kernel/debug/kdb/kdb_bt.c

   1 /*
   2  * Kernel Debugger Architecture Independent Stack Traceback
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (c) 1999-2004 Silicon Graphics, Inc.  All Rights Reserved.
   9  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
  10  */
  11
  12 #include <linux/ctype.h>
  13 #include <linux/string.h>
  14 #include <linux/kernel.h>
  15 #include <linux/sched/signal.h>
  16 #include <linux/sched/debug.h>
  17 #include <linux/kdb.h>
  18 #include <linux/nmi.h>
  19 #include "kdb_private.h"
  20
  21
  22 static void kdb_show_stack(struct task_struct *p, void *addr)
  23 {
  24         kdb_trap_printk++;
  25
  26         if (!addr && kdb_task_has_cpu(p)) {
  27                 int old_lvl = console_loglevel;
  28
  29                 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
  30                 kdb_dump_stack_on_cpu(kdb_process_cpu(p));
  31                 console_loglevel = old_lvl;
  32         } else {
  33                 show_stack(p, addr, KERN_EMERG);
  34         }
  35
  36         kdb_trap_printk--;
  37 }
  38
  39 /*
  40  * kdb_bt
  41  *
  42  *      This function implements the 'bt' command.  Print a stack
  43  *      traceback.
  44  *
  45  *      bt [<address-expression>]       (addr-exp is for alternate stacks)
  46  *      btp <pid>                       Kernel stack for <pid>
  47  *      btt <address-expression>        Kernel stack for task structure at
  48  *                                      <address-expression>
  49  *      bta [DRSTCZEUIMA]               All useful processes, optionally
  50  *                                      filtered by state
  51  *      btc [<cpu>]                     The current process on one cpu,
  52  *                                      default is all cpus
  53  *
  54  *      bt <address-expression> refers to a address on the stack, that location
  55  *      is assumed to contain a return address.
  56  *
  57  *      btt <address-expression> refers to the address of a struct task.
  58  *
  59  * Inputs:
  60  *      argc    argument count
  61  *      argv    argument vector
  62  * Outputs:
  63  *      None.
  64  * Returns:
  65  *      zero for success, a kdb diagnostic if error
  66  * Locking:
  67  *      none.
  68  * Remarks:
  69  *      Backtrack works best when the code uses frame pointers.  But even
  70  *      without frame pointers we should get a reasonable trace.
  71  *
  72  *      mds comes in handy when examining the stack to do a manual traceback or
  73  *      to get a starting point for bt <address-expression>.
  74  */
  75
  76 static int
  77 kdb_bt1(struct task_struct *p, unsigned long mask, bool btaprompt)
  78 {
  79         char ch;
  80
  81         if (kdb_getarea(ch, (unsigned long)p) ||
  82             kdb_getarea(ch, (unsigned long)(p+1)-1))
  83                 return KDB_BADADDR;
  84         if (!kdb_task_state(p, mask))
  85                 return 0;
  86         kdb_printf("Stack traceback for pid %d\n", p->pid);
  87         kdb_ps1(p);
  88         kdb_show_stack(p, NULL);
  89         if (btaprompt) {
  90                 kdb_printf("Enter <q> to end, <cr> or <space> to continue:");
  91                 do {
  92                         ch = kdb_getchar();
  93                 } while (!strchr("\r\n q", ch));
  94                 kdb_printf("\n");
  95
  96                 /* reset the pager */
  97                 kdb_nextline = 1;
  98
  99                 if (ch == 'q')
 100                         return 1;
 101         }
 102         touch_nmi_watchdog();
 103         return 0;
 104 }
 105
 106 static void
 107 kdb_bt_cpu(unsigned long cpu)
 108 {
 109         struct task_struct *kdb_tsk;
 110
 111         if (cpu >= num_possible_cpus() || !cpu_online(cpu)) {
 112                 kdb_printf("WARNING: no process for cpu %ld\n", cpu);
 113                 return;
 114         }
 115
 116         /* If a CPU failed to round up we could be here */
 117         kdb_tsk = KDB_TSK(cpu);
 118         if (!kdb_tsk) {
 119                 kdb_printf("WARNING: no task for cpu %ld\n", cpu);
 120                 return;
 121         }
 122
 123         kdb_bt1(kdb_tsk, ~0UL, false);
 124 }
 125
 126 int
 127 kdb_bt(int argc, const char **argv)
 128 {
 129         int diag;
 130         int btaprompt = 1;
 131         int nextarg;
 132         unsigned long addr;
 133         long offset;
 134
 135         /* Prompt after each proc in bta */
 136         kdbgetintenv("BTAPROMPT", &btaprompt);
 137
 138         if (strcmp(argv[0], "bta") == 0) {
 139                 struct task_struct *g, *p;
 140                 unsigned long cpu;
 141                 unsigned long mask = kdb_task_state_string(argc ? argv[1] :
 142                                                            NULL);
 143                 if (argc == 0)
 144                         kdb_ps_suppressed();
 145                 /* Run the active tasks first */
 146                 for_each_online_cpu(cpu) {
 147                         p = kdb_curr_task(cpu);
 148                         if (kdb_bt1(p, mask, btaprompt))
 149                                 return 0;
 150                 }
 151                 /* Now the inactive tasks */
 152                 kdb_do_each_thread(g, p) {
 153                         if (KDB_FLAG(CMD_INTERRUPT))
 154                                 return 0;
 155                         if (task_curr(p))
 156                                 continue;
 157                         if (kdb_bt1(p, mask, btaprompt))
 158                                 return 0;
 159                 } kdb_while_each_thread(g, p);
 160         } else if (strcmp(argv[0], "btp") == 0) {
 161                 struct task_struct *p;
 162                 unsigned long pid;
 163                 if (argc != 1)
 164                         return KDB_ARGCOUNT;
 165                 diag = kdbgetularg((char *)argv[1], &pid);
 166                 if (diag)
 167                         return diag;
 168                 p = find_task_by_pid_ns(pid, &init_pid_ns);
 169                 if (p)
 170                         return kdb_bt1(p, ~0UL, false);
 171                 kdb_printf("No process with pid == %ld found\n", pid);
 172                 return 0;
 173         } else if (strcmp(argv[0], "btt") == 0) {
 174                 if (argc != 1)
 175                         return KDB_ARGCOUNT;
 176                 diag = kdbgetularg((char *)argv[1], &addr);
 177                 if (diag)
 178                         return diag;
 179                 return kdb_bt1((struct task_struct *)addr, ~0UL, false);
 180         } else if (strcmp(argv[0], "btc") == 0) {
 181                 unsigned long cpu = ~0;
 182                 if (argc > 1)
 183                         return KDB_ARGCOUNT;
 184                 if (argc == 1) {
 185                         diag = kdbgetularg((char *)argv[1], &cpu);
 186                         if (diag)
 187                                 return diag;
 188                 }
 189                 if (cpu != ~0) {
 190                         kdb_bt_cpu(cpu);
 191                 } else {
 192                         /*
 193                          * Recursive use of kdb_parse, do not use argv after
 194                          * this point.
 195                          */
 196                         argv = NULL;
 197                         kdb_printf("btc: cpu status: ");
 198                         kdb_parse("cpu\n");
 199                         for_each_online_cpu(cpu) {
 200                                 kdb_bt_cpu(cpu);
 201                                 touch_nmi_watchdog();
 202                         }
 203                 }
 204                 return 0;
 205         } else {
 206                 if (argc) {
 207                         nextarg = 1;
 208                         diag = kdbgetaddrarg(argc, argv, &nextarg, &addr,
 209                                              &offset, NULL);
 210                         if (diag)
 211                                 return diag;
 212                         kdb_show_stack(kdb_current_task, (void *)addr);
 213                         return 0;
 214                 } else {
 215                         return kdb_bt1(kdb_current_task, ~0UL, false);
 216                 }
 217         }
 218
 219         /* NOTREACHED */
 220         return 0;
 221 }