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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id a14sm2678636wmj.40.2020.12.01.04.22.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Dec 2020 04:22:36 -0800 (PST) Date: Tue, 1 Dec 2020 12:22:32 +0000 From: Brendan Jackman To: Yonghong Song Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , KP Singh , Florent Revest , linux-kernel@vger.kernel.org, Jann Horn Subject: Re: [PATCH v2 bpf-next 07/13] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Message-ID: <20201201122232.GD2114905@google.com> References: <20201127175738.1085417-1-jackmanb@google.com> <20201127175738.1085417-8-jackmanb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 27, 2020 at 08:15:49PM -0800, Yonghong Song wrote: > > > On 11/27/20 9:57 AM, Brendan Jackman wrote: [...] > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index e8b41ccdfb90..cd4c03b25573 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -3602,7 +3602,11 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i > > { > > int err; > > - if (insn->imm != BPF_ADD) { > > + switch (insn->imm) { > > + case BPF_ADD: > > + case BPF_ADD | BPF_FETCH: > > + break; > > + default: > > verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n", insn->imm); > > return -EINVAL; > > } > > @@ -3631,7 +3635,7 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i > > is_pkt_reg(env, insn->dst_reg) || > > is_flow_key_reg(env, insn->dst_reg) || > > is_sk_reg(env, insn->dst_reg)) { > > - verbose(env, "atomic stores into R%d %s is not allowed\n", > > + verbose(env, "BPF_ATOMIC stores into R%d %s is not allowed\n", > > insn->dst_reg, > > reg_type_str[reg_state(env, insn->dst_reg)->type]); > > return -EACCES; > > @@ -3644,8 +3648,20 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i > > return err; > > /* check whether we can write into the same memory */ > > - return check_mem_access(env, insn_idx, insn->dst_reg, insn->off, > > - BPF_SIZE(insn->code), BPF_WRITE, -1, true); > > + err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, > > + BPF_SIZE(insn->code), BPF_WRITE, -1, true); > > + if (err) > > + return err; > > + > > + if (!(insn->imm & BPF_FETCH)) > > + return 0; > > + > > + /* check and record load of old value into src reg */ > > + err = check_reg_arg(env, insn->src_reg, DST_OP); > > + if (err) > > + return err; > > + > > + return 0; > > } > > static int __check_stack_boundary(struct bpf_verifier_env *env, u32 regno, > > @@ -9501,12 +9517,6 @@ static int do_check(struct bpf_verifier_env *env) > > } else if (class == BPF_STX) { > > enum bpf_reg_type *prev_dst_type, dst_reg_type; > > - if (((BPF_MODE(insn->code) != BPF_MEM && > > - BPF_MODE(insn->code) != BPF_ATOMIC) || insn->imm != 0)) { > > - verbose(env, "BPF_STX uses reserved fields\n"); > > - return -EINVAL; > > - } > > - > > if (BPF_MODE(insn->code) == BPF_ATOMIC) { > > err = check_atomic(env, env->insn_idx, insn); > > if (err) > > @@ -9515,6 +9525,11 @@ static int do_check(struct bpf_verifier_env *env) > > continue; > > } > > + if (BPF_MODE(insn->code) != BPF_MEM && insn->imm != 0) { > > "||" here instead of "&&"? Right - thanks again!