[RFC PATCH bpf-next v2 2/4] tracing/kprobe: bpf: Compare instruction pointer with original one
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2017-12-26 07:47:52
Also in:
lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Compare instruction pointer with original one on the stack instead using per-cpu bpf_kprobe_override flag. This patch also consolidates reset_current_kprobe() and preempt_enable_no_resched() blocks. Those can be done in one place. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- kernel/trace/bpf_trace.c | 1 - kernel/trace/trace_kprobe.c | 21 +++++++-------------- 2 files changed, 7 insertions(+), 15 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d663660f8392..cefa9b0e396c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -83,7 +83,6 @@ EXPORT_SYMBOL_GPL(trace_call_bpf); #ifdef CONFIG_BPF_KPROBE_OVERRIDE BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc) { - __this_cpu_write(bpf_kprobe_override, 1); regs_set_return_value(regs, rc); arch_ftrace_kprobe_override_function(regs); return 0;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 265e3e27e8dc..a7c7035963f2 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c@@ -42,8 +42,6 @@ struct trace_kprobe { (offsetof(struct trace_kprobe, tp.args) + \ (sizeof(struct probe_arg) * (n))) -DEFINE_PER_CPU(int, bpf_kprobe_override); - static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk) { return tk->rp.handler != NULL;
@@ -1204,6 +1202,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) int rctx; if (bpf_prog_array_valid(call)) { + unsigned long orig_ip = instruction_pointer(regs); int ret; ret = trace_call_bpf(call, regs);
@@ -1211,12 +1210,13 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) /* * We need to check and see if we modified the pc of the * pt_regs, and if so clear the kprobe and return 1 so that we - * don't do the instruction skipping. Also reset our state so - * we are clean the next pass through. + * don't do the single stepping. + * The ftrace kprobe handler leaves it up to us to re-enable + * preemption here before returning if we've modified the ip. */ - if (__this_cpu_read(bpf_kprobe_override)) { - __this_cpu_write(bpf_kprobe_override, 0); + if (orig_ip != instruction_pointer(regs)) { reset_current_kprobe(); + preempt_enable_no_resched(); return 1; } if (!ret)
@@ -1324,15 +1324,8 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs) if (tk->tp.flags & TP_FLAG_TRACE) kprobe_trace_func(tk, regs); #ifdef CONFIG_PERF_EVENTS - if (tk->tp.flags & TP_FLAG_PROFILE) { + if (tk->tp.flags & TP_FLAG_PROFILE) ret = kprobe_perf_func(tk, regs); - /* - * The ftrace kprobe handler leaves it up to us to re-enable - * preemption here before returning if we've modified the ip. - */ - if (ret) - preempt_enable_no_resched(); - } #endif return ret; }