On Sat, Apr 8, 2023 at 8:34 PM Joanne Koong <joannelkoong@xxxxxxxxx> wrote:
>
> 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.
>
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> ---
> kernel/bpf/helpers.c | 23 +++++++++++++++++++----
> 1 file changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 51b4c4b5dbed..e4e84e92a4c6 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -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);
> @@ -2254,7 +2254,7 @@ __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))
seems like all the uses of __bpf_dynptr_is_rdonly check !ptr->data
explicitly, so maybe move that ptr->data check inside and simplify all
the callers?
Regardless, looks good:
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> return NULL;
>
> /* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.
> @@ -2322,6 +2322,19 @@ __bpf_kfunc int bpf_dynptr_trim(struct bpf_dynptr_kern *ptr, u32 len)
> return bpf_dynptr_adjust(ptr, 0, len);
> }
>
> +__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;
> @@ -2396,6 +2409,8 @@ 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_trim)
> BTF_ID_FLAGS(func, bpf_dynptr_advance)
> +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 = {
> --
> 2.34.1
>
