[PATCH] Kprobes: Use RCU for (un)register synchronization - arch changes

Changes to the arch kprobes infrastructure to take advantage of the locking
changes introduced by usage of RCU for synchronization.  All handlers are now
run without any locks held, so they have to be re-entrant or provide their own
synchronization.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 12 deletions

diff --git a/arch/sparc64/kernel/kprobes.c b/arch/sparc64/kernel/kprobes.c
index b95984154dba..58a815e90373 100644
--- a/arch/sparc64/kernel/kprobes.c
+++ b/arch/sparc64/kernel/kprobes.c
@@ -116,15 +116,11 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
 	if (kprobe_running()) {
-		/* We *are* holding lock here, so this is safe.
-		 * Disarm the probe we just hit, and ignore it.
-		 */
 		p = get_kprobe(addr);
 		if (p) {
 			if (kcb->kprobe_status == KPROBE_HIT_SS) {
 				regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 					kcb->kprobe_orig_tstate_pil);
-				unlock_kprobes();
 				goto no_kprobe;
 			}
 			/* We have reentered the kprobe_handler(), since
@@ -144,14 +140,11 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 			if (p->break_handler && p->break_handler(p, regs))
 				goto ss_probe;
 		}
-		/* If it's not ours, can't be delete race, (we hold lock). */
 		goto no_kprobe;
 	}
 
-	lock_kprobes();
 	p = get_kprobe(addr);
 	if (!p) {
-		unlock_kprobes();
 		if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 			/*
 			 * The breakpoint instruction was removed right
@@ -296,14 +289,12 @@ static inline int post_kprobe_handler(struct pt_regs *regs)
 		goto out;
 	}
 	reset_current_kprobe();
-	unlock_kprobes();
 out:
 	preempt_enable_no_resched();
 
 	return 1;
 }
 
-/* Interrupts disabled, kprobe_lock held. */
 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
 	struct kprobe *cur = kprobe_running();
@@ -316,7 +307,6 @@ static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 		resume_execution(cur, regs, kcb);
 
 		reset_current_kprobe();
-		unlock_kprobes();
 		preempt_enable_no_resched();
 	}
 	return 0;
@@ -331,7 +321,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
-	preempt_disable();
+	rcu_read_lock();
 	switch (val) {
 	case DIE_DEBUG:
 		if (kprobe_handler(args->regs))
@@ -350,7 +340,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	default:
 		break;
 	}
-	preempt_enable();
+	rcu_read_unlock();
 	return ret;
 }