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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id w24-20020a1709067c9800b00a4528658771sm3841399ejo.31.2024.03.06.05.12.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Mar 2024 05:12:06 -0800 (PST) Message-ID: Subject: Re: [PATCH v6 bpf-next 1/4] bpf: Introduce may_goto instruction From: Eduard Zingerman To: Alexei Starovoitov , bpf@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, memxor@gmail.com, john.fastabend@gmail.com, kernel-team@fb.com Date: Wed, 06 Mar 2024 15:12:05 +0200 In-Reply-To: <20240306031929.42666-2-alexei.starovoitov@gmail.com> References: <20240306031929.42666-1-alexei.starovoitov@gmail.com> <20240306031929.42666-2-alexei.starovoitov@gmail.com> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=mQGNBGKNNQEBDACwcUNXZOGTzn4rr7Sd18SA5Wv0Wna/ONE0ZwZEx+sIjyGrPOIhR14/DsOr3ZJer9UJ/WAJwbxOBj6E5Y2iF7grehljNbLr/jMjzPJ+hJpfOEAb5xjCB8xIqDoric1WRcCaRB+tDSk7jcsIIiMish0diTK3qTdu4MB6i/sh4aeFs2nifkNi3LdBuk8Xnk+RJHRoKFJ+C+EoSmQPuDQIRaF9N2m4yO0eG36N8jLwvUXnZzGvHkphoQ9ztbRJp58oh6xT7uH62m98OHbsVgzYKvHyBu/IU2ku5kVG9pLrFp25xfD4YdlMMkJH6l+jk+cpY0cvMTS1b6/g+1fyPM+uzD8Wy+9LtZ4PHwLZX+t4ONb/48i5AKq/jSsb5HWdciLuKEwlMyFAihZamZpEj+9n91NLPX4n7XeThXHaEvaeVVl4hfW/1Qsao7l1YjU/NCHuLaDeH4U1P59bagjwo9d1n5/PESeuD4QJFNqW+zkmE4tmyTZ6bPV6T5xdDRHeiITGc00AEQEAAbQkRWR1YXJkIFppbmdlcm1hbiA8ZWRkeXo4N0BnbWFpbC5jb20+iQHUBBMBCgA+FiEEx+6LrjApQyqnXCYELgxleklgRAkFAmKNNQECGwMFCQPCZwAFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQLgxleklgRAlWZAv/cJ5v3zlEyP0/jMKQBqbVCCHTirPEw+nqxbkeSO6r2FUds0NnGA9a6NPOpBH+qW7a6+n6q3sIbvH7jlss4pzLI7LYlDC6z+egTv7KR5X1xFrY1uR5UGs1beAjnzYeV2hK4yqRUfygsT0Wk5e4FiNBv4+DUZ8r0cNDkO6swJxU55DO21mcteC147+4aDoHZ40R0tsAu+brDGSSoOPpb0RWVsEf9XOBJqWWA+T7mluw nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2024-03-05 at 19:19 -0800, Alexei Starovoitov wrote: > From: Alexei Starovoitov [...] > JCOND stands for conditional pseudo jump. > Since goto_or_nop insn was proposed, it may use the same opcode. > may_goto vs goto_or_nop can be distinguished by src_reg: > code =3D BPF_JMP | BPF_JCOND > src_reg =3D 0 - may_goto > src_reg =3D 1 - goto_or_nop >=20 > Acked-by: Andrii Nakryiko > Signed-off-by: Alexei Starovoitov > --- Acked-by: Eduard Zingerman [...] > @@ -14871,11 +14882,36 @@ static int check_cond_jmp_op(struct bpf_verifie= r_env *env, > int err; > =20 > /* Only conditional jumps are expected to reach here. */ > - if (opcode =3D=3D BPF_JA || opcode > BPF_JSLE) { > + if (opcode =3D=3D BPF_JA || opcode > BPF_JCOND) { > verbose(env, "invalid BPF_JMP/JMP32 opcode %x\n", opcode); > return -EINVAL; > } > =20 > + if (opcode =3D=3D BPF_JCOND) { > + struct bpf_verifier_state *cur_st =3D env->cur_state, *queued_st, *pre= v_st; > + int idx =3D *insn_idx; > + > + if (insn->code !=3D (BPF_JMP | BPF_JCOND) || > + insn->src_reg !=3D BPF_MAY_GOTO || > + insn->dst_reg || insn->imm || insn->off =3D=3D 0) { > + verbose(env, "invalid may_goto off %d imm %d\n", > + insn->off, insn->imm); > + return -EINVAL; > + } > + prev_st =3D find_prev_entry(env, cur_st->parent, idx); > + > + /* branch out 'fallthrough' insn as a new state to explore */ > + queued_st =3D push_stack(env, idx + 1, idx, false); > + if (!queued_st) > + return -ENOMEM; > + > + queued_st->may_goto_depth++; > + if (prev_st) > + widen_imprecise_scalars(env, prev_st, queued_st); > + *insn_idx +=3D insn->off; > + return 0; > + } Nit: for other conditional jumps the fallthrough branch is explored first, I tried the following and the tests keep passing: =20 @@ -14901,14 +14901,13 @@ static int check_cond_jmp_op(struct bpf_verifier_= env *env, prev_st =3D find_prev_entry(env, cur_st->parent, idx); =20 /* branch out 'fallthrough' insn as a new state to explore */ - queued_st =3D push_stack(env, idx + 1, idx, false); + queued_st =3D push_stack(env, idx + insn->off + 1, idx, false); if (!queued_st) return -ENOMEM; =20 - queued_st->may_goto_depth++; + cur_st->may_goto_depth++; if (prev_st) - widen_imprecise_scalars(env, prev_st, queued_st); - *insn_idx +=3D insn->off; + widen_imprecise_scalars(env, prev_st, cur_st); return 0; } =20 Maybe this is a property worth preserving, wdyt? 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