/* * Kernel Debug Core * * Maintainer: Jason Wessel * * Copyright (C) 2000-2001 VERITAS Software Corporation. * Copyright (C) 2002-2004 Timesys Corporation * Copyright (C) 2003-2004 Amit S. Kale * Copyright (C) 2004 Pavel Machek * Copyright (C) 2004-2006 Tom Rini * 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 * * Contributors at various stages not listed above: * Jason Wessel ( jason.wessel@windriver.com ) * George Anzinger * Anurekh Saxena (anurekh.saxena@timesys.com) * Lake Stevens Instrument Division (Glenn Engel) * Jim Kingdon, Cygnus Support. * * Original KGDB stub: David Grothe , * Tigran Aivazian * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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); /* 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; static int __init opt_kgdb_con(char *str) { kgdb_use_con = 1; return 0; } early_param("kgdbcon", opt_kgdb_con); module_param(kgdb_use_con, 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; static atomic_t kgdb_break_tasklet_var; 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 overriden by architectures when needed: */ int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr) { int err; err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE); if (err) return err; return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); } int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle) { return probe_kernel_write((char *)addr, (char *)bundle, BREAK_INSTR_SIZE); } int __weak kgdb_validate_break_address(unsigned long addr) { char tmp_variable[BREAK_INSTR_SIZE]; int err; /* Validate setting the breakpoint and then removing it. In 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. */ err = kgdb_arch_set_breakpoint(addr, tmp_variable); if (err) return err; err = kgdb_arch_remove_breakpoint(addr, tmp_variable); if (err) printk(KERN_ERR "KGDB: Critical breakpoint error, kernel " "memory destroyed at: %lx", addr); return err; } unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) { return instruction_pointer(regs); } int __weak kgdb_arch_init(void) { return 0; } int __weak kgdb_skipexception(int exception, struct pt_regs *regs) { return 0; } /* * 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; if (current->mm && current->mm->mmap_cache) { flush_cache_range(current->mm->mmap_cache, addr, addr + BREAK_INSTR_SIZE); } /* Force flush instruction cache if it was outside the mm */ flush_icache_range(addr, addr + BREAK_INSTR_SIZE); } /* * SW breakpoint management: */ int dbg_activate_sw_breakpoints(void) { unsigned long addr; int error; int ret = 0; int i; for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { if (kgdb_break[i].state != BP_SET) continue; addr = kgdb_break[i].bpt_addr; error = kgdb_arch_set_breakpoint(addr, kgdb_break[i].saved_instr); if (error) { ret = error; printk(KERN_INFO "KGDB: BP install failed: %lx", addr); continue; } kgdb_flush_swbreak_addr(addr); kgdb_break[i].state = BP_ACTIVE; } return ret; } 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) { unsigned long addr; int error; int ret = 0; int i; for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { if (kgdb_break[i].state != BP_ACTIVE) continue; addr = kgdb_break[i].bpt_addr; error = kgdb_arch_remove_breakpoint(addr, kgdb_break[i].saved_instr); if (error) { printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr); ret = error; } kgdb_flush_swbreak_addr(addr); kgdb_break[i].state = BP_SET; } return ret; } 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 dbg_remove_all_break(void) { unsigned long addr; int error; int i; /* Clear memory breakpoints. */ for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { if (kgdb_break[i].state != BP_ACTIVE) goto setundefined; addr = kgdb_break[i].bpt_addr; error = kgdb_arch_remove_breakpoint(addr, kgdb_break[i].saved_instr); if (error) printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n", 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; } /* * 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) printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n"); #else printk(KERN_CRIT "KGDB: Waiting for remote debugger\n"); #endif } return 1; } 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(); printk(KERN_CRIT "KGDB: 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(); panic("Recursive entry to debugger"); } printk(KERN_CRIT "KGDB: 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; } static void dbg_touch_watchdogs(void) { touch_softlockup_watchdog_sync(); clocksource_touch_watchdog(); rcu_cpu_stall_reset(); } 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(); 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: /* * 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_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].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; smp_mb__before_atomic_dec(); atomic_dec(&slaves_in_kgdb); dbg_touch_watchdogs(); local_irq_restore(flags); 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); 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; /* 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 /* Signal the other CPUs to enter kgdb_wait() */ if ((!kgdb_single_step) && kgdb_do_roundup) kgdb_roundup_cpus(flags); #endif /* * Wait for the other CPUs to be notified and be waiting for us: */ while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != online_cpus) cpu_relax(); /* * 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 { 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; } } /* Call the I/O driver's post_exception routine */ if (dbg_io_ops->post_exception) dbg_io_ops->post_exception(); 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].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; smp_mb__before_atomic_dec(); 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); return kgdb_info[cpu].ret_state; } /* * 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; ks->cpu = raw_smp_processor_id(); ks->ex_vector = evector; ks->signo = signo; ks->err_code = ecode; ks->kgdb_usethreadid = 0; ks->linux_regs = regs; if (kgdb_reenter_check(ks)) return 0; /* Ouch, double exception ! */ if (kgdb_info[ks->cpu].enter_kgdb != 0) return 0; return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); } int kgdb_nmicallback(int cpu, void *regs) { #ifdef CONFIG_SMP struct kgdb_state kgdb_var; struct kgdb_state *ks = &kgdb_var; 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; } 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, }; #ifdef CONFIG_MAGIC_SYSRQ static void sysrq_handle_dbg(int key) { if (!dbg_io_ops) { printk(KERN_CRIT "ERROR: No KGDB I/O module available\n"); return; } if (!kgdb_connected) { #ifdef CONFIG_KGDB_KDB if (!dbg_kdb_mode) printk(KERN_CRIT "KGDB or $3#33 for KDB\n"); #else printk(KERN_CRIT "Entering KGDB\n"); #endif } kgdb_breakpoint(); } static struct sysrq_key_op sysrq_dbg_op = { .handler = sysrq_handle_dbg, .help_msg = "debug(G)", .action_msg = "DEBUG", }; #endif static int kgdb_panic_event(struct notifier_block *self, unsigned long val, void *data) { if (dbg_kdb_mode) kdb_printf("PANIC: %s\n", (char *)data); kgdb_breakpoint(); return NOTIFY_DONE; } static struct notifier_block kgdb_panic_event_nb = { .notifier_call = kgdb_panic_event, .priority = INT_MAX, }; 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); } 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(); atomic_notifier_chain_register(&panic_notifier_list, &kgdb_panic_event_nb); #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 the * panic handler 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; atomic_notifier_chain_unregister(&panic_notifier_list, &kgdb_panic_event_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; } } } /* * There are times a tasklet needs to be used vs a compiled in * break point so as to cause an exception outside a kgdb I/O module, * such as is the case with kgdboe, where calling a breakpoint in the * I/O driver itself would be fatal. */ static void kgdb_tasklet_bpt(unsigned long ing) { kgdb_breakpoint(); atomic_set(&kgdb_break_tasklet_var, 0); } static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); void kgdb_schedule_breakpoint(void) { if (atomic_read(&kgdb_break_tasklet_var) || atomic_read(&kgdb_active) != -1 || atomic_read(&kgdb_setting_breakpoint)) return; atomic_inc(&kgdb_break_tasklet_var); tasklet_schedule(&kgdb_tasklet_breakpoint); } EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); static void kgdb_initial_breakpoint(void) { kgdb_break_asap = 0; printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n"); kgdb_breakpoint(); } /** * 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) { int err; spin_lock(&kgdb_registration_lock); if (dbg_io_ops) { spin_unlock(&kgdb_registration_lock); printk(KERN_ERR "kgdb: Another I/O driver is already " "registered with KGDB.\n"); return -EBUSY; } 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); printk(KERN_INFO "kgdb: Registered I/O driver %s.\n", new_dbg_io_ops->name); /* Arm KGDB now. */ kgdb_register_callbacks(); if (kgdb_break_asap) kgdb_initial_breakpoint(); return 0; } EXPORT_SYMBOL_GPL(kgdb_register_io_module); /** * kkgdb_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); printk(KERN_INFO "kgdb: 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. */ 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) kgdb_initial_breakpoint(); return 0; } early_param("kgdbwait", opt_kgdb_wait);