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Subject[PATCH v7 3.2-rc2 25/30] uprobes: call post_xol() unconditionally

Kill sstep_complete(), change uprobe_notify_resume() to use
post_xol() unconditionally.

It is wrong to assume that regs->ip always changes after the step.
rep or jmp/call to self for example. We know that this task has
already done the step, we can rely on DIE_DEBUG notification.

Original-patch-from: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
include/linux/uprobes.h | 3 ++-
kernel/uprobes.c | 38 ++++++++++++--------------------------
2 files changed, 14 insertions(+), 27 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index add5222..70d639c 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -74,7 +74,8 @@ struct uprobe {
enum uprobe_task_state {
UTASK_RUNNING,
UTASK_BP_HIT,
- UTASK_SSTEP
+ UTASK_SSTEP,
+ UTASK_SSTEP_ACK,
};

/*
diff --git a/kernel/uprobes.c b/kernel/uprobes.c
index b440acd..50cde86 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -1313,24 +1313,6 @@ static int pre_ssout(struct uprobe *uprobe, struct pt_regs *regs,
}

/*
- * Verify from Instruction Pointer if singlestep has indeed occurred.
- * If Singlestep has occurred, then do post singlestep fix-ups.
- */
-static bool sstep_complete(struct uprobe *uprobe, struct pt_regs *regs)
-{
- unsigned long vaddr = instruction_pointer(regs);
-
- /*
- * If we have executed out of line, Instruction pointer
- * cannot be same as virtual address of XOL slot.
- */
- if (vaddr == current->utask->xol_vaddr)
- return false;
- post_xol(uprobe, regs);
- return true;
-}
-
-/*
* uprobe_notify_resume gets called in task context just before returning
* to userspace.
*
@@ -1377,15 +1359,18 @@ void uprobe_notify_resume(struct pt_regs *regs)
else
/* Cannot Singlestep; re-execute the instruction. */
goto cleanup_ret;
- } else if (utask->state == UTASK_SSTEP) {
+ } else {
u = utask->active_uprobe;
- if (sstep_complete(u, regs)) {
- put_uprobe(u);
- utask->active_uprobe = NULL;
- utask->state = UTASK_RUNNING;
- user_disable_single_step(current);
- xol_free_insn_slot(current);
- }
+ if (utask->state == UTASK_SSTEP_ACK)
+ post_xol(u, regs);
+ else
+ WARN_ON_ONCE(1);
+
+ put_uprobe(u);
+ utask->active_uprobe = NULL;
+ utask->state = UTASK_RUNNING;
+ user_disable_single_step(current);
+ xol_free_insn_slot(current);
}
return;

@@ -1435,6 +1420,7 @@ int uprobe_post_notifier(struct pt_regs *regs)
/* task is currently not uprobed */
return 0;

+ utask->state = UTASK_SSTEP_ACK;
set_thread_flag(TIF_UPROBE);
return 1;
}


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