Boot failure on s390 with llvm-objcopy #1996
Description
I have been testing the s390 llvm-objcopy pull request, which results in no new build warnings or errors on next-20240215:
$ make -skj"$(nproc)" ARCH=s390 LLVM=1 OBJDUMP=s390x-linux-gnu-objdump mrproper defconfig all However, the resulting kernel image does not boot:
$ boot-qemu.py -a s390 -k . ... Linux version 6.8.0-rc4-next-20240215 (nathan@dev-fedora.aadp) #1 SMP Thu Feb 15 19:50:28 MST 2024 Out of memory allocating 6d7800 bytes 8 aligned in range 0:20000000 Reserved memory ranges: 0000000000000000 a394c3c30d90cdaf DECOMPRESSOR Usable online memory ranges (info source: sclp read info [3]): 0000000000000000 0000000020000000 Usable online memory total: 20000000 Reserved: a394c3c30d90cdaf Free: 0 Call Trace: (sp:0000000000033e90 [<0000000000012fbc>] physmem_alloc_top_down+0x5c/0x104) sp:0000000000033f00 [<0000000000011d56>] startup_kernel+0x3a6/0x77c sp:0000000000033f60 [<00000000000100f4>] startup_normal+0xd4/0xd4 -- System halted With OBJCOPY=s390x-linux-gnu-objcopy, there are no issues when booting:
$ boot-qemu.py -a s390 -k . ... KASLR disabled: CPU has no PRNG KASLR disabled: CPU has no PRNG [ 0.851887] Linux version 6.8.0-rc4-next-20240215 (nathan@dev-fedora.aadp) (ClangBuiltLinux clang version 19.0.0git (https://github.com/llvm/llvm-project db4ea21dfde307f4fc873a6fe56791cd7ae3f0a1), ClangBuiltLinux LLD 19.0.0) #1 SMP Thu Feb 15 19:53:34 MST 2024 [ 0.854515] setup: Linux is running under KVM in 64-bit mode [ 0.878762] setup: The maximum memory size is 512MB [ 0.879514] setup: Relocating AMODE31 section of size 0x00003000 ... Looking at the files that are generated by objcopy during the build, I notice that arch/s390/boot/info.bin is different between the two builds...
$ file {gnu,llvm}-objcopy/arch/s390/boot/info.bin gnu-objcopy/arch/s390/boot/info.bin: data llvm-objcopy/arch/s390/boot/info.bin: empty If I take a directory built with OBJCOPY=llvm-obcopy and move the arch/s390/boot/info.bin from a directory built with OBJCOPY=s390x-linux-gnu-objcopy and run make again, the resulting image boots.
Looking at the build logs, info.bin is generated from vmlinux with
llvm-objcopy -O binary --only-section=.vmlinux.info --set-section-flags .vmlinux.info=load vmlinux arch/s390/boot/info.bin $ llvm-readelf --section-headers vmlinux | rg -F .vmlinux.info [42] .vmlinux.info PROGBITS 0000000000000000 1d45000 000078 00 W 0 0 1 $ llvm-objcopy -O binary --only-section=.vmlinux.info --set-section-flags .vmlinux.info=load vmlinux llvm-info.bin $ s390x-linux-gnu-objcopy -O binary --only-section=.vmlinux.info --set-section-flags .vmlinux.info=load vmlinux gnu-info.bin $ file {gnu,llvm}-info.bin gnu-info.bin: data llvm-info.bin: empty This was done initially as part of https://git.kernel.org/linus/369f91c374514f9491d52fec12f7ee9ef6d44b23.
cc @MaskRay and @uweigand (even though this doesn't seem like anything specific to s390 but just in case)