[RFC][PROTO][PATCH -tip 4/7] kprobes: add get_optinsn_slot()/free_optinsn_slot() for optimized kprobes

[Masami Hiramatsu <mhiramat@redhat.com>]

Add get_optinsn_slot() and free_optinsn_slot() for optimized_probes.
optinsn_slot will be bigger than normal insn_slot because optinsn_slot may
include interrupt emulation code and several instructions which will be
replaced by a jump instruction.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
---

 include/linux/kprobes.h |    2 ++
 kernel/kprobes.c        |   30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 0 deletions(-)


diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 065bb24..c7674bf 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -270,6 +270,8 @@ extern int  arch_optimize_kprobe(struct optimized_kprobe *op);
 extern void arch_unoptimize_kprobe(struct optimized_kprobe *op);
 extern int arch_detour_optimized_kprobe(struct optimized_kprobe *op,
 					struct pt_regs *regs);
+extern kprobe_opcode_t *get_optinsn_slot(void);
+extern void free_optinsn_slot(kprobe_opcode_t *slot, int dirty);
 #endif

 /* Get the kprobe at this addr (if any) - called with preemption disabled */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ba731ff..ddc1d38 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -296,6 +296,31 @@ void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
 	__free_insn_slot(&kprobe_insn_slots, slot, dirty);
 	mutex_unlock(&kprobe_insn_mutex);
 }
+#ifdef CONFIG_OPTPROBES
+/* For optimized_kprobe buffer */
+static DEFINE_MUTEX(kprobe_optinsn_mutex); /* Protects kprobe_optinsn_slots */
+static struct kprobe_insn_cache kprobe_optinsn_slots = {
+	.pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
+	/* .insn_size is initialized later */
+	.nr_garbage = 0,
+};
+/* Get a slot for optimized_kprobe buffer */
+kprobe_opcode_t __kprobes *get_optinsn_slot(void)
+{
+	kprobe_opcode_t *ret = NULL;
+	mutex_lock(&kprobe_optinsn_mutex);
+	ret = __get_insn_slot(&kprobe_optinsn_slots);
+	mutex_unlock(&kprobe_optinsn_mutex);
+	return ret;
+}
+
+void __kprobes free_optinsn_slot(kprobe_opcode_t * slot, int dirty)
+{
+	mutex_lock(&kprobe_optinsn_mutex);
+	__free_insn_slot(&kprobe_optinsn_slots, slot, dirty);
+	mutex_unlock(&kprobe_optinsn_mutex);
+}
+#endif
 #endif

 /* We have preemption disabled.. so it is safe to use __ versions */
@@ -1388,6 +1413,11 @@ static int __init init_kprobes(void)
 		}
 	}

+#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)
+	/* Init kprobe_optinsn_slots */
+	kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
+#endif
+
 	/* By default, kprobes are armed */
 	kprobes_all_disarmed = false;

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com