On 10/1/19 3:43 PM, Will Deacon wrote: > On Tue, Oct 01, 2019 at 03:37:49PM +0100, Vincenzo Frascino wrote: >> On 10/1/19 3:20 PM, Will Deacon wrote: >>> On Tue, Oct 01, 2019 at 03:20:35PM +0100, Vincenzo Frascino wrote: >>>> On 10/1/19 2:27 PM, Catalin Marinas wrote: >>>>> On Tue, Oct 01, 2019 at 02:14:23PM +0100, Will Deacon wrote: >>>>>> On Thu, Sep 26, 2019 at 10:43:38PM +0100, Vincenzo Frascino wrote: >>>>>>> +config COMPATCC_IS_ARM_GCC >>>>>>> + def_bool $(success,$(COMPATCC) --version | head -n 1 | grep -q >>>>>>> "arm-.*-gcc") >>>>>> >>>>>> I've seen toolchains where the first part of the tuple is "armv7-", so >>>>>> they >>>>>> won't get detected here. However, do we really need to detect this? If >>>>>> somebody passes a duff compiler, then the build will fail in the same >>>>>> way as >>>>>> if they passed it to CROSS_COMPILE=. >>>>> >>>>> Not sure what happens if we pass an aarch64 compiler. Can we end up with >>>>> a 64-bit compat vDSO? >>>>> >>>> >>>> I agree with Catalin here. The problem is not only when you pass and >>>> aarch64 >>>> toolchain but even an x86 and so on. >>> >>> I disagree. What happens if you do: >>> >>> $ make ARCH=arm64 CROSS_COMPILE=x86_64-linux-gnu- >>> >>> on your x86 box? >>> >> >> The kernel compilation breaks as follows: >> >> x86_64-linux-gnu-gcc: error: unrecognized command line option >> ‘-mlittle-endian’; >> did you mean ‘-fconvert=little-endian’? >> /data1/Projects/LinuxKernel/linux/scripts/Makefile.build:265: recipe for >> target >> 'scripts/mod/empty.o' failed >> make[2]: *** [scripts/mod/empty.o] Error 1 >> /data1/Projects/LinuxKernel/linux/Makefile:1128: recipe for target >> 'prepare0' failed >> make[1]: *** [prepare0] Error 2 >> make[1]: Leaving directory '/data1/Projects/LinuxKernel/linux-out' >> Makefile:179: recipe for target 'sub-make' failed >> make: *** [sub-make] Error 2 >> >> Similar issue in the compat vdso library compilation if I do (without the >> check): >> >> $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- >> CROSS_COMPILE_COMPAT=x86_64-linux-gnu- >> >> With this check the compilation completes correctly but the compat vdso does >> not >> get built (unless my environment is playing me tricks ;) ). > > My point was that we don't attempt to sanitise the compiler passed via > CROSS_COMPILE, so I don't think we should do anything special for COMPATCC > either. >
I agree on this, but the point I was trying to make is that the kernel should still be able to build even if the compiler for compat vdso is not correct. I do not have a strong opinion though. > Will > -- Regards, Vincenzo
