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Commit 6ded5f38 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Don't use arch_uprobe_abort_xol() in arch_uprobe_post_xol() 



014940ba "uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails"
changed arch_uprobe_post_xol() to use arch_uprobe_abort_xol() if ->post_xol
fails. This was correct and helped to avoid the additional complications,
we need to clear X86_EFLAGS_TF in this case.

However, now that we have uprobe_xol_ops->abort() hook it would be better
to avoid arch_uprobe_abort_xol() here. ->post_xol() should likely do what
->abort() does anyway, we should not do the same work twice. Currently only
handle_riprel_post_xol() can be called twice, this is unnecessary but safe.
Still this is not clean and can lead to the problems in future.

Change arch_uprobe_post_xol() to clear X86_EFLAGS_TF and restore ->ip by
hand and avoid arch_uprobe_abort_xol(). This temporary uglifies the usage
of autask.saved_tf, we will cleanup this later.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarJim Keniston <jkenisto@us.ibm.com>
parent 588fbd61

arch/x86/kernel/uprobes.c

+9 −8
Original line number Diff line number Diff line
@@ -759,22 +759,24 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 
	struct uprobe_task *utask = current->utask;



	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);

	current->thread.trap_nr = utask->autask.saved_trap_nr;



	if (auprobe->ops->post_xol) {

		int err = auprobe->ops->post_xol(auprobe, regs);

		if (err) {

			arch_uprobe_abort_xol(auprobe, regs);

			if (!utask->autask.saved_tf)

				regs->flags &= ~X86_EFLAGS_TF;

			/*

			 * Restart the probed insn. ->post_xol() must ensure

			 * this is really possible if it returns -ERESTART.

			 * Restore ->ip for restart or post mortem analysis.

			 * ->post_xol() must not return -ERESTART unless this

			 * is really possible.

			 */

			regs->ip = utask->vaddr;

			if (err == -ERESTART)

				return 0;

			return err;

		}

	}



	current->thread.trap_nr = utask->autask.saved_trap_nr;

	/*

	 * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP

	 * so we can get an extra SIGTRAP if we do not clear TF. We need
@@ -819,9 +821,8 @@ int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, 


/*

 * This function gets called when XOL instruction either gets trapped or

 * the thread has a fatal signal, or if arch_uprobe_post_xol() failed.

 * Reset the instruction pointer to its probed address for the potential

 * restart or for post mortem analysis.

 * the thread has a fatal signal. Reset the instruction pointer to its

 * probed address for the potential restart or for post mortem analysis.

 */

void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)

{