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[PATCH -tip v9 08/26] kprobes/x86: Call exception handlers directly from do_int3/do_debug
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: linux-kernel at vger dot kernel dot org, Ingo Molnar <mingo at kernel dot org>
- Cc: Andi Kleen <ak at linux dot intel dot com>, Andi Kleen <andi at firstfloor dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, Frederic Weisbecker <fweisbec at gmail dot com>, x86 at kernel dot org, Steven Rostedt <rostedt at goodmis dot org>, fche at redhat dot com, mingo at redhat dot com, systemtap at sourceware dot org, "H. Peter Anvin" <hpa at zytor dot com>, Sasha Levin <sasha dot levin at oracle dot com>, Thomas Gleixner <tglx at linutronix dot de>, Seiji Aguchi <seiji dot aguchi at hds dot com>, Andrew Morton <akpm at linux-foundation dot org>
- Date: Thu, 17 Apr 2014 17:17:33 +0900
- Subject: [PATCH -tip v9 08/26] kprobes/x86: Call exception handlers directly from do_int3/do_debug
- Authentication-results: sourceware.org; auth=none
- References: <20140417081636 dot 26341 dot 87858 dot stgit at ltc230 dot yrl dot intra dot hitachi dot co dot jp>
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.
Changes from v8:
- Update the patch description.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---
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 9454c16..53cdfb2 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 181bdde..4157d648 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 57409f6..e5d4a70 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;