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* cfi: Switch to -fsanitize=kcfiSami Tolvanen2022-09-261-19/+4
| | | | | | | | | | | | | | | | | Switch from Clang's original forward-edge control-flow integrity implementation to -fsanitize=kcfi, which is better suited for the kernel, as it doesn't require LTO, doesn't use a jump table that requires altering function references, and won't break cross-module function address equality. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220908215504.3686827-6-samitolvanen@google.com
* modules: Ensure natural alignment for .altinstructions and __bug_table sectionsHelge Deller2022-07-111-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | In the kernel image vmlinux.lds.S linker scripts the .altinstructions and __bug_table sections are 4- or 8-byte aligned because they hold 32- and/or 64-bit values. Most architectures use altinstructions and BUG() or WARN() in modules as well, but in the module linker script (module.lds.S) those sections are currently missing. As consequence the linker will store their content byte-aligned by default, which then can lead to unnecessary unaligned memory accesses by the CPU when those tables are processed at runtime. Usually unaligned memory accesses are unnoticed, because either the hardware (as on x86 CPUs) or in-kernel exception handlers (e.g. on parisc or sparc) emulate and fix them up at runtime. Nevertheless, such unaligned accesses introduce a performance penalty and can even crash the kernel if there is a bug in the unalignment exception handlers (which happened once to me on the parisc architecture and which is why I noticed that issue at all). This patch fixes a non-critical issue and might be backported at any time. It's trivial and shouldn't introduce any regression because it simply tells the linker to use a different (8-byte alignment) for those sections by default. Signed-off-by: Helge Deller <deller@gmx.de> Link: https://lore.kernel.org/all/Yr8%2Fgr8e8I7tVX4d@p100/ Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
* module: combine constructors in module linker scriptReiner Huober2021-07-191-0/+1
| | | | | | | | | | | | | | | | | | | | | The constructor code for modules must be aware of init code inside different sections. Newer GCC compilers write constructors in more than one section, e.g. ".ctors.65435". These must be combined into a single ".ctors" section. In the module loader, only the ".ctors" section is searched and the constructors therein are initialized, when CONFIG_CONSTRUCTORS=y is set. Other constructors are ignored. This change combines all ".ctors.*" and the ".ctors" section, if any, in <module>.ko into a single ."ctors" section. For code coverage in GCC, this is necessary to show the code coverage for modules, since code coverage uses such constructors when initializing a module in newer version of GCC. Signed-off-by: Reiner Huober <reiner.huober@nokia.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>
* module: ensure __cfi_check alignmentSami Tolvanen2021-04-081-1/+18
| | | | | | | | | | | | | | | | | | | CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page aligned and at the beginning of the .text section. While Clang would normally align the function correctly, it fails to do so for modules with no executable code. This change ensures the correct __cfi_check() location and alignment. It also discards the .eh_frame section, which Clang can generate with certain sanitizers, such as CFI. Link: https://bugs.llvm.org/show_bug.cgi?id=46293 Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Jessica Yu <jeyu@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210408182843.1754385-5-samitolvanen@google.com
* kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabledSean Christopherson2021-04-011-0/+2
| | | | | | | | | | | | | | | | | | | | | | 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: dd2776222abb ("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
* Merge tag 'modules-for-v5.12' of ↵Linus Torvalds2021-02-231-6/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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
| * module: remove EXPORT_UNUSED_SYMBOL*Christoph Hellwig2021-02-081-4/+0
| | | | | | | | | | | | | | | | | | | | 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>
| * module: remove EXPORT_SYMBOL_GPL_FUTUREChristoph Hellwig2021-02-081-2/+0
| | | | | | | | | | | | | | | | | | | | 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>
* | kbuild: lto: merge module sectionsSami Tolvanen2021-01-141-0/+24
|/ | | | | | | | | | | | 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
* kbuild: preprocess module linker scriptMasahiro Yamada2020-09-251-0/+29
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>
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