[Bug kprobes/2452] New: kretprobe spinlock recursive remove

[bibo dot mao at intel dot com]

In new linux kernel version, kretprobe in IA32 is implemented in
kretprobe_trampoline. And probepoint is removed from kretprobe_trampoline,
instead   trampoline_handler is called directly.
Currently if kretprobe hander hit one trap which causes another kretprobe, there
will be SPINLOCK recursive bug. This patch fixes this, and will skip trap during
kretprobe handler execution. 
And the test case is the same in
http://sourceware.org/bugzilla/show_bug.cgi?id=2071.

--- 2.6.16-rc6-mm1.org/arch/i386/kernel/kprobes.c	2006-03-13 12:25:15.000000000
+0800
+++ 2.6.16-rc6-mm1/arch/i386/kernel/kprobes.c	2006-03-13 11:38:26.000000000 +0800
@@ -389,9 +389,11 @@ fastcall void *__kprobes trampoline_hand
 			/* another task is sharing our hash bucket */
                         continue;
 
-		if (ri->rp && ri->rp->handler)
+		if (ri->rp && ri->rp->handler){
+			__get_cpu_var(current_kprobe) = &ri->rp->kp;
 			ri->rp->handler(ri, regs);
-
+			__get_cpu_var(current_kprobe) = NULL;
+		}
 		orig_ret_address = (unsigned long)ri->ret_addr;
 		recycle_rp_inst(ri);

-- 
           Summary: kretprobe spinlock recursive remove
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: bibo dot mao at intel dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=2452

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