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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id o5-20020a05600c510500b0040c1d2c6331sm27072969wms.32.2023.12.14.18.28.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Dec 2023 18:28:22 -0800 (PST) Message-ID: <66b2a6c45045c207d8452ad3b5786a9dc0082d79.camel@gmail.com> Subject: Re: [Bug Report] bpf: incorrectly pruning runtime execution path From: Eduard Zingerman To: Alexei Starovoitov Cc: Andrii Nakryiko , Hao Sun , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , bpf , Linux Kernel Mailing List Date: Fri, 15 Dec 2023 04:28:20 +0200 In-Reply-To: References: <480a5cfefc23446f7c82c5b87eef6306364132b9.camel@gmail.com> <917DAD9F-8697-45B8-8890-D33393F6CDF1@gmail.com> <9dee19c7d39795242c15b2f7aa56fb4a6c3ebffa.camel@gmail.com> <73d021e3f77161668aae833e478b210ed5cd2f4d.camel@gmail.com> <526d4ac8f6788d3323d29fdbad0e0e5d09a534db.camel@gmail.com> <2b49b96de9f8a1cd6d78cc5aebe7c35776cd2c19.camel@gmail.com> 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 3.50.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2023-12-14 at 18:16 -0800, Alexei Starovoitov wrote: [...] > > E.g. for the test-case at hand: > >=20 > > 0: (85) call bpf_get_prandom_u32#7 ; R0=3Dscalar() > > 1: (bf) r7 =3D r0 ; R0=3Dscalar(id=3D1) R7_w=3D= scalar(id=3D1) > > 2: (bf) r8 =3D r0 ; R0=3Dscalar(id=3D1) R8_w=3D= scalar(id=3D1) > > 3: (85) call bpf_get_prandom_u32#7 ; R0=3Dscalar() > > --- checkpoint #1 r7.id =3D 1, r8.id =3D 1 --- > > 4: (25) if r0 > 0x1 goto pc+0 ; R0=3Dscalar(smin=3Dsmin32=3D0= ,smax=3Dumax=3Dsmax32=3Dumax32=3D1,...) > > --- checkpoint #2 r7.id =3D 1, r8.id =3D 1 --- > > 5: (3d) if r8 >=3D r0 goto pc+3 ; R0=3D1 R8=3D0 | record r8.i= d=3D1 in jump history > > 6: (0f) r8 +=3D r8 ; R8=3D0 >=20 > can we detect that any register link is broken and force checkpoint here? Should be possible. I'll try this in the morning and check veristat results= . By the way, I added some stats collection for find_equal_scalars() and see the following results when run on ./test_progs: - maximal number of registers with same id per call: 3 - average number of registers with same id per call: 1.4