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Commit 0578a970 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp() 



If handle_swbp()->add_utask() fails but UPROBE_SKIP_SSTEP is set,
cleanup_ret: path do not restart the insn, this is wrong. Remove
this check and add the additional label for can_skip_sstep() = T
case.

Note also that UPROBE_SKIP_SSTEP can be false positive, we simply
can not trust it unless arch_uprobe_skip_sstep() was already called.

Also, move another UPROBE_SKIP_SSTEP check before can_skip_sstep()
into this helper, this looks more clean and understandable.

Note: probably we should rename "skip" to "emulate" and I think
that "clear UPROBE_SKIP_SSTEP" should be moved to arch_can_skip.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 746a9e6b

kernel/events/uprobes.c

+15 −16
Original line number Original line Diff line number Diff line
@@ -1389,10 +1389,11 @@ bool uprobe_deny_signal(void) 
 */

 */

static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)

static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)

{

{

	if (uprobe->flags & UPROBE_SKIP_SSTEP) {

		if (arch_uprobe_skip_sstep(&uprobe->arch, regs))

		if (arch_uprobe_skip_sstep(&uprobe->arch, regs))

			return true;

			return true;



		uprobe->flags &= ~UPROBE_SKIP_SSTEP;

		uprobe->flags &= ~UPROBE_SKIP_SSTEP;

	}

	return false;

	return false;

}

}
@@ -1494,12 +1495,12 @@ static void handle_swbp(struct pt_regs *regs) 
		utask = add_utask();

		utask = add_utask();

		/* Cannot allocate; re-execute the instruction. */

		/* Cannot allocate; re-execute the instruction. */

		if (!utask)

		if (!utask)

			goto cleanup_ret;

			goto restart;

	}

	}





	handler_chain(uprobe, regs);

	handler_chain(uprobe, regs);

	if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))

	if (can_skip_sstep(uprobe, regs))

		goto cleanup_ret;

		goto out;





	if (!pre_ssout(uprobe, regs, bp_vaddr)) {

	if (!pre_ssout(uprobe, regs, bp_vaddr)) {

		arch_uprobe_enable_step(&uprobe->arch);

		arch_uprobe_enable_step(&uprobe->arch);
@@ -1508,15 +1509,13 @@ static void handle_swbp(struct pt_regs *regs) 
		return;

		return;

	}

	}





cleanup_ret:

restart:

	if (!(uprobe->flags & UPROBE_SKIP_SSTEP))



	/*

	/*

	 * cannot singlestep; cannot skip instruction;

	 * cannot singlestep; cannot skip instruction;

	 * re-execute the instruction.

	 * re-execute the instruction.

	 */

	 */

	instruction_pointer_set(regs, bp_vaddr);

	instruction_pointer_set(regs, bp_vaddr);



out:

	put_uprobe(uprobe);

	put_uprobe(uprobe);

}

}