uprobes: Change handle_trampoline() to find the next chain beforehand (a83cfeb9) · Commits · 戴 / test

No functional changes, preparation. Add the new helper, find_next_ret_chain(), which finds the first !chained entry and returns its ->next. Yes, it is suboptimal. We probably want to turn ->chained into ->start_of_this_chain pointer and avoid another loop. But this needs the boring changes in dup_utask(), so lets do this later. Change the main loop in handle_trampoline() to unwind the stack until ri is equal to the pointer returned by this new helper. Tested-by:

Pratyush Anand <panand@redhat.com> Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Acked-by:

Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by:

Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134013.GA4755@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/events/uprobes.c

+16 −11

Original line number	Diff line number	Diff line
		@@ -1766,11 +1766,22 @@ handle_uretprobe_chain(struct return_instance ri, struct pt_regs regs)
		up_read(&uprobe->register_rwsem);
		}

		static struct return_instance find_next_ret_chain(struct return_instance ri)
		{
		bool chained;

		do {
		chained = ri->chained;
		ri = ri->next; /* can't be NULL if chained */
		} while (chained);

		return ri;
		}

		static void handle_trampoline(struct pt_regs *regs)
		{
		struct uprobe_task *utask;
		struct return_instance *ri;
		bool chained;
		struct return_instance ri, next;

		utask = current->utask;
		if (!utask)
		@@ -1780,24 +1791,18 @@ static void handle_trampoline(struct pt_regs *regs)
		if (!ri)
		goto sigill;

		next = find_next_ret_chain(ri);
		/*
		* TODO: we should throw out return_instance's invalidated by
		* longjmp(), currently we assume that the probed function always
		* returns.
		*/
		instruction_pointer_set(regs, ri->orig_ret_vaddr);

		for (;;) {
		do {
		handle_uretprobe_chain(ri, regs);

		chained = ri->chained;
		ri = free_ret_instance(ri);
		utask->depth--;

		if (!chained)
		break;
		BUG_ON(!ri);
		}
		} while (ri != next);

		utask->return_instances = ri;
		return;

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