Messages in this thread | | | Subject | Re: [PATCH] x86: vdso: Fix leaky vdso link with CC=clang | From | "H. Peter Anvin" <> | Date | Thu, 12 Jul 2018 15:06:54 -0700 |
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On 07/12/18 13:37, Alistair Strachan wrote: > On Thu, Jul 12, 2018 at 1:25 PM H. Peter Anvin <hpa@zytor.com> wrote: >> On 07/12/18 13:10, Alistair Strachan wrote: >>> The vdso{32,64}.so can fail to link with CC=clang when clang tries to >>> find a suitable GCC toolchain to link these libraries with. >>> >>> /usr/bin/ld: arch/x86/entry/vdso/vclock_gettime.o: >>> access beyond end of merged section (782) >>> >>> This happens because the host environment leaked into the cross >>> compiler environment due to the way clang searches for suitable GCC >>> toolchains. >>> >> >> Is this another clang bug that you want a workaround for in the kernel? > > Clang is a retargetable compiler (specified with --target=<something>) > and so it has a mechanism for searching for suitable binutils (from > another "GCC toolchain") to perform assembly and linkage. This > mechanism relies on both --target and --gcc-toolchain when > cross-compiling, otherwise it will fall back to searching /usr. > > The --target and --gcc-toolchain flags are already specified correctly > in the top level Makefile, but the vdso Makefile rolls its own linker > flags and doesn't use KBUILD_CFLAGS. Therefore, these flags get > incorrectly dropped from the vdso $CC link command line, and an > inconsistency is created between the "GCC toolchain" used to generate > the objects for the vdso, and the linker used to link them. >
It sounds like there needs to be a more fundamental symbol than KBUILD_CFLAGS to contain these kinds of things.
-hpa
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