On Wed, May 20, 2020 at 01:39:26PM -0400, Arvind Sankar wrote: > On Wed, May 20, 2020 at 10:34:25AM -0700, Fangrui Song wrote: > > On 2020-05-20, Ard Biesheuvel wrote: > > >On Wed, 20 May 2020 at 17:53, Arvind Sankar <nivedita@xxxxxxxxxxxx> wrote: > > >> > > >> On Wed, May 20, 2020 at 10:28:13AM +0800, kbuild test robot wrote: > > >> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git next > > >> > head: e5fbadd1179cdadeaa44d71a9ec068c5bc100524 > > >> > commit: ce5e3f909fc0ed67e58367b9c56a54c20a51080b [22/40] efi/printf: Add 64-bit and 8-bit integer support > > >> > config: x86_64-defconfig (attached as .config) > > >> > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 135b877874fae96b4372c8a3fbfaa8ff44ff86e3) > > >> > reproduce: > > >> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > > >> > chmod +x ~/bin/make.cross > > >> > # install x86_64 cross compiling tool for clang build > > >> > # apt-get install binutils-x86-64-linux-gnu > > >> > git checkout ce5e3f909fc0ed67e58367b9c56a54c20a51080b > > >> > # save the attached .config to linux build tree > > >> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 > > >> > > > >> > If you fix the issue, kindly add following tag as appropriate > > >> > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > > >> > > > >> > All warnings (new ones prefixed by >>, old ones prefixed by <<): > > >> > > > >> > >> ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol '' > > >> > > > >> > --- > > >> > 0-DAY CI Kernel Test Service, Intel Corporation > > >> > https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx > > >> > > >> Clang folk, is anything actually wrong here? This seems to result from > > >> use of unreachable() annotation, which generates these > > >> .discard.unreachable sections apparently to help objtool. > > >> > > > > > >This came up before, and IIRC, it has already been fixed, only this > > >branch is based on v5.7-rc2. > > > > LLD reports the diagnostic because a PC-relative relocation referencing a > > SHF_ALLOC section from a non-SHF_ALLOC section (.discard.unreachable) cannot be > > reasonably represented. A non-SHF_ALLOC section is not part of the memory image, thus conceptually > > the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at linktime. > > This is actually a nice diagnostic which has caught a number of issues. > > > > % readelf -Wr drivers/firmware/efi/libstub/vsprintf.stub.o > > .. > > Relocation section '.rela.discard.unreachable' at offset 0xe38 contains 1 entry: > > Offset Info Type Symbol's Value Symbol's Name + Addend > > 0000000000000000 0000000600000002 R_X86_64_PC32 0000000000000000 .text + ac0 > > > > --- > > > > The linker command line is: > > > > % ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds arch/x86/boot/compressed/kernel_info.o arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o arch/x86/boot/compressed/cpuflags.o arch/x86/boot/compressed/early_serial_console.o arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o arch/x86/boot/compressed/mem_encrypt.o arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o drivers/firmware/efi/libstub/lib.a arch/x86/boot/compressed/efi_thunk_64.o -o arch/x86/boot/compressed/vmlinux > > ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol '' > > > > arch/x86/boot/compressed/vmlinux has an output section .discard.unreachable , which is likely desired. > > You mean /not/ desired, right? > > > > > Note that arch/x86/kernel/vmlinux.lds.S has an output section description /DISCARD/ : { ... *(.discard.*) ... }, > > but arch/x86/boot/compressed/vmlinux doesn't. > > > > We can let arch/x86/boot/compressed/vmlinux reuse the /DISCARD/ to fix the issue. > > Yep. As an aside, how does one (should I) get onto kbuild-all? It keeps bouncing me as a non-list member currently.
