Messages in this thread | | | From | Arnd Bergmann <> | Date | Wed, 21 Feb 2018 10:48:10 +0100 | Subject | Re: [PATCH 3/7] [HACK] pass endianess flag to LTO linker |
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On Wed, Feb 21, 2018 at 9:37 AM, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > On 20 February 2018 at 21:59, Arnd Bergmann <arnd@arndb.de> wrote: >> We need some way to pass -mbig-endian to the linker during the >> LTO link stage, otherwise we get a waning like >> >> arm-linux-gnueabi/bin/ld: arch/arm/lib/clearbit.o: compiled for a big endian system and target is little endian >> >> for each file we link in. >> >> There is probably a better method of passing that flag, I'm just >> adding it to a different hack that I added earlier for x86 LTO >> here. >> > > In general, LTO requires that *all* C flags are passed to the linker. > Given that linking now involves code generation, any C flag that > affects code generation must be visible to the linker as well, which > includes all the tweaks and overrides that we add per-file or > per-directory. It is not clear to me how much of this is carried in > the intermediate representation as metadata, but we should probably > err on the side of caution here, and update the Kbuild routines to > pass the complete value of KBUILD_CFLAGS (or whatever it is called) to > ld as well.
It looks like we're just missing KBUILD_CPPFLAGS.
However, I wonder for the more general case what happens to files that require non-standard CFLAGS. In some cases we turn off some optimization step for a file, we might remove '-pg', or build for a particular target architecture. Do we have to turn off -flto for any file that requires this for correct behavior?
Arnd
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