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 <o...@redhat.com>
---
arch/x86/kernel/uprobes.c | 17 +++++++++--------
1 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 8fce6ef..4e2cdd5 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -748,22 +748,24 @@ 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
@@ -808,9 +810,8 @@ 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)
{
--
1.5.5.1
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