[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, 6 insertions, 10 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 17e70b1b8d7..fddbac32d44 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -26,7 +26,6 @@
 #include <linux/config.h>
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>
-#include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/preempt.h>
@@ -343,10 +342,11 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
         struct kretprobe_instance *ri = NULL;
         struct hlist_head *head;
         struct hlist_node *node, *tmp;
-        unsigned long orig_ret_address = 0;
+        unsigned long flags, orig_ret_address = 0;
         unsigned long trampoline_address =
                 ((struct fnptr *)kretprobe_trampoline)->ip;
 
+        spin_lock_irqsave(&kretprobe_lock, flags);
         head = kretprobe_inst_table_head(current);
 
         /*
@@ -386,7 +386,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
         regs->cr_iip = orig_ret_address;
 
         reset_current_kprobe();
-        unlock_kprobes();
+        spin_unlock_irqrestore(&kretprobe_lock, flags);
         preempt_enable_no_resched();
 
         /*
@@ -397,6 +397,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
         return 1;
 }
 
+/* Called with kretprobe_lock held */
 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
                                       struct pt_regs *regs)
 {
@@ -612,7 +613,6 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
                         if ((kcb->kprobe_status == KPROBE_HIT_SS) &&
                              (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) {
                                 ia64_psr(regs)->ss = 0;
-                                unlock_kprobes();
                                 goto no_kprobe;
                         }
                         /* We have reentered the pre_kprobe_handler(), since
@@ -641,10 +641,8 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
                 }
         }
 
-        lock_kprobes();
         p = get_kprobe(addr);
         if (!p) {
-                unlock_kprobes();
                 if (!is_ia64_break_inst(regs)) {
                         /*
                          * The breakpoint instruction was removed right
@@ -707,7 +705,6 @@ static int __kprobes post_kprobes_handler(struct pt_regs *regs)
                 goto out;
         }
         reset_current_kprobe();
-        unlock_kprobes();
 
 out:
         preempt_enable_no_resched();
@@ -728,7 +725,6 @@ static int __kprobes kprobes_fault_handler(struct pt_regs *regs, int trapnr)
         if (kcb->kprobe_status & KPROBE_HIT_SS) {
                 resume_execution(cur, regs);
                 reset_current_kprobe();
-                unlock_kprobes();
                 preempt_enable_no_resched();
         }
 
@@ -741,7 +737,7 @@ 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_BREAK:
                 if (pre_kprobes_handler(args))
@@ -757,7 +753,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         default:
                 break;
         }
-        preempt_enable();
+        rcu_read_unlock();
         return ret;
 }