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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id z15-20020a1709060acf00b0099cb0a7098dsm1408468ejf.19.2023.11.08.10.22.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Nov 2023 10:22:06 -0800 (PST) Message-ID: Subject: Re: [PATCH v5 bpf-next 21/23] selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken From: Eduard Zingerman To: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: kernel-team@meta.com Date: Wed, 08 Nov 2023 20:22:04 +0200 In-Reply-To: <20231027181346.4019398-22-andrii@kernel.org> References: <20231027181346.4019398-1-andrii@kernel.org> <20231027181346.4019398-22-andrii@kernel.org> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 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 3.50.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2023-10-27 at 11:13 -0700, Andrii Nakryiko wrote: > Similar to kernel-side BPF verifier logic enhancements, use 32-bit > subrange knowledge for is_branch_taken() logic in reg_bounds selftests. >=20 > Signed-off-by: Andrii Nakryiko > --- > .../selftests/bpf/prog_tests/reg_bounds.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) >=20 > diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/= testing/selftests/bpf/prog_tests/reg_bounds.c > index ac7354cfe139..330618cc12e7 100644 > --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c > +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c > @@ -750,16 +750,27 @@ static int reg_state_branch_taken_op(enum num_t t, = struct reg_state *x, struct r > /* OP_EQ and OP_NE are sign-agnostic */ > enum num_t tu =3D t_unsigned(t); > enum num_t ts =3D t_signed(t); > - int br_u, br_s; > + int br_u, br_s, br; > =20 > br_u =3D range_branch_taken_op(tu, x->r[tu], y->r[tu], op); > br_s =3D range_branch_taken_op(ts, x->r[ts], y->r[ts], op); > =20 > if (br_u >=3D 0 && br_s >=3D 0 && br_u !=3D br_s) > ASSERT_FALSE(true, "branch taken inconsistency!\n"); > - if (br_u >=3D 0) > - return br_u; > - return br_s; > + > + /* if 64-bit ranges are indecisive, use 32-bit subranges to > + * eliminate always/never taken branches, if possible > + */ > + if (br_u =3D=3D -1 && (t =3D=3D U64 || t =3D=3D S64)) { > + br =3D range_branch_taken_op(U32, x->r[U32], y->r[U32], op); > + if (br !=3D -1) > + return br; > + br =3D range_branch_taken_op(S32, x->r[S32], y->r[S32], op); > + if (br !=3D -1) > + return br; I'm not sure that these two checks are consistent with kernel side. In kernel: - for BPF_JEQ we can derive "won't happen" from u32/s32 ranges; - for BPF_JNE we can derive "will happen" from u32/s32 ranges. But here we seem to accept "will happen" for OP_EQ, which does not seem right. E.g. it is possible to have inconclusive upper 32 bits and equal lower 32 bits. What am I missing?