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   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 };
  24
  25 int kdb_stub(struct kgdb_state *ks)
  26 {
  27         int error = 0;
  28         kdb_bp_t *bp;
  29         unsigned long addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
  30         kdb_reason_t reason = KDB_REASON_OOPS;
  31         kdb_dbtrap_t db_result = KDB_DB_NOBPT;
  32         int i;
  33
  34         if (KDB_STATE(REENTRY)) {
  35                 reason = KDB_REASON_SWITCH;
  36                 KDB_STATE_CLEAR(REENTRY);
  37                 addr = instruction_pointer(ks->linux_regs);
  38         }
  39         ks->pass_exception = 0;
  40         if (atomic_read(&kgdb_setting_breakpoint))
  41                 reason = KDB_REASON_KEYBOARD;
  42
  43         for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
  44                 if ((bp->bp_enabled) && (bp->bp_addr == addr)) {
  45                         reason = KDB_REASON_BREAK;
  46                         db_result = KDB_DB_BPT;
  47                         if (addr != instruction_pointer(ks->linux_regs))
  48                                 kgdb_arch_set_pc(ks->linux_regs, addr);
  49                         break;
  50                 }
  51         }
  52         if (reason == KDB_REASON_BREAK || reason == KDB_REASON_SWITCH) {
  53                 for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
  54                         if (bp->bp_free)
  55                                 continue;
  56                         if (bp->bp_addr == addr) {
  57                                 bp->bp_delay = 1;
  58                                 bp->bp_delayed = 1;
  59         /*
  60          * SSBPT is set when the kernel debugger must single step a
  61          * task in order to re-establish an instruction breakpoint
  62          * which uses the instruction replacement mechanism.  It is
  63          * cleared by any action that removes the need to single-step
  64          * the breakpoint.
  65          */
  66                                 reason = KDB_REASON_BREAK;
  67                                 db_result = KDB_DB_BPT;
  68                                 KDB_STATE_SET(SSBPT);
  69                                 break;
  70                         }
  71                 }
  72         }
  73
  74         if (reason != KDB_REASON_BREAK && ks->ex_vector == 0 &&
  75                 ks->signo == SIGTRAP) {
  76                 reason = KDB_REASON_SSTEP;
  77                 db_result = KDB_DB_BPT;
  78         }
  79         /* Set initial kdb state variables */
  80         KDB_STATE_CLEAR(KGDB_TRANS);
  81         kdb_initial_cpu = ks->cpu;
  82         kdb_current_task = kgdb_info[ks->cpu].task;
  83         kdb_current_regs = kgdb_info[ks->cpu].debuggerinfo;
  84         /* Remove any breakpoints as needed by kdb and clear single step */
  85         kdb_bp_remove();
  86         KDB_STATE_CLEAR(DOING_SS);
  87         KDB_STATE_CLEAR(DOING_SSB);
  88         /* zero out any offline cpu data */
  89         for_each_present_cpu(i) {
  90                 if (!cpu_online(i)) {
  91                         kgdb_info[i].debuggerinfo = NULL;
  92                         kgdb_info[i].task = NULL;
  93                 }
  94         }
  95         if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) {
  96                 ks->pass_exception = 1;
  97                 KDB_FLAG_SET(CATASTROPHIC);
  98         }
  99         kdb_initial_cpu = ks->cpu;
 100         if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
 101                 KDB_STATE_CLEAR(SSBPT);
 102                 KDB_STATE_CLEAR(DOING_SS);
 103         } else {
 104                 /* Start kdb main loop */
 105                 error = kdb_main_loop(KDB_REASON_ENTER, reason,
 106                                       ks->err_code, db_result, ks->linux_regs);
 107         }
 108         /*
 109          * Upon exit from the kdb main loop setup break points and restart
 110          * the system based on the requested continue state
 111          */
 112         kdb_initial_cpu = -1;
 113         kdb_current_task = NULL;
 114         kdb_current_regs = NULL;
 115         kdbnearsym_cleanup();
 116         if (error == KDB_CMD_KGDB) {
 117                 if (KDB_STATE(DOING_KGDB) || KDB_STATE(DOING_KGDB2)) {
 118         /*
 119          * This inteface glue which allows kdb to transition in into
 120          * the gdb stub.  In order to do this the '?' or '' gdb serial
 121          * packet response is processed here.  And then control is
 122          * passed to the gdbstub.
 123          */
 124                         if (KDB_STATE(DOING_KGDB))
 125                                 gdbstub_state(ks, "?");
 126                         else
 127                                 gdbstub_state(ks, "");
 128                         KDB_STATE_CLEAR(DOING_KGDB);
 129                         KDB_STATE_CLEAR(DOING_KGDB2);
 130                 }
 131                 return DBG_PASS_EVENT;
 132         }
 133         kdb_bp_install(ks->linux_regs);
 134         dbg_activate_sw_breakpoints();
 135         /* Set the exit state to a single step or a continue */
 136         if (KDB_STATE(DOING_SS))
 137                 gdbstub_state(ks, "s");
 138         else
 139                 gdbstub_state(ks, "c");
 140
 141         KDB_FLAG_CLEAR(CATASTROPHIC);
 142
 143         /* Invoke arch specific exception handling prior to system resume */
 144         kgdb_info[ks->cpu].ret_state = gdbstub_state(ks, "e");
 145         if (ks->pass_exception)
 146                 kgdb_info[ks->cpu].ret_state = 1;
 147         if (error == KDB_CMD_CPU) {
 148                 KDB_STATE_SET(REENTRY);
 149                 /*
 150                  * Force clear the single step bit because kdb emulates this
 151                  * differently vs the gdbstub
 152                  */
 153                 kgdb_single_step = 0;
 154                 dbg_deactivate_sw_breakpoints();
 155                 return DBG_SWITCH_CPU_EVENT;
 156         }
 157         return kgdb_info[ks->cpu].ret_state;
 158 }
 159