When building with OBJDUMP=llvm-objdump, there are a series of warnings from the section comparisons that arch/s390/boot/Makefile performs between vmlinux and arch/s390/boot/vmlinux: llvm-objdump: warning: section '.boot.preserved.data' mentioned in a -j/--section option, but not found in any input file llvm-objdump: warning: section '.boot.data' mentioned in a -j/--section option, but not found in any input file llvm-objdump: warning: section '.boot.preserved.data' mentioned in a -j/--section option, but not found in any input file llvm-objdump: warning: section '.boot.data' mentioned in a -j/--section option, but not found in any input file The warning is a little misleading, as these sections do exist in the input files. It is really pointing out that llvm-objdump does not match GNU objdump's behavior of respecting '-j' / '--section' in combination with '-t' / '--syms': $ s390x-linux-gnu-objdump -t -j .boot.data vmlinux.full vmlinux.full: file format elf64-s390 SYMBOL TABLE: 0000000001951000 l O .boot.data 0000000000003000 sclp_info_sccb 00000000019550e0 l O .boot.data 0000000000000001 sclp_info_sccb_valid 00000000019550e2 g O .boot.data 0000000000001000 early_command_line ... $ llvm-objdump -t -j .boot.data vmlinux.full vmlinux.full: file format elf64-s390 SYMBOL TABLE: 0000000000100040 l O .text 0000000000000010 dw_psw 0000000000000000 l df *ABS* 0000000000000000 main.c 00000000001001b0 l F .text 00000000000000c6 trace_event_raw_event_initcall_level 0000000000100280 l F .text 0000000000000100 perf_trace_initcall_level ... It may be possible to change llvm-objdump's behavior to match GNU objdump's behavior but the difficulty of that task has not yet been explored. The combination of '$(OBJDUMP) -t -j' is not common in the kernel tree on a whole, so workaround this tool difference by grepping for the sections in the full symbol table output in a similar manner to the sed invocation. This results in no visible change for GNU objdump users while fixing the warnings for OBJDUMP=llvm-objdump, further enabling use of LLVM=1 for ARCH=s390 with versions of LLVM that have support for s390 in ld.lld and llvm-objcopy. Reported-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Closes: https://lore.kernel.org/20240219113248.16287-C-hca@xxxxxxxxxxxxx/ Link: https://github.com/ClangBuiltLinux/linux/issues/859 Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> --- s390 llvm-objcopy support may be backported to LLVM 18.1.0 in time for the final release. https://github.com/llvm/llvm-project/pull/82324 s390 ld.lld has already made it into release/18.x: https://github.com/llvm/llvm-project/commit/0a44c3792a6ff799df5f100670d7e19d1bc49f03 If the objcopy change makes 18.1.0 final, features + this change should build cleanly with LLVM 18.1.0+ using LLVM=1 :) --- arch/s390/boot/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile index aecafabc2054..294f08a8811a 100644 --- a/arch/s390/boot/Makefile +++ b/arch/s390/boot/Makefile @@ -60,9 +60,9 @@ clean-files += vmlinux.map quiet_cmd_section_cmp = SECTCMP $* define cmd_section_cmp - s1=`$(OBJDUMP) -t -j "$*" "$<" | sort | \ + s1=`$(OBJDUMP) -t "$<" | grep "\s$*\s\+" | sort | \ sed -n "/0000000000000000/! s/.*\s$*\s\+//p" | sha256sum`; \ - s2=`$(OBJDUMP) -t -j "$*" "$(word 2,$^)" | sort | \ + s2=`$(OBJDUMP) -t "$(word 2,$^)" | grep "\s$*\s\+" | sort | \ sed -n "/0000000000000000/! s/.*\s$*\s\+//p" | sha256sum`; \ if [ "$$s1" != "$$s2" ]; then \ echo "error: section $* differs between $< and $(word 2,$^)" >&2; \ --- base-commit: 778666df60f0d96f215e33e27448de47a2207fb3 change-id: 20240220-s390-work-around-llvm-objdump-t-j-bf8dcdc4f291 Best regards, -- Nathan Chancellor <nathan@xxxxxxxxxx>
