From 6f6343f53d133bae516caf3d254bce37d8774625 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 17 Apr 2014 17:17:33 +0900 Subject: [PATCH] kprobes/x86: Call exception handlers directly from do_int3/do_debug To avoid a kernel crash by probing on lockdep code, call kprobe_int3_handler() and kprobe_debug_handler()(which was formerly called post_kprobe_handler()) directly from do_int3 and do_debug. Currently kprobes uses notify_die() to hook the int3/debug exceptoins. Since there is a locking code in notify_die, the lockdep code can be invoked. And because the lockdep involves printk() related things, theoretically, we need to prohibit probing on such code, which means much longer blacklist we'll have. Instead, hooking the int3/debug for kprobes before notify_die() can avoid this problem. Anyway, most of the int3 handlers in the kernel are already called from do_int3 directly, e.g. ftrace_int3_handler, poke_int3_handler, kgdb_ll_trap. Actually only kprobe_exceptions_notify is on the notifier_call_chain. Signed-off-by: Masami Hiramatsu Reviewed-by: Steven Rostedt Cc: Andrew Morton Cc: Borislav Petkov Cc: Jiri Kosina Cc: Jonathan Lebon Cc: Kees Cook Cc: Rusty Russell Cc: Seiji Aguchi Link: http://lkml.kernel.org/r/20140417081733.26341.24423.stgit@ltc230.yrl.intra.hitachi.co.jp Signed-off-by: Ingo Molnar --- arch/x86/include/asm/kprobes.h | 2 ++ arch/x86/kernel/kprobes/core.c | 24 +++--------------------- arch/x86/kernel/traps.c | 10 ++++++++++ 3 files changed, 15 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 9454c167629f..53cdfb2857ab 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -116,4 +116,6 @@ struct kprobe_ctlblk { extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr); extern int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); +extern int kprobe_int3_handler(struct pt_regs *regs); +extern int kprobe_debug_handler(struct pt_regs *regs); #endif /* _ASM_X86_KPROBES_H */ diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 7751b3dee53a..9b80aec1ea1a 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -559,7 +559,7 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb * Interrupts are disabled on entry as trap3 is an interrupt gate and they * remain disabled throughout this function. */ -static int __kprobes kprobe_handler(struct pt_regs *regs) +int __kprobes kprobe_int3_handler(struct pt_regs *regs) { kprobe_opcode_t *addr; struct kprobe *p; @@ -857,7 +857,7 @@ no_change: * Interrupts are disabled on entry as trap1 is an interrupt gate and they * remain disabled throughout this function. */ -static int __kprobes post_kprobe_handler(struct pt_regs *regs) +int __kprobes kprobe_debug_handler(struct pt_regs *regs) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); @@ -963,22 +963,7 @@ kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *d if (args->regs && user_mode_vm(args->regs)) return ret; - switch (val) { - case DIE_INT3: - if (kprobe_handler(args->regs)) - ret = NOTIFY_STOP; - break; - case DIE_DEBUG: - if (post_kprobe_handler(args->regs)) { - /* - * Reset the BS bit in dr6 (pointed by args->err) to - * denote completion of processing - */ - (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; - ret = NOTIFY_STOP; - } - break; - case DIE_GPF: + if (val == DIE_GPF) { /* * To be potentially processing a kprobe fault and to * trust the result from kprobe_running(), we have @@ -987,9 +972,6 @@ kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *d if (!preemptible() && kprobe_running() && kprobe_fault_handler(args->regs, args->trapnr)) ret = NOTIFY_STOP; - break; - default: - break; } return ret; } diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 57409f6b8c62..e5d4a70814d7 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -334,6 +334,11 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co goto exit; #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */ +#ifdef CONFIG_KPROBES + if (kprobe_int3_handler(regs)) + return; +#endif + if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, SIGTRAP) == NOTIFY_STOP) goto exit; @@ -440,6 +445,11 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6; +#ifdef CONFIG_KPROBES + if (kprobe_debug_handler(regs)) + goto exit; +#endif + if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code, SIGTRAP) == NOTIFY_STOP) goto exit; -- 2.39.5