bpf, x86: Attach a cookie to fentry/fexit/fmod_ret/lsm.

Pass a cookie along with BPF_LINK_CREATE requests.

Add a bpf_cookie field to struct bpf_tracing_link to attach a cookie.
The cookie of a bpf_tracing_link is available by calling
bpf_get_attach_cookie when running the BPF program of the attached
link.

The value of a cookie will be set at bpf_tramp_run_ctx by the
trampoline of the link.

Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220510205923.3206889-4-kuifeng@fb.com

3 files changed, 30 insertions, 6 deletions

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 064eccba641d..c1351df9f7ee 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -117,6 +117,21 @@ static const struct bpf_func_proto bpf_ima_file_hash_proto = {
 	.allowed	= bpf_ima_inode_hash_allowed,
 };
 
+BPF_CALL_1(bpf_get_attach_cookie, void *, ctx)
+{
+	struct bpf_trace_run_ctx *run_ctx;
+
+	run_ctx = container_of(current->bpf_ctx, struct bpf_trace_run_ctx, run_ctx);
+	return run_ctx->bpf_cookie;
+}
+
+static const struct bpf_func_proto bpf_get_attach_cookie_proto = {
+	.func		= bpf_get_attach_cookie,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 static const struct bpf_func_proto *
 bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -141,6 +156,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return prog->aux->sleepable ? &bpf_ima_inode_hash_proto : NULL;
 	case BPF_FUNC_ima_file_hash:
 		return prog->aux->sleepable ? &bpf_ima_file_hash_proto : NULL;
+	case BPF_FUNC_get_attach_cookie:
+		return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto : NULL;
 	default:
 		return tracing_prog_func_proto(func_id, prog);
 	}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d48165fccf49..72e53489165d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2921,7 +2921,8 @@ static const struct bpf_link_ops bpf_tracing_link_lops = {
 
 static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 				   int tgt_prog_fd,
-				   u32 btf_id)
+				   u32 btf_id,
+				   u64 bpf_cookie)
 {
 	struct bpf_link_primer link_primer;
 	struct bpf_prog *tgt_prog = NULL;
@@ -2986,6 +2987,7 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 	bpf_link_init(&link->link.link, BPF_LINK_TYPE_TRACING,
 		      &bpf_tracing_link_lops, prog);
 	link->attach_type = prog->expected_attach_type;
+	link->link.cookie = bpf_cookie;
 
 	mutex_lock(&prog->aux->dst_mutex);
 
@@ -3271,7 +3273,7 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog,
 			tp_name = prog->aux->attach_func_name;
 			break;
 		}
-		return bpf_tracing_prog_attach(prog, 0, 0);
+		return bpf_tracing_prog_attach(prog, 0, 0, 0);
 	case BPF_PROG_TYPE_RAW_TRACEPOINT:
 	case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
 		if (strncpy_from_user(buf, user_tp_name, sizeof(buf) - 1) < 0)
@@ -4524,7 +4526,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
 	case BPF_PROG_TYPE_EXT:
 		ret = bpf_tracing_prog_attach(prog,
 					      attr->link_create.target_fd,
-					      attr->link_create.target_btf_id);
+					      attr->link_create.target_btf_id,
+					      attr->link_create.tracing.cookie);
 		break;
 	case BPF_PROG_TYPE_LSM:
 	case BPF_PROG_TYPE_TRACING:
@@ -4539,7 +4542,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
 		else
 			ret = bpf_tracing_prog_attach(prog,
 						      attr->link_create.target_fd,
-						      attr->link_create.target_btf_id);
+						      attr->link_create.target_btf_id,
+						      attr->link_create.tracing.cookie);
 		break;
 	case BPF_PROG_TYPE_FLOW_DISSECTOR:
 	case BPF_PROG_TYPE_SK_LOOKUP:
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index baf1b65d523e..0e9b3aefc34a 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -30,9 +30,12 @@ static DEFINE_MUTEX(trampoline_mutex);
 bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
 {
 	enum bpf_attach_type eatype = prog->expected_attach_type;
+	enum bpf_prog_type ptype = prog->type;
 
-	return eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
-	       eatype == BPF_MODIFY_RETURN;
+	return (ptype == BPF_PROG_TYPE_TRACING &&
+		(eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
+		 eatype == BPF_MODIFY_RETURN)) ||
+		(ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
 }
 
 void *bpf_jit_alloc_exec_page(void)