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Subject[PATCH -tip v5 8/8] kprobes: Use text_poke_smp_batch for unoptimizing
Date
Use text_poke_smp_batch() on unoptimization path for reducing
the number of stop_machine() issues. If the number of unoptimizing
probes is more than MAX_OPTIMIZE_PROBES(=256), kprobes unoptimizes
first MAX_OPTIMIZE_PROBES probes and kicks optimizer for remaining
probes.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---
arch/x86/kernel/kprobes.c | 40 ++++++++++++++++++++++++++++++++++++++++
include/linux/kprobes.h | 2 ++
kernel/kprobes.c | 10 ++++------
3 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 25a8af7..5940282 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1457,6 +1457,46 @@ void __kprobes arch_optimize_kprobes(struct list_head *oplist)
text_poke_smp_batch(jump_poke_params, c);
}

+static void __kprobes setup_unoptimize_kprobe(struct text_poke_param *tprm,
+ u8 *insn_buf,
+ struct optimized_kprobe *op)
+{
+ /* Set int3 to first byte for kprobes */
+ insn_buf[0] = BREAKPOINT_INSTRUCTION;
+ memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
+
+ tprm->addr = op->kp.addr;
+ tprm->opcode = insn_buf;
+ tprm->len = RELATIVEJUMP_SIZE;
+}
+
+/*
+ * Recover original instructions and breakpoints from relative jumps.
+ * Caller must call with locking kprobe_mutex.
+ */
+extern void arch_unoptimize_kprobes(struct list_head *oplist,
+ struct list_head *done_list)
+{
+ struct optimized_kprobe *op, *tmp;
+ int c = 0;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ /* Setup param */
+ setup_unoptimize_kprobe(&jump_poke_params[c],
+ jump_poke_bufs[c].buf, op);
+ list_move(&op->list, done_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_batch(jump_poke_params, c);
+}
+
/* Replace a relative jump with a breakpoint (int3). */
void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
{
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index fe157ba..b78edb5 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -276,6 +276,8 @@ 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 void arch_optimize_kprobes(struct list_head *oplist);
+extern void arch_unoptimize_kprobes(struct list_head *oplist,
+ struct list_head *done_list);
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 531e101..7663e5d 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -517,9 +517,9 @@ static __kprobes void do_unoptimize_kprobes(struct list_head *free_list)
/* Ditto to do_optimize_kprobes */
get_online_cpus();
mutex_lock(&text_mutex);
- list_for_each_entry_safe(op, tmp, &unoptimizing_list, list) {
- /* Unoptimize kprobes */
- arch_unoptimize_kprobe(op);
+ arch_unoptimize_kprobes(&unoptimizing_list, free_list);
+ /* Loop free_list for disarming */
+ list_for_each_entry_safe(op, tmp, free_list, list) {
/* Disarm probes if marked disabled */
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
@@ -530,8 +530,6 @@ static __kprobes void do_unoptimize_kprobes(struct list_head *free_list)
* (reclaiming is done by do_free_cleaned_kprobes.)
*/
hlist_del_rcu(&op->kp.hlist);
- /* Move only unused probes on free_list */
- list_move(&op->list, free_list);
} else
list_del_init(&op->list);
}
@@ -592,7 +590,7 @@ static __kprobes void kprobe_optimizer(struct work_struct *work)
mutex_unlock(&module_mutex);

/* Step 5: Kick optimizer again if needed */
- if (!list_empty(&optimizing_list))
+ if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
kick_kprobe_optimizer();
else
/* Wake up all waiters */


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