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([2620:10d:c090:500::5:3eff]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b05ffd5f86sm1263617eec.5.2025.12.18.14.36.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Dec 2025 14:36:50 -0800 (PST) Message-ID: <78acd4cd0cb8ed6b4c0c36cb79294efe606a4366.camel@gmail.com> Subject: Re: [PATCH bpf-next v4 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes From: Eduard Zingerman To: Ihor Solodrai , Alan Maguire , Alexei Starovoitov , Andrea Righi , Andrew Morton , Andrii Nakryiko , Bill Wendling , Changwoo Min , Daniel Borkmann , David Vernet , Donglin Peng , Hao Luo , Jiri Olsa , John Fastabend , Jonathan Corbet , Justin Stitt , KP Singh , Martin KaFai Lau , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , Shuah Khan , Song Liu , Stanislav Fomichev , Tejun Heo , Yonghong Song Cc: bpf@vger.kernel.org, dwarves@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, sched-ext@lists.linux.dev Date: Thu, 18 Dec 2025 14:36:47 -0800 In-Reply-To: <9640d2f5-7e6e-4526-a9ab-831bd826f01d@linux.dev> References: <20251218003314.260269-1-ihor.solodrai@linux.dev> <20251218003314.260269-6-ihor.solodrai@linux.dev> <8be2cafa00b759220e73a6ce837ac9a3ff52da1f.camel@gmail.com> <9640d2f5-7e6e-4526-a9ab-831bd826f01d@linux.dev> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: dwarves@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-12-18 at 13:33 -0800, Ihor Solodrai wrote: > On 12/18/25 11:21 AM, Eduard Zingerman wrote: > > On Wed, 2025-12-17 at 16:33 -0800, Ihor Solodrai wrote: > > > This patch implements kconfig re-sync when the pahole version changes > > > between builds, similar to how it happens for compiler version change > > > via CC_VERSION_TEXT. > > >=20 > > > Define PAHOLE_VERSION in the top-level Makefile and export it for > > > config builds. Set CONFIG_PAHOLE_VERSION default to the exported > > > variable. > > >=20 > > > Kconfig records the PAHOLE_VERSION value in > > > include/config/auto.conf.cmd [1]. > > >=20 > > > The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes > > > between builds, make detects a dependency change and triggers > > > syncconfig to update the kconfig [2]. > > >=20 > > > For external module builds, add a warning message in the prepare > > > target, similar to the existing compiler version mismatch warning. > > >=20 > > > Note that if pahole is not installed or available, PAHOLE_VERSION is > > > set to 0 by pahole-version.sh, so the (un)installation of pahole is > > > treated as a version change. > > >=20 > > > See previous discussions for context [3]. > > >=20 > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gi= t/tree/scripts/kconfig/preprocess.c?h=3Dv6.18#n91 > > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gi= t/tree/Makefile?h=3Dv6.18#n815 > > > [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@= oracle.com/ > > >=20 > > > Signed-off-by: Ihor Solodrai > > > --- > >=20 > > When building BPF selftest modules the pahole version change was > > detected, but it seems that BTF rebuild was not triggered: > >=20 > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/= selftests/bpf/test_kmods' > > CC [M] bpf_testmod.o > > CC [M] bpf_test_no_cfi.o > > CC [M] bpf_test_modorder_x.o > > CC [M] bpf_test_modorder_y.o > > CC [M] bpf_test_rqspinlock.o > > MODPOST Module.symvers > > CC [M] bpf_testmod.mod.o > > CC [M] .module-common.o > > CC [M] bpf_test_no_cfi.mod.o > > CC [M] bpf_test_modorder_x.mod.o > > CC [M] bpf_test_modorder_y.mod.o > > CC [M] bpf_test_rqspinlock.mod.o > > LD [M] bpf_test_modorder_x.ko > > LD [M] bpf_testmod.ko > > LD [M] bpf_test_modorder_y.ko > > LD [M] bpf_test_no_cfi.ko > > BTF [M] bpf_test_modorder_x.ko > > LD [M] bpf_test_rqspinlock.ko > > BTF bpf_test_modorder_x.ko > > BTF [M] bpf_test_no_cfi.ko > > BTF [M] bpf_test_modorder_y.ko > > BTF [M] bpf_testmod.ko > > BTF bpf_test_no_cfi.ko > > BTF bpf_test_modorder_y.ko > > BTF [M] bpf_test_rqspinlock.ko > > BTF bpf_testmod.ko > > BTF bpf_test_rqspinlock.ko > > BTFIDS bpf_test_modorder_x.ko > > BTFIDS bpf_test_modorder_y.ko > > BTFIDS bpf_test_no_cfi.ko > > BTFIDS bpf_testmod.ko > > OBJCOPY bpf_test_modorder_x.ko.BTF > > BTFIDS bpf_test_rqspinlock.ko > > OBJCOPY bpf_test_no_cfi.ko.BTF > > OBJCOPY bpf_test_modorder_y.ko.BTF > > OBJCOPY bpf_testmod.ko.BTF > > OBJCOPY bpf_test_rqspinlock.ko.BTF > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/s= elftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > [~/bpf-next] > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/= selftests/bpf/test_kmods' > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/s= elftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > >=20 > > ... update pahole from version 131 to 132 ... > >=20 > > [~/bpf-next] > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/= selftests/bpf/test_kmods' > > warning: pahole version differs from the one used to build the kernel > > The kernel was built with: 131 > > You are using: 132 > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/s= elftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > >=20 > > Is this an expected behavior? >=20 > Yes, it's expected. >=20 > I simply repeated the logic used for compiler version change: for > external modules only the warning is printed. >=20 > See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tr= ee/Makefile?h=3Dv6.18#n1857 >=20 Ok, it does rebuild BTF for the kernel itself. Tested-by: Eduard Zingerman