From 8daaa5f8261bffd2f6217a960f9182d0503a5c44 Mon Sep 17 00:00:00 2001 From: Mike Travis Date: Wed, 2 Oct 2013 10:14:18 -0500 Subject: [PATCH] kdb: Add support for external NMI handler to call KGDB/KDB This patch adds a kgdb_nmicallin() interface that can be used by external NMI handlers to call the KGDB/KDB handler. The primary need for this is for those types of NMI interrupts where all the CPUs have already received the NMI signal. Therefore no send_IPI(NMI) is required, and in fact it will cause a 2nd unhandled NMI to occur. This generates the "Dazed and Confuzed" messages. Since all the CPUs are getting the NMI at roughly the same time, it's not guaranteed that the first CPU that hits the NMI handler will manage to enter KGDB and set the dbg_master_lock before the slaves start entering. The new argument "send_ready" was added for KGDB to signal the NMI handler to release the slave CPUs for entry into KGDB. Signed-off-by: Mike Travis Acked-by: Jason Wessel Reviewed-by: Dimitri Sivanich Reviewed-by: Hedi Berriche Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Link: http://lkml.kernel.org/r/20131002151417.928886849@asylum.americas.sgi.com Signed-off-by: Ingo Molnar --- include/linux/kdb.h | 1 + include/linux/kgdb.h | 1 + kernel/debug/debug_core.c | 32 ++++++++++++++++++++++++++++++-- kernel/debug/debug_core.h | 3 +++ kernel/debug/kdb/kdb_debugger.c | 5 ++++- kernel/debug/kdb/kdb_main.c | 3 +++ 6 files changed, 42 insertions(+), 3 deletions(-) diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 7f6fe6e015bc..290db1269c4c 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -109,6 +109,7 @@ typedef enum { KDB_REASON_RECURSE, /* Recursive entry to kdb; * regs probably valid */ KDB_REASON_SSTEP, /* Single Step trap. - regs valid */ + KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */ } kdb_reason_t; extern int kdb_trap_printk; diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index c6e091bf39a5..dfb4f2ffdaa2 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -310,6 +310,7 @@ extern int kgdb_handle_exception(int ex_vector, int signo, int err_code, struct pt_regs *regs); extern int kgdb_nmicallback(int cpu, void *regs); +extern int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *snd_rdy); extern void gdbstub_exit(int status); extern int kgdb_single_step; diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 0506d447aed2..7d2f35e5df2f 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -575,8 +575,12 @@ return_normal: 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() */ - if ((!kgdb_single_step) && kgdb_do_roundup) + else if ((!kgdb_single_step) && kgdb_do_roundup) kgdb_roundup_cpus(flags); #endif @@ -678,11 +682,11 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) if (arch_kgdb_ops.enable_nmi) arch_kgdb_ops.enable_nmi(0); + 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->kgdb_usethreadid = 0; ks->linux_regs = regs; if (kgdb_reenter_check(ks)) @@ -732,6 +736,30 @@ int kgdb_nmicallback(int cpu, void *regs) return 1; } +int kgdb_nmicallin(int cpu, int trapnr, void *regs, 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 = KGDB_KDB_REASON_SYSTEM_NMI; + ks->linux_regs = regs; + ks->send_ready = send_ready; + kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); + return 0; + } +#endif + return 1; +} + static void kgdb_console_write(struct console *co, const char *s, unsigned count) { diff --git a/kernel/debug/debug_core.h b/kernel/debug/debug_core.h index 2235967e78b0..572aa4f5677c 100644 --- a/kernel/debug/debug_core.h +++ b/kernel/debug/debug_core.h @@ -26,6 +26,7 @@ struct kgdb_state { unsigned long threadid; long kgdb_usethreadid; struct pt_regs *linux_regs; + atomic_t *send_ready; }; /* Exception state values */ @@ -74,11 +75,13 @@ extern int kdb_stub(struct kgdb_state *ks); extern int kdb_parse(const char *cmdstr); extern int kdb_common_init_state(struct kgdb_state *ks); extern int kdb_common_deinit_state(void); +#define KGDB_KDB_REASON_SYSTEM_NMI KDB_REASON_SYSTEM_NMI #else /* ! CONFIG_KGDB_KDB */ static inline int kdb_stub(struct kgdb_state *ks) { return DBG_PASS_EVENT; } +#define KGDB_KDB_REASON_SYSTEM_NMI 0 #endif /* CONFIG_KGDB_KDB */ #endif /* _DEBUG_CORE_H_ */ diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c index 328d18ef31e4..8859ca34dcfe 100644 --- a/kernel/debug/kdb/kdb_debugger.c +++ b/kernel/debug/kdb/kdb_debugger.c @@ -69,7 +69,10 @@ int kdb_stub(struct kgdb_state *ks) if (atomic_read(&kgdb_setting_breakpoint)) reason = KDB_REASON_KEYBOARD; - if (in_nmi()) + if (ks->err_code == KDB_REASON_SYSTEM_NMI && ks->signo == SIGTRAP) + reason = KDB_REASON_SYSTEM_NMI; + + else if (in_nmi()) reason = KDB_REASON_NMI; for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) { diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 00eb8f7fbf41..0b097c8a1e50 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1200,6 +1200,9 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, instruction_pointer(regs)); kdb_dumpregs(regs); break; + case KDB_REASON_SYSTEM_NMI: + kdb_printf("due to System NonMaskable Interrupt\n"); + break; case KDB_REASON_NMI: kdb_printf("due to NonMaskable Interrupt @ " kdb_machreg_fmt "\n", -- 2.39.5