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Yonghong Song authored
Commit 6eb4bd92 ("kallsyms: strip LTO suffixes from static functions")
stripped all function/variable suffixes started with '.' regardless
of whether those suffixes are generated at LTO mode or not. In fact,
as far as I know, in LTO mode, when a static function/variable is
promoted to the global scope, '.llvm.<...>' suffix is added.

The existing mechanism breaks live patch for a LTO kernel even if
no <symbol>.llvm.<...> symbols are involved. For example, for the following
kernel symbols:
  $ grep bpf_verifier_vlog /proc/kallsyms
  ffffffff81549f60 t bpf_verifier_vlog
  ffffffff8268b430 d bpf_verifier_vlog._entry
  ffffffff8282a958 d bpf_verifier_vlog._entry_ptr
  ffffffff82e12a1f d bpf_verifier_vlog.__already_done
'bpf_verifier_vlog' is a static function. '_entry', '_entry_ptr' and
'__already_done' are static variables used inside 'bpf_verifier_vlog',
so llvm promotes them to file-level static with prefix 'bpf_verifier_vlog.'.
Note that the func-level to file-level static function promotion also
happens without LTO.

Given a symbol name 'bpf_verifier_vlog', with LTO kernel, current mechanism will
return 4 symbols to live patch subsystem which current live patching
subsystem cannot handle it. With non-LTO kernel, only one symbol
is returned.

In [1], we have a lengthy discussion, the suggestion is to separate two
cases:
  (1). new symbols with suffix which are generated regardless of whether
       LTO is enabled or not, and
  (2). new symbols with suffix generated only when LTO is enabled.

The cleanup_symbol_name() should only remove suffixes for case (2).
Case (1) should not be changed so it can work uniformly with or without LTO.

This patch removed LTO-only suffix '.llvm.<...>' so live patching and
tracing should work the same way for non-LTO kernel.
The cleanup_symbol_name() in scripts/kallsyms.c is also changed to have the same
filtering pattern so both kernel and kallsyms tool have the same
expectation on the order of symbols.

 [1] https://lore.kernel.org/live-patching/20230615170048.2382735-1-song@kernel.org/T/#u



Fixes: 6eb4bd92 ("kallsyms: strip LTO suffixes from static functions")
Reported-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Reviewed-by: default avatarZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Acked-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230628181926.4102448-1-yhs@fb.com


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
8cc32a9b
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atomic
basic
clang-tools
coccinelle
dtc
dummy-tools
gcc-plugins
gdb
genksyms
kconfig
ksymoops
mod
package
selinux
tracing
.gitignore
Kbuild.include
Kconfig.include
Lindent
Makefile
Makefile.asm-generic
Makefile.build
Makefile.clang
Makefile.clean
Makefile.compiler
Makefile.debug
Makefile.defconf
Makefile.dtbinst
Makefile.extrawarn
Makefile.gcc-plugins
Makefile.headersinst
Makefile.host
Makefile.kasan
Makefile.kcov
Makefile.kcsan
Makefile.kmsan
Makefile.lib
Makefile.modfinal
Makefile.modinst
Makefile.modpost
Makefile.package
Makefile.randstruct
Makefile.ubsan
Makefile.userprogs
Makefile.vmlinux
Makefile.vmlinux_o
as-version.sh
asn1_compiler.c
bloat-o-meter
bootgraph.pl
bpf_doc.py
cc-can-link.sh
cc-version.sh
check-git
check-sysctl-docs
check_extable.sh
checkdeclares.pl
checkincludes.pl
checkkconfigsymbols.py
checkpatch.pl
checkstack.pl
checksyscalls.sh
checkversion.pl
cleanfile
cleanpatch
coccicheck
config
const_structs.checkpatch
decode_stacktrace.sh
decodecode
depmod.sh
dev-needs.sh
diffconfig
documentation-file-ref-check
export_report.pl
extract-ikconfig
extract-module-sig.pl
extract-sys-certs.pl
extract-vmlinux
extract_xc3028.pl
faddr2line
file-size.sh
find-unused-docs.sh
gcc-x86_32-has-stack-protector.sh
gcc-x86_64-has-stack-protector.sh
gen-randstruct-seed.sh
generate_initcall_order.pl
generate_rust_analyzer.py
generate_rust_target.rs
get_abi.pl
get_dvb_firmware
get_feat.pl
get_maintainer.pl
gfp-translate
head-object-list.txt
headerdep.pl
headers_install.sh
insert-sys-cert.c
install.sh
is_rust_module.sh