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Subject[tip:perf/core] kprobes/x86: ftrace based optimization for x86
Commit-ID:  e52538965119319447c0800c534da73142c27be2
Gitweb: http://git.kernel.org/tip/e52538965119319447c0800c534da73142c27be2
Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
AuthorDate: Tue, 5 Jun 2012 19:28:38 +0900
Committer: Steven Rostedt <rostedt@goodmis.org>
CommitDate: Tue, 31 Jul 2012 10:29:59 -0400

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>
---
arch/x86/include/asm/kprobes.h | 1 +
arch/x86/kernel/kprobes.c | 48 ++++++++++++++++++++++++++++++++++++++++
include/linux/kprobes.h | 2 +-
kernel/kprobes.c | 2 +-
4 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 5478825..d3ddd17 100644
--- 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 e2f751e..47ae102 100644
--- 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 aa0d05e..23755ba 100644
--- 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 69c16ef..35b4315 100644
--- 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;

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