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Message-Id: <20240522114755.318238-4-masahiroy@kernel.org>
Date: Wed, 22 May 2024 20:47:55 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
bpf@...r.kernel.org,
Ard Biesheuvel <ardb@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Nicolas Schier <nicolas@...sle.eu>
Subject: [PATCH 3/3] kbuild: merge temp vmlinux for CONFIG_DEBUG_INFO_BTF and CONFIG_KALLSYMS
CONFIG_DEBUG_INFO_BTF=y requires one additional link step.
(.tmp_vmlinux.btf)
CONFIG_KALLSYMS=y requires two additional link steps.
(.tmp_vmlinux.kallsyms1 and .tmp_vmlinux.kallsyms2)
Enabling both requires three additional link steps.
When CONFIG_DEBUG_INFO_BTF=y and CONFIG_KALLSYMS=y, the build step looks
as follows:
KSYMS .tmp_vmlinux.kallsyms0.S
AS .tmp_vmlinux.kallsyms0.o
LD .tmp_vmlinux.btf # temp vmlinux for BTF
BTF .btf.vmlinux.bin.o
LD .tmp_vmlinux.kallsyms1 # temp vmlinux for kallsyms step 1
NM .tmp_vmlinux.kallsyms1.syms
KSYMS .tmp_vmlinux.kallsyms1.S
AS .tmp_vmlinux.kallsyms1.o
LD .tmp_vmlinux.kallsyms2 # temp vmlinux for kallsyms step 2
NM .tmp_vmlinux.kallsyms2.syms
KSYMS .tmp_vmlinux.kallsyms2.S
AS .tmp_vmlinux.kallsyms2.o
LD vmlinux # final vmlinux
This is redundant because the BTF generation and the kallsyms step 1 can
be performed against the same temporary vmlinux.
When both CONFIG_DEBUG_INFO_BTF and CONFIG_KALLSYMS are enabled, we can
reduce the number of link steps.
The build step will look as follows:
KSYMS .tmp_vmlinux0.kallsyms.S
AS .tmp_vmlinux0.kallsyms.o
LD .tmp_vmlinux1 # temp vmlinux for BTF and kallsyms step 1
BTF .tmp_vmlinux1.btf.o
NM .tmp_vmlinux1.syms
KSYMS .tmp_vmlinux1.kallsyms.S
AS .tmp_vmlinux1.kallsyms.o
LD .tmp_vmlinux2 # temp vmlinux for kallsyms step 2
NM .tmp_vmlinux2.syms
KSYMS .tmp_vmlinux2.kallsyms.S
AS .tmp_vmlinux2.kallsyms.o
LD vmlinux # final link
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---
scripts/link-vmlinux.sh | 45 +++++++++++++++++++++--------------------
1 file changed, 23 insertions(+), 22 deletions(-)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index fe7db9a265ca..ea004aae6ce5 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -105,10 +105,10 @@ vmlinux_link()
# generate .BTF typeinfo from DWARF debuginfo
# ${1} - vmlinux image
-# ${2} - file to dump raw BTF data into
gen_btf()
{
local pahole_ver
+ local btf_data=${1}.btf.o
if ! [ -x "$(command -v ${PAHOLE})" ]; then
echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
@@ -121,18 +121,16 @@ gen_btf()
return 1
fi
- 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
@@ -140,9 +138,9 @@ 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=${2}
+ btf_vmlinux_bin_o=${btf_data}
}
# Create ${2}.o file with all symbols from the ${1} object file
@@ -176,15 +174,13 @@ kallsyms()
kallsymso=${2}.o
}
-# Perform one step in kallsyms generation, including temporary linking of
-# vmlinux.
-kallsyms_step()
+# Perform kallsyms for the given temporary vmlinux.
+sysmap_and_kallsyms()
{
- kallsyms_vmlinux=.tmp_vmlinux.kallsyms${1}
+ mksysmap "${1}" "${1}.syms"
+ kallsyms "${1}.syms" "${1}.kallsyms"
- vmlinux_link "${kallsyms_vmlinux}"
- mksysmap "${kallsyms_vmlinux}" "${kallsyms_vmlinux}.syms"
- kallsyms "${kallsyms_vmlinux}.syms" "${kallsyms_vmlinux}"
+ kallsyms_sysmap=${1}.syms
}
# Create map file with all symbols from ${1}
@@ -226,12 +222,15 @@ kallsymso=
btf_vmlinux_bin_o=
if is_enabled CONFIG_KALLSYMS; then
- # kallsyms step 0
- kallsyms /dev/null .tmp_vmlinux.kallsyms0
+ kallsyms /dev/null .tmp_vmlinux0.kallsyms
+fi
+
+if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
+ vmlinux_link .tmp_vmlinux1
fi
if is_enabled CONFIG_DEBUG_INFO_BTF; then
- if ! gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then
+ if ! gen_btf .tmp_vmlinux1; then
echo >&2 "Failed to generate BTF for vmlinux"
echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
exit 1
@@ -264,14 +263,16 @@ if is_enabled CONFIG_KALLSYMS; then
# a) Verify that the System.map from vmlinux matches the map from
# ${kallsymso}.
- kallsyms_step 1
+ sysmap_and_kallsyms .tmp_vmlinux1
size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
- kallsyms_step 2
+ vmlinux_link .tmp_vmlinux2
+ sysmap_and_kallsyms .tmp_vmlinux2
size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
- kallsyms_step 3
+ vmlinux_link .tmp_vmlinux3
+ sysmap_and_kallsyms .tmp_vmlinux3
fi
fi
@@ -295,7 +296,7 @@ fi
# step a (see comment above)
if is_enabled CONFIG_KALLSYMS; then
- if ! cmp -s System.map ${kallsyms_vmlinux}.syms; then
+ if ! cmp -s System.map ${kallsyms_sysmap}; then
echo >&2 Inconsistent kallsyms data
echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
exit 1
--
2.40.1
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