Commit 2fcc8241 authored by Kui-Feng Lee's avatar Kui-Feng Lee Committed by Andrii Nakryiko
Browse files

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: default avatarKui-Feng Lee <kuifeng@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220510205923.3206889-4-kuifeng@fb.com
parent e384c7b7

arch/x86/net/bpf_jit_comp.c

+3 −2
Original line number Diff line number Diff line
@@ -1769,9 +1769,10 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, 
	u8 *jmp_insn;

	int ctx_cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);

	struct bpf_prog *p = l->link.prog;

	u64 cookie = l->cookie;



	/* mov rdi, 0 */

	emit_mov_imm64(&prog, BPF_REG_1, 0, 0);

	/* mov rdi, cookie */

	emit_mov_imm64(&prog, BPF_REG_1, (long) cookie >> 32, (u32) (long) cookie);



	/* Prepare struct bpf_tramp_run_ctx.

	 *

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -1102,6 +1102,7 @@ struct bpf_link_ops { 
struct bpf_tramp_link {

	struct bpf_link link;

	struct hlist_node tramp_hlist;

	u64 cookie;

};



struct bpf_tracing_link {

include/uapi/linux/bpf.h

+9 −0
Original line number Diff line number Diff line
@@ -1490,6 +1490,15 @@ union bpf_attr { 
				__aligned_u64	addrs;

				__aligned_u64	cookies;

			} kprobe_multi;

			struct {

				/* this is overlaid with the target_btf_id above. */

				__u32		target_btf_id;

				/* black box user-provided value passed through

				 * to BPF program at the execution time and

				 * accessible through bpf_get_attach_cookie() BPF helper

				 */

				__u64		cookie;

			} tracing;

		};

	} link_create;

kernel/bpf/bpf_lsm.c

+17 −0
Original line number Diff line number Diff line
@@ -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);

	}

kernel/bpf/syscall.c

+8 −4
Original line number Diff line number Diff line
@@ -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: