bpf: Support llvm-objcopy for vmlinux BTF

Commit da5fb18 ("bpf: Support pre-2.25-binutils objcopy for vmlinux BTF") switched from --dump-section to --only-section/--change-section-address for BTF export assuming those ("legacy") options should cover all objcopy versions. Turns out llvm-objcopy doesn't implement --change-section-address [1], but it does support --dump-section. Let's partially roll back and try to use --dump-section first and fall back to --only-section/--change-section-address for the older binutils. 1. https://bugs.llvm.org/show_bug.cgi?id=45217 Fixes: df786c9 ("bpf: Force .BTF section start to zero when dumping from vmlinux") Tested-by: Nick Desaulniers <[email protected]> Reported-by: Nathan Chancellor <[email protected]> Link: ClangBuiltLinux#871 Signed-off-by: Stanislav Fomichev <[email protected]>
0day-ci · Mar 17, 2020 · d2770fa · d2770fa
1 parent 90db6d7
commit d2770fa
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
@@ -127,6 +127,16 @@ gen_btf()
 		cut -d, -f1 | cut -d' ' -f2)
 	bin_format=$(LANG=C ${OBJDUMP} -f ${1} | grep 'file format' | \
 		awk '{print $4}')
+
+	# Compatibility issues:
+	# - pre-2.25 binutils objcopy doesn't support --dump-section
+	# - llvm-objcopy doesn't support --change-section-address, but
+	#   does support --dump-section
+	#
+	# Try to use --dump-section which should cover both recent
+	# binutils and llvm-objcopy and fall back to --only-section
+	# for pre-2.25 binutils.
+	${OBJCOPY} --dump-section .BTF=$bin_file ${1} 2>/dev/null || \
 	${OBJCOPY} --change-section-address .BTF=0 \
 		--set-section-flags .BTF=alloc -O binary \
 		--only-section=.BTF ${1} .btf.vmlinux.bin