uprobes: Do not allocate current->utask unnecessary

handle_swbp() does get_utask() before can_skip_sstep() for no reason,
we do not need ->utask if can_skip_sstep() succeeds.

Move get_utask() to pre_ssout() who actually starts to use it. Move
the initialization of utask->active_uprobe/state as well. This way
the whole initialization is consolidated in pre_ssout().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>

1 files changed, 6 insertions, 10 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 0527379dac5b..071edcb3e62d 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1308,7 +1308,9 @@ pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
         unsigned long xol_vaddr;
         int err;
 
-        utask = current->utask;
+        utask = get_utask();
+        if (!utask)
+                return -ENOMEM;
 
         xol_vaddr = xol_get_insn_slot(uprobe);
         if (!xol_vaddr)
@@ -1323,6 +1325,8 @@ pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
                 return err;
         }
 
+        utask->active_uprobe = uprobe;
+        utask->state = UTASK_SSTEP;
         return 0;
 }
 
@@ -1474,7 +1478,6 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
  */
 static void handle_swbp(struct pt_regs *regs)
 {
-        struct uprobe_task *utask;
         struct uprobe *uprobe;
         unsigned long bp_vaddr;
         int uninitialized_var(is_swbp);
@@ -1512,19 +1515,12 @@ static void handle_swbp(struct pt_regs *regs)
         if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
                 goto out;
 
-        utask = get_utask();
-        if (!utask)
-                goto out;       /* re-execute the instruction. */
-
         handler_chain(uprobe, regs);
         if (can_skip_sstep(uprobe, regs))
                 goto out;
 
-        if (!pre_ssout(uprobe, regs, bp_vaddr)) {
-                utask->active_uprobe = uprobe;
-                utask->state = UTASK_SSTEP;
+        if (!pre_ssout(uprobe, regs, bp_vaddr))
                 return;
-        }
 
         /* can_skip_sstep() succeeded, or restart if can't singlestep */
 out: