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freebsd-skq/sys/kern/subr_kdb.c

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/*-
* Copyright (c) 2004 The FreeBSD Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_kdb.h"
#include "opt_stack.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/cons.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/smp.h>
#include <sys/stack.h>
#include <sys/sysctl.h>
#include <machine/kdb.h>
#include <machine/pcb.h>
#ifdef SMP
#include <machine/smp.h>
#endif
int kdb_active = 0;
static void *kdb_jmpbufp = NULL;
struct kdb_dbbe *kdb_dbbe = NULL;
static struct pcb kdb_pcb;
struct pcb *kdb_thrctx = NULL;
struct thread *kdb_thread = NULL;
struct trapframe *kdb_frame = NULL;
#ifdef BREAK_TO_DEBUGGER
#define KDB_BREAK_TO_DEBUGGER 1
#else
#define KDB_BREAK_TO_DEBUGGER 0
#endif
#ifdef ALT_BREAK_TO_DEBUGGER
#define KDB_ALT_BREAK_TO_DEBUGGER 1
#else
#define KDB_ALT_BREAK_TO_DEBUGGER 0
#endif
static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
KDB_BACKEND(null, NULL, NULL, NULL, NULL);
SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
0, kdb_sysctl_available, "A", "list of available KDB backends");
SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
0, kdb_sysctl_current, "A", "currently selected KDB backend");
SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
kdb_sysctl_enter, "I", "set to enter the debugger");
SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
kdb_sysctl_panic, "I", "set to panic the kernel");
SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
kdb_sysctl_trap, "I", "set to cause a page fault via data access");
SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_SECURE,
&kdb_break_to_debugger, 0, "Enable break to debugger");
SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_SECURE,
&kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
/*
* Flag to indicate to debuggers why the debugger was entered.
*/
const char * volatile kdb_why = KDB_WHY_UNSET;
static int
kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
{
struct kdb_dbbe **iter;
struct sbuf sbuf;
int error;
sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
SET_FOREACH(iter, kdb_dbbe_set) {
if ((*iter)->dbbe_active == 0)
sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
}
error = sbuf_finish(&sbuf);
sbuf_delete(&sbuf);
return (error);
}
static int
kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
{
char buf[16];
int error;
if (kdb_dbbe != NULL)
strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
else
*buf = '\0';
error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
if (error != 0 || req->newptr == NULL)
return (error);
if (kdb_active)
return (EBUSY);
return (kdb_dbbe_select(buf));
}
static int
kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
{
int error, i;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error == 0) {
i = 0;
error = sysctl_handle_int(oidp, &i, 0, req);
}
if (error != 0 || req->newptr == NULL)
return (error);
if (kdb_active)
return (EBUSY);
kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
return (0);
}
static int
kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
{
int error, i;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error == 0) {
i = 0;
error = sysctl_handle_int(oidp, &i, 0, req);
}
if (error != 0 || req->newptr == NULL)
return (error);
panic("kdb_sysctl_panic");
return (0);
}
static int
kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
{
int error, i;
int *addr = (int *)0x10;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error == 0) {
i = 0;
error = sysctl_handle_int(oidp, &i, 0, req);
}
if (error != 0 || req->newptr == NULL)
return (error);
return (*addr);
}
static int
kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
{
int error, i;
void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error == 0) {
i = 0;
error = sysctl_handle_int(oidp, &i, 0, req);
}
if (error != 0 || req->newptr == NULL)
return (error);
(*fp)(0x11111111, 0x22222222, 0x33333333);
return (0);
}
void
kdb_panic(const char *msg)
{
printf("KDB: panic\n");
panic("%s", msg);
}
void
kdb_reboot(void)
{
printf("KDB: reboot requested\n");
shutdown_nice(0);
}
/*
* Solaris implements a new BREAK which is initiated by a character sequence
* CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
* Remote Console.
*
* Note that this function may be called from almost anywhere, with interrupts
* disabled and with unknown locks held, so it must not access data other than
* its arguments. Its up to the caller to ensure that the state variable is
* consistent.
*/
#define KEY_CR 13 /* CR '\r' */
#define KEY_TILDE 126 /* ~ */
#define KEY_CRTLB 2 /* ^B */
#define KEY_CRTLP 16 /* ^P */
#define KEY_CRTLR 18 /* ^R */
/* States of th KDB "alternate break sequence" detecting state machine. */
enum {
KDB_ALT_BREAK_SEEN_NONE,
KDB_ALT_BREAK_SEEN_CR,
KDB_ALT_BREAK_SEEN_CR_TILDE,
};
int
kdb_break(void)
{
if (!kdb_break_to_debugger)
return (0);
kdb_enter(KDB_WHY_BREAK, "Break to debugger");
return (KDB_REQ_DEBUGGER);
}
static int
kdb_alt_break_state(int key, int *state)
{
int brk;
/* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
if (key == KEY_CR) {
*state = KDB_ALT_BREAK_SEEN_CR;
return (0);
}
brk = 0;
switch (*state) {
case KDB_ALT_BREAK_SEEN_CR:
*state = KDB_ALT_BREAK_SEEN_NONE;
if (key == KEY_TILDE)
*state = KDB_ALT_BREAK_SEEN_CR_TILDE;
break;
case KDB_ALT_BREAK_SEEN_CR_TILDE:
*state = KDB_ALT_BREAK_SEEN_NONE;
if (key == KEY_CRTLB)
brk = KDB_REQ_DEBUGGER;
else if (key == KEY_CRTLP)
brk = KDB_REQ_PANIC;
else if (key == KEY_CRTLR)
brk = KDB_REQ_REBOOT;
break;
case KDB_ALT_BREAK_SEEN_NONE:
default:
*state = KDB_ALT_BREAK_SEEN_NONE;
break;
}
return (brk);
}
static int
kdb_alt_break_internal(int key, int *state, int force_gdb)
{
int brk;
if (!kdb_alt_break_to_debugger)
return (0);
brk = kdb_alt_break_state(key, state);
switch (brk) {
case KDB_REQ_DEBUGGER:
if (force_gdb)
kdb_dbbe_select("gdb");
kdb_enter(KDB_WHY_BREAK, "Break to debugger");
break;
case KDB_REQ_PANIC:
if (force_gdb)
kdb_dbbe_select("gdb");
kdb_panic("Panic sequence on console");
break;
case KDB_REQ_REBOOT:
kdb_reboot();
break;
}
return (0);
}
int
kdb_alt_break(int key, int *state)
{
return (kdb_alt_break_internal(key, state, 0));
}
/*
* This variation on kdb_alt_break() is used only by dcons, which has its own
* configuration flag to force GDB use regardless of the global KDB
* configuration.
*/
int
kdb_alt_break_gdb(int key, int *state)
{
return (kdb_alt_break_internal(key, state, 1));
}
/*
* Print a backtrace of the calling thread. The backtrace is generated by
* the selected debugger, provided it supports backtraces. If no debugger
* is selected or the current debugger does not support backtraces, this
* function silently returns.
*/
void
kdb_backtrace(void)
{
if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
printf("KDB: stack backtrace:\n");
kdb_dbbe->dbbe_trace();
}
#ifdef STACK
else {
struct stack st;
printf("KDB: stack backtrace:\n");
stack_zero(&st);
stack_save(&st);
stack_print_ddb(&st);
}
#endif
}
/*
* Similar to kdb_backtrace() except that it prints a backtrace of an
* arbitrary thread rather than the calling thread.
*/
void
kdb_backtrace_thread(struct thread *td)
{
if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
kdb_dbbe->dbbe_trace_thread(td);
}
#ifdef STACK
else {
struct stack st;
printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
stack_zero(&st);
stack_save_td(&st, td);
stack_print_ddb(&st);
}
#endif
}
/*
* Set/change the current backend.
*/
int
kdb_dbbe_select(const char *name)
{
struct kdb_dbbe *be, **iter;
SET_FOREACH(iter, kdb_dbbe_set) {
be = *iter;
if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
kdb_dbbe = be;
return (0);
}
}
return (EINVAL);
}
/*
* Enter the currently selected debugger. If a message has been provided,
* it is printed first. If the debugger does not support the enter method,
* it is entered by using breakpoint(), which enters the debugger through
* kdb_trap(). The 'why' argument will contain a more mechanically usable
* string than 'msg', and is relied upon by DDB scripting to identify the
* reason for entering the debugger so that the right script can be run.
*/
void
kdb_enter(const char *why, const char *msg)
{
if (kdb_dbbe != NULL && kdb_active == 0) {
if (msg != NULL)
printf("KDB: enter: %s\n", msg);
kdb_why = why;
breakpoint();
kdb_why = KDB_WHY_UNSET;
}
}
/*
* Initialize the kernel debugger interface.
*/
void
kdb_init(void)
{
struct kdb_dbbe *be, **iter;
int cur_pri, pri;
kdb_active = 0;
kdb_dbbe = NULL;
cur_pri = -1;
SET_FOREACH(iter, kdb_dbbe_set) {
be = *iter;
pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
be->dbbe_active = (pri >= 0) ? 0 : -1;
if (pri > cur_pri) {
cur_pri = pri;
kdb_dbbe = be;
}
}
if (kdb_dbbe != NULL) {
printf("KDB: debugger backends:");
SET_FOREACH(iter, kdb_dbbe_set) {
be = *iter;
if (be->dbbe_active == 0)
printf(" %s", be->dbbe_name);
}
printf("\n");
printf("KDB: current backend: %s\n",
kdb_dbbe->dbbe_name);
}
}
/*
* Handle contexts.
*/
void *
kdb_jmpbuf(jmp_buf new)
{
void *old;
old = kdb_jmpbufp;
kdb_jmpbufp = new;
return (old);
}
void
kdb_reenter(void)
{
if (!kdb_active || kdb_jmpbufp == NULL)
return;
printf("KDB: reentering\n");
kdb_backtrace();
longjmp(kdb_jmpbufp, 1);
/* NOTREACHED */
}
/*
* Thread related support functions.
*/
struct pcb *
kdb_thr_ctx(struct thread *thr)
{
#if defined(SMP) && defined(KDB_STOPPEDPCB)
struct pcpu *pc;
#endif
if (thr == curthread)
return (&kdb_pcb);
#if defined(SMP) && defined(KDB_STOPPEDPCB)
STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
if (pc->pc_curthread == thr &&
CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
return (KDB_STOPPEDPCB(pc));
}
#endif
return (thr->td_pcb);
}
struct thread *
kdb_thr_first(void)
{
struct proc *p;
struct thread *thr;
p = LIST_FIRST(&allproc);
while (p != NULL) {
if (p->p_flag & P_INMEM) {
thr = FIRST_THREAD_IN_PROC(p);
if (thr != NULL)
return (thr);
}
p = LIST_NEXT(p, p_list);
}
return (NULL);
}
struct thread *
kdb_thr_from_pid(pid_t pid)
{
struct proc *p;
p = LIST_FIRST(&allproc);
while (p != NULL) {
if (p->p_flag & P_INMEM && p->p_pid == pid)
return (FIRST_THREAD_IN_PROC(p));
p = LIST_NEXT(p, p_list);
}
return (NULL);
}
struct thread *
kdb_thr_lookup(lwpid_t tid)
{
struct thread *thr;
thr = kdb_thr_first();
while (thr != NULL && thr->td_tid != tid)
thr = kdb_thr_next(thr);
return (thr);
}
struct thread *
kdb_thr_next(struct thread *thr)
{
struct proc *p;
p = thr->td_proc;
thr = TAILQ_NEXT(thr, td_plist);
do {
if (thr != NULL)
return (thr);
p = LIST_NEXT(p, p_list);
if (p != NULL && (p->p_flag & P_INMEM))
thr = FIRST_THREAD_IN_PROC(p);
} while (p != NULL);
return (NULL);
}
int
kdb_thr_select(struct thread *thr)
{
if (thr == NULL)
return (EINVAL);
kdb_thread = thr;
kdb_thrctx = kdb_thr_ctx(thr);
return (0);
}
/*
* Enter the debugger due to a trap.
*/
int
kdb_trap(int type, int code, struct trapframe *tf)
{
#ifdef SMP
cpuset_t other_cpus;
#endif
struct kdb_dbbe *be;
register_t intr;
int handled;
#ifdef SMP
int did_stop_cpus;
#endif
be = kdb_dbbe;
if (be == NULL || be->dbbe_trap == NULL)
return (0);
/* We reenter the debugger through kdb_reenter(). */
if (kdb_active)
return (0);
intr = intr_disable();
#ifdef SMP
if (!SCHEDULER_STOPPED()) {
other_cpus = all_cpus;
CPU_CLR(PCPU_GET(cpuid), &other_cpus);
stop_cpus_hard(other_cpus);
did_stop_cpus = 1;
} else
did_stop_cpus = 0;
#endif
kdb_active++;
kdb_frame = tf;
/* Let MD code do its thing first... */
kdb_cpu_trap(type, code);
makectx(tf, &kdb_pcb);
kdb_thr_select(curthread);
cngrab();
for (;;) {
handled = be->dbbe_trap(type, code);
if (be == kdb_dbbe)
break;
be = kdb_dbbe;
if (be == NULL || be->dbbe_trap == NULL)
break;
printf("Switching to %s back-end\n", be->dbbe_name);
}
cnungrab();
kdb_active--;
#ifdef SMP
if (did_stop_cpus)
restart_cpus(stopped_cpus);
#endif
intr_restore(intr);
return (handled);
}
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