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68c76ad4 |
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27-Oct-2022 |
Ard Biesheuvel <ardb@kernel.org> |
arm64: unwind: add asynchronous unwind tables to kernel and modules Enable asynchronous unwind table generation for both the core kernel as well as modules, and emit the resulting .eh_frame sections as init code so we can use the unwind directives for code patching at boot or module load time. This will be used by dynamic shadow call stack support, which will rely on code patching rather than compiler codegen to emit the shadow call stack push and pop instructions. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Link: https://lore.kernel.org/r/20221027155908.1940624-2-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
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89245600 |
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08-Sep-2022 |
Sami Tolvanen <samitolvanen@google.com> |
cfi: Switch to -fsanitize=kcfi 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
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87c482bd |
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08-Jul-2022 |
Helge Deller <deller@gmx.de> |
modules: Ensure natural alignment for .altinstructions and __bug_table sections 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>
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4c5afb74 |
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06-Jul-2021 |
Reiner Huober <reiner.huober@nokia.com> |
module: combine constructors in module linker script 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>
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28aad1c2 |
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08-Apr-2021 |
Sami Tolvanen <samitolvanen@google.com> |
module: ensure __cfi_check alignment 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
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6a3193cd |
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22-Mar-2021 |
Sean Christopherson <seanjc@google.com> |
kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabled 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
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36794822 |
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02-Feb-2021 |
Christoph Hellwig <hch@lst.de> |
module: remove EXPORT_UNUSED_SYMBOL* 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>
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f1c3d73e |
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02-Feb-2021 |
Christoph Hellwig <hch@lst.de> |
module: remove EXPORT_SYMBOL_GPL_FUTURE 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>
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dd277622 |
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11-Dec-2020 |
Sami Tolvanen <samitolvanen@google.com> |
kbuild: lto: merge module sections 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
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596b0474 |
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07-Sep-2020 |
Masahiro Yamada <masahiroy@kernel.org> |
kbuild: preprocess module linker script 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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