Commit 290248a5 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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bpf: Allow to specify kernel module BTFs when attaching BPF programs 



Add ability for user-space programs to specify non-vmlinux BTF when attaching
BTF-powered BPF programs: raw_tp, fentry/fexit/fmod_ret, LSM, etc. For this,
attach_prog_fd (now with the alias name attach_btf_obj_fd) should specify FD
of a module or vmlinux BTF object. For backwards compatibility reasons,
0 denotes vmlinux BTF. Only kernel BTF (vmlinux or module) can be specified.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-11-andrii@kernel.org
parent 22dc4a0f

include/linux/btf.h

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj, 


int btf_get_fd_by_id(u32 id);

u32 btf_obj_id(const struct btf *btf);

bool btf_is_kernel(const struct btf *btf);

bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,

			   const struct btf_member *m,

			   u32 expected_offset, u32 expected_size);

include/uapi/linux/bpf.h

+6 −1
Original line number Diff line number Diff line
@@ -557,7 +557,12 @@ union bpf_attr { 
		__aligned_u64	line_info;	/* line info */

		__u32		line_info_cnt;	/* number of bpf_line_info records */

		__u32		attach_btf_id;	/* in-kernel BTF type id to attach to */

		__u32		attach_prog_fd; /* 0 to attach to vmlinux */

		union {

			/* valid prog_fd to attach to bpf prog */

			__u32		attach_prog_fd;

			/* or valid module BTF object fd or 0 to attach to vmlinux */

			__u32		attach_btf_obj_fd;

		};

	};



	struct { /* anonymous struct used by BPF_OBJ_* commands */

kernel/bpf/btf.c

+5 −0
Original line number Diff line number Diff line
@@ -5738,6 +5738,11 @@ u32 btf_obj_id(const struct btf *btf) 
	return btf->id;

}



bool btf_is_kernel(const struct btf *btf)

{

	return btf->kernel_btf;

}



static int btf_id_cmp_func(const void *a, const void *b)

{

	const int *pa = a, *pb = b;

kernel/bpf/syscall.c

+51 −31
Original line number Diff line number Diff line
@@ -1926,12 +1926,16 @@ static void bpf_prog_load_fixup_attach_type(union bpf_attr *attr) 
static int

bpf_prog_load_check_attach(enum bpf_prog_type prog_type,

			   enum bpf_attach_type expected_attach_type,

			   u32 btf_id, u32 prog_fd)

			   struct btf *attach_btf, u32 btf_id,

			   struct bpf_prog *dst_prog)

{

	if (btf_id) {

		if (btf_id > BTF_MAX_TYPE)

			return -EINVAL;



		if (!attach_btf && !dst_prog)

			return -EINVAL;



		switch (prog_type) {

		case BPF_PROG_TYPE_TRACING:

		case BPF_PROG_TYPE_LSM:
@@ -1943,7 +1947,10 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, 
		}

	}



	if (prog_fd && prog_type != BPF_PROG_TYPE_TRACING &&

	if (attach_btf && (!btf_id || dst_prog))

		return -EINVAL;



	if (dst_prog && prog_type != BPF_PROG_TYPE_TRACING &&

	    prog_type != BPF_PROG_TYPE_EXT)

		return -EINVAL;
@@ -2060,7 +2067,8 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type) 
static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)

{

	enum bpf_prog_type type = attr->prog_type;

	struct bpf_prog *prog;

	struct bpf_prog *prog, *dst_prog = NULL;

	struct btf *attach_btf = NULL;

	int err;

	char license[128];

	bool is_gpl;
@@ -2102,44 +2110,56 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr) 
	if (is_perfmon_prog_type(type) && !perfmon_capable())

		return -EPERM;



	/* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog

	 * or btf, we need to check which one it is

	 */

	if (attr->attach_prog_fd) {

		dst_prog = bpf_prog_get(attr->attach_prog_fd);

		if (IS_ERR(dst_prog)) {

			dst_prog = NULL;

			attach_btf = btf_get_by_fd(attr->attach_btf_obj_fd);

			if (IS_ERR(attach_btf))

				return -EINVAL;

			if (!btf_is_kernel(attach_btf)) {

				btf_put(attach_btf);

				return -EINVAL;

			}

		}

	} else if (attr->attach_btf_id) {

		/* fall back to vmlinux BTF, if BTF type ID is specified */

		attach_btf = bpf_get_btf_vmlinux();

		if (IS_ERR(attach_btf))

			return PTR_ERR(attach_btf);

		if (!attach_btf)

			return -EINVAL;

		btf_get(attach_btf);

	}



	bpf_prog_load_fixup_attach_type(attr);

	if (bpf_prog_load_check_attach(type, attr->expected_attach_type,

				       attr->attach_btf_id,

				       attr->attach_prog_fd))

				       attach_btf, attr->attach_btf_id,

				       dst_prog)) {

		if (dst_prog)

			bpf_prog_put(dst_prog);

		if (attach_btf)

			btf_put(attach_btf);

		return -EINVAL;

	}



	/* plain bpf_prog allocation */

	prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);

	if (!prog)

	if (!prog) {

		if (dst_prog)

			bpf_prog_put(dst_prog);

		if (attach_btf)

			btf_put(attach_btf);

		return -ENOMEM;

	}



	prog->expected_attach_type = attr->expected_attach_type;

	prog->aux->attach_btf = attach_btf;

	prog->aux->attach_btf_id = attr->attach_btf_id;



	if (attr->attach_btf_id && !attr->attach_prog_fd) {

		struct btf *btf;



		btf = bpf_get_btf_vmlinux();

		if (IS_ERR(btf))

			return PTR_ERR(btf);

		if (!btf)

			return -EINVAL;



		btf_get(btf);

		prog->aux->attach_btf = btf;

	}



	if (attr->attach_prog_fd) {

		struct bpf_prog *dst_prog;



		dst_prog = bpf_prog_get(attr->attach_prog_fd);

		if (IS_ERR(dst_prog)) {

			err = PTR_ERR(dst_prog);

			goto free_prog;

		}

	prog->aux->dst_prog = dst_prog;

	}



	prog->aux->offload_requested = !!attr->prog_ifindex;

	prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;

tools/include/uapi/linux/bpf.h

+6 −1
Original line number Diff line number Diff line
@@ -557,7 +557,12 @@ union bpf_attr { 
		__aligned_u64	line_info;	/* line info */

		__u32		line_info_cnt;	/* number of bpf_line_info records */

		__u32		attach_btf_id;	/* in-kernel BTF type id to attach to */

		__u32		attach_prog_fd; /* 0 to attach to vmlinux */

		union {

			/* valid prog_fd to attach to bpf prog */

			__u32		attach_prog_fd;

			/* or valid module BTF object fd or 0 to attach to vmlinux */

			__u32		attach_btf_obj_fd;

		};

	};



	struct { /* anonymous struct used by BPF_OBJ_* commands */