The following commit has been merged into the perf/core branch of tip:
Commit-ID: 78ff2733ff352175eb7f4418a34654346e1b6cd2
Gitweb: https://git.kernel.org/tip/78ff2733ff352175eb7f4418a34654346e1b6cd2
Author: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
AuthorDate: Wed, 28 Oct 2020 23:31:10 +09:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 09 Dec 2020 17:08:57 +01:00
x86/kprobes: Restore BTF if the single-stepping is cancelled
Fix to restore BTF if single-stepping causes a page fault and
it is cancelled.
Usually the BTF flag was restored when the single stepping is done
(in resume_execution()). However, if a page fault happens on the
single stepping instruction, the fault handler is invoked and
the single stepping is cancelled. Thus, the BTF flag is not
restored.
Fixes: 1ecc798c6764 ("x86: debugctlmsr kprobes")
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/160389546985.106936.12727996109376240993.stgit@devnote2
---
arch/x86/kernel/kprobes/core.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 547c7ab..39f7d8c 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -937,6 +937,11 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
* So clear it by resetting the current kprobe:
*/
regs->flags &= ~X86_EFLAGS_TF;
+ /*
+ * Since the single step (trap) has been cancelled,
+ * we need to restore BTF here.
+ */
+ restore_btf();
/*
* If the TF flag was set before the kprobe hit,
|