[PATCH dwarves v6 3/6] bpf, x86: Attach a cookie to fentry/fexit/fmod_ret.

[Kui-Feng Lee <kuifeng@fb.com>]

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>
---
 arch/x86/net/bpf_jit_comp.c | 12 ++++++++++--
 include/linux/bpf.h         |  1 +
 kernel/bpf/syscall.c        | 10 +++++++---
 kernel/trace/bpf_trace.c    | 17 +++++++++++++++++
 4 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index bf4576a6938c..52a5eba2d5e8 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1764,13 +1764,21 @@ 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 1eae81df154e..45963972785b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1060,6 +1060,7 @@ 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/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 56e69a582b21..966f2d40ae55 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2697,7 +2697,8 @@ 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;
@@ -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);
 
@@ -3058,7 +3060,7 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
 			tp_name = prog->aux->attach_func_name;
 			break;
 		}
-		err = bpf_tracing_prog_attach(prog, 0, 0);
+		err = bpf_tracing_prog_attach(prog, 0, 0, 0);
 		if (err >= 0)
 			return err;
 		goto out_put_prog;
@@ -4250,7 +4252,9 @@ static int tracing_bpf_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
 	else if (prog->type == BPF_PROG_TYPE_EXT)
 		return bpf_tracing_prog_attach(prog,
 					       attr->link_create.target_fd,
-					       attr->link_create.target_btf_id);
+					       attr->link_create.target_btf_id,
+					       0);
+
 	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)
-- 
2.30.2