From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D107C04A68 for ; Thu, 28 Jul 2022 17:29:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229835AbiG1R3A (ORCPT ); Thu, 28 Jul 2022 13:29:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229663AbiG1R27 (ORCPT ); Thu, 28 Jul 2022 13:28:59 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 298E63E76A for ; Thu, 28 Jul 2022 10:28:58 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id e8-20020a17090a280800b001f2fef7886eso2835786pjd.3 for ; Thu, 28 Jul 2022 10:28:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=L7zmhvmmg53yhzzlqglcFNKZOkVBLt7Rby/pdfIW4M0=; b=ITb8Gndu3m81+fv68CmpWO/LRJqX31mUA5riUWaURBFuSVGrPJFNYRToIRKzIJsdzf ZZHziGrjZrSnXK/TsazBPd8n/x5SG/nHyk/a7y5J54LqTHSSkDx5VoqbJydVkc8XpfL1 7aweQRce5/voFKQok5gyNseDHuIR98RMySM9nUoHPIMOLnU8n8PUTBd2/wWSXP0odiPl qzqYrLsk0m2bSCLu4/SJ2bHhfq7Buh5xotP5PhaTvOKNxitnLHkDuAH5uyr+mbcfLkzx mynGzs35t5yFmVtputBzyli+ZkGo0l0LcJ8Y3txIry9GvsG0+k85qRXXPu+n+dinhMty geqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=L7zmhvmmg53yhzzlqglcFNKZOkVBLt7Rby/pdfIW4M0=; b=WJt8rtY5CtyxKI6LcmV7GrO30scm8JJzKS4PWFO0qRf1d5fsvtHx2ru0Hg4lf79c32 jt6a/T/I/y73gIir9chLpxX2IAcJOBcEdtbCvSRrp3dvf3++DuYKe8heORpRfO9ZG5Mv CfntOl2X6WHyYVMMuUlllFZy0VbPRLK4wF7NITCrf/jjvxykV/uwCsJFyWgqc6eSGJGd B9tshBvydX/GxN6l/oBw7pEb7kIwwYw9l/Qckuhu0LeYzyoBfWwalR8ra09ramOk6Omq KegWB6cP6sCEjqFRmPpA0laJdNCSgXibMIcfiyEw8dM/j9lijv4R1LSpMo7T+ACh6vqq cvpQ== X-Gm-Message-State: AJIora+CDhdEJc7guYSW9Y3u1b8KPUUs+mz69FNYrXAn9o+kkP0oYGfc 32nMXHLIwFWu4UHWry3NOOIFZk19tthaTR86fDoBJw== X-Google-Smtp-Source: AGRyM1uzyJvMmkPfn7N2uQpQVSIGkxzDCyoFtOuKuipUZMmQ1lXZLW8m86kqK9A142HJ5wNGNbAjkIRKf5VtKnopFkU= X-Received: by 2002:a17:903:1111:b0:16a:acf4:e951 with SMTP id n17-20020a170903111100b0016aacf4e951mr27214508plh.72.1659029337146; Thu, 28 Jul 2022 10:28:57 -0700 (PDT) MIME-Version: 1.0 References: <20220726184706.954822-1-joannelkoong@gmail.com> <20220726184706.954822-2-joannelkoong@gmail.com> In-Reply-To: From: Stanislav Fomichev Date: Thu, 28 Jul 2022 10:28:45 -0700 Message-ID: Subject: Re: [PATCH bpf-next v1 1/3] bpf: Add skb dynptrs To: Joanne Koong Cc: bpf , Andrii Nakryiko , Daniel Borkmann , Alexei Starovoitov Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Jul 28, 2022 at 9:49 AM Joanne Koong wrote: > > On Wed, Jul 27, 2022 at 10:14 AM wrote: > > > > On 07/26, Joanne Koong wrote: > > > Add skb dynptrs, which are dynptrs whose underlying pointer points > > > to a skb. The dynptr acts on skb data. skb dynptrs have two main > > > benefits. One is that they allow operations on sizes that are not > > > statically known at compile-time (eg variable-sized accesses). > > > Another is that parsing the packet data through dynptrs (instead of > > > through direct access of skb->data and skb->data_end) can be more > > > ergonomic and less brittle (eg does not need manual if checking for > > > being within bounds of data_end). > > > > > For bpf prog types that don't support writes on skb data, the dynptr is > > > read-only (writes and data slices are not permitted). For reads on the > > > dynptr, this includes reading into data in the non-linear paged buffers > > > but for writes and data slices, if the data is in a paged buffer, the > > > user must first call bpf_skb_pull_data to pull the data into the linear > > > portion. > > > > > Additionally, any helper calls that change the underlying packet buffer > > > (eg bpf_skb_pull_data) invalidates any data slices of the associated > > > dynptr. > > > > > Right now, skb dynptrs can only be constructed from skbs that are > > > the bpf program context - as such, there does not need to be any > > > reference tracking or release on skb dynptrs. > > > > > Signed-off-by: Joanne Koong > > > --- > > > include/linux/bpf.h | 8 ++++- > > > include/linux/filter.h | 4 +++ > > > include/uapi/linux/bpf.h | 42 ++++++++++++++++++++++++-- > > > kernel/bpf/helpers.c | 54 +++++++++++++++++++++++++++++++++- > > > kernel/bpf/verifier.c | 43 +++++++++++++++++++++++---- > > > net/core/filter.c | 53 ++++++++++++++++++++++++++++++--- > > > tools/include/uapi/linux/bpf.h | 42 ++++++++++++++++++++++++-- > > > 7 files changed, 229 insertions(+), 17 deletions(-) > > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > > index 20c26aed7896..7fbd4324c848 100644 > > > --- a/include/linux/bpf.h > > > +++ b/include/linux/bpf.h > > > @@ -407,11 +407,14 @@ enum bpf_type_flag { > > > /* Size is known at compile time. */ > > > MEM_FIXED_SIZE = BIT(10 + BPF_BASE_TYPE_BITS), > > > > > + /* DYNPTR points to sk_buff */ > > > + DYNPTR_TYPE_SKB = BIT(11 + BPF_BASE_TYPE_BITS), > > > + > > > __BPF_TYPE_FLAG_MAX, > > > __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1, > > > }; > > > > > -#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF) > > > +#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | > > > DYNPTR_TYPE_SKB) > > > > > /* Max number of base types. */ > > > #define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS) > > > @@ -2556,12 +2559,15 @@ enum bpf_dynptr_type { > > > BPF_DYNPTR_TYPE_LOCAL, > > > /* Underlying data is a ringbuf record */ > > > BPF_DYNPTR_TYPE_RINGBUF, > > > + /* Underlying data is a sk_buff */ > > > + BPF_DYNPTR_TYPE_SKB, > > > }; > > > > > void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data, > > > enum bpf_dynptr_type type, u32 offset, u32 size); > > > void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr); > > > int bpf_dynptr_check_size(u32 size); > > > +void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr); > > > > > #ifdef CONFIG_BPF_LSM > > > void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype); > > > diff --git a/include/linux/filter.h b/include/linux/filter.h > > > index a5f21dc3c432..649063d9cbfd 100644 > > > --- a/include/linux/filter.h > > > +++ b/include/linux/filter.h > > > @@ -1532,4 +1532,8 @@ static __always_inline int > > > __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifind > > > return XDP_REDIRECT; > > > } > > > > > +int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void > > > *to, u32 len); > > > +int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void > > > *from, > > > + u32 len, u64 flags); > > > + > > > #endif /* __LINUX_FILTER_H__ */ > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > > index 59a217ca2dfd..0730cd198a7f 100644 > > > --- a/include/uapi/linux/bpf.h > > > +++ b/include/uapi/linux/bpf.h > > > @@ -5241,11 +5241,22 @@ union bpf_attr { > > > * Description > > > * Write *len* bytes from *src* into *dst*, starting from *offset* > > > * into *dst*. > > > - * *flags* is currently unused. > > > + * > > > + * *flags* must be 0 except for skb-type dynptrs. > > > + * > > > + * For skb-type dynptrs: > > > + * * if *offset* + *len* extends into the skb's paged buffers, the > > > user > > > + * should manually pull the skb with bpf_skb_pull and then try > > > again. > > > + * > > > + * * *flags* are a combination of **BPF_F_RECOMPUTE_CSUM** > > > (automatically > > > + * recompute the checksum for the packet after storing the bytes) and > > > + * **BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\ > > > + * **->swhash** and *skb*\ **->l4hash** to 0). > > > * 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 or if *flags* is not 0. > > > + * is a read-only dynptr or if *flags* is not correct, -EAGAIN if for > > > + * skb-type dynptrs the write extends into the skb's paged buffers. > > > * > > > * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len) > > > * Description > > > @@ -5253,10 +5264,19 @@ union bpf_attr { > > > * > > > * *len* must be a statically known value. The returned data slice > > > * is invalidated whenever the dynptr is invalidated. > > > + * > > > + * For skb-type dynptrs: > > > + * * if *offset* + *len* extends into the skb's paged buffers, > > > + * the user should manually pull the skb with bpf_skb_pull and > > > then > > > + * try again. > > > + * > > > + * * the data slice is automatically invalidated anytime a > > > + * helper call that changes the underlying packet buffer > > > + * (eg bpf_skb_pull) is called. > > > * Return > > > * Pointer to the underlying dynptr data, NULL if the dynptr is > > > * read-only, if the dynptr is invalid, or if the offset and length > > > - * is out of bounds. > > > + * is out of bounds or in a paged buffer for skb-type dynptrs. > > > * > > > * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr > > > *th, u32 th_len) > > > * Description > > > @@ -5331,6 +5351,21 @@ union bpf_attr { > > > * **-EACCES** if the SYN cookie is not valid. > > > * > > > * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. > > > + * > > > + * long bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags, struct > > > bpf_dynptr *ptr) > > > + * Description > > > + * Get a dynptr to the data in *skb*. *skb* must be the BPF program > > > + * context. Depending on program type, the dynptr may be read-only, > > > + * in which case trying to obtain a direct data slice to it through > > > + * bpf_dynptr_data will return an error. > > > + * > > > + * Calls that change the *skb*'s underlying packet buffer > > > + * (eg bpf_skb_pull_data) do not invalidate the dynptr, but they do > > > + * invalidate any data slices associated with the dynptr. > > > + * > > > + * *flags* is currently unused, it must be 0 for now. > > > + * Return > > > + * 0 on success or -EINVAL if flags is not 0. > > > */ > > > #define __BPF_FUNC_MAPPER(FN) \ > > > FN(unspec), \ > > > @@ -5541,6 +5576,7 @@ union bpf_attr { > > > FN(tcp_raw_gen_syncookie_ipv6), \ > > > FN(tcp_raw_check_syncookie_ipv4), \ > > > FN(tcp_raw_check_syncookie_ipv6), \ > > > + FN(dynptr_from_skb), \ > > > /* */ > > > > > /* 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 1f961f9982d2..21a806057e9e 100644 > > > --- a/kernel/bpf/helpers.c > > > +++ b/kernel/bpf/helpers.c > > > @@ -1425,11 +1425,21 @@ static bool bpf_dynptr_is_rdonly(struct > > > bpf_dynptr_kern *ptr) > > > return ptr->size & DYNPTR_RDONLY_BIT; > > > } > > > > > +void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr) > > > +{ > > > + 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 enum bpf_dynptr_type bpf_dynptr_get_type(const struct > > > bpf_dynptr_kern *ptr) > > > +{ > > > + return (ptr->size & ~(DYNPTR_RDONLY_BIT)) >> DYNPTR_TYPE_SHIFT; > > > +} > > > + > > > static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr) > > > { > > > return ptr->size & DYNPTR_SIZE_MASK; > > > @@ -1500,6 +1510,7 @@ static const struct bpf_func_proto > > > bpf_dynptr_from_mem_proto = { > > > BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, struct > > > bpf_dynptr_kern *, src, > > > u32, offset, u64, flags) > > > { > > > + enum bpf_dynptr_type type; > > > int err; > > > > > if (!src->data || flags) > > > @@ -1509,6 +1520,11 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, > > > struct bpf_dynptr_kern *, src > > > if (err) > > > return err; > > > > > + type = bpf_dynptr_get_type(src); > > > + > > > + if (type == BPF_DYNPTR_TYPE_SKB) > > > + return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len); > > > + > > > memcpy(dst, src->data + src->offset + offset, len); > > > > > return 0; > > > @@ -1528,15 +1544,38 @@ static const struct bpf_func_proto > > > bpf_dynptr_read_proto = { > > > BPF_CALL_5(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, > > > void *, src, > > > u32, len, u64, flags) > > > { > > > + enum bpf_dynptr_type type; > > > int err; > > > > > - if (!dst->data || flags || bpf_dynptr_is_rdonly(dst)) > > > + if (!dst->data || bpf_dynptr_is_rdonly(dst)) > > > return -EINVAL; > > > > > err = bpf_dynptr_check_off_len(dst, offset, len); > > > if (err) > > > return err; > > > > > + type = bpf_dynptr_get_type(dst); > > > + > > > + if (flags) { > > > + if (type == BPF_DYNPTR_TYPE_SKB) { > > > + if (flags & ~(BPF_F_RECOMPUTE_CSUM | BPF_F_INVALIDATE_HASH)) > > > + return -EINVAL; > > > + } else { > > > + return -EINVAL; > > > + } > > > + } > > > + > > > + if (type == BPF_DYNPTR_TYPE_SKB) { > > > + struct sk_buff *skb = dst->data; > > > + > > > + /* if the data is paged, the caller needs to pull it first */ > > > + if (dst->offset + offset + len > skb->len - skb->data_len) > > > > Use skb_headlen instead of 'skb->len - skb->data_len' ? > Awesome, will replace this (and the one in bpf_dynptr_data) with > skb_headlen() for v2. thanks! > > > > > + return -EAGAIN; > > > + > > > + return __bpf_skb_store_bytes(skb, dst->offset + offset, src, len, > > > + flags); > > > + } > > > + > > > memcpy(dst->data + dst->offset + offset, src, len); > > > > > return 0; > > > @@ -1555,6 +1594,7 @@ static const struct bpf_func_proto > > > bpf_dynptr_write_proto = { > > > > > BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern *, ptr, u32, offset, > > > u32, len) > > > { > > > + enum bpf_dynptr_type type; > > > int err; > > > > > if (!ptr->data) > > > @@ -1567,6 +1607,18 @@ BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern > > > *, ptr, u32, offset, u32, len > > > if (bpf_dynptr_is_rdonly(ptr)) > > > return 0; > > > > > + type = bpf_dynptr_get_type(ptr); > > > + > > > + if (type == BPF_DYNPTR_TYPE_SKB) { > > > + struct sk_buff *skb = ptr->data; > > > + > > > + /* if the data is paged, the caller needs to pull it first */ > > > + if (ptr->offset + offset + len > skb->len - skb->data_len) > > > + return 0; > > > > Same here? > > > > > + > > > + return (unsigned long)(skb->data + ptr->offset + offset); > > > + } > > > + > > > return (unsigned long)(ptr->data + ptr->offset + offset); > > > } > > > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > > index 0d523741a543..0838653eeb4e 100644 > > > --- a/kernel/bpf/verifier.c > > > +++ b/kernel/bpf/verifier.c > > > @@ -263,6 +263,7 @@ struct bpf_call_arg_meta { > > > u32 subprogno; > > > struct bpf_map_value_off_desc *kptr_off_desc; > > > u8 uninit_dynptr_regno; > > > + enum bpf_dynptr_type type; > > > }; > > > > > struct btf *btf_vmlinux; > > > @@ -678,6 +679,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum > > > bpf_arg_type arg_type) > > > return BPF_DYNPTR_TYPE_LOCAL; > > > case DYNPTR_TYPE_RINGBUF: > > > return BPF_DYNPTR_TYPE_RINGBUF; > > > + case DYNPTR_TYPE_SKB: > > > + return BPF_DYNPTR_TYPE_SKB; > > > default: > > > return BPF_DYNPTR_TYPE_INVALID; > > > } > > > @@ -5820,12 +5823,14 @@ int check_func_arg_reg_off(struct > > > bpf_verifier_env *env, > > > return __check_ptr_off_reg(env, reg, regno, fixed_off_ok); > > > } > > > > > -static u32 stack_slot_get_id(struct bpf_verifier_env *env, struct > > > bpf_reg_state *reg) > > > +static void stack_slot_get_dynptr_info(struct bpf_verifier_env *env, > > > struct bpf_reg_state *reg, > > > + struct bpf_call_arg_meta *meta) > > > { > > > struct bpf_func_state *state = func(env, reg); > > > int spi = get_spi(reg->off); > > > > > - return state->stack[spi].spilled_ptr.id; > > > + meta->ref_obj_id = state->stack[spi].spilled_ptr.id; > > > + meta->type = state->stack[spi].spilled_ptr.dynptr.type; > > > } > > > > > static int check_func_arg(struct bpf_verifier_env *env, u32 arg, > > > @@ -6052,6 +6057,9 @@ static int check_func_arg(struct bpf_verifier_env > > > *env, u32 arg, > > > case DYNPTR_TYPE_RINGBUF: > > > err_extra = "ringbuf "; > > > break; > > > + case DYNPTR_TYPE_SKB: > > > + err_extra = "skb "; > > > + break; > > > default: > > > break; > > > } > > > @@ -6065,8 +6073,10 @@ static int check_func_arg(struct bpf_verifier_env > > > *env, u32 arg, > > > verbose(env, "verifier internal error: multiple refcounted args in > > > BPF_FUNC_dynptr_data"); > > > return -EFAULT; > > > } > > > - /* Find the id of the dynptr we're tracking the reference of */ > > > - meta->ref_obj_id = stack_slot_get_id(env, reg); > > > + /* Find the id and the type of the dynptr we're tracking > > > + * the reference of. > > > + */ > > > + stack_slot_get_dynptr_info(env, reg, meta); > > > } > > > } > > > break; > > > @@ -7406,7 +7416,11 @@ static int check_helper_call(struct > > > bpf_verifier_env *env, struct bpf_insn *insn > > > regs[BPF_REG_0].type = PTR_TO_TCP_SOCK | ret_flag; > > > } else if (base_type(ret_type) == RET_PTR_TO_ALLOC_MEM) { > > > mark_reg_known_zero(env, regs, BPF_REG_0); > > > - regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag; > > > + if (func_id == BPF_FUNC_dynptr_data && > > > + meta.type == BPF_DYNPTR_TYPE_SKB) > > > + regs[BPF_REG_0].type = PTR_TO_PACKET | ret_flag; > > > + else > > > + regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag; > > > regs[BPF_REG_0].mem_size = meta.mem_size; > > > } else if (base_type(ret_type) == RET_PTR_TO_MEM_OR_BTF_ID) { > > > const struct btf_type *t; > > > @@ -14132,6 +14146,25 @@ static int do_misc_fixups(struct > > > bpf_verifier_env *env) > > > goto patch_call_imm; > > > } > > > > > > [..] > > > > > + if (insn->imm == BPF_FUNC_dynptr_from_skb) { > > > + if (!may_access_direct_pkt_data(env, NULL, BPF_WRITE)) > > > + insn_buf[0] = BPF_MOV32_IMM(BPF_REG_4, true); > > > + else > > > + insn_buf[0] = BPF_MOV32_IMM(BPF_REG_4, false); > > > + insn_buf[1] = *insn; > > > + cnt = 2; > > > + > > > + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); > > > + if (!new_prog) > > > + return -ENOMEM; > > > + > > > + delta += cnt - 1; > > > + env->prog = new_prog; > > > + prog = new_prog; > > > + insn = new_prog->insnsi + i + delta; > > > + goto patch_call_imm; > > > + } > > > > Would it be easier to have two separate helpers: > > - BPF_FUNC_dynptr_from_skb > > - BPF_FUNC_dynptr_from_skb_readonly > > > > And make the verifier rewrite insn->imm to > > BPF_FUNC_dynptr_from_skb_readonly when needed? > > > > if (insn->imm == BPF_FUNC_dynptr_from_skb) { > > if (!may_access_direct_pkt_data(env, NULL, BPF_WRITE)) > > insn->imm = BPF_FUNC_dynptr_from_skb_readonly; > > } > > > > Or it's also ugly because we'd have to leak that new helper into UAPI? > > (I wonder whether that hidden 4th argument is too magical, but probably > > fine?) > To me, having 2 separate helpers feels more cluttered and having to > expose it in the uapi (though I think there is probably some way to > avoid this by doing some sort of ad hoc processing) doesn't seem > ideal. If you feel strongly about this though, I am happy to change > this to use two separate helpers. We do this sort of manual > instruction patching for the sleepable flags in > bpf_task/sk/inode_storage_get and for the callback args in > bpf_timer_set_callback as well - if we use separate helpers here, we > should do that for the other cases as well to maintain consistency. No, I don't feel strongly, let's keep it, especially if there is prior art :-) I am just wondering whether there is some better alternative, but extra helpers also have their downsides.