[PATCH bpf-next 4/5] bpf: Add bpf_get_func_ip helper for kprobe programs

From: Jiri Olsa <hidden>
Date: 2021-06-29 19:30:03
Also in: bpf
Subsystem: bpf [core], 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

Adding bpf_get_func_ip helper for BPF_PROG_TYPE_KPROBE programs,
so it's now possible to call bpf_get_func_ip from both kprobe and
kretprobe programs.

Taking the caller's address from 'struct kprobe::addr', which is
defined for both kprobe and kretprobe.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       |  2 +-
 kernel/bpf/verifier.c          |  2 ++
 kernel/trace/bpf_trace.c       | 14 ++++++++++++++
 kernel/trace/trace_kprobe.c    | 20 ++++++++++++++++++--
 kernel/trace/trace_probe.h     |  5 +++++
 tools/include/uapi/linux/bpf.h |  2 +-
 6 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 83e87ffdbb6e..4894f99a1993 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -4783,7 +4783,7 @@ union bpf_attr {
  *
  * u64 bpf_get_func_ip(void *ctx)
  * 	Description
- * 		Get address of the traced function (for tracing programs).
+ * 		Get address of the traced function (for tracing and kprobe programs).
  * 	Return
  * 		Address of the traced function.
  */

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 701ff7384fa7..b66e0a7104f8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c

@@ -5979,6 +5979,8 @@ static bool has_get_func_ip(struct bpf_verifier_env *env)
 			return -ENOTSUPP;
 		}
 		return 0;
+	} else if (type == BPF_PROG_TYPE_KPROBE) {
+		return 0;
 	}
 
 	verbose(env, "func %s#%d not supported for program type %d\n",

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9edd3b1a00ad..1a5bddce9abd 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -961,6 +961,18 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs)
+{
+	return trace_current_kprobe_addr();
+}
+
+static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {
+	.func		= bpf_get_func_ip_kprobe,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 const struct bpf_func_proto *
 bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {

@@ -1092,6 +1104,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_override_return:
 		return &bpf_override_return_proto;
 #endif
+	case BPF_FUNC_get_func_ip:
+		return &bpf_get_func_ip_proto_kprobe;
 	default:
 		return bpf_tracing_func_proto(func_id, prog);
 	}

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ea6178cb5e33..b07d5888db14 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c

@@ -1570,6 +1570,18 @@ static int kretprobe_event_define_fields(struct trace_event_call *event_call)
 }
 
 #ifdef CONFIG_PERF_EVENTS
+/* Used by bpf get_func_ip helper */
+DEFINE_PER_CPU(u64, current_kprobe_addr) = 0;
+
+u64 trace_current_kprobe_addr(void)
+{
+	return *this_cpu_ptr(&current_kprobe_addr);
+}
+
+static void trace_current_kprobe_set(struct trace_kprobe *tk)
+{
+	__this_cpu_write(current_kprobe_addr, (u64) tk->rp.kp.addr);
+}
 
 /* Kprobe profile handler */
 static int

@@ -1585,6 +1597,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 		unsigned long orig_ip = instruction_pointer(regs);
 		int ret;
 
+		trace_current_kprobe_set(tk);
 		ret = trace_call_bpf(call, regs);
 
 		/*

@@ -1631,8 +1644,11 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
 	int size, __size, dsize;
 	int rctx;
 
-	if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
-		return;
+	if (bpf_prog_array_valid(call)) {
+		trace_current_kprobe_set(tk);
+		if (!trace_call_bpf(call, regs))
+			return;
+	}
 
 	head = this_cpu_ptr(call->perf_events);
 	if (hlist_empty(head))

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 227d518e5ba5..19c979834916 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h

@@ -199,6 +199,7 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(symbol);
 #ifdef CONFIG_KPROBE_EVENTS
 bool trace_kprobe_on_func_entry(struct trace_event_call *call);
 bool trace_kprobe_error_injectable(struct trace_event_call *call);
+u64 trace_current_kprobe_addr(void);
 #else
 static inline bool trace_kprobe_on_func_entry(struct trace_event_call *call)
 {

@@ -209,6 +210,10 @@ static inline bool trace_kprobe_error_injectable(struct trace_event_call *call)
 {
 	return false;
 }
+static inline u64 trace_current_kprobe_addr(void)
+{
+	return 0;
+}
 #endif /* CONFIG_KPROBE_EVENTS */
 
 struct probe_arg {

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 83e87ffdbb6e..4894f99a1993 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h

@@ -4783,7 +4783,7 @@ union bpf_attr {
  *
  * u64 bpf_get_func_ip(void *ctx)
  * 	Description
- * 		Get address of the traced function (for tracing programs).
+ * 		Get address of the traced function (for tracing and kprobe programs).
  * 	Return
  * 		Address of the traced function.
  */

-- 
2.31.1

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