kprobes/x86: ftrace based optimization for x86

Add function tracer based kprobe optimization support
handlers on x86. This allows kprobes to use function
tracer for probing on mcount call.

Link: http://lkml.kernel.org/r/20120605102838.27845.26317.stgit@localhost.localdomain
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: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ Updated to new port of ftrace save regs functions ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 54788253915739a2a07faa87f8186ab261e0a065..d3ddd17405d07b1e288828a949ac9ecb363c3c2e 100644 (file)
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -27,6 +27,7 @@
 #include <asm/insn.h>
 
 #define  __ARCH_WANT_KPROBES_INSN_SLOT
+#define  ARCH_SUPPORTS_KPROBES_ON_FTRACE
 
 struct pt_regs;
 struct kprobe;

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index e2f751efb7b1ef25ce9329a49128a48c1dcf9c3f..47ae1023a93c131b4e552b6c94f4a900e985b5a3 100644 (file)
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1052,6 +1052,54 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
        return 0;
 }
 
+#ifdef KPROBES_CAN_USE_FTRACE
+/* Ftrace callback handler for kprobes */
+void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+                                    struct ftrace_ops *ops, struct pt_regs *regs)
+{
+       struct kprobe *p;
+       struct kprobe_ctlblk *kcb;
+       unsigned long flags;
+
+       /* Disable irq for emulating a breakpoint and avoiding preempt */
+       local_irq_save(flags);
+
+       p = get_kprobe((kprobe_opcode_t *)ip);
+       if (unlikely(!p) || kprobe_disabled(p))
+               goto end;
+
+       kcb = get_kprobe_ctlblk();
+       if (kprobe_running()) {
+               kprobes_inc_nmissed_count(p);
+       } else {
+               regs->ip += sizeof(kprobe_opcode_t);
+
+               __this_cpu_write(current_kprobe, p);
+               kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+               if (p->pre_handler)
+                       p->pre_handler(p, regs);
+
+               if (unlikely(p->post_handler)) {
+                       /* Emulate singlestep as if there is a 5byte nop */
+                       regs->ip = ip + MCOUNT_INSN_SIZE;
+                       kcb->kprobe_status = KPROBE_HIT_SSDONE;
+                       p->post_handler(p, regs, 0);
+               }
+               __this_cpu_write(current_kprobe, NULL);
+               regs->ip = ip;  /* Recover for next callback */
+       }
+end:
+       local_irq_restore(flags);
+}
+
+int __kprobes arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+       p->ainsn.insn = NULL;
+       p->ainsn.boostable = -1;
+       return 0;
+}
+#endif
+
 int __init arch_init_kprobes(void)
 {
        return arch_init_optprobes();

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index aa0d05e852e3b2697a0c0255ec48d85cd180a3d1..23755ba42abc456a06ffd663d0b3817570c1e7cb 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -318,7 +318,7 @@ extern int proc_kprobes_optimization_handler(struct ctl_table *table,
 #endif /* CONFIG_OPTPROBES */
 #ifdef KPROBES_CAN_USE_FTRACE
 extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
-                                 struct pt_regs *regs);
+                                 struct ftrace_ops *ops, struct pt_regs *regs);
 extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
 #endif
 

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 69c16efc315be203da89a59c51a576c03637ca86..35b4315d84f578104a0ea322861d43773c52e625 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -921,7 +921,7 @@ static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
 
 #ifdef KPROBES_CAN_USE_FTRACE
 static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
-       .regs_func = kprobe_ftrace_handler,
+       .func = kprobe_ftrace_handler,
        .flags = FTRACE_OPS_FL_SAVE_REGS,
 };
 static int kprobe_ftrace_enabled;