mirror of
https://github.com/LineageOS/android_kernel_fxtec_sm6115.git
synced 2026-08-18 19:37:09 +00:00
Make .BTF section allocated and expose its contents through sysfs.
/sys/kernel/btf directory is created to contain all the BTFs present
inside kernel. Currently there is only kernel's main BTF, represented as
/sys/kernel/btf/kernel file. Once kernel modules' BTFs are supported,
each module will expose its BTF as /sys/kernel/btf/<module-name> file.
Current approach relies on a few pieces coming together:
1. pahole is used to take almost final vmlinux image (modulo .BTF and
kallsyms) and generate .BTF section by converting DWARF info into
BTF. This section is not allocated and not mapped to any segment,
though, so is not yet accessible from inside kernel at runtime.
2. objcopy dumps .BTF contents into binary file and subsequently
convert binary file into linkable object file with automatically
generated symbols _binary__btf_kernel_bin_start and
_binary__btf_kernel_bin_end, pointing to start and end, respectively,
of BTF raw data.
3. final vmlinux image is generated by linking this object file (and
kallsyms, if necessary). sysfs_btf.c then creates
/sys/kernel/btf/kernel file and exposes embedded BTF contents through
it. This allows, e.g., libbpf and bpftool access BTF info at
well-known location, without resorting to searching for vmlinux image
on disk (location of which is not standardized and vmlinux image
might not be even available in some scenarios, e.g., inside qemu
during testing).
Alternative approach using .incbin assembler directive to embed BTF
contents directly was attempted but didn't work, because sysfs_proc.o is
not re-compiled during link-vmlinux.sh stage. This is required, though,
to update embedded BTF data (initially empty data is embedded, then
pahole generates BTF info and we need to regenerate sysfs_btf.o with
updated contents, but it's too late at that point).
If BTF couldn't be generated due to missing or too old pahole,
sysfs_btf.c handles that gracefully by detecting that
_binary__btf_kernel_bin_start (weak symbol) is 0 and not creating
/sys/kernel/btf at all.
v2->v3:
- added Documentation/ABI/testing/sysfs-kernel-btf (Greg K-H);
- created proper kobject (btf_kobj) for btf directory (Greg K-H);
- undo v2 change of reusing vmlinux, as it causes extra kallsyms pass
due to initially missing __binary__btf_kernel_bin_{start/end} symbols;
v1->v2:
- allow kallsyms stage to re-use vmlinux generated by gen_btf();
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: Ife57356dd14b9ae0d2e3801eea7c602c6245952f
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
463 lines
12 KiB
Bash
Executable File
463 lines
12 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 selected by $(KBUILD_VMLINUX_INIT) and
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# $(KBUILD_VMLINUX_MAIN) and $(KBUILD_VMLINUX_LIBS). Most are built-in.a files
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# from top-level directories in the kernel tree, others are specified in
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# arch/$(ARCH)/Makefile. Ordering when linking is important, and
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# $(KBUILD_VMLINUX_INIT) must be first. $(KBUILD_VMLINUX_LIBS) are archives
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# which are linked conditionally (not within --whole-archive), and do not
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# 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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# +-< $(KBUILD_VMLINUX_INIT)
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# | +--< init/version.o + more
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# |
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# +--< $(KBUILD_VMLINUX_MAIN)
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# | +--< drivers/built-in.a mm/built-in.a + more
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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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# +-< ${kallsymso} (see description in KALLSYMS section)
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#
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# vmlinux version (uname -v) cannot be updated during normal
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# descending-into-subdirs phase since we do not yet know if we need to
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# update vmlinux.
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# Therefore this step is delayed until just before final link of vmlinux.
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#
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# System.map is generated to document addresses of all kernel symbols
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# Error out on error
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set -e
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# Nice output in kbuild format
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# Will be supressed by "make -s"
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info()
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{
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if [ "${quiet}" != "silent_" ]; then
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printf " %-7s %s\n" "${1}" "${2}"
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fi
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}
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# Thin archive build here makes a final archive with symbol table and indexes
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# from vmlinux objects INIT and MAIN, which can be used as input to linker.
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# KBUILD_VMLINUX_LIBS archives should already have symbol table and indexes
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# added.
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#
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# Traditional incremental style of link does not require this step
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#
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# built-in.a output file
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#
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archive_builtin()
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{
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info AR built-in.a
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rm -f built-in.a;
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${AR} rcsTP${KBUILD_ARFLAGS} built-in.a \
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${KBUILD_VMLINUX_INIT} \
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${KBUILD_VMLINUX_MAIN}
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# rebuild with llvm-ar to update the symbol table
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if [ -n "${CONFIG_LTO_CLANG}" ]; then
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mv -f built-in.a built-in.a.tmp
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${LLVM_AR} rcsT${KBUILD_ARFLAGS} built-in.a $(${AR} t built-in.a.tmp)
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rm -f built-in.a.tmp
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fi
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}
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# If CONFIG_LTO_CLANG is selected, generate a linker script to ensure correct
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# ordering of initcalls, and with CONFIG_MODVERSIONS also enabled, collect the
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# previously generated symbol versions into the same script.
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lto_lds()
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{
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if [ -z "${CONFIG_LTO_CLANG}" ]; then
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return
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fi
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${srctree}/scripts/generate_initcall_order.pl \
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built-in.a ${KBUILD_VMLINUX_LIBS} \
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> .tmp_lto.lds
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if [ -n "${CONFIG_MODVERSIONS}" ]; then
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for a in built-in.a ${KBUILD_VMLINUX_LIBS}; do
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for o in $(${AR} t $a); do
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if [ -f ${o}.symversions ]; then
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cat ${o}.symversions >> .tmp_lto.lds
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fi
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done
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done
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fi
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echo "-T .tmp_lto.lds"
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}
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# Link of vmlinux.o used for section mismatch analysis
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# ${1} output file
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modpost_link()
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{
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local objects
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objects="--whole-archive \
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built-in.a \
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--no-whole-archive \
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--start-group \
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${KBUILD_VMLINUX_LIBS} \
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--end-group"
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if [ -n "${CONFIG_LTO_CLANG}" ]; then
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# This might take a while, so indicate that we're doing
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# an LTO link
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info LTO vmlinux.o
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fi
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${LD} ${KBUILD_LDFLAGS} -r -o ${1} $(lto_lds) ${objects}
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}
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# If CONFIG_LTO_CLANG is selected, we postpone running recordmcount until
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# we have compiled LLVM IR to an object file.
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recordmcount()
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{
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if [ -z "${CONFIG_LTO_CLANG}" ]; then
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return
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fi
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if [ -n "${CONFIG_FTRACE_MCOUNT_RECORD}" ]; then
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scripts/recordmcount ${RECORDMCOUNT_FLAGS} $*
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fi
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}
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# Link of vmlinux
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# ${1} - output file
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# ${@:2} - optional extra .o files
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vmlinux_link()
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{
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local lds="${objtree}/${KBUILD_LDS}"
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local objects
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if [ "${SRCARCH}" != "um" ]; then
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if [ -z "${CONFIG_LTO_CLANG}" ]; then
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objects="--whole-archive \
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built-in.a \
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--no-whole-archive \
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--start-group \
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${KBUILD_VMLINUX_LIBS} \
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--end-group \
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${@:2}"
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else
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objects="--start-group \
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vmlinux.o \
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--end-group \
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${@:2}"
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fi
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${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} -o ${1} \
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-T ${lds} ${objects}
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else
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objects="-Wl,--whole-archive \
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built-in.a \
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-Wl,--no-whole-archive \
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-Wl,--start-group \
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${KBUILD_VMLINUX_LIBS} \
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-Wl,--end-group \
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${@:2}"
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${CC} ${CFLAGS_vmlinux} -o ${1} \
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-Wl,-T,${lds} \
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${objects} \
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-lutil -lrt -lpthread
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rm -f linux
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fi
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}
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# generate .BTF typeinfo from DWARF debuginfo
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# ${1} - vmlinux image
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# ${2} - file to dump raw BTF data into
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gen_btf()
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{
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local pahole_ver
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local bin_arch
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if ! [ -x "$(command -v ${PAHOLE})" ]; then
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info "BTF" "${1}: pahole (${PAHOLE}) is not available"
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return 1
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fi
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pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
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if [ "${pahole_ver}" -lt "113" ]; then
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info "BTF" "${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13"
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return 1
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fi
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info "BTF" ${2}
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vmlinux_link ${1}
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LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
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# dump .BTF section into raw binary file to link with final vmlinux
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bin_arch=$(${OBJDUMP} -f ${1} | grep architecture | \
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cut -d, -f1 | cut -d' ' -f2)
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${OBJCOPY} --dump-section .BTF=.btf.kernel.bin ${1} 2>/dev/null
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${OBJCOPY} -I binary -O ${CONFIG_OUTPUT_FORMAT} -B ${bin_arch} \
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--rename-section .data=.BTF .btf.kernel.bin ${2}
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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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info KSYM ${2}
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local kallsymopt;
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if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
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kallsymopt="${kallsymopt} --all-symbols"
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fi
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if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
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kallsymopt="${kallsymopt} --absolute-percpu"
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fi
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if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
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kallsymopt="${kallsymopt} --base-relative"
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fi
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local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
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${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
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local afile="`basename ${2} .o`.S"
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${NM} -n ${1} | scripts/kallsyms ${kallsymopt} > ${afile}
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${CC} ${aflags} -c -o ${2} ${afile}
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}
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# Generates ${2} .o file with RTIC MP's from the ${1} object file (vmlinux)
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# ${3} the file name where the sizes of the RTIC MP structure are stored
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# just in case, save copy of the RTIC mp to ${4}
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# Note: RTIC_MPGEN has to be set if MPGen is available
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rtic_mp()
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{
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# assume that RTIC_MP_O generation may fail
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RTIC_MP_O=
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local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
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${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
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${RTIC_MPGEN} --objcopy="${OBJCOPY}" --objdump="${OBJDUMP}" \
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--binpath='' --vmlinux=${1} --config=${KCONFIG_CONFIG} && \
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cat rtic_mp.c | ${CC} ${aflags} -c -o ${2} -x c - && \
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cp rtic_mp.c ${4} && \
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${NM} --print-size --size-sort ${2} > ${3} && \
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RTIC_MP_O=${2} || echo “RTIC MP generation has failed”
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# NM - save generated variable sizes for verification
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# RTIC_MP_O is our retval - great success if set to generated .o file
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# Echo statement above prints the error message in case any of the
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# above RTIC MP generation commands fail and it ensures rtic mp failure
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# does not cause kernel compilation to fail.
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}
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# Create map file with all symbols from ${1}
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# See mksymap for additional details
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mksysmap()
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{
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${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
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}
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sortextable()
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{
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${objtree}/scripts/sortextable ${1}
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}
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# Delete output files in case of error
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cleanup()
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{
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rm -f .btf.*
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rm -f .tmp_System.map
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rm -f .tmp_kallsyms*
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rm -f .tmp_lto.lds
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rm -f .tmp_vmlinux*
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rm -f built-in.a
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rm -f System.map
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rm -f vmlinux
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rm -f vmlinux.o
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rm -f .tmp_rtic_mp_sz*
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rm -f rtic_mp.*
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}
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on_exit()
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{
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if [ $? -ne 0 ]; then
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cleanup
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fi
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}
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trap on_exit EXIT
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on_signals()
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{
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exit 1
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}
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trap on_signals HUP INT QUIT TERM
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#
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#
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# Use "make V=1" to debug this script
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case "${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 [ "$1" = "clean" ]; then
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cleanup
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exit 0
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fi
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# We need access to CONFIG_ symbols
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. include/config/auto.conf
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# Update version
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info GEN .version
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if [ -r .version ]; then
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VERSION=$(expr 0$(cat .version) + 1)
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echo $VERSION > .version
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else
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rm -f .version
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echo 1 > .version
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fi;
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# final build of init/
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${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
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archive_builtin
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#link vmlinux.o
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modpost_link vmlinux.o
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# modpost vmlinux.o to check for section mismatches
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${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o
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if [ -n "${CONFIG_LTO_CLANG}" ]; then
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# Call recordmcount if needed
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recordmcount vmlinux.o
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fi
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# Generate RTIC MP placeholder compile unit of the correct size
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# and add it to the list of link objects
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# this needs to be done before generating kallsyms
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if [ ! -z ${RTIC_MPGEN+x} ]; then
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rtic_mp vmlinux.o rtic_mp.o .tmp_rtic_mp_sz1 .tmp_rtic_mp1.c
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KBUILD_VMLINUX_LIBS+=" "
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KBUILD_VMLINUX_LIBS+=$RTIC_MP_O
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fi
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btf_kernel_bin_o=""
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if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
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if gen_btf .tmp_vmlinux.btf .btf.kernel.bin.o ; then
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btf_kernel_bin_o=.btf.kernel.bin.o
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fi
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fi
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kallsymso=""
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kallsyms_vmlinux=""
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if [ -n "${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 three step process:
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# 1) Link .tmp_vmlinux1 so it has all symbols and sections,
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# but __kallsyms is empty.
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# Running kallsyms on that gives us .tmp_kallsyms1.o with
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# the right size
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# 2) Link .tmp_vmlinux2 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_kallsyms2.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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kallsymso=.tmp_kallsyms2.o
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kallsyms_vmlinux=.tmp_vmlinux2
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# step 1
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vmlinux_link .tmp_vmlinux1 ${btf_kernel_bin_o}
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kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o
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# step 2
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vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_kernel_bin_o}
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kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o
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# step 3
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size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" .tmp_kallsyms1.o)
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size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" .tmp_kallsyms2.o)
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if [ $size1 -ne $size2 ] || [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
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kallsymso=.tmp_kallsyms3.o
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kallsyms_vmlinux=.tmp_vmlinux3
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vmlinux_link .tmp_vmlinux3 .tmp_kallsyms2.o ${btf_kernel_bin_o}
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kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o
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fi
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fi
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# Update RTIC MP object by replacing the place holder
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# with actual MP data of the same size
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# Also double check that object size did not change
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# Note: Check initilally if RTIC_MP_O is not empty or uninitialized,
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# as incase RTIC_MPGEN is set and failure occurs in RTIC_MP_O
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# generation, below check for comparing object sizes fails
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# due to an empty RTIC_MP_O object.
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if [ ! -z ${RTIC_MP_O} ]; then
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rtic_mp "${kallsyms_vmlinux}" rtic_mp.o .tmp_rtic_mp_sz2 \
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.tmp_rtic_mp2.c
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if ! cmp -s .tmp_rtic_mp_sz1 .tmp_rtic_mp_sz2; then
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echo >&2 'ERROR: RTIC MP object files size mismatch'
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exit 1
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fi
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fi
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info LD vmlinux
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vmlinux_link vmlinux "${kallsymso}" "${btf_kernel_bin_o}"
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if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then
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info SORTEX vmlinux
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sortextable vmlinux
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fi
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info SYSMAP System.map
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mksysmap vmlinux System.map
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# step a (see comment above)
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if [ -n "${CONFIG_KALLSYMS}" ]; then
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mksysmap ${kallsyms_vmlinux} .tmp_System.map
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if ! cmp -s System.map .tmp_System.map; then
|
|
echo >&2 Inconsistent kallsyms data
|
|
echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
|
|
exit 1
|
|
fi
|
|
fi
|
|
|
|
# Starting Android Q, the DTB's are part of dtb.img and not part
|
|
# of the kernel image. RTIC DTS relies on the kernel environment
|
|
# and could not build outside of the kernel. Generate RTIC DTS after
|
|
# successful kernel build if MPGen is enabled. The DTB will be
|
|
# generated with dtb.img in kernel_definitions.mk.
|
|
if [ ! -z ${RTIC_MPGEN+x} ]; then
|
|
${RTIC_MPGEN} --objcopy="${OBJCOPY}" --objdump="${OBJDUMP}" \
|
|
--binpath="" --vmlinux="vmlinux" --config=${KCONFIG_CONFIG} \
|
|
--cc="${CC} ${KBUILD_AFLAGS}" --dts=rtic_mp.dts \
|
|
|| echo “RTIC MP DTS generation has failed”
|
|
# Echo statement above prints the error message in case above
|
|
# RTIC MP DTS generation command fails and it ensures rtic mp
|
|
# failure does not cause kernel compilation to fail.
|
|
fi
|