// SPDX-License-Identifier: GPL-2.0-only
/*
* Kernel Debug Core
*
* Maintainer: Jason Wessel <[email protected]>
*
* Copyright (C) 2000-2001 VERITAS Software Corporation.
* Copyright (C) 2002-2004 Timesys Corporation
* Copyright (C) 2003-2004 Amit S. Kale <[email protected]>
* Copyright (C) 2004 Pavel Machek <[email protected]>
* Copyright (C) 2004-2006 Tom Rini <[email protected]>
* Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
* Copyright (C) 2005-2009 Wind River Systems, Inc.
* Copyright (C) 2007 MontaVista Software, Inc.
* Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <[email protected]>
*
* Contributors at various stages not listed above:
* Jason Wessel ( [email protected] )
* George Anzinger <[email protected]>
* Anurekh Saxena ([email protected])
* Lake Stevens Instrument Division (Glenn Engel)
* Jim Kingdon, Cygnus Support.
*
* Original KGDB stub: David Grothe <[email protected]>,
* Tigran Aivazian <[email protected]>
*/
#define pr_fmt(fmt) "KGDB: " fmt
#include <linux/pid_namespace.h>
#include <linux/clocksource.h>
#include <linux/serial_core.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/console.h>
#include <linux/threads.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/nmi.h>
#include <linux/pid.h>
#include <linux/smp.h>
#include <linux/mm.h>
#include <linux/rcupdate.h>
#include <linux/irq.h>
#include <linux/security.h>
#include <asm/cacheflush.h>
#include <asm/byteorder.h>
#include <linux/atomic.h>
#include "debug_core.h"
static int kgdb_break_asap;
struct debuggerinfo_struct kgdb_info[NR_CPUS];
/* kgdb_connected - Is a host GDB connected to us? */
int kgdb_connected;
EXPORT_SYMBOL_GPL(kgdb_connected);
/* All the KGDB handlers are installed */
int kgdb_io_module_registered;
/* Guard for recursive entry */
static int exception_level;
struct kgdb_io *dbg_io_ops;
static DEFINE_SPINLOCK(kgdb_registration_lock);
/* Action for the reboot notifier, a global allow kdb to change it */
static int kgdbreboot;
/* kgdb console driver is loaded */
static int kgdb_con_registered;
/* determine if kgdb console output should be used */
static int kgdb_use_con;
/* Flag for alternate operations for early debugging */
bool dbg_is_early = true;
/* Next cpu to become the master debug core */
int dbg_switch_cpu;
/* Use kdb or gdbserver mode */
int dbg_kdb_mode = 1;
module_param(kgdb_use_con, int, 0644);
module_param(kgdbreboot, int, 0644);
/*
* Holds information about breakpoints in a kernel. These breakpoints are
* added and removed by gdb.
*/
static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = {
[0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
};
/*
* The CPU# of the active CPU, or -1 if none:
*/
atomic_t kgdb_active = ATOMIC_INIT(-1);
EXPORT_SYMBOL_GPL(kgdb_active);
static DEFINE_RAW_SPINLOCK(dbg_master_lock);
static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
/*
* We use NR_CPUs not PERCPU, in case kgdb is used to debug early
* bootup code (which might not have percpu set up yet):
*/
static atomic_t masters_in_kgdb;
static atomic_t slaves_in_kgdb;
atomic_t kgdb_setting_breakpoint;
struct task_struct *kgdb_usethread;
struct task_struct *kgdb_contthread;
int kgdb_single_step;
static pid_t kgdb_sstep_pid;
/* to keep track of the CPU which is doing the single stepping*/
atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
/*
* If you are debugging a problem where roundup (the collection of
* all other CPUs) is a problem [this should be extremely rare],
* then use the nokgdbroundup option to avoid roundup. In that case
* the other CPUs might interfere with your debugging context, so
* use this with care:
*/
static int kgdb_do_roundup = 1;
static int __init opt_nokgdbroundup(char *str)
{
kgdb_do_roundup = 0;
return 0;
}
early_param("nokgdbroundup", opt_nokgdbroundup);
/*
* Finally, some KGDB code :-)
*/
/*
* Weak aliases for breakpoint management,
* can be overridden by architectures when needed:
*/
int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
BREAK_INSTR_SIZE);
if (err)
return err;
err = copy_to_kernel_nofault((char *)bpt->bpt_addr,
arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
return err;
}
NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint);
int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
return copy_to_kernel_nofault((char *)bpt->bpt_addr,
(char *)bpt->saved_instr, BREAK_INSTR_SIZE);
}
NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint);
int __weak kgdb_validate_break_address(unsigned long addr)
{
struct kgdb_bkpt tmp;
int err;
if (kgdb_within_blocklist(addr))
return -EINVAL;
/* Validate setting the breakpoint and then removing it. If the
* remove fails, the kernel needs to emit a bad message because we
* are deep trouble not being able to put things back the way we
* found them.
*/
tmp.bpt_addr = addr;
err = kgdb_arch_set_breakpoint(&tmp);
if (err)
return err;
err = kgdb_arch_remove_breakpoint(&tmp);
if (err)
pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
addr);
return err;
}
unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
{
return instruction_pointer(regs);
}
NOKPROBE_SYMBOL(kgdb_arch_pc);
int __weak kgdb_arch_init(void)
{
return 0;
}
int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
{
return 0;
}
NOKPROBE_SYMBOL(kgdb_skipexception);
#ifdef CONFIG_SMP
/*
* Default (weak) implementation for kgdb_roundup_cpus
*/
void __weak kgdb_call_nmi_hook(void *ignored)
{
/*
* NOTE: get_irq_regs() is supposed to get the registers from
* before the IPI interrupt happened and so is supposed to
* show where the processor was. In some situations it's
* possible we might be called without an IPI, so it might be
* safer to figure out how to make kgdb_breakpoint() work
* properly here.
*/
kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
}
NOKPROBE_SYMBOL(kgdb_call_nmi_hook);
static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) =
CSD_INIT(kgdb_call_nmi_hook, NULL);
void __weak kgdb_roundup_cpus(void)
{
call_single_data_t *csd;
int this_cpu = raw_smp_processor_id();
int cpu;
int ret;
for_each_online_cpu(cpu) {
/* No need to roundup ourselves */
if (cpu == this_cpu)
continue;
csd = &per_cpu(kgdb_roundup_csd, cpu);
/*
* If it didn't round up last time, don't try again
* since smp_call_function_single_async() will block.
*
* If rounding_up is false then we know that the
* previous call must have at least started and that
* means smp_call_function_single_async() won't block.
*/
if (kgdb_info[cpu].rounding_up)
continue;
kgdb_info[cpu].rounding_up = true;
ret = smp_call_function_single_async(cpu, csd);
if (ret)
kgdb_info[cpu].rounding_up = false;
}
}
NOKPROBE_SYMBOL(kgdb_roundup_cpus);
#endif
/*
* Some architectures need cache flushes when we set/clear a
* breakpoint:
*/
static void kgdb_flush_swbreak_addr(unsigned long addr)
{
if (!CACHE_FLUSH_IS_SAFE)
return;
/* Force flush instruction cache if it was outside the mm */
flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}
NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr);
/*
* SW breakpoint management:
*/
int dbg_activate_sw_breakpoints(void)
{
int error;
int ret = 0;
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_SET)
continue;
error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
if (error) {
ret = error;
pr_info("BP install failed: %lx\n",
kgdb_break[i].bpt_addr);
continue;
}
kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
kgdb_break[i].state = BP_ACTIVE;
}
return ret;
}
NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
int dbg_set_sw_break(unsigned long addr)
{
int err = kgdb_validate_break_address(addr);
int breakno = -1;
int i;
if (err)
return err;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_SET) &&
(kgdb_break[i].bpt_addr == addr))
return -EEXIST;
}
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_REMOVED &&
kgdb_break[i].bpt_addr == addr) {
breakno = i;
break;
}
}
if (breakno == -1) {
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_UNDEFINED) {
breakno = i;
break;
}
}
}
if (breakno == -1)
return -E2BIG;
kgdb_break[breakno].state = BP_SET;
kgdb_break[breakno].type = BP_BREAKPOINT;
kgdb_break[breakno].bpt_addr = addr;
return 0;
}
int dbg_deactivate_sw_breakpoints(void)
{
int error;
int ret = 0;
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_ACTIVE)
continue;
error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
if (error) {
pr_info("BP remove failed: %lx\n",
kgdb_break[i].bpt_addr);
ret = error;
}
kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
kgdb_break[i].state = BP_SET;
}
return ret;
}
NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
int dbg_remove_sw_break(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_SET) &&
(kgdb_break[i].bpt_addr == addr)) {
kgdb_break[i].state = BP_REMOVED;
return 0;
}
}
return -ENOENT;
}
int kgdb_isremovedbreak(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if ((kgdb_break[i].state == BP_REMOVED) &&
(kgdb_break[i].bpt_addr == addr))
return 1;
}
return 0;
}
int kgdb_has_hit_break(unsigned long addr)
{
int i;
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state == BP_ACTIVE &&
kgdb_break[i].bpt_addr == addr)
return 1;
}
return 0;
}
int dbg_remove_all_break(void)
{
int error;
int i;
/* Clear memory breakpoints. */
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (kgdb_break[i].state != BP_ACTIVE)
goto setundefined;
error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
if (error)
pr_err("breakpoint remove failed: %lx\n",
kgdb_break[i].bpt_addr);
setundefined:
kgdb_break[i].state = BP_UNDEFINED;
}
/* Clear hardware breakpoints. */
if (arch_kgdb_ops.remove_all_hw_break)
arch_kgdb_ops.remove_all_hw_break();
return 0;
}
void kgdb_free_init_mem(void)
{
int i;
/* Clear init memory breakpoints. */
for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
kgdb_break[i].state = BP_UNDEFINED;
}
}
#ifdef CONFIG_KGDB_KDB
void kdb_dump_stack_on_cpu(int cpu)
{
if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
dump_stack();
return;
}
if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
cpu);
return;
}
/*
* In general, architectures don't support dumping the stack of a
* "running" process that's not the current one. From the point of
* view of the Linux, kernel processes that are looping in the kgdb
* slave loop are still "running". There's also no API (that actually
* works across all architectures) that can do a stack crawl based
* on registers passed as a parameter.
*
* Solve this conundrum by asking slave CPUs to do the backtrace
* themselves.
*/
kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
cpu_relax();
}
#endif
/*
* Return true if there is a valid kgdb I/O module. Also if no
* debugger is attached a message can be printed to the console about
* waiting for the debugger to attach.
*
* The print_wait argument is only to be true when called from inside
* the core kgdb_handle_exception, because it will wait for the
* debugger to attach.
*/
static int kgdb_io_ready(int print_wait)
{
if (!dbg_io_ops)
return 0;
if (kgdb_connected)
return 1;
if (atomic_read(&kgdb_setting_breakpoint))
return 1;
if (print_wait) {
#ifdef CONFIG_KGDB_KDB
if (!dbg_kdb_mode)
pr_crit("waiting... or $3#33 for KDB\n");
#else
pr_crit("Waiting for remote debugger\n");
#endif
}
return 1;
}
NOKPROBE_SYMBOL(kgdb_io_ready);
static int kgdb_reenter_check(struct kgdb_state *ks)
{
unsigned long addr;
if (atomic_read(&kgdb_active) != raw_smp_processor_id())
return 0;
/* Panic on recursive debugger calls: */
exception_level++;
addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
dbg_deactivate_sw_breakpoints();
/*
* If the break point removed ok at the place exception
* occurred, try to recover and print a warning to the end
* user because the user planted a breakpoint in a place that
* KGDB needs in order to function.
*/
if (dbg_remove_sw_break(addr) == 0) {
exception_level = 0;
kgdb_skipexception(ks->ex_vector, ks->linux_regs);
dbg_activate_sw_breakpoints();
pr_crit("re-enter error: breakpoint removed %lx\n", addr);
WARN_ON_ONCE(1);
return 1;
}
dbg_remove_all_break();
kgdb_skipexception(ks->ex_vector, ks->linux_regs);
if (exception_level > 1) {
dump_stack();
kgdb_io_module_registered = false;
panic("Recursive entry to debugger");
}
pr_crit("re-enter exception: ALL breakpoints killed\n");
#ifdef CONFIG_KGDB_KDB
/* Allow kdb to debug itself one level */
return 0;
#endif
dump_stack();
panic("Recursive entry to debugger");
return 1;
}
NOKPROBE_SYMBOL(kgdb_reenter_check);
static void dbg_touch_watchdogs(void)
{
touch_softlockup_watchdog_sync();
clocksource_touch_watchdog();
rcu_cpu_stall_reset();
}
NOKPROBE_SYMBOL(dbg_touch_watchdogs);
static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
int exception_state)
{
unsigned long flags;
int sstep_tries = 100;
int error;
int cpu;
int trace_on = 0;
int online_cpus = num_online_cpus();
u64 time_left;
kgdb_info[ks->cpu].enter_kgdb++;
kgdb_info[ks->cpu].exception_state |= exception_state;
if (exception_state == DCPU_WANT_MASTER)
atomic_inc(&masters_in_kgdb);
else
atomic_inc(&slaves_in_kgdb);
if (arch_kgdb_ops.disable_hw_break)
arch_kgdb_ops.disable_hw_break(regs);
acquirelock:
rcu_read_lock();
/*
* Interrupts will be restored by the 'trap return' code, except when
* single stepping.
*/
local_irq_save(flags);
cpu = ks->cpu;
kgdb_info[cpu].debuggerinfo = regs;
kgdb_info[cpu].task = current;
kgdb_info[cpu].ret_state = 0;
kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
/* Make sure the above info reaches the primary CPU */
smp_mb();
if (exception_level == 1) {
if (raw_spin_trylock(&dbg_master_lock))
atomic_xchg(&kgdb_active, cpu);
goto cpu_master_loop;
}
/*
* CPU will loop if it is a slave or request to become a kgdb
* master cpu and acquire the kgdb_active lock:
*/
while (1) {
cpu_loop:
if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
goto cpu_master_loop;
} else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
if (raw_spin_trylock(&dbg_master_lock)) {
atomic_xchg(&kgdb_active, cpu);
break;
}
} else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
dump_stack();
kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
} else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
if (!raw_spin_is_locked(&dbg_slave_lock))
goto return_normal;
} else {
return_normal:
/* Return to normal operation by executing any
* hw breakpoint fixup.
*/
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
smp_mb__before_atomic();
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
return 0;
}
cpu_relax();
}
/*
* For single stepping, try to only enter on the processor
* that was single stepping. To guard against a deadlock, the
* kernel will only try for the value of sstep_tries before
* giving up and continuing on.
*/
if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
(kgdb_info[cpu].task &&
kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
atomic_set(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
goto acquirelock;
}
if (!kgdb_io_ready(1)) {
kgdb_info[cpu].ret_state = 1;
goto kgdb_restore; /* No I/O connection, resume the system */
}
/*
* Don't enter if we have hit a removed breakpoint.
*/
if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
goto kgdb_restore;
atomic_inc(&ignore_console_lock_warning);
/* Call the I/O driver's pre_exception routine */
if (dbg_io_ops->pre_exception)
dbg_io_ops->pre_exception();
/*
* Get the passive CPU lock which will hold all the non-primary
* CPU in a spin state while the debugger is active
*/
if (!kgdb_single_step)
raw_spin_lock(&dbg_slave_lock);
#ifdef CONFIG_SMP
/* If send_ready set, slaves are already waiting */
if (ks->send_ready)
atomic_set(ks->send_ready, 1);
/* Signal the other CPUs to enter kgdb_wait() */
else if ((!kgdb_single_step) && kgdb_do_roundup)
kgdb_roundup_cpus();
#endif
/*
* Wait for the other CPUs to be notified and be waiting for us:
*/
time_left = MSEC_PER_SEC;
while (kgdb_do_roundup && --time_left &&
(atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
online_cpus)
udelay(1000);
if (!time_left)
pr_crit("Timed out waiting for secondary CPUs.\n");
/*
* At this point the primary processor is completely
* in the debugger and all secondary CPUs are quiescent
*/
dbg_deactivate_sw_breakpoints();
kgdb_single_step = 0;
kgdb_contthread = current;
exception_level = 0;
trace_on = tracing_is_on();
if (trace_on)
tracing_off();
while (1) {
cpu_master_loop:
if (dbg_kdb_mode) {
kgdb_connected = 1;
error = kdb_stub(ks);
if (error == -1)
continue;
kgdb_connected = 0;
} else {
/*
* This is a brutal way to interfere with the debugger
* and prevent gdb being used to poke at kernel memory.
* This could cause trouble if lockdown is applied when
* there is already an active gdb session. For now the
* answer is simply "don't do that". Typically lockdown
* *will* be applied before the debug core gets started
* so only developers using kgdb for fairly advanced
* early kernel debug can be biten by this. Hopefully
* they are sophisticated enough to take care of
* themselves, especially with help from the lockdown
* message printed on the console!
*/
if (security_locked_down(LOCKDOWN_DBG_WRITE_KERNEL)) {
if (IS_ENABLED(CONFIG_KGDB_KDB)) {
/* Switch back to kdb if possible... */
dbg_kdb_mode = 1;
continue;
} else {
/* ... otherwise just bail */
break;
}
}
error = gdb_serial_stub(ks);
}
if (error == DBG_PASS_EVENT) {
dbg_kdb_mode = !dbg_kdb_mode;
} else if (error == DBG_SWITCH_CPU_EVENT) {
kgdb_info[dbg_switch_cpu].exception_state |=
DCPU_NEXT_MASTER;
goto cpu_loop;
} else {
kgdb_info[cpu].ret_state = error;
break;
}
}
dbg_activate_sw_breakpoints();
/* Call the I/O driver's post_exception routine */
if (dbg_io_ops->post_exception)
dbg_io_ops->post_exception();
atomic_dec(&ignore_console_lock_warning);
if (!kgdb_single_step) {
raw_spin_unlock(&dbg_slave_lock);
/* Wait till all the CPUs have quit from the debugger. */
while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
cpu_relax();
}
kgdb_restore:
if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
if (kgdb_info[sstep_cpu].task)
kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
else
kgdb_sstep_pid = 0;
}
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
smp_mb__before_atomic();
atomic_dec(&masters_in_kgdb);
/* Free kgdb_active */
atomic_set(&kgdb_active, -1);
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
rcu_read_unlock();
return kgdb_info[cpu].ret_state;
}
NOKPROBE_SYMBOL(kgdb_cpu_enter);
/*
* kgdb_handle_exception() - main entry point from a kernel exception
*
* Locking hierarchy:
* interface locks, if any (begin_session)
* kgdb lock (kgdb_active)
*/
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
{
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
int ret = 0;
if (arch_kgdb_ops.enable_nmi)
arch_kgdb_ops.enable_nmi(0);
/*
* Avoid entering the debugger if we were triggered due to an oops
* but panic_timeout indicates the system should automatically
* reboot on panic. We don't want to get stuck waiting for input
* on such systems, especially if its "just" an oops.
*/
if (signo != SIGTRAP && panic_timeout)
return 1;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = raw_smp_processor_id();
ks->ex_vector = evector;
ks->signo = signo;
ks->err_code = ecode;
ks->linux_regs = regs;
if (kgdb_reenter_check(ks))
goto out; /* Ouch, double exception ! */
if (kgdb_info[ks->cpu].enter_kgdb != 0)
goto out;
ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
out:
if (arch_kgdb_ops.enable_nmi)
arch_kgdb_ops.enable_nmi(1);
return ret;
}
NOKPROBE_SYMBOL(kgdb_handle_exception);
/*
* GDB places a breakpoint at this function to know dynamically loaded objects.
*/
static int module_event(struct notifier_block *self, unsigned long val,
void *data)
{
return 0;
}
static struct notifier_block dbg_module_load_nb = {
.notifier_call = module_event,
};
int kgdb_nmicallback(int cpu, void *regs)
{
#ifdef CONFIG_SMP
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
kgdb_info[cpu].rounding_up = false;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = cpu;
ks->linux_regs = regs;
if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
raw_spin_is_locked(&dbg_master_lock)) {
kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
return 0;
}
#endif
return 1;
}
NOKPROBE_SYMBOL(kgdb_nmicallback);
int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
atomic_t *send_ready)
{
#ifdef CONFIG_SMP
if (!kgdb_io_ready(0) || !send_ready)
return 1;
if (kgdb_info[cpu].enter_kgdb == 0) {
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = cpu;
ks->ex_vector = trapnr;
ks->signo = SIGTRAP;
ks->err_code = err_code;
ks->linux_regs = regs;
ks->send_ready = send_ready;
kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
return 0;
}
#endif
return 1;
}
NOKPROBE_SYMBOL(kgdb_nmicallin);
static void kgdb_console_write(struct console *co, const char *s,
unsigned count)
{
unsigned long flags;
/* If we're debugging, or KGDB has not connected, don't try
* and print. */
if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
return;
local_irq_save(flags);
gdbstub_msg_write(s, count);
local_irq_restore(flags);
}
static struct console kgdbcons = {
.name = "kgdb",
.write = kgdb_console_write,
.flags = CON_PRINTBUFFER | CON_ENABLED,
.index = -1,
};
static int __init opt_kgdb_con(char *str)
{
kgdb_use_con = 1;
if (kgdb_io_module_registered && !kgdb_con_registered) {
register_console(&kgdbcons);
kgdb_con_registered = 1;
}
return 0;
}
early_param("kgdbcon", opt_kgdb_con);
#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handle_dbg(u8 key)
{
if (!dbg_io_ops) {
pr_crit("ERROR: No KGDB I/O module available\n");
return;
}
if (!kgdb_connected) {
#ifdef CONFIG_KGDB_KDB
if (!dbg_kdb_mode)
pr_crit("KGDB or $3#33 for KDB\n");
#else
pr_crit("Entering KGDB\n");
#endif
}
kgdb_breakpoint();
}
static const struct sysrq_key_op sysrq_dbg_op = {
.handler = sysrq_handle_dbg,
.help_msg = "debug(g)",
.action_msg = "DEBUG",
};
#endif
void kgdb_panic(const char *msg)
{
if (!kgdb_io_module_registered)
return;
/*
* We don't want to get stuck waiting for input from user if
* "panic_timeout" indicates the system should automatically
* reboot on panic.
*/
if (panic_timeout)
return;
debug_locks_off();
console_flush_on_panic(CONSOLE_FLUSH_PENDING);
if (dbg_kdb_mode)
kdb_printf("PANIC: %s\n", msg);
kgdb_breakpoint();
}
static void kgdb_initial_breakpoint(void)
{
kgdb_break_asap = 0;
pr_crit("Waiting for connection from remote gdb...\n");
kgdb_breakpoint();
}
void __weak kgdb_arch_late(void)
{
}
void __init dbg_late_init(void)
{
dbg_is_early = false;
if (kgdb_io_module_registered)
kgdb_arch_late();
kdb_init(KDB_INIT_FULL);
if (kgdb_io_module_registered && kgdb_break_asap)
kgdb_initial_breakpoint();
}
static int
dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
{
/*
* Take the following action on reboot notify depending on value:
* 1 == Enter debugger
* 0 == [the default] detach debug client
* -1 == Do nothing... and use this until the board resets
*/
switch (kgdbreboot) {
case 1:
kgdb_breakpoint();
goto done;
case -1:
goto done;
}
if (!dbg_kdb_mode)
gdbstub_exit(code);
done:
return NOTIFY_DONE;
}
static struct notifier_block dbg_reboot_notifier = {
.notifier_call = dbg_notify_reboot,
.next = NULL,
.priority = INT_MAX,
};
static void kgdb_register_callbacks(void)
{
if (!kgdb_io_module_registered) {
kgdb_io_module_registered = 1;
kgdb_arch_init();
if (!dbg_is_early)
kgdb_arch_late();
register_module_notifier(&dbg_module_load_nb);
register_reboot_notifier(&dbg_reboot_notifier);
#ifdef CONFIG_MAGIC_SYSRQ
register_sysrq_key('g', &sysrq_dbg_op);
#endif
if (kgdb_use_con && !kgdb_con_registered) {
register_console(&kgdbcons);
kgdb_con_registered = 1;
}
}
}
static void kgdb_unregister_callbacks(void)
{
/*
* When this routine is called KGDB should unregister from
* handlers and clean up, making sure it is not handling any
* break exceptions at the time.
*/
if (kgdb_io_module_registered) {
kgdb_io_module_registered = 0;
unregister_reboot_notifier(&dbg_reboot_notifier);
unregister_module_notifier(&dbg_module_load_nb);
kgdb_arch_exit();
#ifdef CONFIG_MAGIC_SYSRQ
unregister_sysrq_key('g', &sysrq_dbg_op);
#endif
if (kgdb_con_registered) {
unregister_console(&kgdbcons);
kgdb_con_registered = 0;
}
}
}
/**
* kgdb_register_io_module - register KGDB IO module
* @new_dbg_io_ops: the io ops vector
*
* Register it with the KGDB core.
*/
int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
{
struct kgdb_io *old_dbg_io_ops;
int err;
spin_lock(&kgdb_registration_lock);
old_dbg_io_ops = dbg_io_ops;
if (old_dbg_io_ops) {
if (!old_dbg_io_ops->deinit) {
spin_unlock(&kgdb_registration_lock);
pr_err("KGDB I/O driver %s can't replace %s.\n",
new_dbg_io_ops->name, old_dbg_io_ops->name);
return -EBUSY;
}
pr_info("Replacing I/O driver %s with %s\n",
old_dbg_io_ops->name, new_dbg_io_ops->name);
}
if (new_dbg_io_ops->init) {
err = new_dbg_io_ops->init();
if (err) {
spin_unlock(&kgdb_registration_lock);
return err;
}
}
dbg_io_ops = new_dbg_io_ops;
spin_unlock(&kgdb_registration_lock);
if (old_dbg_io_ops) {
old_dbg_io_ops->deinit();
return 0;
}
pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
/* Arm KGDB now. */
kgdb_register_callbacks();
if (kgdb_break_asap &&
(!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
kgdb_initial_breakpoint();
return 0;
}
EXPORT_SYMBOL_GPL(kgdb_register_io_module);
/**
* kgdb_unregister_io_module - unregister KGDB IO module
* @old_dbg_io_ops: the io ops vector
*
* Unregister it with the KGDB core.
*/
void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
{
BUG_ON(kgdb_connected);
/*
* KGDB is no longer able to communicate out, so
* unregister our callbacks and reset state.
*/
kgdb_unregister_callbacks();
spin_lock(&kgdb_registration_lock);
WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
dbg_io_ops = NULL;
spin_unlock(&kgdb_registration_lock);
if (old_dbg_io_ops->deinit)
old_dbg_io_ops->deinit();
pr_info("Unregistered I/O driver %s, debugger disabled\n",
old_dbg_io_ops->name);
}
EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
int dbg_io_get_char(void)
{
int ret = dbg_io_ops->read_char();
if (ret == NO_POLL_CHAR)
return -1;
if (!dbg_kdb_mode)
return ret;
if (ret == 127)
return 8;
return ret;
}
/**
* kgdb_breakpoint - generate breakpoint exception
*
* This function will generate a breakpoint exception. It is used at the
* beginning of a program to sync up with a debugger and can be used
* otherwise as a quick means to stop program execution and "break" into
* the debugger.
*/
noinline void kgdb_breakpoint(void)
{
atomic_inc(&kgdb_setting_breakpoint);
wmb(); /* Sync point before breakpoint */
arch_kgdb_breakpoint();
wmb(); /* Sync point after breakpoint */
atomic_dec(&kgdb_setting_breakpoint);
}
EXPORT_SYMBOL_GPL(kgdb_breakpoint);
static int __init opt_kgdb_wait(char *str)
{
kgdb_break_asap = 1;
kdb_init(KDB_INIT_EARLY);
if (kgdb_io_module_registered &&
IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
kgdb_initial_breakpoint();
return 0;
}
early_param("kgdbwait", opt_kgdb_wait);
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