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authorKees Cook <keescook@chromium.org>2020-03-03 18:18:34 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2020-03-04 18:36:33 +0100
commitaf73d78bd384aa9b8789aa6e7ddbb165f971276f (patch)
tree9fa6615db19920fb595e45cd9abdf69b53ee764f /scripts
parent0641cadac46710bf7f87fa46067194ec1d932d90 (diff)
kbuild: Remove debug info from kallsyms linking
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
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 dd484e92752e..ac569e197bfa 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} ${kallsymso}
@@ -190,7 +202,6 @@ cleanup()
{
rm -f .btf.*
rm -f .tmp_System.map
- rm -f .tmp_kallsyms*
rm -f .tmp_vmlinux*
rm -f System.map
rm -f vmlinux
@@ -257,9 +268,8 @@ tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
btf_vmlinux_bin_o=""
if [ -n "${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