Commit 263ae152 authored by Joanne Koong's avatar Joanne Koong Committed by Andrii Nakryiko
Browse files

bpf: Add bpf_dynptr_from_mem for local dynptrs 



This patch adds a new api bpf_dynptr_from_mem:

long bpf_dynptr_from_mem(void *data, u32 size, u64 flags, struct bpf_dynptr *ptr);

which initializes a dynptr to point to a bpf program's local memory. For now
only local memory that is of reg type PTR_TO_MAP_VALUE is supported.

Signed-off-by: default avatarJoanne Koong <joannelkoong@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-3-joannelkoong@gmail.com
parent 97e03f52

include/uapi/linux/bpf.h

+12 −0
Original line number Diff line number Diff line
@@ -5178,6 +5178,17 @@ union bpf_attr { 
 *		Dynamically cast a *sk* pointer to a *mptcp_sock* pointer.

 *	Return

 *		*sk* if casting is valid, or **NULL** otherwise.

 *

 * long bpf_dynptr_from_mem(void *data, u32 size, u64 flags, struct bpf_dynptr *ptr)

 *	Description

 *		Get a dynptr to local memory *data*.

 *

 *		*data* must be a ptr to a map value.

 *		The maximum *size* supported is DYNPTR_MAX_SIZE.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if the size exceeds DYNPTR_MAX_SIZE,

 *		-EINVAL if flags is not 0.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -5377,6 +5388,7 @@ union bpf_attr { 
	FN(kptr_xchg),			\

	FN(map_lookup_percpu_elem),     \

	FN(skc_to_mptcp_sock),		\

	FN(dynptr_from_mem),		\

	/* */



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

kernel/bpf/helpers.c

+65 −0
Original line number Diff line number Diff line
@@ -1412,6 +1412,69 @@ const struct bpf_func_proto bpf_kptr_xchg_proto = { 
	.arg2_btf_id  = BPF_PTR_POISON,

};



/* Since the upper 8 bits of dynptr->size is reserved, the

 * maximum supported size is 2^24 - 1.

 */

#define DYNPTR_MAX_SIZE	((1UL << 24) - 1)

#define DYNPTR_TYPE_SHIFT	28



static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_type type)

{

	ptr->size |= type << DYNPTR_TYPE_SHIFT;

}



static int bpf_dynptr_check_size(u32 size)

{

	return size > DYNPTR_MAX_SIZE ? -E2BIG : 0;

}



static void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,

			    enum bpf_dynptr_type type, u32 offset, u32 size)

{

	ptr->data = data;

	ptr->offset = offset;

	ptr->size = size;

	bpf_dynptr_set_type(ptr, type);

}



static void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr)

{

	memset(ptr, 0, sizeof(*ptr));

}



BPF_CALL_4(bpf_dynptr_from_mem, void *, data, u32, size, u64, flags, struct bpf_dynptr_kern *, ptr)

{

	int err;



	err = bpf_dynptr_check_size(size);

	if (err)

		goto error;



	/* flags is currently unsupported */

	if (flags) {

		err = -EINVAL;

		goto error;

	}



	bpf_dynptr_init(ptr, data, BPF_DYNPTR_TYPE_LOCAL, 0, size);



	return 0;



error:

	bpf_dynptr_set_null(ptr);

	return err;

}



const struct bpf_func_proto bpf_dynptr_from_mem_proto = {

	.func		= bpf_dynptr_from_mem,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,

	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,

	.arg3_type	= ARG_ANYTHING,

	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_UNINIT,

};



const struct bpf_func_proto bpf_get_current_task_proto __weak;

const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;

const struct bpf_func_proto bpf_probe_read_user_proto __weak;
@@ -1466,6 +1529,8 @@ bpf_base_func_proto(enum bpf_func_id func_id) 
		return &bpf_loop_proto;

	case BPF_FUNC_strncmp:

		return &bpf_strncmp_proto;

	case BPF_FUNC_dynptr_from_mem:

		return &bpf_dynptr_from_mem_proto;

	default:

		break;

	}

kernel/bpf/verifier.c

+6 −0
Original line number Diff line number Diff line
@@ -7204,6 +7204,12 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn 
		err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,

					set_loop_callback_state);

		break;

	case BPF_FUNC_dynptr_from_mem:

		if (regs[BPF_REG_1].type != PTR_TO_MAP_VALUE) {

			verbose(env, "Unsupported reg type %s for bpf_dynptr_from_mem data\n",

				reg_type_str(env, regs[BPF_REG_1].type));

			return -EACCES;

		}

	}



	if (err)

tools/include/uapi/linux/bpf.h

+12 −0
Original line number Diff line number Diff line
@@ -5178,6 +5178,17 @@ union bpf_attr { 
 *		Dynamically cast a *sk* pointer to a *mptcp_sock* pointer.

 *	Return

 *		*sk* if casting is valid, or **NULL** otherwise.

 *

 * long bpf_dynptr_from_mem(void *data, u32 size, u64 flags, struct bpf_dynptr *ptr)

 *	Description

 *		Get a dynptr to local memory *data*.

 *

 *		*data* must be a ptr to a map value.

 *		The maximum *size* supported is DYNPTR_MAX_SIZE.

 *		*flags* is currently unused.

 *	Return

 *		0 on success, -E2BIG if the size exceeds DYNPTR_MAX_SIZE,

 *		-EINVAL if flags is not 0.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -5377,6 +5388,7 @@ union bpf_attr { 
	FN(kptr_xchg),			\

	FN(map_lookup_percpu_elem),     \

	FN(skc_to_mptcp_sock),		\

	FN(dynptr_from_mem),		\

	/* */



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