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authorKees Cook <keescook@chromium.org>2020-03-03 18:18:34 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-05-27 17:46:44 +0200
commitbb6524537dc2f8b2a2bae63926b02e5e008be0fd (patch)
treeb6446a674b15558eb104f1bcf30127ef8a7292d7 /scripts
parentee71c590dd8dcfa2afeed51d510c07991fce694a (diff)
kbuild: Remove debug info from kallsyms linking
[ Upstream commit af73d78bd384aa9b8789aa6e7ddbb165f971276f ] When CONFIG_DEBUG_INFO is enabled, the two kallsyms linking steps spend time collecting and writing the dwarf sections to the temporary output files. kallsyms does not need this information, and leaving it off halves their linking time. This is especially noticeable without CONFIG_DEBUG_INFO_REDUCED. The BTF linking stage, however, does still need those details. Refactor the BTF and kallsyms generation stages slightly for more regularized temporary names. Skip debug during kallsyms links. Additionally move "info BTF" to the correct place since commit 8959e39272d6 ("kbuild: Parameterize kallsyms generation and correct reporting"), which added "info LD ..." to vmlinux_link calls. For a full debug info build with BTF, my link time goes from 1m06s to 0m54s, saving about 12 seconds, or 18%. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/202003031814.4AEA3351@keescook Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'scripts')
-rwxr-xr-xscripts/link-vmlinux.sh28
1 files changed, 19 insertions, 9 deletions
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 408b5c0b99b1..aa1386079f0c 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -63,12 +63,18 @@ vmlinux_link()
local lds="${objtree}/${KBUILD_LDS}"
local output=${1}
local objects
+ local strip_debug
info LD ${output}
# skip output file argument
shift
+ # The kallsyms linking does not need debug symbols included.
+ if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
+ strip_debug=-Wl,--strip-debug
+ fi
+
if [ "${SRCARCH}" != "um" ]; then
objects="--whole-archive \
${KBUILD_VMLINUX_OBJS} \
@@ -79,6 +85,7 @@ vmlinux_link()
${@}"
${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \
+ ${strip_debug#-Wl,} \
-o ${output} \
-T ${lds} ${objects}
else
@@ -91,6 +98,7 @@ vmlinux_link()
${@}"
${CC} ${CFLAGS_vmlinux} \
+ ${strip_debug} \
-o ${output} \
-Wl,-T,${lds} \
${objects} \
@@ -106,6 +114,8 @@ gen_btf()
{
local pahole_ver
local bin_arch
+ local bin_format
+ local bin_file
if ! [ -x "$(command -v ${PAHOLE})" ]; then
echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
@@ -118,8 +128,9 @@ gen_btf()
return 1
fi
- info "BTF" ${2}
vmlinux_link ${1}
+
+ info "BTF" ${2}
LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
# dump .BTF section into raw binary file to link with final vmlinux
@@ -127,11 +138,12 @@ gen_btf()
cut -d, -f1 | cut -d' ' -f2)
bin_format=$(LANG=C ${OBJDUMP} -f ${1} | grep 'file format' | \
awk '{print $4}')
+ bin_file=.btf.vmlinux.bin
${OBJCOPY} --change-section-address .BTF=0 \
--set-section-flags .BTF=alloc -O binary \
- --only-section=.BTF ${1} .btf.vmlinux.bin
+ --only-section=.BTF ${1} $bin_file
${OBJCOPY} -I binary -O ${bin_format} -B ${bin_arch} \
- --rename-section .data=.BTF .btf.vmlinux.bin ${2}
+ --rename-section .data=.BTF $bin_file ${2}
}
# Create ${2} .o file with all symbols from the ${1} object file
@@ -166,8 +178,8 @@ kallsyms()
kallsyms_step()
{
kallsymso_prev=${kallsymso}
- kallsymso=.tmp_kallsyms${1}.o
- kallsyms_vmlinux=.tmp_vmlinux${1}
+ kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
+ kallsymso=${kallsyms_vmlinux}.o
vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
kallsyms ${kallsyms_vmlinux} ${kallsymso}
@@ -190,7 +202,6 @@ cleanup()
{
rm -f .btf.*
rm -f .tmp_System.map
- rm -f .tmp_kallsyms*
rm -f .tmp_vmlinux*
rm -f System.map
rm -f vmlinux
@@ -253,9 +264,8 @@ ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
btf_vmlinux_bin_o=""
if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
- if gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then
- btf_vmlinux_bin_o=.btf.vmlinux.bin.o
- else
+ btf_vmlinux_bin_o=.btf.vmlinux.bin.o
+ if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
echo >&2 "Failed to generate BTF for vmlinux"
echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
exit 1