From 13bbbfbea7598ea9f8d9c3d73bf053bb57f9c4b2 Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Mon, 23 May 2022 14:07:10 -0700 Subject: [PATCH] bpf: Add bpf_dynptr_read and bpf_dynptr_write This patch adds two helper functions, bpf_dynptr_read and bpf_dynptr_write: long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset); long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len); The dynptr passed into these functions must be valid dynptrs that have been initialized. Signed-off-by: Joanne Koong Signed-off-by: Andrii Nakryiko Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220523210712.3641569-5-joannelkoong@gmail.com --- include/uapi/linux/bpf.h | 19 ++++++++++ kernel/bpf/helpers.c | 78 ++++++++++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 19 ++++++++++ 3 files changed, 116 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 081a555..efe2505 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5221,6 +5221,23 @@ union bpf_attr { * 'bpf_ringbuf_discard'. * Return * Nothing. Always succeeds. + * + * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset) + * Description + * Read *len* bytes from *src* into *dst*, starting from *offset* + * into *src*. + * Return + * 0 on success, -E2BIG if *offset* + *len* exceeds the length + * of *src*'s data, -EINVAL if *src* is an invalid dynptr. + * + * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len) + * Description + * Write *len* bytes from *src* into *dst*, starting from *offset* + * into *dst*. + * Return + * 0 on success, -E2BIG if *offset* + *len* exceeds the length + * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst* + * is a read-only dynptr. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5424,6 +5441,8 @@ union bpf_attr { FN(ringbuf_reserve_dynptr), \ FN(ringbuf_submit_dynptr), \ FN(ringbuf_discard_dynptr), \ + FN(dynptr_read), \ + FN(dynptr_write), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index abb0899..8cef3fb 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1417,12 +1417,24 @@ const struct bpf_func_proto bpf_kptr_xchg_proto = { */ #define DYNPTR_MAX_SIZE ((1UL << 24) - 1) #define DYNPTR_TYPE_SHIFT 28 +#define DYNPTR_SIZE_MASK 0xFFFFFF +#define DYNPTR_RDONLY_BIT BIT(31) + +static bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr) +{ + return ptr->size & DYNPTR_RDONLY_BIT; +} static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_type type) { ptr->size |= type << DYNPTR_TYPE_SHIFT; } +static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr) +{ + return ptr->size & DYNPTR_SIZE_MASK; +} + int bpf_dynptr_check_size(u32 size) { return size > DYNPTR_MAX_SIZE ? -E2BIG : 0; @@ -1442,6 +1454,16 @@ void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr) memset(ptr, 0, sizeof(*ptr)); } +static int bpf_dynptr_check_off_len(struct bpf_dynptr_kern *ptr, u32 offset, u32 len) +{ + u32 size = bpf_dynptr_get_size(ptr); + + if (len > size || offset > size - len) + return -E2BIG; + + return 0; +} + BPF_CALL_4(bpf_dynptr_from_mem, void *, data, u32, size, u64, flags, struct bpf_dynptr_kern *, ptr) { int err; @@ -1475,6 +1497,58 @@ const struct bpf_func_proto bpf_dynptr_from_mem_proto = { .arg4_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_UNINIT, }; +BPF_CALL_4(bpf_dynptr_read, void *, dst, u32, len, struct bpf_dynptr_kern *, src, u32, offset) +{ + int err; + + if (!src->data) + return -EINVAL; + + err = bpf_dynptr_check_off_len(src, offset, len); + if (err) + return err; + + memcpy(dst, src->data + src->offset + offset, len); + + return 0; +} + +const struct bpf_func_proto bpf_dynptr_read_proto = { + .func = bpf_dynptr_read, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_UNINIT_MEM, + .arg2_type = ARG_CONST_SIZE_OR_ZERO, + .arg3_type = ARG_PTR_TO_DYNPTR, + .arg4_type = ARG_ANYTHING, +}; + +BPF_CALL_4(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *, src, u32, len) +{ + int err; + + if (!dst->data || bpf_dynptr_is_rdonly(dst)) + return -EINVAL; + + err = bpf_dynptr_check_off_len(dst, offset, len); + if (err) + return err; + + memcpy(dst->data + dst->offset + offset, src, len); + + return 0; +} + +const struct bpf_func_proto bpf_dynptr_write_proto = { + .func = bpf_dynptr_write, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_DYNPTR, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_PTR_TO_MEM | MEM_RDONLY, + .arg4_type = ARG_CONST_SIZE_OR_ZERO, +}; + 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; @@ -1537,6 +1611,10 @@ bpf_base_func_proto(enum bpf_func_id func_id) return &bpf_strncmp_proto; case BPF_FUNC_dynptr_from_mem: return &bpf_dynptr_from_mem_proto; + case BPF_FUNC_dynptr_read: + return &bpf_dynptr_read_proto; + case BPF_FUNC_dynptr_write: + return &bpf_dynptr_write_proto; default: break; } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 081a555..efe2505 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5221,6 +5221,23 @@ union bpf_attr { * 'bpf_ringbuf_discard'. * Return * Nothing. Always succeeds. + * + * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset) + * Description + * Read *len* bytes from *src* into *dst*, starting from *offset* + * into *src*. + * Return + * 0 on success, -E2BIG if *offset* + *len* exceeds the length + * of *src*'s data, -EINVAL if *src* is an invalid dynptr. + * + * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len) + * Description + * Write *len* bytes from *src* into *dst*, starting from *offset* + * into *dst*. + * Return + * 0 on success, -E2BIG if *offset* + *len* exceeds the length + * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst* + * is a read-only dynptr. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5424,6 +5441,8 @@ union bpf_attr { FN(ringbuf_reserve_dynptr), \ FN(ringbuf_submit_dynptr), \ FN(ringbuf_discard_dynptr), \ + FN(dynptr_read), \ + FN(dynptr_write), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper -- 2.7.4