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Thu, 17 Oct 2024 19:24:18 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fjasle.eu; s=mail; t=1729193055; bh=gFKgzeE/ZauvTc40+kc1ZCpG82IQ5sf0SexsQDq8u7s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EjmLiDXoqRkWjuuvGJxxLV5+aTCDOrWLbvlR5lMckKvY/H0XxAO944jsq04kKP23W a7oHrR5a/RehEXoCX37Bnn9nBEYK3zrG3pTWJEitbXkwkG0uokxOgmlNnxEdKJYBzU d/ixP73e0olpxUThVwOlAFWPDG9DHu3qIfb/laNU= Received: by leknes.fjasle.eu (Postfix, from userid 1000) id 6D0BB3D187; Thu, 17 Oct 2024 21:24:15 +0200 (CEST) Date: Thu, 17 Oct 2024 21:24:15 +0200 From: Nicolas Schier To: Ron Economos Cc: Masahiro Yamada , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Kees Cook , Nathan Chancellor , Ben Hutchings Subject: Re: [PATCH 4/4] kbuild: cross-compile linux-headers package when possible Message-ID: References: <20240727074526.1771247-1-masahiroy@kernel.org> <20240727074526.1771247-5-masahiroy@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Report-Abuse: Please forward a copy of this message, including all headers, to Feedback-ID: 1174286m:1174286a9YXZ7r:1174286sZpGuzd6fP X-smtpcorp-track: T46pSHyCx3WZ.cZJtxmOcqpEO.M3GJtQ_8EXU On Thu, Oct 17, 2024 at 07:45:57AM -0700 Ron Economos wrote: > On 7/27/24 12:42 AM, Masahiro Yamada wrote: > > A long standing issue in the upstream kernel packaging is that the > > linux-headers package is not cross-compiled. > > > > For example, you can cross-build Debian packages for arm64 by running > > the following command: > > > > $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bindeb-pkg > > > > However, the generated linux-headers-*_arm64.deb is useless because the > > host programs in it were built for your build machine architecture > > (likely x86), not arm64. > > > > The Debian kernel maintains its own Makefiles to cross-compile host > > tools without relying on Kbuild. [1] > > > > Instead of adding such full custom Makefiles, this commit adds a small > > piece of code to cross-compile host programs located under the scripts/ > > directory. > > > > A straightforward solution is to pass HOSTCC=${CROSS_COMPILE}gcc, but it > > would also cross-compile scripts/basic/fixdep, which needs to be native > > to process the if_changed_dep macro. (This approach may work under some > > circumstances; you can execute foreign architecture programs with the > > help of binfmt_misc because Debian systems enable CONFIG_BINFMT_MISC, > > but it would require installing QEMU and libc for that architecture.) > > > > A trick is to use the external module build (KBUILD_EXTMOD=), which > > does not rebuild scripts/basic/fixdep. ${CC} needs to be able to link > > userspace programs (CONFIG_CC_CAN_LINK=y). > > > > There are known limitations: > > > > - GCC plugins > > > > It would possible to rebuild GCC plugins for the target architecture > > by passing HOSTCXX=${CROSS_COMPILE}g++ with necessary packages > > installed, but gcc on the installed system emits > > "cc1: error: incompatible gcc/plugin versions". I did not find a > > solution for this because 'gcc' on a foreign architecture is a > > different compiler after all. > > > > - objtool and resolve_btfids > > > > These are built by the tools build system. They are not covered by > > the current solution. > > > > I only tested this with Debian, but it should work for other package > > systems as well. > > > > [1]: https://salsa.debian.org/kernel-team/linux/-/blob/debian/6.9.9-1/debian/rules.real#L586 > > > > Signed-off-by: Masahiro Yamada > > --- > > > > scripts/package/install-extmod-build | 34 ++++++++++++++++++++++++++++ > > 1 file changed, 34 insertions(+) > > > > diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build > > index cc335945dfbc..0b56d3d7b48f 100755 > > --- a/scripts/package/install-extmod-build > > +++ b/scripts/package/install-extmod-build > > @@ -43,4 +43,38 @@ mkdir -p "${destdir}" > > fi > > } | tar -c -f - -T - | tar -xf - -C "${destdir}" > > +# When ${CC} and ${HOSTCC} differ, we are likely cross-compiling. Rebuild host > > +# programs using ${CC}. This assumes CC=${CROSS_COMPILE}gcc, which is usually > > +# the case for package building. It does not cross-compile when CC=clang. > > +# > > +# This caters to host programs that participate in Kbuild. objtool and > > +# resolve_btfids are out of scope. > > +if [ "${CC}" != "${HOSTCC}" ] && is_enabled CONFIG_CC_CAN_LINK; then > > + echo "Rebuilding host programs with ${CC}..." > > + > > + cat <<-'EOF' > "${destdir}/Kbuild" > > + subdir-y := scripts > > + EOF > > + > > + # HOSTCXX is not overridden. The C++ compiler is used to build: > > + # - scripts/kconfig/qconf, which is unneeded for external module builds > > + # - GCC plugins, which will not work on the installed system even with > > + # being rebuilt. > > + # > > + # Use the single-target build to avoid the modpost invocation, which > > + # would overwrite Module.symvers. > > + "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/ > > + > > + cat <<-'EOF' > "${destdir}/scripts/Kbuild" > > + subdir-y := basic > > + hostprogs-always-y := mod/modpost > > + mod/modpost-objs := $(addprefix mod/, modpost.o file2alias.o sumversion.o symsearch.o) > > + EOF > > + > > + # Run once again to rebuild scripts/basic/ and scripts/mod/modpost. > > + "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/ > > + > > + rm -f "${destdir}/Kbuild" "${destdir}/scripts/Kbuild" > > +fi > > + > > find "${destdir}" \( -name '.*.cmd' -o -name '*.o' \) -delete > > This patch causes a build error when cross-compiling for RISC-V. I'm using > the cross-compiler from https://github.com/riscv-collab/riscv-gnu-toolchain. > When trying to build .debs with: > > make CROSS_COMPILE=riscv64-unknown-linux-gnu- ARCH=riscv INSTALL_MOD_STRIP=1 > "KCFLAGS=-mtune=sifive-7-series" LOCALVERSION= bindeb-pkg > > I get the following error: > > Rebuilding host programs with riscv64-unknown-linux-gnu-gcc... >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/genksyms.o >   YACC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/parse.tab.[ch] >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/parse.tab.o >   LEX debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/lex.lex.c >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/lex.lex.o >   HOSTLD debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/genksyms/genksyms >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/selinux/genheaders/genheaders >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/selinux/mdp/mdp >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/kallsyms >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/sorttable >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/asn1_compiler >   HOSTCC debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/sign-file > > debian/linux-headers-6.12.0-rc3/usr/src/linux-headers-6.12.0-rc3/scripts/sign-file.c:25:10: > fatal error: openssl/opensslv.h: No such file or directory >    25 | #include >       |          ^~~~~~~~~~~~~~~~~~~~ > compilation terminated. I guess you have openssl/opensslv.h available on your system, do you? (In Debian/Ubuntu package libssl-dev or similar) Can you natively build a kernel with a similar kernel config? Kind regards, Nicolas