Re: [PATCHv3 bpf-next 4/7] bpf: Add bpf_get_func_ip helper for kprobe programs

On Sat, Jul 10, 2021 at 04:55:12PM +0900, Masami Hiramatsu wrote:

On Wed,  7 Jul 2021 23:47:48 +0200
Jiri Olsa [off-list ref] wrote:

quoted

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.

Note that the kp->addr of kretprobe will be the callee function
address, even if the handler is called when the end of the callee.

yes, that's what we need

Anyway, this looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

thanks,
jirka

Thank you,

quoted

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       |  2 +-
 kernel/bpf/verifier.c          |  2 ++
 kernel/trace/bpf_trace.c       | 17 +++++++++++++++++
 tools/include/uapi/linux/bpf.h |  2 +-
 4 files changed, 21 insertions(+), 2 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 f975a3aa9368..79eb9d81a198 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c

@@ -5979,6 +5979,8 @@ static int 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..55acf56b0c3a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -17,6 +17,7 @@
 #include <linux/error-injection.h>
 #include <linux/btf_ids.h>
 #include <linux/bpf_lsm.h>
+#include <linux/kprobes.h>
 
 #include <net/bpf_sk_storage.h>
 

@@ -961,6 +962,20 @@ 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)
+{
+	struct kprobe *kp = kprobe_running();
+
+	return kp ? (u64) kp->addr : 0;
+}
+
+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 +1107,8 @@ 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/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

-- 
Masami Hiramatsu [off-list ref]