[RFC PATCH v2 02/13] bpf: Allow loading BPF_TRACE_MAP programs

[Joe Burton <jevburton.kernel@xxxxxxxxx>]

From: Joe Burton <jevburton@xxxxxxxxxx>

Add new attach type, BPF_TRACE_MAP. Tracing programs may specify this
type when loading. The verifier then checks that the traced function
has been registered for map tracing.

Signed-off-by: Joe Burton <jevburton@xxxxxxxxxx>
---
 include/linux/bpf.h      |  1 +
 include/uapi/linux/bpf.h |  1 +
 kernel/bpf/map_trace.c   | 25 +++++++++++++++++++++++++
 kernel/bpf/verifier.c    |  6 ++++++
 4 files changed, 33 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index dad62d5571c9..272f0ac49285 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1539,6 +1539,7 @@ void bpf_iter_unreg_target(const struct bpf_iter_reg *reg_info);
 bool bpf_iter_prog_supported(struct bpf_prog *prog);
 const struct bpf_func_proto *
 bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
+bool bpf_map_trace_prog_supported(struct bpf_prog *prog);
 int bpf_map_trace_reg_target(const struct bpf_map_trace_reg *reg_info);
 int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_prog *prog);
 int bpf_iter_new_fd(struct bpf_link *link);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 17e8f4113369..0883c5dfb5d8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1003,6 +1003,7 @@ enum bpf_attach_type {
 	BPF_SK_REUSEPORT_SELECT,
 	BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
 	BPF_PERF_EVENT,
+	BPF_TRACE_MAP,
 	__MAX_BPF_ATTACH_TYPE
 };
 
diff --git a/kernel/bpf/map_trace.c b/kernel/bpf/map_trace.c
index d8f829535f7e..d2c6df20f55c 100644
--- a/kernel/bpf/map_trace.c
+++ b/kernel/bpf/map_trace.c
@@ -31,3 +31,28 @@ int bpf_map_trace_reg_target(const struct bpf_map_trace_reg *reg_info)
 
 	return 0;
 }
+
+bool bpf_map_trace_prog_supported(struct bpf_prog *prog)
+{
+	const char *attach_fname = prog->aux->attach_func_name;
+	u32 prog_btf_id = prog->aux->attach_btf_id;
+	struct bpf_map_trace_target_info *tinfo;
+	bool supported = false;
+
+	mutex_lock(&targets_mutex);
+	list_for_each_entry(tinfo, &targets, list) {
+		if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
+			supported = true;
+			break;
+		}
+		if (!strcmp(attach_fname, tinfo->reg_info->target)) {
+			tinfo->btf_id = prog->aux->attach_btf_id;
+			supported = true;
+			break;
+		}
+	}
+	mutex_unlock(&targets_mutex);
+
+	return supported;
+}
+
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1433752db740..babcb135dc0d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9464,6 +9464,7 @@ static int check_return_code(struct bpf_verifier_env *env)
 			break;
 		case BPF_TRACE_RAW_TP:
 		case BPF_MODIFY_RETURN:
+		case BPF_TRACE_MAP:
 			return 0;
 		case BPF_TRACE_ITER:
 			break;
@@ -13496,6 +13497,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 
 		break;
 	case BPF_TRACE_ITER:
+	case BPF_TRACE_MAP:
 		if (!btf_type_is_func(t)) {
 			bpf_log(log, "attach_btf_id %u is not a function\n",
 				btf_id);
@@ -13672,6 +13674,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		if (!bpf_iter_prog_supported(prog))
 			return -EINVAL;
 		return 0;
+	} else if (prog->expected_attach_type == BPF_TRACE_MAP) {
+		if (!bpf_map_trace_prog_supported(prog))
+			return -EINVAL;
+		return 0;
 	}
 
 	if (prog->type == BPF_PROG_TYPE_LSM) {
-- 
2.33.0.685.g46640cef36-goog