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[2a03:2880:20ff:3::face:b00c]) by smtp.gmail.com with ESMTPSA id bt9-20020ac86909000000b00342f5408ea5sm3789160qtb.49.2022.08.08.08.54.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Aug 2022 08:54:02 -0700 (PDT) From: David Vernet To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, john.fastabend@gmail.com, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, tj@kernel.org, joannelkoong@gmail.com, linux-kernel@vger.kernel.org, Kernel-team@fb.com Subject: [PATCH 3/5] bpf: Add bpf_user_ringbuf_drain() helper Date: Mon, 8 Aug 2022 08:53:39 -0700 Message-Id: <20220808155341.2479054-3-void@manifault.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220808155341.2479054-1-void@manifault.com> References: <20220808155341.2479054-1-void@manifault.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that we have a BPF_MAP_TYPE_USER_RINGBUF map type, we need to add a helper function that allows BPF programs to drain samples from the ring buffer, and invoke a callback for each. This patch adds a new bpf_user_ringbuf_drain() helper that provides this abstraction. In order to support this, we needed to also add a new PTR_TO_DYNPTR register type to reflect a dynptr that was allocated by a helper function and passed to a BPF program. The verifier currently only supports PTR_TO_DYNPTR registers that are also DYNPTR_TYPE_LOCAL and MEM_ALLOC. Signed-off-by: David Vernet --- include/linux/bpf.h | 6 +- include/uapi/linux/bpf.h | 8 ++ kernel/bpf/helpers.c | 2 + kernel/bpf/ringbuf.c | 157 +++++++++++++++++++++++++++++++-- kernel/bpf/verifier.c | 57 +++++++++++- tools/include/uapi/linux/bpf.h | 8 ++ 6 files changed, 228 insertions(+), 10 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 20c26aed7896..4d0d5f2a3ac8 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -401,7 +401,7 @@ enum bpf_type_flag { /* DYNPTR points to memory local to the bpf program. */ DYNPTR_TYPE_LOCAL = BIT(8 + BPF_BASE_TYPE_BITS), - /* DYNPTR points to a ringbuf record. */ + /* DYNPTR points to a kernel-produced ringbuf record. */ DYNPTR_TYPE_RINGBUF = BIT(9 + BPF_BASE_TYPE_BITS), /* Size is known at compile time. */ @@ -606,6 +606,7 @@ enum bpf_reg_type { PTR_TO_MEM, /* reg points to valid memory region */ PTR_TO_BUF, /* reg points to a read/write buffer */ PTR_TO_FUNC, /* reg points to a bpf program function */ + PTR_TO_DYNPTR, /* reg points to a dynptr */ __BPF_REG_TYPE_MAX, /* Extended reg_types. */ @@ -2410,6 +2411,7 @@ extern const struct bpf_func_proto bpf_loop_proto; extern const struct bpf_func_proto bpf_copy_from_user_task_proto; extern const struct bpf_func_proto bpf_set_retval_proto; extern const struct bpf_func_proto bpf_get_retval_proto; +extern const struct bpf_func_proto bpf_user_ringbuf_drain_proto; const struct bpf_func_proto *tracing_prog_func_proto( enum bpf_func_id func_id, const struct bpf_prog *prog); @@ -2554,7 +2556,7 @@ enum bpf_dynptr_type { BPF_DYNPTR_TYPE_INVALID, /* Points to memory that is local to the bpf program */ BPF_DYNPTR_TYPE_LOCAL, - /* Underlying data is a ringbuf record */ + /* Underlying data is a kernel-produced ringbuf record */ BPF_DYNPTR_TYPE_RINGBUF, }; diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index a341f877b230..ca125648d7fd 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5332,6 +5332,13 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * long bpf_user_ringbuf_drain(struct bpf_map *map, void *callback_fn, void *ctx, u64 flags) + * Description + * Drain samples from the specified user ringbuffer, and invoke the + * provided callback for each such sample. + * Return + * An error if a sample could not be drained. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5542,6 +5549,7 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(user_ringbuf_drain), \ /* */ /* 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..b8097876014c 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1647,6 +1647,8 @@ bpf_base_func_proto(enum bpf_func_id func_id) return &bpf_dynptr_write_proto; case BPF_FUNC_dynptr_data: return &bpf_dynptr_data_proto; + case BPF_FUNC_user_ringbuf_drain: + return &bpf_user_ringbuf_drain_proto; default: break; } diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 29e2de42df15..fc589fc8eb7c 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -291,16 +291,33 @@ static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb) } static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp, - struct poll_table_struct *pts) + struct poll_table_struct *pts, + bool kernel_producer) { struct bpf_ringbuf_map *rb_map; + bool buffer_empty; rb_map = container_of(map, struct bpf_ringbuf_map, map); poll_wait(filp, &rb_map->rb->waitq, pts); - if (ringbuf_avail_data_sz(rb_map->rb)) - return EPOLLIN | EPOLLRDNORM; - return 0; + buffer_empty = !ringbuf_avail_data_sz(rb_map->rb); + + if (kernel_producer) + return buffer_empty ? 0 : EPOLLIN | EPOLLRDNORM; + else + return buffer_empty ? EPOLLOUT | EPOLLWRNORM : 0; +} + +static __poll_t ringbuf_map_poll_kern(struct bpf_map *map, struct file *filp, + struct poll_table_struct *pts) +{ + return ringbuf_map_poll(map, filp, pts, true); +} + +static __poll_t ringbuf_map_poll_user(struct bpf_map *map, struct file *filp, + struct poll_table_struct *pts) +{ + return ringbuf_map_poll(map, filp, pts, false); } BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map) @@ -309,7 +326,7 @@ const struct bpf_map_ops ringbuf_map_ops = { .map_alloc = ringbuf_map_alloc, .map_free = ringbuf_map_free, .map_mmap = ringbuf_map_mmap_kern, - .map_poll = ringbuf_map_poll, + .map_poll = ringbuf_map_poll_kern, .map_lookup_elem = ringbuf_map_lookup_elem, .map_update_elem = ringbuf_map_update_elem, .map_delete_elem = ringbuf_map_delete_elem, @@ -323,6 +340,7 @@ const struct bpf_map_ops user_ringbuf_map_ops = { .map_alloc = ringbuf_map_alloc, .map_free = ringbuf_map_free, .map_mmap = ringbuf_map_mmap_user, + .map_poll = ringbuf_map_poll_user, .map_lookup_elem = ringbuf_map_lookup_elem, .map_update_elem = ringbuf_map_update_elem, .map_delete_elem = ringbuf_map_delete_elem, @@ -605,3 +623,132 @@ const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = { .arg1_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE, .arg2_type = ARG_ANYTHING, }; + +static int __bpf_user_ringbuf_poll(struct bpf_ringbuf *rb, void **sample, + u32 *size) +{ + unsigned long cons_pos, prod_pos; + u32 sample_len, total_len; + u32 *hdr; + int err; + int busy = 0; + + /* If another consumer is already consuming a sample, wait for them to + * finish. + */ + if (!atomic_try_cmpxchg(&rb->busy, &busy, 1)) + return -EBUSY; + + /* Synchronizes with smp_store_release() in user-space. */ + prod_pos = smp_load_acquire(&rb->producer_pos); + /* Synchronizes with smp_store_release() in + * __bpf_user_ringbuf_sample_release(). + */ + cons_pos = smp_load_acquire(&rb->consumer_pos); + if (cons_pos >= prod_pos) { + atomic_set(&rb->busy, 0); + return -ENODATA; + } + + hdr = (u32 *)((uintptr_t)rb->data + (cons_pos & rb->mask)); + sample_len = *hdr; + + /* Check that the sample can fit into a dynptr. */ + err = bpf_dynptr_check_size(sample_len); + if (err) { + atomic_set(&rb->busy, 0); + return err; + } + + /* Check that the sample fits within the region advertised by the + * consumer position. + */ + total_len = sample_len + BPF_RINGBUF_HDR_SZ; + if (total_len > prod_pos - cons_pos) { + atomic_set(&rb->busy, 0); + return -E2BIG; + } + + /* Check that the sample fits within the data region of the ring buffer. + */ + if (total_len > rb->mask + 1) { + atomic_set(&rb->busy, 0); + return -E2BIG; + } + + /* consumer_pos is updated when the sample is released. + */ + + *sample = (void *)((uintptr_t)rb->data + + ((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask)); + *size = sample_len; + + return 0; +} + +static void +__bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t size, + u64 flags) +{ + + + /* To release the ringbuffer, just increment the producer position to + * signal that a new sample can be consumed. The busy bit is cleared by + * userspace when posting a new sample to the ringbuffer. + */ + smp_store_release(&rb->consumer_pos, rb->consumer_pos + size + + BPF_RINGBUF_HDR_SZ); + + if (flags & BPF_RB_FORCE_WAKEUP || !(flags & BPF_RB_NO_WAKEUP)) + irq_work_queue(&rb->work); + + atomic_set(&rb->busy, 0); +} + +BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map, + void *, callback_fn, void *, callback_ctx, u64, flags) +{ + struct bpf_ringbuf *rb; + long num_samples = 0, ret = 0; + int err; + bpf_callback_t callback = (bpf_callback_t)callback_fn; + u64 wakeup_flags = BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP; + + if (unlikely(flags & ~wakeup_flags)) + return -EINVAL; + + /* The two wakeup flags are mutually exclusive. */ + if (unlikely((flags & wakeup_flags) == wakeup_flags)) + return -EINVAL; + + rb = container_of(map, struct bpf_ringbuf_map, map)->rb; + do { + u32 size; + void *sample; + + err = __bpf_user_ringbuf_poll(rb, &sample, &size); + + if (!err) { + struct bpf_dynptr_kern dynptr; + + bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL, + 0, size); + ret = callback((u64)&dynptr, + (u64)(uintptr_t)callback_ctx, 0, 0, 0); + + __bpf_user_ringbuf_sample_release(rb, size, flags); + num_samples++; + } + } while (err == 0 && num_samples < 4096 && ret == 0); + + return num_samples; +} + +const struct bpf_func_proto bpf_user_ringbuf_drain_proto = { + .func = bpf_user_ringbuf_drain, + .ret_type = RET_INTEGER, + .arg1_type = ARG_CONST_MAP_PTR, + .arg2_type = ARG_PTR_TO_FUNC, + .arg3_type = ARG_PTR_TO_STACK_OR_NULL, + .arg4_type = ARG_ANYTHING, +}; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4a9562c62af0..99dfdc3ed187 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -555,6 +555,7 @@ static const char *reg_type_str(struct bpf_verifier_env *env, [PTR_TO_BUF] = "buf", [PTR_TO_FUNC] = "func", [PTR_TO_MAP_KEY] = "map_key", + [PTR_TO_DYNPTR] = "dynptr_ptr", }; if (type & PTR_MAYBE_NULL) { @@ -5656,6 +5657,12 @@ static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } static const struct bpf_reg_types const_str_ptr_types = { .types = { PTR_TO_MAP_VALUE } }; static const struct bpf_reg_types timer_types = { .types = { PTR_TO_MAP_VALUE } }; static const struct bpf_reg_types kptr_types = { .types = { PTR_TO_MAP_VALUE } }; +static const struct bpf_reg_types dynptr_types = { + .types = { + PTR_TO_STACK, + PTR_TO_DYNPTR | MEM_ALLOC | DYNPTR_TYPE_LOCAL, + } +}; static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { [ARG_PTR_TO_MAP_KEY] = &map_key_value_types, @@ -5682,7 +5689,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { [ARG_PTR_TO_CONST_STR] = &const_str_ptr_types, [ARG_PTR_TO_TIMER] = &timer_types, [ARG_PTR_TO_KPTR] = &kptr_types, - [ARG_PTR_TO_DYNPTR] = &stack_ptr_types, + [ARG_PTR_TO_DYNPTR] = &dynptr_types, }; static int check_reg_type(struct bpf_verifier_env *env, u32 regno, @@ -6025,6 +6032,13 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, err = check_mem_size_reg(env, reg, regno, true, meta); break; case ARG_PTR_TO_DYNPTR: + /* We only need to check for initialized / uninitialized helper + * dynptr args if the dynptr is not MEM_ALLOC, as the assumption + * is that if it is, that a helper function initialized the + * dynptr on behalf of the BPF program. + */ + if (reg->type & MEM_ALLOC) + break; if (arg_type & MEM_UNINIT) { if (!is_dynptr_reg_valid_uninit(env, reg)) { verbose(env, "Dynptr has to be an uninitialized dynptr\n"); @@ -6197,7 +6211,9 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, goto error; break; case BPF_MAP_TYPE_USER_RINGBUF: - goto error; + if (func_id != BPF_FUNC_user_ringbuf_drain) + goto error; + break; case BPF_MAP_TYPE_STACK_TRACE: if (func_id != BPF_FUNC_get_stackid) goto error; @@ -6317,6 +6333,10 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env, if (map->map_type != BPF_MAP_TYPE_RINGBUF) goto error; break; + case BPF_FUNC_user_ringbuf_drain: + if (map->map_type != BPF_MAP_TYPE_USER_RINGBUF) + goto error; + break; case BPF_FUNC_get_stackid: if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) goto error; @@ -6901,6 +6921,29 @@ static int set_find_vma_callback_state(struct bpf_verifier_env *env, return 0; } +static int set_user_ringbuf_callback_state(struct bpf_verifier_env *env, + struct bpf_func_state *caller, + struct bpf_func_state *callee, + int insn_idx) +{ + /* bpf_user_ringbuf_drain(struct bpf_map *map, void *callback_fn, void + * callback_ctx, u64 flags); + * callback_fn(struct bpf_dynptr_t* dynptr, void *callback_ctx); + */ + __mark_reg_not_init(env, &callee->regs[BPF_REG_0]); + callee->regs[BPF_REG_1].type = PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_ALLOC; + __mark_reg_known_zero(&callee->regs[BPF_REG_1]); + callee->regs[BPF_REG_2] = caller->regs[BPF_REG_3]; + + /* unused */ + __mark_reg_not_init(env, &callee->regs[BPF_REG_3]); + __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); + __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); + + callee->in_callback_fn = true; + return 0; +} + static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) { struct bpf_verifier_state *state = env->cur_state; @@ -7345,6 +7388,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn } } break; + case BPF_FUNC_user_ringbuf_drain: + err = __check_func_call(env, insn, insn_idx_p, meta.subprogno, + set_user_ringbuf_callback_state); + break; } if (err) @@ -7477,11 +7524,15 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn /* Find the id of the dynptr we're acquiring a reference to */ for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) { if (arg_type_is_dynptr(fn->arg_type[i])) { + struct bpf_reg_state *reg = ®s[BPF_REG_1 + i]; + if (dynptr_id) { verbose(env, "verifier internal error: multiple dynptr args in func\n"); return -EFAULT; } - dynptr_id = stack_slot_get_id(env, ®s[BPF_REG_1 + i]); + + if (!(reg->type & MEM_ALLOC)) + dynptr_id = stack_slot_get_id(env, reg); } } /* For release_reference() */ diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index ce0ce713faf9..e5e4ab12177c 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5332,6 +5332,13 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * long bpf_user_ringbuf_drain(struct bpf_map *map, void *callback_fn, void *ctx, u64 flags) + * Description + * Drain samples from the specified user ringbuffer, and invoke the + * provided callback for each such sample. + * Return + * An error if a sample could not be drained. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5542,6 +5549,7 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(bpf_user_ringbuf_drain), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper -- 2.30.2