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Subject[PATCH v3 2.6.39-rc1-tip 16/26] 16: x86: uprobes exception notifier for x86.

Provides a uprobes exception notifier for x86. This uprobes_exception
notifier gets called in interrupt context and routes int3 and singlestep
exception when a uprobed process encounters a INT3 or a singlestep exception.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
arch/x86/include/asm/uprobes.h | 3 +++
arch/x86/kernel/signal.c | 14 ++++++++++++++
arch/x86/kernel/uprobes.c | 29 +++++++++++++++++++++++++++++
3 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 0c9c8b6..bb5c03c 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -22,6 +22,7 @@
* Srikar Dronamraju
* Jim Keniston
*/
+#include <linux/notifier.h>

typedef u8 uprobe_opcode_t;
#define MAX_UINSN_BYTES 16
@@ -49,4 +50,6 @@ extern int pre_xol(struct uprobe *uprobe, struct pt_regs *regs);
extern int post_xol(struct uprobe *uprobe, struct pt_regs *regs);
extern void arch_uprobe_enable_sstep(struct pt_regs *regs);
extern void arch_uprobe_disable_sstep(struct pt_regs *regs);
+extern int uprobes_exception_notify(struct notifier_block *self,
+ unsigned long val, void *data);
#endif /* _ASM_UPROBES_H */
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 4fd173c..0b06b94 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -20,6 +20,7 @@
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/user-return-notifier.h>
+#include <linux/uprobes.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
@@ -848,6 +849,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);

+ if (thread_info_flags & _TIF_UPROBE) {
+ clear_thread_flag(TIF_UPROBE);
+#ifdef CONFIG_X86_32
+ /*
+ * On x86_32, do_notify_resume() gets called with
+ * interrupts disabled. Hence enable interrupts if they
+ * are still disabled.
+ */
+ local_irq_enable();
+#endif
+ uprobe_notify_resume(regs);
+ }
+
if (thread_info_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
tracehook_notify_resume(regs);
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index bf98841..e0ce207 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -583,3 +583,32 @@ void arch_uprobe_disable_sstep(struct pt_regs *regs)
clear_thread_flag(TIF_FORCED_TF);
regs->flags &= ~X86_EFLAGS_TF;
}
+
+/*
+ * Wrapper routine for handling exceptions.
+ */
+int uprobes_exception_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ struct pt_regs *regs = args->regs;
+ int ret = NOTIFY_DONE;
+
+ /* We are only interested in userspace traps */
+ if (regs && !user_mode_vm(regs))
+ return NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_INT3:
+ /* Run your handler here */
+ if (uprobe_bkpt_notifier(regs))
+ ret = NOTIFY_STOP;
+ break;
+ case DIE_DEBUG:
+ if (uprobe_post_notifier(regs))
+ ret = NOTIFY_STOP;
+ default:
+ break;
+ }
+ return ret;
+}

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