uprobes: Introduce arch_uprobe_enable/disable_step()

As Oleg pointed out in [0] uprobe should not use the ptrace interface
for enabling/disabling single stepping.

[0] http://lkml.kernel.org/r/20120730141638.GA5306@redhat.com

Add the new "__weak arch" helpers which simply call user_*_single_step()
as a preparation. This is only needed to not break the powerpc port, we
will fold this logic into arch_uprobe_pre/post_xol() hooks later.

We should also change handle_singlestep(), _disable_step(&uprobe->arch)
should be called before put_uprobe().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

2 files changed, 14 insertions, 2 deletions

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 6d4fe79a1a6a..e6f0331e3d45 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -112,6 +112,8 @@ extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm);
 extern void uprobe_free_utask(struct task_struct *t);
 extern void uprobe_copy_process(struct task_struct *t);
 extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
+extern void __weak arch_uprobe_enable_step(struct arch_uprobe *arch);
+extern void __weak arch_uprobe_disable_step(struct arch_uprobe *arch);
 extern int uprobe_post_sstep_notifier(struct pt_regs *regs);
 extern int uprobe_pre_sstep_notifier(struct pt_regs *regs);
 extern void uprobe_notify_resume(struct pt_regs *regs);
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index e4a906ce2e1d..912ef48d28ab 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1444,6 +1444,16 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
         return uprobe;
 }
 
+void __weak arch_uprobe_enable_step(struct arch_uprobe *arch)
+{
+        user_enable_single_step(current);
+}
+
+void __weak arch_uprobe_disable_step(struct arch_uprobe *arch)
+{
+        user_disable_single_step(current);
+}
+
 /*
  * Run handler and ask thread to singlestep.
  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1490,7 +1500,7 @@ static void handle_swbp(struct pt_regs *regs)
 
         utask->state = UTASK_SSTEP;
         if (!pre_ssout(uprobe, regs, bp_vaddr)) {
-                user_enable_single_step(current);
+                arch_uprobe_enable_step(&uprobe->arch);
                 return;
         }
 
@@ -1526,10 +1536,10 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
         else
                 WARN_ON_ONCE(1);
 
+        arch_uprobe_disable_step(&uprobe->arch);
         put_uprobe(uprobe);
         utask->active_uprobe = NULL;
         utask->state = UTASK_RUNNING;
-        user_disable_single_step(current);
         xol_free_insn_slot(current);
 
         spin_lock_irq(&current->sighand->siglock);