kprobes: Use text_poke_smp_batch for optimizing

Use text_poke_smp_batch() in optimization path for reducing
the number of stop_machine() issues. If the number of optimizing
probes is more than MAX_OPTIMIZE_PROBES(=256), kprobes optimizes
first MAX_OPTIMIZE_PROBES probes and kicks optimizer for
remaining probes.

Changes in v5:
- Use kick_kprobe_optimizer() instead of directly calling
  schedule_delayed_work().
- Rescheduling optimizer outside of kprobe mutex lock.

Changes in v2:
- Allocate code buffer and parameters in arch_init_kprobes()
  instead of using static arraies.
- Merge previous max optimization limit patch into this patch.
  So, this patch introduces upper limit of optimization at
  once.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20101203095428.2961.8994.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 69 insertions, 19 deletions

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index da51dc8e77cb..25a8af76feb5 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1405,10 +1405,16 @@ int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
         return 0;
 }
 
-/* Replace a breakpoint (int3) with a relative jump.  */
-int __kprobes arch_optimize_kprobe(struct optimized_kprobe *op)
+#define MAX_OPTIMIZE_PROBES 256
+static struct text_poke_param *jump_poke_params;
+static struct jump_poke_buffer {
+        u8 buf[RELATIVEJUMP_SIZE];
+} *jump_poke_bufs;
+
+static void __kprobes setup_optimize_kprobe(struct text_poke_param *tprm,
+                                            u8 *insn_buf,
+                                            struct optimized_kprobe *op)
 {
-        unsigned char jmp_code[RELATIVEJUMP_SIZE];
         s32 rel = (s32)((long)op->optinsn.insn -
                         ((long)op->kp.addr + RELATIVEJUMP_SIZE));
 
@@ -1416,16 +1422,39 @@ int __kprobes arch_optimize_kprobe(struct optimized_kprobe *op)
         memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
                RELATIVE_ADDR_SIZE);
 
-        jmp_code[0] = RELATIVEJUMP_OPCODE;
-        *(s32 *)(&jmp_code[1]) = rel;
+        insn_buf[0] = RELATIVEJUMP_OPCODE;
+        *(s32 *)(&insn_buf[1]) = rel;
+
+        tprm->addr = op->kp.addr;
+        tprm->opcode = insn_buf;
+        tprm->len = RELATIVEJUMP_SIZE;
+}
+
+/*
+ * Replace breakpoints (int3) with relative jumps.
+ * Caller must call with locking kprobe_mutex and text_mutex.
+ */
+void __kprobes arch_optimize_kprobes(struct list_head *oplist)
+{
+        struct optimized_kprobe *op, *tmp;
+        int c = 0;
+
+        list_for_each_entry_safe(op, tmp, oplist, list) {
+                WARN_ON(kprobe_disabled(&op->kp));
+                /* Setup param */
+                setup_optimize_kprobe(&jump_poke_params[c],
+                                      jump_poke_bufs[c].buf, op);
+                list_del_init(&op->list);
+                if (++c >= MAX_OPTIMIZE_PROBES)
+                        break;
+        }
 
         /*
          * text_poke_smp doesn't support NMI/MCE code modifying.
          * However, since kprobes itself also doesn't support NMI/MCE
          * code probing, it's not a problem.
          */
-        text_poke_smp(op->kp.addr, jmp_code, RELATIVEJUMP_SIZE);
-        return 0;
+        text_poke_smp_batch(jump_poke_params, c);
 }
 
 /* Replace a relative jump with a breakpoint (int3).  */
@@ -1457,11 +1486,35 @@ static int  __kprobes setup_detour_execution(struct kprobe *p,
         }
         return 0;
 }
+
+static int __kprobes init_poke_params(void)
+{
+        /* Allocate code buffer and parameter array */
+        jump_poke_bufs = kmalloc(sizeof(struct jump_poke_buffer) *
+                                 MAX_OPTIMIZE_PROBES, GFP_KERNEL);
+        if (!jump_poke_bufs)
+                return -ENOMEM;
+
+        jump_poke_params = kmalloc(sizeof(struct text_poke_param) *
+                                   MAX_OPTIMIZE_PROBES, GFP_KERNEL);
+        if (!jump_poke_params) {
+                kfree(jump_poke_bufs);
+                jump_poke_bufs = NULL;
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+#else   /* !CONFIG_OPTPROBES */
+static int __kprobes init_poke_params(void)
+{
+        return 0;
+}
 #endif
 
 int __init arch_init_kprobes(void)
 {
-        return 0;
+        return init_poke_params();
 }
 
 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e7d1b2e0070d..fe157ba6aa0e 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -275,7 +275,7 @@ extern int arch_prepared_optinsn(struct arch_optimized_insn *optinsn);
 extern int arch_check_optimized_kprobe(struct optimized_kprobe *op);
 extern int arch_prepare_optimized_kprobe(struct optimized_kprobe *op);
 extern void arch_remove_optimized_kprobe(struct optimized_kprobe *op);
-extern int  arch_optimize_kprobe(struct optimized_kprobe *op);
+extern void arch_optimize_kprobes(struct list_head *oplist);
 extern void arch_unoptimize_kprobe(struct optimized_kprobe *op);
 extern kprobe_opcode_t *get_optinsn_slot(void);
 extern void free_optinsn_slot(kprobe_opcode_t *slot, int dirty);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 134754d18bb4..531e10164836 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -480,8 +480,6 @@ static DECLARE_COMPLETION(optimizer_comp);
  */
 static __kprobes void do_optimize_kprobes(void)
 {
-        struct optimized_kprobe *op, *tmp;
-
         /* Optimization never be done when disarmed */
         if (kprobes_all_disarmed || !kprobes_allow_optimization ||
             list_empty(&optimizing_list))
@@ -499,12 +497,7 @@ static __kprobes void do_optimize_kprobes(void)
          */
         get_online_cpus();
         mutex_lock(&text_mutex);
-        list_for_each_entry_safe(op, tmp, &optimizing_list, list) {
-                WARN_ON(kprobe_disabled(&op->kp));
-                if (arch_optimize_kprobe(op) < 0)
-                        op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
-                list_del_init(&op->list);
-        }
+        arch_optimize_kprobes(&optimizing_list);
         mutex_unlock(&text_mutex);
         put_online_cpus();
 }
@@ -598,8 +591,12 @@ static __kprobes void kprobe_optimizer(struct work_struct *work)
         mutex_unlock(&kprobe_mutex);
         mutex_unlock(&module_mutex);
 
-        /* Wake up all waiters */
-        complete_all(&optimizer_comp);
+        /* Step 5: Kick optimizer again if needed */
+        if (!list_empty(&optimizing_list))
+                kick_kprobe_optimizer();
+        else
+                /* Wake up all waiters */
+                complete_all(&optimizer_comp);
 }
 
 /* Wait for completing optimization and unoptimization */