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1a8fa7faf4
Recent changes in BTF generation [1] rely on ${OBJCOPY} command to
update .BTF_ids section data in target ELF files.
This exposed a bug in llvm-objcopy --update-section code path, that
may lead to corruption of a target ELF file. Specifically, because of
the bug st_shndx of some symbols may be (incorrectly) set to 0xffff
(SHN_XINDEX) [2][3].
While there is a pending fix for LLVM, it'll take some time before it
lands (likely in 22.x). And the kernel build must keep working with
older LLVM toolchains in the foreseeable future.
Using GNU objcopy for .BTF_ids update would work, but it would require
changes to LLVM-based build process, likely breaking existing build
environments as discussed in [2].
To work around llvm-objcopy bug, implement --patch_btfids code path in
resolve_btfids as a drop-in replacement for:
${OBJCOPY} --update-section .BTF_ids=${btf_ids} ${elf}
Which works specifically for .BTF_ids section:
${RESOLVE_BTFIDS} --patch_btfids ${btf_ids} ${elf}
This feature in resolve_btfids can be removed at some point in the
future, when llvm-objcopy with a relevant bugfix becomes common.
[1] https://lore.kernel.org/bpf/20251219181321.1283664-1-ihor.solodrai@linux.dev/
[2] https://lore.kernel.org/bpf/20251224005752.201911-1-ihor.solodrai@linux.dev/
[3] https://github.com/llvm/llvm-project/issues/168060#issuecomment-3533552952
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/r/20251231012558.1699758-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
292 lines
6.9 KiB
Bash
Executable file
292 lines
6.9 KiB
Bash
Executable file
#!/bin/sh
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# SPDX-License-Identifier: GPL-2.0
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#
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# link vmlinux
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#
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# vmlinux is linked from the objects in vmlinux.a and $(KBUILD_VMLINUX_LIBS).
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# vmlinux.a contains objects that are linked unconditionally.
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# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
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# (not within --whole-archive), and do not require symbol indexes added.
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#
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# vmlinux
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# ^
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# |
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# +--< vmlinux.a
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# |
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# +--< $(KBUILD_VMLINUX_LIBS)
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# | +--< lib/lib.a + more
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# |
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# +-< ${kallsymso} (see description in KALLSYMS section)
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#
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# vmlinux version (uname -v) cannot be updated during normal
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# descending-into-subdirs phase since we do not yet know if we need to
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# update vmlinux.
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# Therefore this step is delayed until just before final link of vmlinux.
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#
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# System.map is generated to document addresses of all kernel symbols
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# Error out on error
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set -e
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LD="$1"
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KBUILD_LDFLAGS="$2"
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LDFLAGS_vmlinux="$3"
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VMLINUX="$4"
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is_enabled() {
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grep -q "^$1=y" include/config/auto.conf
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}
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# Nice output in kbuild format
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# Will be supressed by "make -s"
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info()
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{
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printf " %-7s %s\n" "${1}" "${2}"
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}
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# Link of vmlinux
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# ${1} - output file
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vmlinux_link()
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{
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local output=${1}
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local objs
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local libs
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local ld
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local ldflags
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local ldlibs
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info LD ${output}
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# skip output file argument
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shift
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if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ||
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is_enabled CONFIG_KLP_BUILD; then
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# Use vmlinux.o instead of performing the slow LTO link again.
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objs=vmlinux.o
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libs=
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else
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objs=vmlinux.a
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libs="${KBUILD_VMLINUX_LIBS}"
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fi
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if is_enabled CONFIG_GENERIC_BUILTIN_DTB; then
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objs="${objs} .builtin-dtbs.o"
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fi
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objs="${objs} .vmlinux.export.o"
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objs="${objs} init/version-timestamp.o"
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if [ "${SRCARCH}" = "um" ]; then
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wl=-Wl,
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ld="${CC}"
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ldflags="${CFLAGS_vmlinux}"
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ldlibs="-lutil -lrt -lpthread"
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else
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wl=
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ld="${LD}"
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ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
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ldlibs=
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fi
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ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
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# The kallsyms linking does not need debug symbols included.
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if [ -n "${strip_debug}" ] ; then
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ldflags="${ldflags} ${wl}--strip-debug"
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fi
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if [ -n "${generate_map}" ]; then
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ldflags="${ldflags} ${wl}-Map=vmlinux.map"
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fi
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${ld} ${ldflags} -o ${output} \
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${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
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${wl}--start-group ${libs} ${wl}--end-group \
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${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
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}
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# Create ${2}.o file with all symbols from the ${1} object file
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kallsyms()
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{
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local kallsymopt;
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if is_enabled CONFIG_KALLSYMS_ALL; then
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kallsymopt="${kallsymopt} --all-symbols"
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fi
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info KSYMS "${2}.S"
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scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
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info AS "${2}.o"
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${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
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${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
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kallsymso=${2}.o
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}
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# Perform kallsyms for the given temporary vmlinux.
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sysmap_and_kallsyms()
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{
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mksysmap "${1}" "${1}.syms"
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kallsyms "${1}.syms" "${1}.kallsyms"
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kallsyms_sysmap=${1}.syms
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}
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# Create map file with all symbols from ${1}
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# See mksymap for additional details
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mksysmap()
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{
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info NM ${2}
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${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
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}
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sorttable()
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{
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${NM} -S ${1} > .tmp_vmlinux.nm-sort
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${objtree}/scripts/sorttable -s .tmp_vmlinux.nm-sort ${1}
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}
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cleanup()
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{
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rm -f .btf.*
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rm -f .tmp_vmlinux.nm-sort
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rm -f System.map
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rm -f vmlinux
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rm -f vmlinux.map
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}
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# Use "make V=1" to debug this script
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case "${KBUILD_VERBOSE}" in
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*1*)
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set -x
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;;
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esac
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if [ "$1" = "clean" ]; then
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cleanup
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exit 0
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fi
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${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
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arch_vmlinux_o=
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if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
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arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o
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fi
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btf_vmlinux_bin_o=
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btfids_vmlinux=
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kallsymso=
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strip_debug=
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generate_map=
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# Use "make UT=1" to trigger warnings on unused tracepoints
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case "${WARN_ON_UNUSED_TRACEPOINTS}" in
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*1*)
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${objtree}/scripts/tracepoint-update vmlinux.o
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;;
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esac
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if is_enabled CONFIG_KALLSYMS; then
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true > .tmp_vmlinux0.syms
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kallsyms .tmp_vmlinux0.syms .tmp_vmlinux0.kallsyms
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fi
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if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
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# The kallsyms linking does not need debug symbols, but the BTF does.
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if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
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strip_debug=1
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fi
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vmlinux_link .tmp_vmlinux1
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fi
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if is_enabled CONFIG_DEBUG_INFO_BTF; then
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if ! ${srctree}/scripts/gen-btf.sh .tmp_vmlinux1; then
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echo >&2 "Failed to generate BTF for vmlinux"
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echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
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exit 1
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fi
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btf_vmlinux_bin_o=.tmp_vmlinux1.btf.o
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btfids_vmlinux=.tmp_vmlinux1.BTF_ids
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fi
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if is_enabled CONFIG_KALLSYMS; then
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# kallsyms support
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# Generate section listing all symbols and add it into vmlinux
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# It's a four step process:
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# 0) Generate a dummy __kallsyms with empty symbol list.
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# 1) Link .tmp_vmlinux1.kallsyms so it has all symbols and sections,
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# with a dummy __kallsyms.
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# Running kallsyms on that gives us .tmp_vmlinux1.kallsyms.o with
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# the right size
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# 2) Link .tmp_vmlinux2.kallsyms so it now has a __kallsyms section of
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# the right size, but due to the added section, some
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# addresses have shifted.
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# From here, we generate a correct .tmp_vmlinux2.kallsyms.o
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# 3) That link may have expanded the kernel image enough that
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# more linker branch stubs / trampolines had to be added, which
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# introduces new names, which further expands kallsyms. Do another
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# pass if that is the case. In theory it's possible this results
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# in even more stubs, but unlikely.
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# KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
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# other bugs.
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# 4) The correct ${kallsymso} is linked into the final vmlinux.
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#
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# a) Verify that the System.map from vmlinux matches the map from
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# ${kallsymso}.
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# The kallsyms linking does not need debug symbols included.
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strip_debug=1
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sysmap_and_kallsyms .tmp_vmlinux1
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size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
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vmlinux_link .tmp_vmlinux2
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sysmap_and_kallsyms .tmp_vmlinux2
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size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
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if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
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vmlinux_link .tmp_vmlinux3
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sysmap_and_kallsyms .tmp_vmlinux3
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fi
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fi
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strip_debug=
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if is_enabled CONFIG_VMLINUX_MAP; then
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generate_map=1
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fi
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vmlinux_link "${VMLINUX}"
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if is_enabled CONFIG_DEBUG_INFO_BTF; then
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info OBJCOPY ${btfids_vmlinux}
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${RESOLVE_BTFIDS} --patch_btfids ${btfids_vmlinux} ${VMLINUX}
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fi
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mksysmap "${VMLINUX}" System.map
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if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
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info SORTTAB "${VMLINUX}"
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if ! sorttable "${VMLINUX}"; then
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echo >&2 Failed to sort kernel tables
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exit 1
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fi
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fi
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# step a (see comment above)
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if is_enabled CONFIG_KALLSYMS; then
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if ! cmp -s System.map "${kallsyms_sysmap}"; then
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echo >&2 Inconsistent kallsyms data
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echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
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exit 1
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fi
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fi
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# For fixdep
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echo "${VMLINUX}: $0" > ".${VMLINUX}.d"
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