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Subject[PATCHv7 2.6.35-rc3-tip 6/11] uprobes: X86 support for Uprobes

uprobes: X86 support for Uprobes

Changelog from V5: Using local_irq_enable() instead of
native_irq_enable and no more disabling irqs as suggested by Oleg
Nesterov.

Provides x86 specific details for uprobes.
This includes interrupt notifier for uprobes, enabling/disabling
singlestep.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
---
arch/x86/kernel/signal.c | 13 +++++++++++
arch/x86/kernel/uprobes.c | 52 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 4fd173c..3657563 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -848,6 +848,19 @@ 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 1eb85bb..9456328 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -26,6 +26,7 @@
#include <linux/ptrace.h>
#include <linux/uprobes.h>

+#include <linux/kdebug.h>
#include <asm/insn.h>

#ifdef CONFIG_X86_32
@@ -545,3 +546,54 @@ struct user_bkpt_arch_info user_bkpt_arch_info = {
.analyze_insn = analyze_insn,
.post_xol = post_xol,
};
+
+/*
+ * 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;
+}
+
+void arch_uprobe_enable_sstep(struct pt_regs *regs)
+{
+ /*
+ * Enable single-stepping by
+ * - Set TF on stack
+ * - Set TIF_SINGLESTEP: Guarantees that TF is set when
+ * returning to user mode.
+ * - Indicate that TF is set by us.
+ */
+ regs->flags |= X86_EFLAGS_TF;
+ set_thread_flag(TIF_SINGLESTEP);
+ set_thread_flag(TIF_FORCED_TF);
+}
+
+void arch_uprobe_disable_sstep(struct pt_regs *regs)
+{
+ /* Disable single-stepping by clearing what we set */
+ clear_thread_flag(TIF_SINGLESTEP);
+ clear_thread_flag(TIF_FORCED_TF);
+ regs->flags &= ~X86_EFLAGS_TF;
+}

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