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

014940bad8e4 "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: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index b3c2a92cce6c8de7363688f2f4378989a2f8c0ab..2efb93f960309417f2941b5aecb762e513968382 100644 (file)
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -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)
 {