From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Fri, 18 Jun 2021 07:06:46 +0000 Subject: [PATCH -tip v8 09/13] kprobes: Enable stacktrace from pt_regs in kretprobe handler Message-Id: <162400000592.506599.4695807810528866713.stgit@devnote2> List-Id: References: <162399992186.506599.8457763707951687195.stgit@devnote2> In-Reply-To: <162399992186.506599.8457763707951687195.stgit@devnote2> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Steven Rostedt , Josh Poimboeuf , Ingo Molnar Cc: X86 ML , Masami Hiramatsu , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, Thomas Gleixner , Borislav Petkov , Peter Zijlstra , kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org, Abhishek Sagar , Andrii Nakryiko Since the ORC unwinder from pt_regs requires setting up regs->ip correctly, set the correct return address to the regs->ip before calling user kretprobe handler. This allows the kretrprobe handler to trace stack from the kretprobe's pt_regs by stack_trace_save_regs() (eBPF will do this), instead of stack tracing from the handler context by stack_trace_save() (ftrace will do this). Suggested-by: Josh Poimboeuf Signed-off-by: Masami Hiramatsu Tested-by: Andrii Nakryik --- Changes in v8: - Update comment to clarify why this is needed. Changes in v3: - Cast the correct_ret_addr to unsigned long. --- kernel/kprobes.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 650cbe738666..ba729ed05cb3 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1896,6 +1896,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, BUG_ON(1); } + /* Set the instruction pointer to the correct address */ + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); + /* Run them. */ first = current->kretprobe_instances.first; while (first) {