[bpf-next,v4,3/5] bpf, x86: Attach a cookie to fentry/fexit/fmod_ret.

Commit Message

Kui-Feng Lee April 11, 2022, 5:34 p.m. UTC

Add a bpf_cookie field to struct bpf_tracing_link to attach a cookie
to a link of a trace hook.  A 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 <[e-mail]>
---
 arch/x86/net/bpf_jit_comp.c    | 11 +++++++++--
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       |  8 ++++++++
 kernel/bpf/syscall.c           | 27 +++++++++++++++++++++++----
 kernel/trace/bpf_trace.c       | 17 +++++++++++++++++
 tools/include/uapi/linux/bpf.h |  7 +++++++
 6 files changed, 65 insertions(+), 6 deletions(-)

Patch

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 0f521be68f7b..18d02dcd810a 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1764,13 +1764,20 @@  static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
 			   struct bpf_tramp_link *l, int stack_size,
 			   bool save_ret)
 {
+	u64 cookie = 0;
 	u8 *prog = *pprog;
 	u8 *jmp_insn;
 	int ctx_cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
 	struct bpf_prog *p = l->link.prog;
 
-	/* mov rdi, 0 */
-	emit_mov_imm64(&prog, BPF_REG_1, 0, 0);
+	if (l->link.type == BPF_LINK_TYPE_TRACING) {
+		struct bpf_tracing_link *tr_link =
+			container_of(l, struct bpf_tracing_link, link);
+		cookie = tr_link->cookie;
+	}
+
+	/* mov rdi, cookie */
+	emit_mov_imm64(&prog, BPF_REG_1, (long) cookie >> 32, (u32) (long) cookie);
 
 	/* Prepare struct bpf_tramp_run_ctx.
 	 *
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a94891bfab7f..2a6f70ebd84a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1062,6 +1062,7 @@  struct bpf_tracing_link {
 	enum bpf_attach_type attach_type;
 	struct bpf_trampoline *trampoline;
 	struct bpf_prog *tgt_prog;
+	u64 cookie;
 };
 
 struct bpf_link_primer {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a4f557338af7..5e901e6d17ea 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1436,6 +1436,7 @@  union bpf_attr {
 	struct { /* anonymous struct used by BPF_RAW_TRACEPOINT_OPEN command */
 		__u64 name;
 		__u32 prog_fd;
+		__u64 bpf_cookie;
 	} raw_tracepoint;
 
 	struct { /* anonymous struct for BPF_BTF_LOAD */
@@ -1490,6 +1491,13 @@  union bpf_attr {
 				__aligned_u64	addrs;
 				__aligned_u64	cookies;
 			} kprobe_multi;
+			struct {
+				/* black box user-provided value passed through
+				 * to BPF program at the execution time and
+				 * accessible through bpf_get_attach_cookie() BPF helper
+				 */
+				__u64		bpf_cookie;
+			} tracing;
 		};
 	} link_create;
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e8f06311a0b5..e0e0c58fe247 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2695,9 +2695,10 @@  static const struct bpf_link_ops bpf_tracing_link_lops = {
 	.fill_link_info = bpf_tracing_link_fill_link_info,
 };
 
-static int bpf_tracing_prog_attach(struct bpf_prog *prog,
-				   int tgt_prog_fd,
-				   u32 btf_id)
+static int bpf_tracing_prog_attach_cookie(struct bpf_prog *prog,
+					  int tgt_prog_fd,
+					  u32 btf_id,
+					  u64 bpf_cookie)
 {
 	struct bpf_link_primer link_primer;
 	struct bpf_prog *tgt_prog = NULL;
@@ -2762,6 +2763,7 @@  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->cookie = bpf_cookie;
 
 	mutex_lock(&prog->aux->dst_mutex);
 
@@ -2871,6 +2873,13 @@  static int bpf_tracing_prog_attach(struct bpf_prog *prog,
 	return err;
 }
 
+static int bpf_tracing_prog_attach(struct bpf_prog *prog,
+				   int tgt_prog_fd,
+				   u32 btf_id)
+{
+	return bpf_tracing_prog_attach_cookie(prog, tgt_prog_fd, btf_id, 0);
+}
+
 struct bpf_raw_tp_link {
 	struct bpf_link link;
 	struct bpf_raw_event_map *btp;
@@ -3023,7 +3032,7 @@  static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *pro
 }
 #endif /* CONFIG_PERF_EVENTS */
 
-#define BPF_RAW_TRACEPOINT_OPEN_LAST_FIELD raw_tracepoint.prog_fd
+#define BPF_RAW_TRACEPOINT_OPEN_LAST_FIELD raw_tracepoint.bpf_cookie
 
 static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
 {
@@ -3187,6 +3196,10 @@  attach_type_to_prog_type(enum bpf_attach_type attach_type)
 		return BPF_PROG_TYPE_SK_LOOKUP;
 	case BPF_XDP:
 		return BPF_PROG_TYPE_XDP;
+	case BPF_TRACE_FENTRY:
+	case BPF_TRACE_FEXIT:
+	case BPF_MODIFY_RETURN:
+		return BPF_PROG_TYPE_TRACING;
 	default:
 		return BPF_PROG_TYPE_UNSPEC;
 	}
@@ -4251,6 +4264,12 @@  static int tracing_bpf_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
 		return bpf_tracing_prog_attach(prog,
 					       attr->link_create.target_fd,
 					       attr->link_create.target_btf_id);
+	else if (prog->type == BPF_PROG_TYPE_TRACING)
+		return bpf_tracing_prog_attach_cookie(prog,
+						      0,
+						      0,
+						      attr->link_create.tracing.bpf_cookie);
+
 	return -EINVAL;
 }
 
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b26f3da943de..c5713d5fba45 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1088,6 +1088,21 @@  static const struct bpf_func_proto bpf_get_attach_cookie_proto_pe = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_get_attach_cookie_tracing, 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_tracing = {
+	.func		= bpf_get_attach_cookie_tracing,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
 {
 #ifndef CONFIG_X86
@@ -1716,6 +1731,8 @@  tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_ret_proto : NULL;
 	case BPF_FUNC_get_func_arg_cnt:
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_cnt_proto : NULL;
+	case BPF_FUNC_get_attach_cookie:
+		return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto_tracing : NULL;
 	default:
 		fn = raw_tp_prog_func_proto(func_id, prog);
 		if (!fn && prog->expected_attach_type == BPF_TRACE_ITER)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a4f557338af7..a5ee57f09e04 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1490,6 +1490,13 @@  union bpf_attr {
 				__aligned_u64	addrs;
 				__aligned_u64	cookies;
 			} kprobe_multi;
+			struct {
+				/* black box user-provided value passed through
+				 * to BPF program at the execution time and
+				 * accessible through bpf_get_attach_cookie() BPF helper
+				 */
+				__u64		bpf_cookie;
+			} tracing;
 		};
 	} link_create;