After commit 600605853f87 ("scripts/gen-btf.sh: Fix .btf.o generation when compiling for RISCV"), there is an error from llvm-objcopy when CONFIG_LTO_CLANG is enabled: llvm-objcopy: error: '.tmp_vmlinux1.btf.o': The file was not recognized as a valid object file Failed to generate BTF for vmlinux KBUILD_CFLAGS includes CC_FLAGS_LTO, which makes clang emit an LLVM IR object, rather than an ELF one as expected by llvm-objcopy. Most areas of the kernel deal with this by filtering out CC_FLAGS_LTO from KBUILD_CFLAGS for the particular object or directory but this is not so easy to do in bash. Just include '-fno-lto' after KBUILD_CFLAGS to ensure an ELF object is consistently created as the initial .o file. Additionally, while there is no reported or discovered bug yet, the absence of KBUILD_CPPFLAGS from this command could result in incorrect endianness because KBUILD_CPPFLAGS typically contains '-mbig-endian' and '-mlittle-endian' so that biendian toolchains can be used. Include it in this ${CC} command to hopefully limit necessary changes to this command for the foreseeable future. Fixes: 600605853f87 ("scripts/gen-btf.sh: Fix .btf.o generation when compiling for RISCV") Signed-off-by: Nathan Chancellor --- Changes in v2: - Conservatively include KBUILD_CPPFLAGS as well, as it contains endianness flags for some targets. - Link to v1: https://patch.msgid.link/20260105-fix-gen-btf-sh-lto-v1-1-18052ea055a9@kernel.org --- scripts/gen-btf.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/scripts/gen-btf.sh b/scripts/gen-btf.sh index d6457661b9b6..be21ccee3487 100755 --- a/scripts/gen-btf.sh +++ b/scripts/gen-btf.sh @@ -87,7 +87,7 @@ gen_btf_o() # SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all # deletes all symbols including __start_BTF and __stop_BTF, which will # be redefined in the linker script. - echo "" | ${CC} ${CLANG_FLAGS} ${KBUILD_CFLAGS} -c -x c -o ${btf_data} - + echo "" | ${CC} ${CLANG_FLAGS} ${KBUILD_CPPFLAGS} ${KBUILD_CFLAGS} -fno-lto -c -x c -o ${btf_data} - ${OBJCOPY} --add-section .BTF=${ELF_FILE}.BTF \ --set-section-flags .BTF=alloc,readonly ${btf_data} ${OBJCOPY} --only-section=.BTF --strip-all ${btf_data} --- base-commit: a069190b590e108223cd841a1c2d0bfb92230ecc change-id: 20260105-fix-gen-btf-sh-lto-007fe4908070 Best regards, -- Nathan Chancellor