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([2620:10d:c092:400::5:5b97]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e723437d8sm41858435e9.3.2025.10.03.11.59.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Oct 2025 11:59:05 -0700 (PDT) Message-ID: <8b38e920-4317-4c0a-8f1a-7354ca2b53d1@gmail.com> Date: Fri, 3 Oct 2025 19:59:04 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 07/10] bpf: add kfuncs and helpers support for file dynptrs To: Andrii Nakryiko Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com, Mykyta Yatsenko References: <20251003160416.585080-1-mykyta.yatsenko5@gmail.com> <20251003160416.585080-8-mykyta.yatsenko5@gmail.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/3/25 19:38, Andrii Nakryiko wrote: > On Fri, Oct 3, 2025 at 9:04 AM Mykyta Yatsenko > wrote: >> From: Mykyta Yatsenko >> >> Add support for file dynptr. >> >> Introduce struct bpf_dynptr_file_impl to hold internal state for file >> dynptrs, with 64-bit size and offset support. >> >> Introduce lifecycle management kfuncs: >> - bpf_dynptr_from_file() for initialization >> - bpf_dynptr_file_discard() for destruction >> >> Extend existing helpers to support file dynptrs in: >> - bpf_dynptr_read() >> - bpf_dynptr_slice() >> >> Signed-off-by: Mykyta Yatsenko >> --- >> kernel/bpf/helpers.c | 97 +++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 95 insertions(+), 2 deletions(-) >> > [...] > >> +static int bpf_file_fetch_bytes(struct bpf_dynptr_file_impl *df, u64 offset, void *buf, u64 len) >> +{ >> + const void *ptr; >> + >> + if (!buf || len == 0) > len == 0 doesn't return error for LOCAL and RINGBUF (at least), I > don't think we should deviate. Just treat len == 0 as no-op. > >> + return -EINVAL; >> + >> + df->freader.buf = buf; >> + df->freader.buf_sz = len; >> + ptr = freader_fetch(&df->freader, offset + df->offset, len); >> + if (!ptr) >> + return df->freader.err; >> + >> + if (ptr != buf) /* Force copying into the buffer */ >> + memcpy(buf, ptr, len); >> + >> + return 0; >> +} >> + >> void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data, >> enum bpf_dynptr_type type, u32 offset, u32 size) >> { >> @@ -1782,6 +1832,8 @@ static int __bpf_dynptr_read(void *dst, u64 len, const struct bpf_dynptr_kern *s >> case BPF_DYNPTR_TYPE_SKB_META: >> memmove(dst, bpf_skb_meta_pointer(src->data, src->offset + offset), len); >> return 0; >> + case BPF_DYNPTR_TYPE_FILE: >> + return bpf_file_fetch_bytes(src->data, offset, dst, len); >> default: >> WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type); >> return -EFAULT; >> @@ -2177,6 +2229,35 @@ void bpf_rb_root_free(const struct btf_field *field, void *rb_root, >> } >> } >> >> +enum bpf_is_sleepable { >> + MAY_SLEEP, >> + MAY_NOT_SLEEP, >> +}; > might be a bit of an overkill to have enum for this, but I don't feel > strongly about this > >> + >> +static int make_file_dynptr(struct file *file, u32 flags, enum bpf_is_sleepable sleepable, >> + struct bpf_dynptr_kern *ptr) >> +{ > nit: put it right before bpf_dynptr_from_file()? No problem, but that makes patch look uglier, bpf_dynptr_from_file is substituted with make_file_dynptr. > >> + struct bpf_dynptr_file_impl *state; >> + >> + /* flags is currently unsupported */ >> + if (flags) { >> + bpf_dynptr_set_null(ptr); >> + return -EINVAL; >> + } >> + >> + state = bpf_mem_alloc(&bpf_global_ma, sizeof(struct bpf_dynptr_file_impl)); >> + if (!state) { >> + bpf_dynptr_set_null(ptr); >> + return -ENOMEM; >> + } >> + state->offset = 0; >> + state->size = U64_MAX; /* Don't restrict size, as file may change anyways */ >> + freader_init_from_file(&state->freader, NULL, 0, file, sleepable == MAY_SLEEP); >> + bpf_dynptr_init(ptr, state, BPF_DYNPTR_TYPE_FILE, 0, 0); >> + bpf_dynptr_set_rdonly(ptr); >> + return 0; >> +} >> + >> __bpf_kfunc_start_defs(); >> >> __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign) >> @@ -2720,6 +2801,9 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr *p, u64 offset, >> } >> case BPF_DYNPTR_TYPE_SKB_META: >> return bpf_skb_meta_pointer(ptr->data, ptr->offset + offset); >> + case BPF_DYNPTR_TYPE_FILE: >> + err = bpf_file_fetch_bytes(ptr->data, offset, buffer__opt, buffer__szk); >> + return err ? NULL : buffer__opt; >> default: >> WARN_ONCE(true, "unknown dynptr type %d\n", type); >> return NULL; >> @@ -2814,7 +2898,7 @@ __bpf_kfunc int bpf_dynptr_adjust(const struct bpf_dynptr *p, u64 start, u64 end >> if (start > size || end > size) >> return -ERANGE; >> >> - ptr->offset += start; >> + bpf_dynptr_advance_offset(ptr, start); >> bpf_dynptr_set_size(ptr, end - start); >> >> return 0; >> @@ -4201,11 +4285,20 @@ __bpf_kfunc int bpf_task_work_schedule_resume(struct task_struct *task, struct b >> >> __bpf_kfunc int bpf_dynptr_from_file(struct file *file, u32 flags, struct bpf_dynptr *ptr__uninit) >> { >> - return 0; >> + return make_file_dynptr(file, flags, MAY_NOT_SLEEP, (struct bpf_dynptr_kern *)ptr__uninit); >> } >> >> __bpf_kfunc int bpf_dynptr_file_discard(struct bpf_dynptr *dynptr) >> { >> + struct bpf_dynptr_kern *ptr = (struct bpf_dynptr_kern *)dynptr; >> + struct bpf_dynptr_file_impl *df; >> + >> + if (bpf_dynptr_get_type(ptr) == BPF_DYNPTR_TYPE_INVALID) >> + return 0; > nit: let's just do what dynptr_read does: > > if (!dynptr->data) > return 0; Thanks for nits, I'll apply them. >> + >> + df = ptr->data; >> + freader_cleanup(&df->freader); >> + bpf_mem_free(&bpf_global_ma, df); >> return 0; >> } >> >> -- >> 2.51.0 >>