[PATCH v3 1/3] kbuild: refactor variables in scripts/link-vmlinux.sh

Masahiro Yamada
2024-06-10T11:27:05Z

Clean up the variables in scripts/link-vmlinux.sh

- Specify the extra objects directly in vmlinux_link()
- Move the AS rule to kallsyms()
- Set kallsymso and btf_vmlinux_bin_o where they are generated
- Remove unneeded variable, kallsymso_prev
- Introduce the btf_data variable
- Introduce the strip_debug flag instead of checking the output name

No functional change intended.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Changes in v3:
- Use ${strip_debug} for cleanup

scripts/link-vmlinux.sh | 67 +++++++++++++++++++++--------------------
1 file changed, 35 insertions(+), 32 deletions(-)

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 518c70b8db50..3d9d7257143a 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -45,7 +45,6 @@ info()

# Link of vmlinux
# ${1} - output file
-# ${2}, ${3}, ... - optional extra .o files
vmlinux_link()
{
local output=${1}
@@ -90,7 +89,7 @@ vmlinux_link()
ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"

# The kallsyms linking does not need debug symbols included.
- if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
+ if [ -n "${strip_debug}" ] ; then
ldflags="${ldflags} ${wl}--strip-debug"
fi

@@ -101,7 +100,7 @@ vmlinux_link()
${ld} ${ldflags} -o ${output} \
${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
${wl}--start-group ${libs} ${wl}--end-group \
- $@ ${ldlibs}
+ ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
}

# generate .BTF typeinfo from DWARF debuginfo
@@ -110,6 +109,7 @@ vmlinux_link()
gen_btf()
{
local pahole_ver
+ local btf_data=${2}

if ! [ -x "$(command -v ${PAHOLE})" ]; then
echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
@@ -124,16 +124,16 @@ gen_btf()

vmlinux_link ${1}

- info "BTF" ${2}
+ info BTF "${btf_data}"
LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}

- # Create ${2} which contains just .BTF section but no symbols. Add
+ # Create ${btf_data} which contains just .BTF section but no symbols. Add
# 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. Add 2>/dev/null to suppress GNU
# objcopy warnings: "empty loadable segment detected at ..."
${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \
- --strip-all ${1} ${2} 2>/dev/null
+ --strip-all ${1} "${btf_data}" 2>/dev/null
# Change e_type to ET_REL so that it can be used to link final vmlinux.
# GNU ld 2.35+ and lld do not allow an ET_EXEC input.
if is_enabled CONFIG_CPU_BIG_ENDIAN; then
@@ -141,10 +141,12 @@ gen_btf()
else
et_rel='\1\0'
fi
- printf "${et_rel}" | dd of=${2} conv=notrunc bs=1 seek=16 status=none
+ printf "${et_rel}" | dd of="${btf_data}" conv=notrunc bs=1 seek=16 status=none
+
+ btf_vmlinux_bin_o=${btf_data}
}

-# Create ${2} .S file with all symbols from the ${1} object file
+# Create ${2}.o file with all symbols from the ${1} object file
kallsyms()
{
local kallsymopt;
@@ -165,27 +167,25 @@ kallsyms()
kallsymopt="${kallsymopt} --lto-clang"
fi

- info KSYMS ${2}
- scripts/kallsyms ${kallsymopt} ${1} > ${2}
+ info KSYMS "${2}.S"
+ scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
+
+ info AS "${2}.o"
+ ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
+ ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
+
+ kallsymso=${2}.o
}

# Perform one step in kallsyms generation, including temporary linking of
# vmlinux.
kallsyms_step()
{
- kallsymso_prev=${kallsymso}
kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
- kallsymso=${kallsyms_vmlinux}.o
- kallsyms_S=${kallsyms_vmlinux}.S

- vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
- mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
- kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
-
- info AS ${kallsymso}
- ${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
- ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
- -c -o ${kallsymso} ${kallsyms_S}
+ vmlinux_link "${kallsyms_vmlinux}"
+ mksysmap "${kallsyms_vmlinux}" "${kallsyms_vmlinux}.syms"
+ kallsyms "${kallsyms_vmlinux}.syms" "${kallsyms_vmlinux}"
}

# Create map file with all symbols from ${1}
@@ -223,19 +223,18 @@ fi

${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o

-btf_vmlinux_bin_o=""
+btf_vmlinux_bin_o=
+kallsymso=
+strip_debug=
+
if is_enabled CONFIG_DEBUG_INFO_BTF; then
- btf_vmlinux_bin_o=.btf.vmlinux.bin.o
- if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
+ 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
fi
fi

-kallsymso=""
-kallsymso_prev=""
-kallsyms_vmlinux=""
if is_enabled CONFIG_KALLSYMS; then

# kallsyms support
@@ -261,11 +260,13 @@ if is_enabled CONFIG_KALLSYMS; then
# a) Verify that the System.map from vmlinux matches the map from
# ${kallsymso}.

- kallsyms_step 1
- kallsyms_step 2
+ # The kallsyms linking does not need debug symbols included.
+ strip_debug=1

- # step 3
- size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
+ kallsyms_step 1
+ size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
+
+ kallsyms_step 2
size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})

if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
@@ -273,7 +274,9 @@ if is_enabled CONFIG_KALLSYMS; then
fi
fi

-vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
+strip_debug=
+
+vmlinux_link vmlinux

# fill in BTF IDs
if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
--
2.43.0