linux/scripts/link-vmlinux.sh
Zhen Lei 010a0aad39 kallsyms: Correctly sequence symbols when CONFIG_LTO_CLANG=y
LLVM appends various suffixes for local functions and variables, suffixes
observed:
 - foo.llvm.[0-9a-f]+
 - foo.[0-9a-f]+

Therefore, when CONFIG_LTO_CLANG=y, kallsyms_lookup_name() needs to
truncate the suffix of the symbol name before comparing the local function
or variable name.

Old implementation code:
-	if (strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);
-	if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);

The preceding process is traversed by address from low to high. That is,
for those with the same name after the suffix is removed, the one with
the smallest address is returned first. Therefore, when sorting in the
tool, if the raw names are the same, they should be sorted by address in
ascending order.

ASCII[.]   = 2e
ASCII[0-9] = 30,39
ASCII[A-Z] = 41,5a
ASCII[_]   = 5f
ASCII[a-z] = 61,7a

According to the preceding ASCII code values, the following sorting result
is strictly followed.
 ---------------------------------
|    main-key     |    sub-key    |
|---------------------------------|
|                 |  addr_lowest  |
| <name>          |      ...      |
| <name>.<suffix> |      ...      |
|                 |  addr_highest |
|---------------------------------|
| <name>?<others> |               |   //? is [_A-Za-z0-9]
 ---------------------------------

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-11-12 18:47:36 -08:00

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#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
#
# link vmlinux
#
# vmlinux is linked from the objects in vmlinux.a and $(KBUILD_VMLINUX_LIBS).
# vmlinux.a contains objects that are linked unconditionally.
# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
# (not within --whole-archive), and do not require symbol indexes added.
#
# vmlinux
# ^
# |
# +--< vmlinux.a
# |
# +--< $(KBUILD_VMLINUX_LIBS)
# | +--< lib/lib.a + more
# |
# +-< ${kallsymso} (see description in KALLSYMS section)
#
# vmlinux version (uname -v) cannot be updated during normal
# descending-into-subdirs phase since we do not yet know if we need to
# update vmlinux.
# Therefore this step is delayed until just before final link of vmlinux.
#
# System.map is generated to document addresses of all kernel symbols
# Error out on error
set -e
LD="$1"
KBUILD_LDFLAGS="$2"
LDFLAGS_vmlinux="$3"
is_enabled() {
grep -q "^$1=y" include/config/auto.conf
}
# Nice output in kbuild format
# Will be supressed by "make -s"
info()
{
printf " %-7s %s\n" "${1}" "${2}"
}
# Link of vmlinux
# ${1} - output file
# ${2}, ${3}, ... - optional extra .o files
vmlinux_link()
{
local output=${1}
local objs
local libs
local ld
local ldflags
local ldlibs
info LD ${output}
# skip output file argument
shift
if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
# Use vmlinux.o instead of performing the slow LTO link again.
objs=vmlinux.o
libs=
else
objs=vmlinux.a
libs="${KBUILD_VMLINUX_LIBS}"
fi
if is_enabled CONFIG_MODULES; then
objs="${objs} .vmlinux.export.o"
fi
objs="${objs} init/version-timestamp.o"
if [ "${SRCARCH}" = "um" ]; then
wl=-Wl,
ld="${CC}"
ldflags="${CFLAGS_vmlinux}"
ldlibs="-lutil -lrt -lpthread"
else
wl=
ld="${LD}"
ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
ldlibs=
fi
ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
# The kallsyms linking does not need debug symbols included.
if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
ldflags="${ldflags} ${wl}--strip-debug"
fi
if is_enabled CONFIG_VMLINUX_MAP; then
ldflags="${ldflags} ${wl}-Map=${output}.map"
fi
${ld} ${ldflags} -o ${output} \
${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
${wl}--start-group ${libs} ${wl}--end-group \
$@ ${ldlibs}
}
# generate .BTF typeinfo from DWARF debuginfo
# ${1} - vmlinux image
# ${2} - file to dump raw BTF data into
gen_btf()
{
local pahole_ver
if ! [ -x "$(command -v ${PAHOLE})" ]; then
echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
return 1
fi
pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
if [ "${pahole_ver}" -lt "116" ]; then
echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"
return 1
fi
vmlinux_link ${1}
info "BTF" ${2}
LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
# Create ${2} 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} ${2} 2>/dev/null
# Change e_type to ET_REL so that it can be used to link final vmlinux.
# Unlike GNU ld, lld does not allow an ET_EXEC input.
printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none
}
# Create ${2} .S file with all symbols from the ${1} object file
kallsyms()
{
local kallsymopt;
if is_enabled CONFIG_KALLSYMS_ALL; then
kallsymopt="${kallsymopt} --all-symbols"
fi
if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
kallsymopt="${kallsymopt} --absolute-percpu"
fi
if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
kallsymopt="${kallsymopt} --base-relative"
fi
if is_enabled CONFIG_LTO_CLANG; then
kallsymopt="${kallsymopt} --lto-clang"
fi
info KSYMS ${2}
scripts/kallsyms ${kallsymopt} ${1} > ${2}
}
# Perform one step in kallsyms generation, including temporary linking of
# vmlinux.
kallsyms_step()
{
kallsymso_prev=${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 ${kallsyms_S}
${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
-c -o ${kallsymso} ${kallsyms_S}
}
# Create map file with all symbols from ${1}
# See mksymap for additional details
mksysmap()
{
info NM ${2}
${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
}
sorttable()
{
${objtree}/scripts/sorttable ${1}
}
# Delete output files in case of error
cleanup()
{
rm -f .btf.*
rm -f System.map
rm -f vmlinux
rm -f vmlinux.map
}
# Use "make V=1" to debug this script
case "${KBUILD_VERBOSE}" in
*1*)
set -x
;;
esac
if [ "$1" = "clean" ]; then
cleanup
exit 0
fi
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
btf_vmlinux_bin_o=""
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
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
# Generate section listing all symbols and add it into vmlinux
# It's a three step process:
# 1) Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections,
# but __kallsyms is empty.
# Running kallsyms on that gives us .tmp_kallsyms1.o with
# the right size
# 2) Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of
# the right size, but due to the added section, some
# addresses have shifted.
# From here, we generate a correct .tmp_vmlinux.kallsyms2.o
# 3) That link may have expanded the kernel image enough that
# more linker branch stubs / trampolines had to be added, which
# introduces new names, which further expands kallsyms. Do another
# pass if that is the case. In theory it's possible this results
# in even more stubs, but unlikely.
# KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
# other bugs.
# 4) The correct ${kallsymso} is linked into the final vmlinux.
#
# a) Verify that the System.map from vmlinux matches the map from
# ${kallsymso}.
kallsyms_step 1
kallsyms_step 2
# step 3
size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso_prev})
size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
kallsyms_step 3
fi
fi
vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
# fill in BTF IDs
if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
info BTFIDS vmlinux
${RESOLVE_BTFIDS} vmlinux
fi
mksysmap vmlinux System.map
if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
info SORTTAB vmlinux
if ! sorttable vmlinux; then
echo >&2 Failed to sort kernel tables
exit 1
fi
fi
# step a (see comment above)
if is_enabled CONFIG_KALLSYMS; then
if ! cmp -s System.map ${kallsyms_vmlinux}.syms; then
echo >&2 Inconsistent kallsyms data
echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
exit 1
fi
fi
# For fixdep
echo "vmlinux: $0" > .vmlinux.d