[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>
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 99565a66..ad46929 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -31,7 +31,6 @@
#include <linux/config.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
-#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
@@ -123,6 +122,7 @@
regs->eip = (unsigned long)&p->ainsn.insn;
}
+/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
struct pt_regs *regs)
{
@@ -168,15 +168,12 @@
}
/* Check we're not actually recursing */
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 &&
*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
regs->eflags &= ~TF_MASK;
regs->eflags |= kcb->kprobe_saved_eflags;
- unlock_kprobes();
goto no_kprobe;
}
/* We have reentered the kprobe_handler(), since
@@ -197,14 +194,11 @@
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 (regs->eflags & VM_MASK) {
/* We are in virtual-8086 mode. Return 0 */
goto no_kprobe;
@@ -268,9 +262,10 @@
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 =(unsigned long)&kretprobe_trampoline;
+ spin_lock_irqsave(&kretprobe_lock, flags);
head = kretprobe_inst_table_head(current);
/*
@@ -310,7 +305,7 @@
regs->eip = orig_ret_address;
reset_current_kprobe();
- unlock_kprobes();
+ spin_unlock_irqrestore(&kretprobe_lock, flags);
preempt_enable_no_resched();
/*
@@ -395,7 +390,7 @@
/*
* Interrupts are disabled on entry as trap1 is an interrupt gate and they
- * remain disabled thoroughout this function. And we hold kprobe lock.
+ * remain disabled thoroughout this function.
*/
static inline int post_kprobe_handler(struct pt_regs *regs)
{
@@ -419,7 +414,6 @@
goto out;
}
reset_current_kprobe();
- unlock_kprobes();
out:
preempt_enable_no_resched();
@@ -434,7 +428,6 @@
return 1;
}
-/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
@@ -448,7 +441,6 @@
regs->eflags |= kcb->kprobe_old_eflags;
reset_current_kprobe();
- unlock_kprobes();
preempt_enable_no_resched();
}
return 0;
@@ -463,7 +455,7 @@
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
- preempt_disable();
+ rcu_read_lock();
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
@@ -482,7 +474,7 @@
default:
break;
}
- preempt_enable();
+ rcu_read_unlock();
return ret;
}