kprobes/x86: Fix removed int3 checking order (829e9245) · Commits · 戴 / test

Fix kprobe/x86 to check removed int3 when failing to get kprobe from hlist. Since we have a time window between checking int3 exists on probed address and getting kprobe on that address, we can have following scenario: ------- CPU1 CPU2 hit int3 check int3 exists remove int3 remove kprobe from hlist get kprobe from hlist no kprobe->OOPS! ------- This patch moves int3 checking if there is no kprobe on that address for fixing this problem as follows: ------ CPU1 CPU2 hit int3 remove int3 remove kprobe from hlist get kprobe from hlist no kprobe->check int3 exists ->rollback&retry ------ Signed-off-by:

Masami Hiramatsu <mhiramat@redhat.com> Acked-by:

Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: systemtap <systemtap@sources.redhat.com> Cc: DLE <dle-develop@lists.sourceforge.net> Cc: Dave Anderson <anderson@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20100427223348.2322.9112.stgit@localhost6.localdomain6> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/kprobes.c

+13 −14

Original line number	Diff line number	Diff line
		@@ -534,20 +534,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
		struct kprobe_ctlblk *kcb;

		addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
		if (*addr != BREAKPOINT_INSTRUCTION) {
		/*
		* The breakpoint instruction was removed right
		* after we hit it. Another cpu has removed
		* either a probepoint or a debugger breakpoint
		* at this address. In either case, no further
		* handling of this interrupt is appropriate.
		* Back up over the (now missing) int3 and run
		* the original instruction.
		*/
		regs->ip = (unsigned long)addr;
		return 1;
		}

		/*
		* We don't want to be preempted for the entire
		* duration of kprobe processing. We conditionally
		@@ -579,6 +565,19 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
		setup_singlestep(p, regs, kcb, 0);
		return 1;
		}
		} else if (*addr != BREAKPOINT_INSTRUCTION) {
		/*
		* The breakpoint instruction was removed right
		* after we hit it. Another cpu has removed
		* either a probepoint or a debugger breakpoint
		* at this address. In either case, no further
		* handling of this interrupt is appropriate.
		* Back up over the (now missing) int3 and run
		* the original instruction.
		*/
		regs->ip = (unsigned long)addr;
		preempt_enable_no_resched();
		return 1;
		} else if (kprobe_running()) {
		p = __get_cpu_var(current_kprobe);
		if (p->break_handler && p->break_handler(p, regs)) {

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