uprobes/x86: Fix arch_uprobe_disable_step() && UTASK_SSTEP_TRAPPED interaction

arch_uprobe_disable_step() should also take UTASK_SSTEP_TRAPPED into
account. In this case the probed insn was not executed, we need to
clear X86_EFLAGS_TF if it was set by us and that is all.

Again, this code will look more clean when we move it into
arch_uprobe_post_xol() and arch_uprobe_abort_xol().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 7e993d1..9538f00 100644 (file)
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -706,14 +706,20 @@ void arch_uprobe_disable_step(struct arch_uprobe *auprobe)
 {
        struct task_struct *task = current;
        struct arch_uprobe_task *autask = &task->utask->autask;
+       bool trapped = (task->utask->state == UTASK_SSTEP_TRAPPED);
        struct pt_regs *regs = task_pt_regs(task);
        /*
         * The state of TIF_BLOCKSTEP was not saved so we can get an extra
         * SIGTRAP if we do not clear TF. We need to examine the opcode to
         * make it right.
         */
-       if (autask->saved_tf)
-               send_sig(SIGTRAP, task, 0);
-       else if (!(auprobe->fixups & UPROBE_FIX_SETF))
-               regs->flags &= ~X86_EFLAGS_TF;
+       if (unlikely(trapped)) {
+               if (!autask->saved_tf)
+                       regs->flags &= ~X86_EFLAGS_TF;
+       } else {
+               if (autask->saved_tf)
+                       send_sig(SIGTRAP, task, 0);
+               else if (!(auprobe->fixups & UPROBE_FIX_SETF))
+                       regs->flags &= ~X86_EFLAGS_TF;
+       }
 }