
        if (diag)
            return diag;
        kdb_set_current_task((struct task_struct *)addr);
        return kdb_bt1((struct task_struct *)addr, ~0UL, argcount, 0);
    } else if (strcmp(argv[0], "btc") == 0) {
        unsigned long cpu = ~0;
        struct task_struct *save_current_task = kdb_current_task;
        char buf[80];
        if (argc > 1)
            return KDB_ARGCOUNT;
        if (argc == 1) {
            diag = kdbgetularg((char *)argv[1], &cpu);
            if (diag)
                return diag;
        }
        /* Recursive use of kdb_parse, do not use argv after
         * this point */
        argv = NULL;
        if (cpu != ~0) {
            if (cpu >= num_possible_cpus() || !cpu_online(cpu)) {
                kdb_printf("no process for cpu %ld\n", cpu);
                return 0;
            }
            sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
            kdb_parse(buf);
            return 0;
        }
        kdb_printf("btc: cpu status: ");
        kdb_parse("cpu\n");
        for_each_online_cpu(cpu) {
            sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
            kdb_parse(buf);
            touch_nmi_watchdog();
        }
        kdb_set_current_task(save_current_task);
        return 0;
    } else {
        if (argc) {
            nextarg = 1;
            diag = kdbgetaddrarg(argc, argv, &nextarg, &addr,
                         &offset, NULL);
            if (diag)
                return diag;
            kdb_show_stack(kdb_current_task, (void *)addr);
            return 0;
        } else {
            return kdb_bt1(kdb_current_task, ~0UL, argcount, 0);
        }
    }

    /* NOTREACHED */
    return 0;
}