Commit 79a7f8bd authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Introduce bpf_sys_bpf() helper and program type. 



Add placeholders for bpf_sys_bpf() helper and new program type.
Make sure to check that expected_attach_type is zero for future extensibility.
Allow tracing helper functions to be used in this program type, since they will
only execute from user context via bpf_prog_test_run.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-2-alexei.starovoitov@gmail.com
parent fa7b83bf

include/linux/bpf.h

+10 −0
Original line number Diff line number Diff line
@@ -1826,6 +1826,9 @@ static inline bool bpf_map_is_dev_bound(struct bpf_map *map) 


struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr);

void bpf_map_offload_map_free(struct bpf_map *map);

int bpf_prog_test_run_syscall(struct bpf_prog *prog,

			      const union bpf_attr *kattr,

			      union bpf_attr __user *uattr);

#else

static inline int bpf_prog_offload_init(struct bpf_prog *prog,

					union bpf_attr *attr)
@@ -1851,6 +1854,13 @@ static inline struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr) 
static inline void bpf_map_offload_map_free(struct bpf_map *map)

{

}



static inline int bpf_prog_test_run_syscall(struct bpf_prog *prog,

					    const union bpf_attr *kattr,

					    union bpf_attr __user *uattr)

{

	return -ENOTSUPP;

}

#endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */



#if defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL)

include/linux/bpf_types.h

+2 −0
Original line number Diff line number Diff line
@@ -77,6 +77,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LSM, lsm, 
	       void *, void *)

#endif /* CONFIG_BPF_LSM */

#endif

BPF_PROG_TYPE(BPF_PROG_TYPE_SYSCALL, bpf_syscall,

	      void *, void *)



BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)

BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)

include/uapi/linux/bpf.h

+8 −0
Original line number Diff line number Diff line
@@ -937,6 +937,7 @@ enum bpf_prog_type { 
	BPF_PROG_TYPE_EXT,

	BPF_PROG_TYPE_LSM,

	BPF_PROG_TYPE_SK_LOOKUP,

	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */

};



enum bpf_attach_type {
@@ -4735,6 +4736,12 @@ union bpf_attr { 
 *		be zero-terminated except when **str_size** is 0.

 *

 *		Or **-EBUSY** if the per-CPU memory copy buffer is busy.

 *

 * long bpf_sys_bpf(u32 cmd, void *attr, u32 attr_size)

 * 	Description

 * 		Execute bpf syscall with given arguments.

 * 	Return

 * 		A syscall result.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -4903,6 +4910,7 @@ union bpf_attr { 
	FN(check_mtu),			\

	FN(for_each_map_elem),		\

	FN(snprintf),			\

	FN(sys_bpf),			\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/syscall.c

+53 −0
Original line number Diff line number Diff line
@@ -2014,6 +2014,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, 
		if (expected_attach_type == BPF_SK_LOOKUP)

			return 0;

		return -EINVAL;

	case BPF_PROG_TYPE_SYSCALL:

	case BPF_PROG_TYPE_EXT:

		if (expected_attach_type)

			return -EINVAL;
@@ -4508,3 +4509,55 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz 


	return err;

}



static bool syscall_prog_is_valid_access(int off, int size,

					 enum bpf_access_type type,

					 const struct bpf_prog *prog,

					 struct bpf_insn_access_aux *info)

{

	if (off < 0 || off >= U16_MAX)

		return false;

	if (off % size != 0)

		return false;

	return true;

}



BPF_CALL_3(bpf_sys_bpf, int, cmd, void *, attr, u32, attr_size)

{

	return -EINVAL;

}



const struct bpf_func_proto bpf_sys_bpf_proto = {

	.func		= bpf_sys_bpf,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_ANYTHING,

	.arg2_type	= ARG_PTR_TO_MEM,

	.arg3_type	= ARG_CONST_SIZE,

};



const struct bpf_func_proto * __weak

tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)

{

	return bpf_base_func_proto(func_id);

}



static const struct bpf_func_proto *

syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)

{

	switch (func_id) {

	case BPF_FUNC_sys_bpf:

		return &bpf_sys_bpf_proto;

	default:

		return tracing_prog_func_proto(func_id, prog);

	}

}



const struct bpf_verifier_ops bpf_syscall_verifier_ops = {

	.get_func_proto  = syscall_prog_func_proto,

	.is_valid_access = syscall_prog_is_valid_access,

};



const struct bpf_prog_ops bpf_syscall_prog_ops = {

	.test_run = bpf_prog_test_run_syscall,

};

kernel/bpf/verifier.c

+8 −0
Original line number Diff line number Diff line
@@ -13196,6 +13196,14 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) 
	int ret;

	u64 key;



	if (prog->type == BPF_PROG_TYPE_SYSCALL) {

		if (prog->aux->sleepable)

			/* attach_btf_id checked to be zero already */

			return 0;

		verbose(env, "Syscall programs can only be sleepable\n");

		return -EINVAL;

	}



	if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING &&

	    prog->type != BPF_PROG_TYPE_LSM) {

		verbose(env, "Only fentry/fexit/fmod_ret and lsm programs can be sleepable\n");