From patchwork Mon Aug 14 17:28:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 13353131 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE010C2FF for ; Mon, 14 Aug 2023 17:28:40 +0000 (UTC) Received: from 69-171-232-180.mail-mxout.facebook.com (69-171-232-180.mail-mxout.facebook.com [69.171.232.180]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51C6610D5 for ; Mon, 14 Aug 2023 10:28:38 -0700 (PDT) Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id 520A424C21F81; Mon, 14 Aug 2023 10:28:25 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau Subject: [PATCH bpf-next 03/15] bpf: Add alloc/xchg/direct_access support for local percpu kptr Date: Mon, 14 Aug 2023 10:28:25 -0700 Message-Id: <20230814172825.1363378-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230814172809.1361446-1-yonghong.song@linux.dev> References: <20230814172809.1361446-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,RDNS_DYNAMIC,SPF_HELO_PASS,SPF_SOFTFAIL, TVD_RCVD_IP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net Add two new kfunc's, bpf_percpu_obj_new_impl() and bpf_percpu_obj_drop_impl(), to allocate a percpu obj. Two functions are very similar to bpf_obj_new_impl() and bpf_obj_drop_impl(). The major difference is related to percpu handling. bpf_rcu_read_lock() struct val_t __percpu *v = map_val->percpu_data; ... bpf_rcu_read_unlock() For a percpu data map_val like above 'v', the reg->type is set as PTR_TO_BTF_ID | MEM_PERCPU | MEM_RCU if inside rcu critical section. MEM_RCU marking here is similar to NON_OWN_REF as 'v' is not a owning referenace. But NON_OWN_REF is trusted and typically inside the spinlock while MEM_RCU is under rcu read lock. RCU is preferred here since percpu data structures mean potential concurrent access into its contents. Also, bpf_percpu_obj_new_impl() is restricted to only accept scalar struct which means nested kptr's are not allowed but some other special field, e.g., bpf_list_head, bpf_spin_lock, etc. could be nested (nested 'struct'). Later patch will improve verifier to handle such nested special fields. Signed-off-by: Yonghong Song --- include/linux/bpf.h | 3 +- kernel/bpf/helpers.c | 49 +++++++++++++++++++++++ kernel/bpf/syscall.c | 21 +++++++--- kernel/bpf/verifier.c | 90 ++++++++++++++++++++++++++++++++++--------- 4 files changed, 137 insertions(+), 26 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index e6348fd0a785..a2cb380c43c7 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -197,7 +197,8 @@ struct btf_field_kptr { struct btf *btf; struct module *module; /* dtor used if btf_is_kernel(btf), otherwise the type is - * program-allocated, dtor is NULL, and __bpf_obj_drop_impl is used + * program-allocated, dtor is NULL, and __bpf_obj_drop_impl + * or __bpf_percpu_drop_impl is used */ btf_dtor_kfunc_t dtor; u32 btf_id; diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index eb91cae0612a..dd14cb7da4af 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1900,6 +1900,29 @@ __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign) return p; } +__bpf_kfunc void *bpf_percpu_obj_new_impl(u64 local_type_id__k, void *meta__ign) +{ + struct btf_struct_meta *meta = meta__ign; + const struct btf_record *rec; + u64 size = local_type_id__k; + void __percpu *pptr; + void *p; + int cpu; + + p = bpf_mem_alloc(&bpf_global_percpu_ma, size); + if (!p) + return NULL; + if (meta) { + pptr = *((void __percpu **)p); + rec = meta->record; + for_each_possible_cpu(cpu) { + bpf_obj_init(rec, per_cpu_ptr(pptr, cpu)); + } + } + + return p; +} + /* Must be called under migrate_disable(), as required by bpf_mem_free */ void __bpf_obj_drop_impl(void *p, const struct btf_record *rec) { @@ -1924,6 +1947,30 @@ __bpf_kfunc void bpf_obj_drop_impl(void *p__alloc, void *meta__ign) __bpf_obj_drop_impl(p, meta ? meta->record : NULL); } +/* Must be called under migrate_disable(), as required by bpf_mem_free_rcu */ +void __bpf_percpu_obj_drop_impl(void *p, const struct btf_record *rec) +{ + void __percpu *pptr; + int cpu; + + if (rec) { + pptr = *((void __percpu **)p); + for_each_possible_cpu(cpu) { + bpf_obj_free_fields(rec, per_cpu_ptr(pptr, cpu)); + } + } + + bpf_mem_free_rcu(&bpf_global_percpu_ma, p); +} + +__bpf_kfunc void bpf_percpu_obj_drop_impl(void *p__alloc, void *meta__ign) +{ + struct btf_struct_meta *meta = meta__ign; + void *p = p__alloc; + + __bpf_percpu_obj_drop_impl(p, meta ? meta->record : NULL); +} + __bpf_kfunc void *bpf_refcount_acquire_impl(void *p__refcounted_kptr, void *meta__ign) { struct btf_struct_meta *meta = meta__ign; @@ -2436,7 +2483,9 @@ BTF_SET8_START(generic_btf_ids) BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE) #endif BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_percpu_obj_new_impl, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE) +BTF_ID_FLAGS(func, bpf_percpu_obj_drop_impl, KF_RELEASE) BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_push_front_impl) BTF_ID_FLAGS(func, bpf_list_push_back_impl) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 1c30b6ee84d4..9ceb6fd9a0e2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -627,6 +627,7 @@ void bpf_obj_free_timer(const struct btf_record *rec, void *obj) } extern void __bpf_obj_drop_impl(void *p, const struct btf_record *rec); +extern void __bpf_percpu_obj_drop_impl(void *p, const struct btf_record *rec); void bpf_obj_free_fields(const struct btf_record *rec, void *obj) { @@ -660,13 +661,21 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj) if (!btf_is_kernel(field->kptr.btf)) { pointee_struct_meta = btf_find_struct_meta(field->kptr.btf, field->kptr.btf_id); - if (field->type != BPF_KPTR_PERCPU_REF) + + if (field->type == BPF_KPTR_PERCPU_REF) { + migrate_disable(); + __bpf_percpu_obj_drop_impl(xchgd_field, pointee_struct_meta ? + pointee_struct_meta->record : + NULL); + migrate_enable(); + } else { WARN_ON_ONCE(!pointee_struct_meta); - migrate_disable(); - __bpf_obj_drop_impl(xchgd_field, pointee_struct_meta ? - pointee_struct_meta->record : - NULL); - migrate_enable(); + migrate_disable(); + __bpf_obj_drop_impl(xchgd_field, pointee_struct_meta ? + pointee_struct_meta->record : + NULL); + migrate_enable(); + } } else { field->kptr.dtor(xchgd_field); } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4ccca1f6c998..a985fbf18a11 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -304,7 +304,7 @@ struct bpf_kfunc_call_arg_meta { /* arg_{btf,btf_id,owning_ref} are used by kfunc-specific handling, * generally to pass info about user-defined local kptr types to later * verification logic - * bpf_obj_drop + * bpf_obj_drop/bpf_percpu_obj_drop * Record the local kptr type to be drop'd * bpf_refcount_acquire (via KF_ARG_PTR_TO_REFCOUNTED_KPTR arg type) * Record the local kptr type to be refcount_incr'd and use @@ -4997,13 +4997,20 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, if (kptr_field->type == BPF_KPTR_UNREF) perm_flags |= PTR_UNTRUSTED; + if (kptr_field->type == BPF_KPTR_PERCPU_REF) + perm_flags |= MEM_PERCPU | MEM_ALLOC; + if (base_type(reg->type) != PTR_TO_BTF_ID || (type_flag(reg->type) & ~perm_flags)) goto bad_type; - if (!btf_is_kernel(reg->btf)) { + if (kptr_field->type != BPF_KPTR_PERCPU_REF && !btf_is_kernel(reg->btf)) { verbose(env, "R%d must point to kernel BTF\n", regno); return -EINVAL; } + if (kptr_field->type == BPF_KPTR_PERCPU_REF && btf_is_kernel(reg->btf)) { + verbose(env, "R%d must point to prog BTF\n", regno); + return -EINVAL; + } /* We need to verify reg->type and reg->btf, before accessing reg->btf */ reg_name = btf_type_name(reg->btf, reg->btf_id); @@ -5084,7 +5091,17 @@ static bool rcu_safe_kptr(const struct btf_field *field) { const struct btf_field_kptr *kptr = &field->kptr; - return field->type == BPF_KPTR_REF && rcu_protected_object(kptr->btf, kptr->btf_id); + return field->type == BPF_KPTR_PERCPU_REF || + (field->type == BPF_KPTR_REF && rcu_protected_object(kptr->btf, kptr->btf_id)); +} + +static u32 btf_ld_kptr_type(struct bpf_verifier_env *env, struct btf_field *kptr_field) +{ + if (!rcu_safe_kptr(kptr_field) || !in_rcu_cs(env)) + return PTR_MAYBE_NULL | PTR_UNTRUSTED; + if (kptr_field->type != BPF_KPTR_PERCPU_REF) + return PTR_MAYBE_NULL | MEM_RCU; + return PTR_MAYBE_NULL | MEM_RCU | MEM_PERCPU; } static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno, @@ -5110,7 +5127,8 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno, /* We only allow loading referenced kptr, since it will be marked as * untrusted, similar to unreferenced kptr. */ - if (class != BPF_LDX && kptr_field->type == BPF_KPTR_REF) { + if (class != BPF_LDX && + (kptr_field->type == BPF_KPTR_REF || kptr_field->type == BPF_KPTR_PERCPU_REF)) { verbose(env, "store to referenced kptr disallowed\n"); return -EACCES; } @@ -5121,10 +5139,7 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno, * value from map as PTR_TO_BTF_ID, with the correct type. */ mark_btf_ld_reg(env, cur_regs(env), value_regno, PTR_TO_BTF_ID, kptr_field->kptr.btf, - kptr_field->kptr.btf_id, - rcu_safe_kptr(kptr_field) && in_rcu_cs(env) ? - PTR_MAYBE_NULL | MEM_RCU : - PTR_MAYBE_NULL | PTR_UNTRUSTED); + kptr_field->kptr.btf_id, btf_ld_kptr_type(env, kptr_field)); /* For mark_ptr_or_null_reg */ val_reg->id = ++env->id_gen; } else if (class == BPF_STX) { @@ -5178,6 +5193,7 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno, switch (field->type) { case BPF_KPTR_UNREF: case BPF_KPTR_REF: + case BPF_KPTR_PERCPU_REF: if (src != ACCESS_DIRECT) { verbose(env, "kptr cannot be accessed indirectly by helper\n"); return -EACCES; @@ -7316,7 +7332,7 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno, verbose(env, "off=%d doesn't point to kptr\n", kptr_off); return -EACCES; } - if (kptr_field->type != BPF_KPTR_REF) { + if (kptr_field->type != BPF_KPTR_REF && kptr_field->type != BPF_KPTR_PERCPU_REF) { verbose(env, "off=%d kptr isn't referenced kptr\n", kptr_off); return -EACCES; } @@ -7827,8 +7843,10 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno, if (base_type(arg_type) == ARG_PTR_TO_MEM) type &= ~DYNPTR_TYPE_FLAG_MASK; - if (meta->func_id == BPF_FUNC_kptr_xchg && type_is_alloc(type)) + if (meta->func_id == BPF_FUNC_kptr_xchg && type_is_alloc(type)) { type &= ~MEM_ALLOC; + type &= ~MEM_PERCPU; + } for (i = 0; i < ARRAY_SIZE(compatible->types); i++) { expected = compatible->types[i]; @@ -7918,6 +7936,14 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno, } /* Handled by helper specific checks */ break; + case PTR_TO_BTF_ID | MEM_PERCPU | MEM_ALLOC: + if (meta->func_id != BPF_FUNC_kptr_xchg) { + verbose(env, "verifier internal error: unimplemented handling of MEM_PERCPU | MEM_ALLOC\n"); + return -EFAULT; + } + if (map_kptr_match_type(env, meta->kptr_field, reg, regno)) + return -EACCES; + break; case PTR_TO_BTF_ID | MEM_PERCPU: case PTR_TO_BTF_ID | MEM_PERCPU | PTR_TRUSTED: /* Handled by helper specific checks */ @@ -9885,8 +9911,11 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn if (func_id == BPF_FUNC_kptr_xchg) { ret_btf = meta.kptr_field->kptr.btf; ret_btf_id = meta.kptr_field->kptr.btf_id; - if (!btf_is_kernel(ret_btf)) + if (!btf_is_kernel(ret_btf)) { regs[BPF_REG_0].type |= MEM_ALLOC; + if (meta.kptr_field->type == BPF_KPTR_PERCPU_REF) + regs[BPF_REG_0].type |= MEM_PERCPU; + } } else { if (fn->ret_btf_id == BPF_PTR_POISON) { verbose(env, "verifier internal error:"); @@ -10271,6 +10300,8 @@ enum special_kfunc_type { KF_bpf_dynptr_slice, KF_bpf_dynptr_slice_rdwr, KF_bpf_dynptr_clone, + KF_bpf_percpu_obj_new_impl, + KF_bpf_percpu_obj_drop_impl, }; BTF_SET_START(special_kfunc_set) @@ -10291,6 +10322,8 @@ BTF_ID(func, bpf_dynptr_from_xdp) BTF_ID(func, bpf_dynptr_slice) BTF_ID(func, bpf_dynptr_slice_rdwr) BTF_ID(func, bpf_dynptr_clone) +BTF_ID(func, bpf_percpu_obj_new_impl) +BTF_ID(func, bpf_percpu_obj_drop_impl) BTF_SET_END(special_kfunc_set) BTF_ID_LIST(special_kfunc_list) @@ -10313,6 +10346,8 @@ BTF_ID(func, bpf_dynptr_from_xdp) BTF_ID(func, bpf_dynptr_slice) BTF_ID(func, bpf_dynptr_slice_rdwr) BTF_ID(func, bpf_dynptr_clone) +BTF_ID(func, bpf_percpu_obj_new_impl) +BTF_ID(func, bpf_percpu_obj_drop_impl) static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta) { @@ -11003,7 +11038,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ } break; case KF_ARG_PTR_TO_ALLOC_BTF_ID: - if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) { + if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC) && + reg->type != (PTR_TO_BTF_ID | MEM_PERCPU | MEM_ALLOC)) { verbose(env, "arg#%d expected pointer to allocated object\n", i); return -EINVAL; } @@ -11012,7 +11048,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ return -EINVAL; } if (meta->btf == btf_vmlinux && - meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) { + (meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl] || + meta->func_id == special_kfunc_list[KF_bpf_percpu_obj_drop_impl])) { meta->arg_btf = reg->btf; meta->arg_btf_id = reg->btf_id; } @@ -11410,6 +11447,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, /* Only exception is bpf_obj_new_impl */ if (meta.btf != btf_vmlinux || (meta.func_id != special_kfunc_list[KF_bpf_obj_new_impl] && + meta.func_id != special_kfunc_list[KF_bpf_percpu_obj_new_impl] && meta.func_id != special_kfunc_list[KF_bpf_refcount_acquire_impl])) { verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n"); return -EINVAL; @@ -11423,11 +11461,15 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, ptr_type = btf_type_skip_modifiers(desc_btf, t->type, &ptr_type_id); if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) { - if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl]) { + if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl] || + meta.func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl]) { struct btf *ret_btf; u32 ret_btf_id; - if (unlikely(!bpf_global_ma_set)) + if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl] && !bpf_global_ma_set) + return -ENOMEM; + + if (meta.func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl] && !bpf_global_percpu_ma_set) return -ENOMEM; if (((u64)(u32)meta.arg_constant.value) != meta.arg_constant.value) { @@ -11440,13 +11482,18 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, /* This may be NULL due to user not supplying a BTF */ if (!ret_btf) { - verbose(env, "bpf_obj_new requires prog BTF\n"); + verbose(env, "bpf_obj_new/bpf_percpu_obj_new requires prog BTF\n"); return -EINVAL; } ret_t = btf_type_by_id(ret_btf, ret_btf_id); if (!ret_t || !__btf_type_is_struct(ret_t)) { - verbose(env, "bpf_obj_new type ID argument must be of a struct\n"); + verbose(env, "bpf_obj_new/bpf_percpu_obj_new type ID argument must be of a struct\n"); + return -EINVAL; + } + if (meta.func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl] && + !__btf_type_is_scalar_struct(env, ret_btf, ret_t, 0)) { + verbose(env, "bpf_percpu_obj_new type ID argument must be of a struct of scalars\n"); return -EINVAL; } @@ -11454,6 +11501,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC; regs[BPF_REG_0].btf = ret_btf; regs[BPF_REG_0].btf_id = ret_btf_id; + if (meta.func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl]) + regs[BPF_REG_0].type |= MEM_PERCPU; insn_aux->obj_new_size = ret_t->size; insn_aux->kptr_struct_meta = @@ -11594,7 +11643,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, regs[BPF_REG_0].id = ++env->id_gen; } else if (btf_type_is_void(t)) { if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) { - if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) { + if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl] || + meta.func_id == special_kfunc_list[KF_bpf_percpu_obj_drop_impl]) { insn_aux->kptr_struct_meta = btf_find_struct_meta(meta.arg_btf, meta.arg_btf_id); @@ -18266,7 +18316,8 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, insn->imm = BPF_CALL_IMM(desc->addr); if (insn->off) return 0; - if (desc->func_id == special_kfunc_list[KF_bpf_obj_new_impl]) { + if (desc->func_id == special_kfunc_list[KF_bpf_obj_new_impl] || + desc->func_id == special_kfunc_list[KF_bpf_percpu_obj_new_impl]) { struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta; struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) }; u64 obj_new_size = env->insn_aux_data[insn_idx].obj_new_size; @@ -18277,6 +18328,7 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, insn_buf[3] = *insn; *cnt = 4; } else if (desc->func_id == special_kfunc_list[KF_bpf_obj_drop_impl] || + desc->func_id == special_kfunc_list[KF_bpf_percpu_obj_drop_impl] || desc->func_id == special_kfunc_list[KF_bpf_refcount_acquire_impl]) { struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta; struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };