kernel/debug/kdb/kdb_debugger.c

   1 /*
   2  * Created by: Jason Wessel <jason.wessel@windriver.com>
   3  *
   4  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
   5  *
   6  * This file is licensed under the terms of the GNU General Public
   7  * License version 2. This program is licensed "as is" without any
   8  * warranty of any kind, whether express or implied.
   9  */
  10
  11 #include <linux/kgdb.h>
  12 #include <linux/kdb.h>
  13 #include <linux/kdebug.h>
  14 #include "kdb_private.h"
  15 #include "../debug_core.h"
  16
  17 /*
  18  * KDB interface to KGDB internals
  19  */
  20 get_char_func kdb_poll_funcs[] = {
  21         dbg_io_get_char,
  22         NULL,
  23         NULL,
  24         NULL,
  25         NULL,
  26         NULL,
  27 };
  28 EXPORT_SYMBOL_GPL(kdb_poll_funcs);
  29
  30 int kdb_poll_idx = 1;
  31 EXPORT_SYMBOL_GPL(kdb_poll_idx);
  32
  33 int kdb_stub(struct kgdb_state *ks)
  34 {
  35         int error = 0;
  36         kdb_bp_t *bp;
  37         unsigned long addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
  38         kdb_reason_t reason = KDB_REASON_OOPS;
  39         kdb_dbtrap_t db_result = KDB_DB_NOBPT;
  40         int i;
  41
  42         if (KDB_STATE(REENTRY)) {
  43                 reason = KDB_REASON_SWITCH;
  44                 KDB_STATE_CLEAR(REENTRY);
  45                 addr = instruction_pointer(ks->linux_regs);
  46         }
  47         ks->pass_exception = 0;
  48         if (atomic_read(&kgdb_setting_breakpoint))
  49                 reason = KDB_REASON_KEYBOARD;
  50
  51         for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
  52                 if ((bp->bp_enabled) && (bp->bp_addr == addr)) {
  53                         reason = KDB_REASON_BREAK;
  54                         db_result = KDB_DB_BPT;
  55                         if (addr != instruction_pointer(ks->linux_regs))
  56                                 kgdb_arch_set_pc(ks->linux_regs, addr);
  57                         break;
  58                 }
  59         }
  60         if (reason == KDB_REASON_BREAK || reason == KDB_REASON_SWITCH) {
  61                 for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
  62                         if (bp->bp_free)
  63                                 continue;
  64                         if (bp->bp_addr == addr) {
  65                                 bp->bp_delay = 1;
  66                                 bp->bp_delayed = 1;
  67         /*
  68          * SSBPT is set when the kernel debugger must single step a
  69          * task in order to re-establish an instruction breakpoint
  70          * which uses the instruction replacement mechanism.  It is
  71          * cleared by any action that removes the need to single-step
  72          * the breakpoint.
  73          */
  74                                 reason = KDB_REASON_BREAK;
  75                                 db_result = KDB_DB_BPT;
  76                                 KDB_STATE_SET(SSBPT);
  77                                 break;
  78                         }
  79                 }
  80         }
  81
  82         if (reason != KDB_REASON_BREAK && ks->ex_vector == 0 &&
  83                 ks->signo == SIGTRAP) {
  84                 reason = KDB_REASON_SSTEP;
  85                 db_result = KDB_DB_BPT;
  86         }
  87         /* Set initial kdb state variables */
  88         KDB_STATE_CLEAR(KGDB_TRANS);
  89         kdb_initial_cpu = atomic_read(&kgdb_active);
  90         kdb_current_task = kgdb_info[ks->cpu].task;
  91         kdb_current_regs = kgdb_info[ks->cpu].debuggerinfo;
  92         /* Remove any breakpoints as needed by kdb and clear single step */
  93         kdb_bp_remove();
  94         KDB_STATE_CLEAR(DOING_SS);
  95         KDB_STATE_CLEAR(DOING_SSB);
  96         KDB_STATE_SET(PAGER);
  97         /* zero out any offline cpu data */
  98         for_each_present_cpu(i) {
  99                 if (!cpu_online(i)) {
 100                         kgdb_info[i].debuggerinfo = NULL;
 101                         kgdb_info[i].task = NULL;
 102                 }
 103         }
 104         if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) {
 105                 ks->pass_exception = 1;
 106                 KDB_FLAG_SET(CATASTROPHIC);
 107         }
 108         if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
 109                 KDB_STATE_CLEAR(SSBPT);
 110                 KDB_STATE_CLEAR(DOING_SS);
 111         } else {
 112                 /* Start kdb main loop */
 113                 error = kdb_main_loop(KDB_REASON_ENTER, reason,
 114                                       ks->err_code, db_result, ks->linux_regs);
 115         }
 116         /*
 117          * Upon exit from the kdb main loop setup break points and restart
 118          * the system based on the requested continue state
 119          */
 120         kdb_initial_cpu = -1;
 121         kdb_current_task = NULL;
 122         kdb_current_regs = NULL;
 123         KDB_STATE_CLEAR(PAGER);
 124         kdbnearsym_cleanup();
 125         if (error == KDB_CMD_KGDB) {
 126                 if (KDB_STATE(DOING_KGDB) || KDB_STATE(DOING_KGDB2)) {
 127         /*
 128          * This inteface glue which allows kdb to transition in into
 129          * the gdb stub.  In order to do this the '?' or '' gdb serial
 130          * packet response is processed here.  And then control is
 131          * passed to the gdbstub.
 132          */
 133                         if (KDB_STATE(DOING_KGDB))
 134                                 gdbstub_state(ks, "?");
 135                         else
 136                                 gdbstub_state(ks, "");
 137                         KDB_STATE_CLEAR(DOING_KGDB);
 138                         KDB_STATE_CLEAR(DOING_KGDB2);
 139                 }
 140                 return DBG_PASS_EVENT;
 141         }
 142         kdb_bp_install(ks->linux_regs);
 143         dbg_activate_sw_breakpoints();
 144         /* Set the exit state to a single step or a continue */
 145         if (KDB_STATE(DOING_SS))
 146                 gdbstub_state(ks, "s");
 147         else
 148                 gdbstub_state(ks, "c");
 149
 150         KDB_FLAG_CLEAR(CATASTROPHIC);
 151
 152         /* Invoke arch specific exception handling prior to system resume */
 153         kgdb_info[ks->cpu].ret_state = gdbstub_state(ks, "e");
 154         if (ks->pass_exception)
 155                 kgdb_info[ks->cpu].ret_state = 1;
 156         if (error == KDB_CMD_CPU) {
 157                 KDB_STATE_SET(REENTRY);
 158                 /*
 159                  * Force clear the single step bit because kdb emulates this
 160                  * differently vs the gdbstub
 161                  */
 162                 kgdb_single_step = 0;
 163                 dbg_deactivate_sw_breakpoints();
 164                 return DBG_SWITCH_CPU_EVENT;
 165         }
 166         return kgdb_info[ks->cpu].ret_state;
 167 }
 168