When kernel panic occurs, a kernel module can use either the panic_notifier or die_notifier to obtain the debugging information.
However, in case of these exceptions like do_undefinstr(), regs and esr data are not passed on. Although a module might be able to find those data in the console messages, parsing text messages is very expensive behavior for a module especially on mobile devices. These bare tracepoints allow a module to probe regs and esr information for debugging purpose. _tp suffix comes from bare tracepoints of sched/core.c Signed-off-by: Sangmoon Kim <sangmoon....@samsung.com> --- arch/arm64/kernel/traps.c | 15 +++++++++++++ include/trace/events/traps.h | 41 ++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+) create mode 100644 include/trace/events/traps.h diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index a05d34f0e82a..e58797743442 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -45,6 +45,17 @@ #include <asm/system_misc.h> #include <asm/sysreg.h> +#define CREATE_TRACE_POINTS +#include <trace/events/traps.h> + +/* + * Export tracepoints that act as a bare tracehook (ie: have no trace event + * associated with them) to allow external modules to probe them. + */ +EXPORT_TRACEPOINT_SYMBOL_GPL(traps_undefinstr_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(traps_bad_mode_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(traps_serror_panic_tp); + static const char *handler[] = { "Synchronous Abort", "IRQ", @@ -403,6 +414,8 @@ void do_undefinstr(struct pt_regs *regs) if (call_undef_hook(regs) == 0) return; + if (!user_mode(regs)) + trace_traps_undefinstr_tp(regs, 0); BUG_ON(!user_mode(regs)); force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0); } @@ -766,6 +779,7 @@ asmlinkage void notrace bad_mode(struct pt_regs *regs, int reason, unsigned int __show_regs(regs); local_daif_mask(); + trace_traps_bad_mode_tp(regs, esr); panic("bad mode"); } @@ -832,6 +846,7 @@ void __noreturn arm64_serror_panic(struct pt_regs *regs, u32 esr) if (regs) __show_regs(regs); + trace_traps_serror_panic_tp(regs, esr); nmi_panic(regs, "Asynchronous SError Interrupt"); cpu_park_loop(); diff --git a/include/trace/events/traps.h b/include/trace/events/traps.h new file mode 100644 index 000000000000..b4f53db90ce7 --- /dev/null +++ b/include/trace/events/traps.h @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM traps + +#if !defined(_TRACE_TRAPS_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_TRAPS_H + +#include <linux/tracepoint.h> + +/* + * Following tracepoints are not exported in tracefs and provide hooking + * mechanisms only for testing and debugging purposes. + * + * Postfixed with _tp to make them easily identifiable in the code. + */ + +/* + * Tracepoint for unhandled undefined exception at EL1. + */ +DECLARE_TRACE(traps_undefinstr_tp, + TP_PROTO(struct pt_regs *regs, unsigned int esr), + TP_ARGS(regs, esr)); + +/* + * Tracepoint for bad_mode for the impossible case in the exception vector. + */ +DECLARE_TRACE(traps_bad_mode_tp, + TP_PROTO(struct pt_regs *regs, unsigned int esr), + TP_ARGS(regs, esr)); + +/* + * Tracepoint for unhandled SError exception. + */ +DECLARE_TRACE(traps_serror_panic_tp, + TP_PROTO(struct pt_regs *regs, unsigned int esr), + TP_ARGS(regs, esr)); + +#endif /* _TRACE_TRAPS_H */ + +/* This part must be outside protection */ +#include <trace/define_trace.h> -- 2.17.1