From 5dd11d5d47d248850c58292513f0e164ba98b01e Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Thu, 20 May 2010 21:04:26 -0500 Subject: [PATCH] mips,kgdb: kdb low level trap catch and stack trace The only way the debugger can handle a trap in inside rcu_lock, notify_die, or atomic_notifier_call_chain without a recursive fault is to have a low level "first opportunity handler" do_trap_or_bp() handler. Generally this will be something the vast majority of folks will not need, but for those who need it, it is added as a kernel .config option called KGDB_LOW_LEVEL_TRAP. Also added was a die notification for oops such that kdb can catch an oops for analysis. There appeared to be no obvious way to pass the struct pt_regs from the original exception back to the stack back tracer, so a special case was added to show_stack() for when kdb is active because you generally desire to generally look at the back trace of the original exception. Signed-off-by: Jason Wessel Acked-by: Ralf Baechle --- arch/mips/include/asm/kgdb.h | 2 ++ arch/mips/kernel/kgdb.c | 22 +++++++++++++++++++++- arch/mips/kernel/traps.c | 13 +++++++++++++ lib/Kconfig.kgdb | 2 +- 4 files changed, 37 insertions(+), 2 deletions(-) diff --git a/arch/mips/include/asm/kgdb.h b/arch/mips/include/asm/kgdb.h index 48223b09396c..19002d605ac4 100644 --- a/arch/mips/include/asm/kgdb.h +++ b/arch/mips/include/asm/kgdb.h @@ -38,6 +38,8 @@ extern int kgdb_early_setup; extern void *saved_vectors[32]; extern void handle_exception(struct pt_regs *regs); extern void breakinst(void); +extern int kgdb_ll_trap(int cmd, const char *str, + struct pt_regs *regs, long err, int trap, int sig); #endif /* __KERNEL__ */ diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c index 6ed4c83c869b..9b78ff6e9b84 100644 --- a/arch/mips/kernel/kgdb.c +++ b/arch/mips/kernel/kgdb.c @@ -203,7 +203,7 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd, if (atomic_read(&kgdb_active) != -1) kgdb_nmicallback(smp_processor_id(), regs); - if (kgdb_handle_exception(trap, compute_signal(trap), 0, regs)) + if (kgdb_handle_exception(trap, compute_signal(trap), cmd, regs)) return NOTIFY_DONE; if (atomic_read(&kgdb_setting_breakpoint)) @@ -217,6 +217,26 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd, return NOTIFY_STOP; } +#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP +int kgdb_ll_trap(int cmd, const char *str, + struct pt_regs *regs, long err, int trap, int sig) +{ + struct die_args args = { + .regs = regs, + .str = str, + .err = err, + .trapnr = trap, + .signr = sig, + + }; + + if (!kgdb_io_module_registered) + return NOTIFY_DONE; + + return kgdb_mips_notify(NULL, cmd, &args); +} +#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */ + static struct notifier_block kgdb_notifier = { .notifier_call = kgdb_mips_notify, }; diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index d612c6dcb746..950bde8813fc 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include @@ -185,6 +186,11 @@ void show_stack(struct task_struct *task, unsigned long *sp) regs.regs[29] = task->thread.reg29; regs.regs[31] = 0; regs.cp0_epc = task->thread.reg31; +#ifdef CONFIG_KGDB_KDB + } else if (atomic_read(&kgdb_active) != -1 && + kdb_current_regs) { + memcpy(®s, kdb_current_regs, sizeof(regs)); +#endif /* CONFIG_KGDB_KDB */ } else { prepare_frametrace(®s); } @@ -360,6 +366,8 @@ void __noreturn die(const char * str, struct pt_regs * regs) unsigned long dvpret = dvpe(); #endif /* CONFIG_MIPS_MT_SMTC */ + notify_die(DIE_OOPS, str, (struct pt_regs *)regs, SIGSEGV, 0, 0); + console_verbose(); spin_lock_irq(&die_lock); bust_spinlocks(1); @@ -704,6 +712,11 @@ static void do_trap_or_bp(struct pt_regs *regs, unsigned int code, siginfo_t info; char b[40]; +#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP + if (kgdb_ll_trap(DIE_TRAP, str, regs, code, 0, 0) == NOTIFY_STOP) + return; +#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */ + if (notify_die(DIE_TRAP, str, regs, code, 0, 0) == NOTIFY_STOP) return; diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb index c56ccb4ad292..43cb93fa2651 100644 --- a/lib/Kconfig.kgdb +++ b/lib/Kconfig.kgdb @@ -59,7 +59,7 @@ config KGDB_TESTS_BOOT_STRING config KGDB_LOW_LEVEL_TRAP bool "KGDB: Allow debugging with traps in notifiers" - depends on X86 + depends on X86 || MIPS default n help This will add an extra call back to kgdb for the breakpoint -- 2.30.2