Merge module sections only when using Clang LTO. With ld.bfd, merging
sections does not appear to update the symbol tables for the module,
e.g. 'readelf -s' shows the value that a symbol would have had, if
sections were not merged. ld.lld does not show this problem.
The stale symbol table breaks gdb's function disassembler, and presumably
other things, e.g.
gdb -batch -ex "file arch/x86/kvm/kvm.ko" -ex "disassemble kvm_init"
reads the wrong bytes and dumps garbage.
Fixes: dd2776222a ("kbuild: lto: merge module sections")
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210322234438.502582-1-seanjc@google.com
Summary of modules changes for the 5.12 merge window:
- Retire EXPORT_UNUSED_SYMBOL() and EXPORT_SYMBOL_GPL_FUTURE(). These export
types were introduced between 2006 - 2008. All the of the unused symbols have
been long removed and gpl future symbols were converted to gpl quite a long
time ago, and I don't believe these export types have been used ever since.
So, I think it should be safe to retire those export types now. (Christoph Hellwig)
- Refactor and clean up some aged code cruft in the module loader (Christoph Hellwig)
- Build {,module_}kallsyms_on_each_symbol only when livepatching is enabled, as
it is the only caller (Christoph Hellwig)
- Unexport find_module() and module_mutex and fix the last module
callers to not rely on these anymore. Make module_mutex internal to
the module loader. (Christoph Hellwig)
- Harden ELF checks on module load and validate ELF structures before checking
the module signature (Frank van der Linden)
- Fix undefined symbol warning for clang (Fangrui Song)
- Fix smatch warning (Dan Carpenter)
Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux
Pull module updates from Jessica Yu:
- Retire EXPORT_UNUSED_SYMBOL() and EXPORT_SYMBOL_GPL_FUTURE(). These
export types were introduced between 2006 - 2008. All the of the
unused symbols have been long removed and gpl future symbols were
converted to gpl quite a long time ago, and I don't believe these
export types have been used ever since. So, I think it should be safe
to retire those export types now (Christoph Hellwig)
- Refactor and clean up some aged code cruft in the module loader
(Christoph Hellwig)
- Build {,module_}kallsyms_on_each_symbol only when livepatching is
enabled, as it is the only caller (Christoph Hellwig)
- Unexport find_module() and module_mutex and fix the last module
callers to not rely on these anymore. Make module_mutex internal to
the module loader (Christoph Hellwig)
- Harden ELF checks on module load and validate ELF structures before
checking the module signature (Frank van der Linden)
- Fix undefined symbol warning for clang (Fangrui Song)
- Fix smatch warning (Dan Carpenter)
* tag 'modules-for-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
module: potential uninitialized return in module_kallsyms_on_each_symbol()
module: remove EXPORT_UNUSED_SYMBOL*
module: remove EXPORT_SYMBOL_GPL_FUTURE
module: move struct symsearch to module.c
module: pass struct find_symbol_args to find_symbol
module: merge each_symbol_section into find_symbol
module: remove each_symbol_in_section
module: mark module_mutex static
kallsyms: only build {,module_}kallsyms_on_each_symbol when required
kallsyms: refactor {,module_}kallsyms_on_each_symbol
module: use RCU to synchronize find_module
module: unexport find_module and module_mutex
drm: remove drm_fb_helper_modinit
powerpc/powernv: remove get_cxl_module
module: harden ELF info handling
module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for undefined symbols
EXPORT_UNUSED_SYMBOL* is not actually used anywhere. Remove the
unused functionality as we generally just remove unused code anyway.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
As far as I can tell this has never been used at all, and certainly
not any time recently.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
LLD always splits sections with LTO, which increases module sizes. This
change adds linker script rules to merge the split sections in the final
module.
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-6-samitolvanen@google.com
There was a request to preprocess the module linker script like we
do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512)
The difference between vmlinux.lds and module.lds is that the latter
is needed for external module builds, thus must be cleaned up by
'make mrproper' instead of 'make clean'. Also, it must be created
by 'make modules_prepare'.
You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by
'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to
arch/$(SRCARCH)/include/asm/module.lds.h, which is included from
scripts/module.lds.S.
scripts/module.lds is fine because 'make clean' keeps all the
build artifacts under scripts/.
You can add arch-specific sections in <asm/module.lds.h>.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
Sean Christopherson