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Andrii Nakryiko 341dfcf8d7 btf: expose BTF info through sysfs 
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>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-08-13 16:14:15 +02:00
..
atomic locking/atomics: Use sed(1) instead of non-standard head(1) option 2019-06-25 10:17:07 +02:00
basic fixdep: check return value of printf() and putchar() 2019-07-01 10:30:39 +09:00
coccinelle Kbuild updates for v5.3 (2nd) 2019-07-20 09:34:55 -07:00
dtc Devicetree updates for v5.3: 2019-07-11 18:35:30 -07:00
gcc-plugins docs: move gcc_plugins.txt to core-api and rename to .rst 2019-07-15 09:20:27 -03:00
gdb scripts/gdb: add helpers to find and list devices 2019-07-16 19:23:24 -07:00
genksyms genksyms: Teach parser about 128-bit built-in types 2019-06-24 03:43:03 +09:00
kconfig kconfig: fix missing choice values in auto.conf 2019-07-17 22:37:51 +09:00
ksymoops
mod kbuild: remove the first line of *.mod files 2019-07-18 02:19:31 +09:00
package kbuild: create *.mod with full directory path and remove MODVERDIR 2019-07-18 02:19:31 +09:00
selinux treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
tracing treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
.gitignore scripts: remove unnecessary ihex2fw and check-lc_ctypes from .gitignore 2018-12-22 00:37:52 +09:00
adjust_autoksyms.sh kbuild: remove the first line of *.mod files 2019-07-18 02:19:31 +09:00
asn1_compiler.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
bin2c.c kbuild: move bin2c back to scripts/ from scripts/basic/ 2018-07-18 01:18:05 +09:00
bloat-o-meter bloat-o-meter: ignore __addressable_ symbols 2018-12-28 12:11:44 -08:00
bootgraph.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 391 2019-06-05 17:37:11 +02:00
bpf_helpers_doc.py bpf: fix script for generating man page on BPF helpers 2019-05-13 01:12:45 +02:00
cc-can-link.sh bpfilter: check compiler capability in Kconfig 2018-06-28 13:36:39 +09:00
check_extable.sh License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
checkincludes.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
checkkconfigsymbols.py treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
checkpatch.pl checkpatch.pl: warn on duplicate sysctl local variable 2019-07-16 19:23:22 -07:00
checkstack.pl scripts/checkstack.pl: Fix arm64 wrong or unknown architecture 2019-06-05 02:33:10 +09:00
checksyscalls.sh checksyscalls: fix up mq_timedreceive and stat exceptions 2019-02-19 21:27:53 +01:00
checkversion.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
clang-version.sh kbuild: update comment block of scripts/clang-version.sh 2019-03-04 22:34:54 +09:00
cleanfile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cleanpatch License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
coccicheck coccicheck: return proper error code on fail 2018-08-14 08:58:56 +09:00
config License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
conmakehash.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 54 2019-05-24 17:36:42 +02:00
const_structs.checkpatch
decode_stacktrace.sh scripts/decode_stacktrace: Accept dash/underscore in modules 2019-07-12 11:05:41 -07:00
decodecode scripts/decodecode: set ARCH when running natively on arm/arm64 2018-12-28 12:11:44 -08:00
depmod.sh kbuild: modules_install: warn when missing System.map file 2018-09-09 09:14:07 +09:00
diffconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
documentation-file-ref-check scripts/documentation-file-ref-check: ignore output dir 2019-06-14 14:43:01 -06:00
export_report.pl kbuild: export_report: read modules.order instead of .tmp_versions/*.mod 2019-07-18 02:19:31 +09:00
extract_xc3028.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 339 2019-06-05 17:37:07 +02:00
extract-cert.c
extract-ikconfig
extract-module-sig.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
extract-sys-certs.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
extract-vmlinux treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 378 2019-06-05 17:37:10 +02:00
faddr2line scripts/faddr2line: fix location of start_kernel in comment 2018-11-18 10:15:09 -08:00
file-size.sh kbuild: Use ls(1) instead of stat(1) to obtain file size 2018-03-26 02:01:24 +09:00
find-unused-docs.sh scripts: Add a script to find unused documentation 2017-10-23 08:01:37 -06:00
gcc-goto.sh jump_label: move 'asm goto' support test to Kconfig 2019-01-06 09:46:51 +09:00
gcc-ld License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
gcc-plugin.sh License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
gcc-version.sh kbuild: clean up scripts/gcc-version.sh 2019-03-04 22:35:04 +09:00
gcc-x86_32-has-stack-protector.sh stack-protector: test compiler capability in Kconfig and drop AUTO mode 2018-06-08 18:56:00 +09:00
gcc-x86_64-has-stack-protector.sh stack-protector: Fix test with 32-bit userland and CONFIG_64BIT=y 2018-06-25 23:21:13 +09:00
gen_compile_commands.py scripts: add a tool to produce a compile_commands.json file 2018-12-19 23:41:36 +09:00
gen_ksymdeps.sh kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS 2018-12-01 23:13:14 +09:00
get_abi.pl doc: ABI scripts: add a SPDX header file 2019-06-21 16:58:37 +02:00
get_dvb_firmware treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
get_maintainer.pl get_maintainer: add ability to skip moderated mailing lists 2019-07-16 19:23:22 -07:00
gfp-translate treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
headerdep.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
headers_check.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
headers_install.sh kbuild: simplify scripts/headers_install.sh 2019-06-15 19:57:02 +09:00
insert-sys-cert.c
kallsyms.c kallsyms: exclude kasan local symbols on s390 2019-07-08 02:25:59 +09:00
Kbuild.include kbuild: remove unused hostcc-option 2019-07-17 22:37:51 +09:00
Kconfig.include treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
kernel-doc kernel-doc: Don't try to mark up function names 2019-06-26 11:14:15 -06:00
ld-version.sh License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
leaking_addresses.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
Lindent License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
link-vmlinux.sh btf: expose BTF info through sysfs 2019-08-13 16:14:15 +02:00
Makefile kbuild: remove build_unifdef target in scripts/Makefile 2019-06-15 19:57:01 +09:00
Makefile.asm-generic kbuild: force all architectures except um to include mandatory-y 2019-03-17 12:56:32 +09:00
Makefile.build kbuild: split out *.mod out of {single,multi}-used-m rules 2019-07-18 02:19:31 +09:00
Makefile.clean kbuild: remove deprecated host-progs variable 2018-08-09 21:51:17 +09:00
Makefile.dtbinst DeviceTree for 4.15: 2017-11-14 18:25:40 -08:00
Makefile.extrawarn kbuild: Remove unnecessary -Wno-unused-value 2019-06-24 03:43:03 +09:00
Makefile.gcc-plugins gcc-plugins: structleak: Generalize to all variable types 2019-03-04 09:29:41 -08:00
Makefile.headersinst kbuild: fix 'No such file or directory' warning for headers_install 2019-06-24 03:43:03 +09:00
Makefile.host Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
Makefile.kasan kasan: remove use after scope bugs detection. 2019-03-05 21:07:13 -08:00
Makefile.kcov treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile.lib kbuild: compile-test headers listed in header-test-m as well 2019-07-17 22:37:51 +09:00
Makefile.modbuiltin kbuild: get rid of kernel/ prefix from in-tree modules.{order,builtin} 2019-07-17 22:39:27 +09:00
Makefile.modinst kbuild: modinst: read modules.order instead of $(MODVERDIR)/*.mod 2019-07-17 22:39:27 +09:00
Makefile.modpost kbuild: create *.mod with full directory path and remove MODVERDIR 2019-07-18 02:19:31 +09:00
Makefile.modsign kbuild: modsign: read modules.order instead of $(MODVERDIR)/*.mod 2019-07-17 22:39:27 +09:00
Makefile.ubsan ubsan: Remove vla bound checks. 2019-05-06 11:12:09 -07:00
makelst License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
markup_oops.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 373 2019-06-05 17:37:10 +02:00
mkcompile_h kbuild: remove unnecessary in-subshell execution 2019-01-28 09:11:17 +09:00
mkmakefile kbuild: mkmakefile: generate a simple wrapper of top Makefile 2019-04-02 23:27:38 +09:00
mksysmap
mkuboot.sh License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
module-common.lds
modules-check.sh kbuild: get rid of kernel/ prefix from in-tree modules.{order,builtin} 2019-07-17 22:39:27 +09:00
namespace.pl kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
objdiff treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 199 2019-05-30 11:29:23 -07:00
parse-maintainers.pl parse-maintainers: add ability to specify filenames 2017-11-17 16:10:01 -08:00
patch-kernel License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pnmtologo.c
profile2linkerlist.pl License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
prune-kernel License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
recordmcount.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 378 2019-06-05 17:37:10 +02:00
recordmcount.h powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
recordmcount.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
setlocalversion scripts/setlocalversion: Improve -dirty check with git-status --no-optional-locks 2018-11-21 23:57:33 +09:00
show_delta treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 438 2019-06-05 17:37:17 +02:00
sign-file.c
sortextable.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 378 2019-06-05 17:37:10 +02:00
sortextable.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 378 2019-06-05 17:37:10 +02:00
spdxcheck-test.sh scripts: add spdxcheck.py self test 2018-12-28 12:11:44 -08:00
spdxcheck.py spdxcheck.py: fix directory structures 2019-06-01 15:51:31 -07:00
spelling.txt scripts/spelling.txt: add more spellings to spelling.txt 2019-07-12 11:05:41 -07:00
sphinx-pre-install scripts/sphinx-pre-install: fix out-of-tree build 2019-06-26 16:08:21 -06:00
split-man.pl MAINTAINERS & files: Canonize the e-mails I use at files 2018-05-04 06:21:06 -04:00
stackdelta License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
stackusage License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
subarch.include selftests: add headers_install to lib.mk 2018-09-05 08:12:09 -06:00
tags.sh kbuild: add a flag to force absolute path for srctree 2019-07-11 00:05:09 +09:00
unifdef.c unifdef: use memcpy instead of strncpy 2018-11-30 14:45:01 -08:00
ver_linux ver_linux: Assign constant RE to variable name for clarity 2019-01-22 13:34:35 +01:00
xen-hypercalls.sh License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xz_wrap.sh