arch/powerpc/boot/wrapper hard codes GNU tools

[nathanchance]

I have split this off from ClangBuiltLinux/continuous-integration2#265, as we are tracking the other issue I noted in that thread as #774.

With D115419 applied to the toolchain and the following diff to quickly work around #774:

diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 3c5baaa6f1e7..45dc62ba1541 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -39,6 +39,8 @@ asflags-y := -D__VDSO64__ -s
 targets += vdso64.lds
 CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)

+vdsold-$(CONFIG_LD_IS_LLD) := -fuse-ld=lld
+
 # link rule for the .so file, .lds has to be first
 $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE
        $(call if_changed,vdso64ld_and_check)
@@ -53,4 +55,4 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE

 # actual build commands
 quiet_cmd_vdso64ld_and_check = VDSO64L $@
-      cmd_vdso64ld_and_check = $(CC) $(c_flags) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
+      cmd_vdso64ld_and_check = $(CC) $(c_flags) $(vdsold-y) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)

$ make -skj"$(nproc)" ARCH=powerpc LLVM=1 powernv_defconfig all
ld.lld: warning: cannot find entry symbol _start; not setting start address
objcopy: Unable to recognise the format of the input file `vmlinux'
make[2]: *** [arch/powerpc/boot/Makefile:391: arch/powerpc/boot/zImage.pseries] Error 1
objcopy: Unable to recognise the format of the input file `vmlinux'
make[2]: *** [arch/powerpc/boot/Makefile:391: arch/powerpc/boot/zImage.epapr] Error 1
make[2]: Target 'arch/powerpc/boot/zImage' not remade because of errors.
make[1]: *** [arch/powerpc/Makefile:283: zImage] Error 2

CROSS_COMPILE is used in arch/powerpc/boot/wrapper to prefix the GNU tools:

$ rg -F '${CROSS}' arch/powerpc/boot/wrapper
196:LC_ALL=C elfformat="`${CROSS}objdump -p "$kernel" | grep 'file format' | awk '{print $4}'`"
220:LD_VERSION=$(${CROSS}ld --version | ld_version)
366:    rodynamic=$(if ${CROSS}ld -V 2>&1 | grep -q LLD ; then echo "-z rodynamic"; fi)
382:${CROSS}objcopy $objflags "$kernel" "$vmz.$$"
435:version=`${CROSS}strings "$kernel" | grep '^Linux version [-0-9.]' | \
442:membase=`${CROSS}objdump -p "$kernel" | grep -m 1 LOAD | awk '{print $7}'`
477:    ${CROSS}objcopy $4 $1 \
507:    ${CROSS}ld -m $format -T $lds $text_start $pie $nodl $rodynamic $notext -o "$ofile" $map \
513:base=0x`${CROSS}nm "$ofile" | grep ' _start$' | cut -d' ' -f1`
514:entry=`${CROSS}objdump -f "$ofile" | grep '^start address ' | cut -d' ' -f3`
518:    ${CROSS}objcopy -O binary "$ofile".elf "$ofile"
527:    ${CROSS}objcopy -O aixcoff-rs6000 --set-start "$entry" "$ofile"
555:    system_reset_overlay=0x`${CROSS}nm "$ofile" \
559:    system_reset_kernel=0x`${CROSS}nm "$ofile" \
566:    ${CROSS}objcopy -O binary "$ofile" "$ofile.bin"
584:    size=$(${CROSS}nm --no-sort --radix=d "$ofile" | egrep ' _end$' | cut -d' ' -f1)

I have a prototype series to fix this: https://git.kernel.org/pub/scm/linux/kernel/git/nathan/linux.git/log/?h=wip/llvm-1-powerpc-boot-wrapper

The original CI issue above has a couple of errors that were uncovered, hence the other patches in the series.

[nickdesaulniers]

now that #774 is resolved, anything left to do here?

[nickdesaulniers]

I can still reproduce this failure. @nathanchance do you have cycles to dust off your series and whip it into shape for upstreaming?

$ make LLVM=1 ARCH=powerpc defconfig all -j128 -s
objcopy: Unable to recognise the format of the input file `vmlinux'
objcopy: Unable to recognise the format of the input file `vmlinux'
objcopy: Unable to recognise the format of the input file `vmlinux'
objcopy: Unable to recognise the format of the input file `vmlinux'
objcopy: Unable to recognise the format of the input file `vmlinux'
make[3]: *** [arch/powerpc/boot/Makefile:399: arch/powerpc/boot/zImage.epapr] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: *** [arch/powerpc/boot/Makefile:399: arch/powerpc/boot/zImage.maple] Error 1
make[3]: *** [arch/powerpc/boot/Makefile:399: arch/powerpc/boot/zImage.pmac] Error 1
make[3]: *** [arch/powerpc/boot/Makefile:399: arch/powerpc/boot/zImage.pseries] Error 1
make[3]: *** [arch/powerpc/boot/Makefile:406: arch/powerpc/boot/dtbImage.ps3] Error 1
make[2]: *** [arch/powerpc/Makefile:235: zImage] Error 2
make[1]: *** [/android0/kernel-all/Makefile:359: __build_one_by_one] Error 2
make: *** [Makefile:234: __sub-make] Error 2

Jason asked about ppc here, so he might be observing this build failure for the defconfig as well.

[nathanchance]

I can still reproduce this failure. @nathanchance do you have cycles to dust off your series and whip it into shape for upstreaming?

Yeah, I will do my best to get the series into a shippable state for 6.7.

[nickdesaulniers]

#774 might be relevant here. I thought #774 (comment) might have fixed this already, or at least allow you to drop the first patch from your series perhaps?

[nathanchance]

Yeah, that patch is no longer necessary with https://git.kernel.org/linus/4406b12214f6592909b63dabdea86d69f1b5ba2e. I think the rest are still relevant.