Commit 540ccf96 authored by Joanne Koong's avatar Joanne Koong Committed by Daniel Borkmann
Browse files

bpf: Add bpf_dynptr_is_null and bpf_dynptr_is_rdonly 



bpf_dynptr_is_null returns true if the dynptr is null / invalid
(determined by whether ptr->data is NULL), else false if
the dynptr is a valid dynptr.

bpf_dynptr_is_rdonly returns true if the dynptr is read-only,
else false if the dynptr is read-writable. If the dynptr is
null / invalid, false is returned by default.

Signed-off-by: default avatarJoanne Koong <joannelkoong@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20230420071414.570108-3-joannelkoong@gmail.com
parent 987d0242

kernel/bpf/helpers.c

+19 −4
Original line number Diff line number Diff line
@@ -1423,7 +1423,7 @@ static const struct bpf_func_proto bpf_kptr_xchg_proto = { 
#define DYNPTR_SIZE_MASK	0xFFFFFF

#define DYNPTR_RDONLY_BIT	BIT(31)



static bool bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr)

static bool __bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr)

{

	return ptr->size & DYNPTR_RDONLY_BIT;

}
@@ -1570,7 +1570,7 @@ BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern *, dst, u32, offset, v 
	enum bpf_dynptr_type type;

	int err;



	if (!dst->data || bpf_dynptr_is_rdonly(dst))

	if (!dst->data || __bpf_dynptr_is_rdonly(dst))

		return -EINVAL;



	err = bpf_dynptr_check_off_len(dst, offset, len);
@@ -1626,7 +1626,7 @@ BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern *, ptr, u32, offset, u3 
	if (err)

		return 0;



	if (bpf_dynptr_is_rdonly(ptr))

	if (__bpf_dynptr_is_rdonly(ptr))

		return 0;



	type = bpf_dynptr_get_type(ptr);
@@ -2276,7 +2276,7 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset 
__bpf_kfunc void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr_kern *ptr, u32 offset,

					void *buffer, u32 buffer__szk)

{

	if (!ptr->data || bpf_dynptr_is_rdonly(ptr))

	if (!ptr->data || __bpf_dynptr_is_rdonly(ptr))

		return NULL;



	/* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.
@@ -2322,6 +2322,19 @@ __bpf_kfunc int bpf_dynptr_adjust(struct bpf_dynptr_kern *ptr, u32 start, u32 en 
	return 0;

}



__bpf_kfunc bool bpf_dynptr_is_null(struct bpf_dynptr_kern *ptr)

{

	return !ptr->data;

}



__bpf_kfunc bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)

{

	if (!ptr->data)

		return false;



	return __bpf_dynptr_is_rdonly(ptr);

}



__bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)

{

	return obj;
@@ -2395,6 +2408,8 @@ BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW) 
BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL)

BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)

BTF_ID_FLAGS(func, bpf_dynptr_adjust)

BTF_ID_FLAGS(func, bpf_dynptr_is_null)

BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)

BTF_SET8_END(common_btf_ids)



static const struct btf_kfunc_id_set common_kfunc_set = {