kdb_debugger.c

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/*
 * Created by: Jason Wessel <[email protected]>
 *
 * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/kdebug.h>
#include <linux/export.h>
#include <linux/hardirq.h>
#include "kdb_private.h"
#include "../debug_core.h"

/*
 * KDB interface to KGDB internals
 */
get_char_func kdb_poll_funcs[] = {
    dbg_io_get_char,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
};
EXPORT_SYMBOL_GPL(kdb_poll_funcs);

int kdb_poll_idx = 1;
EXPORT_SYMBOL_GPL(kdb_poll_idx);

static struct kgdb_state *kdb_ks;

int kdb_stub(struct kgdb_state *ks)
{
    int error = 0;
    kdb_bp_t *bp;
    unsigned long addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
    kdb_reason_t reason = KDB_REASON_OOPS;
    kdb_dbtrap_t db_result = KDB_DB_NOBPT;
    int i;

    kdb_ks = ks;
    if (KDB_STATE(REENTRY)) {
        reason = KDB_REASON_SWITCH;
        KDB_STATE_CLEAR(REENTRY);
        addr = instruction_pointer(ks->linux_regs);
    }
    ks->pass_exception = 0;
    if (atomic_read(&kgdb_setting_breakpoint))
        reason = KDB_REASON_KEYBOARD;

    if (in_nmi())
        reason = KDB_REASON_NMI;

    for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
        if ((bp->bp_enabled) && (bp->bp_addr == addr)) {
            reason = KDB_REASON_BREAK;
            db_result = KDB_DB_BPT;
            if (addr != instruction_pointer(ks->linux_regs))
                kgdb_arch_set_pc(ks->linux_regs, addr);
            break;
        }
    }
    if (reason == KDB_REASON_BREAK || reason == KDB_REASON_SWITCH) {
        for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
            if (bp->bp_free)
                continue;
            if (bp->bp_addr == addr) {
                bp->bp_delay = 1;
                bp->bp_delayed = 1;
    /*
     * SSBPT is set when the kernel debugger must single step a
     * task in order to re-establish an instruction breakpoint
     * which uses the instruction replacement mechanism.  It is
     * cleared by any action that removes the need to single-step
     * the breakpoint.
     */
                reason = KDB_REASON_BREAK;
                db_result = KDB_DB_BPT;
                KDB_STATE_SET(SSBPT);
                break;
            }
        }
    }

    if (reason != KDB_REASON_BREAK && ks->ex_vector == 0 &&
        ks->signo == SIGTRAP) {
        reason = KDB_REASON_SSTEP;
        db_result = KDB_DB_BPT;
    }
    /* Set initial kdb state variables */
    KDB_STATE_CLEAR(KGDB_TRANS);
    kdb_initial_cpu = atomic_read(&kgdb_active);
    kdb_current_task = kgdb_info[ks->cpu].task;
    kdb_current_regs = kgdb_info[ks->cpu].debuggerinfo;
    /* Remove any breakpoints as needed by kdb and clear single step */
    kdb_bp_remove();
    KDB_STATE_CLEAR(DOING_SS);
    KDB_STATE_CLEAR(DOING_SSB);
    KDB_STATE_SET(PAGER);
    /* zero out any offline cpu data */
    for_each_present_cpu(i) {
        if (!cpu_online(i)) {
            kgdb_info[i].debuggerinfo = NULL;
            kgdb_info[i].task = NULL;
        }
    }
    if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) {
        ks->pass_exception = 1;
        KDB_FLAG_SET(CATASTROPHIC);
    }
    if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
        KDB_STATE_CLEAR(SSBPT);
        KDB_STATE_CLEAR(DOING_SS);
    } else {
        /* Start kdb main loop */
        error = kdb_main_loop(KDB_REASON_ENTER, reason,
                      ks->err_code, db_result, ks->linux_regs);
    }
    /*
     * Upon exit from the kdb main loop setup break points and restart
     * the system based on the requested continue state
     */
    kdb_initial_cpu = -1;
    kdb_current_task = NULL;
    kdb_current_regs = NULL;
    KDB_STATE_CLEAR(PAGER);
    kdbnearsym_cleanup();
    if (error == KDB_CMD_KGDB) {
        if (KDB_STATE(DOING_KGDB))
            KDB_STATE_CLEAR(DOING_KGDB);
        return DBG_PASS_EVENT;
    }
    kdb_bp_install(ks->linux_regs);
    dbg_activate_sw_breakpoints();
    /* Set the exit state to a single step or a continue */
    if (KDB_STATE(DOING_SS))
        gdbstub_state(ks, "s");
    else
        gdbstub_state(ks, "c");

    KDB_FLAG_CLEAR(CATASTROPHIC);

    /* Invoke arch specific exception handling prior to system resume */
    kgdb_info[ks->cpu].ret_state = gdbstub_state(ks, "e");
    if (ks->pass_exception)
        kgdb_info[ks->cpu].ret_state = 1;
    if (error == KDB_CMD_CPU) {
        KDB_STATE_SET(REENTRY);
        /*
         * Force clear the single step bit because kdb emulates this
         * differently vs the gdbstub
         */
        kgdb_single_step = 0;
        dbg_deactivate_sw_breakpoints();
        return DBG_SWITCH_CPU_EVENT;
    }
    return kgdb_info[ks->cpu].ret_state;
}

void kdb_gdb_state_pass(char *buf)
{
    gdbstub_state(kdb_ks, buf);
}