kernel.git/arch/x86/Makefile, branch linux-5.19.y

lkdtm: Disable return thunks in rodata.c

2022-07-20T17:24:53Z

The following warning was seen: WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:557 apply_returns (arch/x86/kernel/alternative.c:557 (discriminator 1)) Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc4-00008-gee88d363d156 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014 RIP: 0010:apply_returns (arch/x86/kernel/alternative.c:557 (discriminator 1)) Code: ff ff 74 cb 48 83 c5 04 49 39 ee 0f 87 81 fe ff ff e9 22 ff ff ff 0f 0b 48 83 c5 04 49 39 ee 0f 87 6d fe ff ff e9 0e ff ff ff <0f> 0b 48 83 c5 04 49 39 ee 0f 87 59 fe ff ff e9 fa fe ff ff 48 89 The warning happened when apply_returns() failed to convert "JMP __x86_return_thunk" to RET. It was instead a JMP to nowhere, due to the thunk relocation not getting resolved. That rodata.o code is objcopy'd to .rodata, and later memcpy'd, so relocations don't work (and are apparently silently ignored). LKDTM is only used for testing, so the naked RET should be fine. So just disable return thunks for that file. While at it, disable objtool and KCSAN for the file. Fixes: 0b53c374b9ef ("x86/retpoline: Use -mfunction-return") Reported-by: kernel test robot Debugged-by: Peter Zijlstra Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/lkml/Ys58BxHxoDZ7rfpr@xsang-OptiPlex-9020/

x86/retbleed: Add fine grained Kconfig knobs

2022-06-29T15:43:41Z

Do fine-grained Kconfig for all the various retbleed parts. NOTE: if your compiler doesn't support return thunks this will silently 'upgrade' your mitigation to IBPB, you might not like this. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov

x86/retpoline: Use -mfunction-return

2022-06-27T08:33:58Z

Utilize -mfunction-return=thunk-extern when available to have the compiler replace RET instructions with direct JMPs to the symbol __x86_return_thunk. This does not affect assembler (.S) sources, only C sources. -mfunction-return=thunk-extern has been available since gcc 7.3 and clang 15. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Nick Desaulniers Reviewed-by: Josh Poimboeuf Tested-by: Nick Desaulniers Signed-off-by: Borislav Petkov

Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2022-05-26T19:09:50Z

Pull Kbuild updates from Masahiro Yamada: - Add HOSTPKG_CONFIG env variable to allow users to override pkg-config - Support W=e as a shorthand for KCFLAGS=-Werror - Fix CONFIG_IKHEADERS build to support toybox cpio - Add scripts/dummy-tools/pahole to ease distro packagers' life - Suppress false-positive warnings from checksyscalls.sh for W=2 build - Factor out the common code of arch/*/boot/install.sh into scripts/install.sh - Support 'kernel-install' tool in scripts/prune-kernel - Refactor module-versioning to link the symbol versions at the final link of vmlinux and modules - Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in an arch-agnostic way - Refactor modpost, Makefiles * tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (56 commits) genksyms: adjust the output format to modpost kbuild: stop merging *.symversions kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS modpost: extract symbol versions from *.cmd files modpost: add sym_find_with_module() helper modpost: change the license of EXPORT_SYMBOL to bool type modpost: remove left-over cross_compile declaration kbuild: record symbol versions in *.cmd files kbuild: generate a list of objects in vmlinux modpost: move *.mod.c generation to write_mod_c_files() modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header scripts/prune-kernel: Use kernel-install if available kbuild: factor out the common installation code into scripts/install.sh modpost: split new_symbol() to symbol allocation and hash table addition modpost: make sym_add_exported() always allocate a new symbol modpost: make multiple export error modpost: dump Module.symvers in the same order of modules.order modpost: traverse the namespace_list in order modpost: use doubly linked list for dump_lists modpost: traverse unresolved symbols in order ...

kbuild: factor out the common installation code into scripts/install.sh

2022-05-11T12:45:53Z

Many architectures have similar install.sh scripts. The first half is really generic; it verifies that the kernel image and System.map exist, then executes ~/bin/${INSTALLKERNEL} or /sbin/${INSTALLKERNEL} if available. The second half is kind of arch-specific; it copies the kernel image and System.map to the destination, but the code is slightly different. Factor out the generic part into scripts/install.sh. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

x86/configs: Add x86 debugging Kconfig fragment plus docs

2022-04-06T17:56:29Z

The kernel has a wide variety of debugging options to help catch and squash bugs. However, new debugging is added all the time and the existing options can be hard to find. Add a Kconfig fragment with the debugging options which tip maintainers expect to be used to test contributions. This should make it easier for contributors to test their code and find issues before submission. [ bp: Add to "make help" output, fix DEBUG_INFO selection as pointed out by Nathan Chancellor . ] Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220331175728.299103A0@davehans-spike.ostc.intel.com

x86: Remove toolchain check for X32 ABI capability

2022-03-15T09:32:48Z

Commit 0bf6276392e9 ("x32: Warn and disable rather than error if binutils too old") added a small test in arch/x86/Makefile because binutils 2.22 or newer is needed to properly support elf32-x86-64. This check is no longer necessary, as the minimum supported version of binutils is 2.23, which is enforced at configuration time with scripts/min-tool-version.sh. Remove this check and replace all uses of CONFIG_X86_X32 with CONFIG_X86_X32_ABI, as two symbols are no longer necessary. [nathan: Rebase, fix up a few places where CONFIG_X86_X32 was still used, and simplify commit message to satisfy -tip requirements] Signed-off-by: Masahiro Yamada Signed-off-by: Nathan Chancellor Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220314194842.3452-2-nathan@kernel.org

x86/ibt: Base IBT bits

2022-03-15T09:32:33Z

Add Kconfig, Makefile and basic instruction support for x86 IBT. (Ab)use __DISABLE_EXPORTS to disable IBT since it's already employed to mark compressed and purgatory. Additionally mark realmode with it as well to avoid inserting ENDBR instructions there. While ENDBR is technically a NOP, inserting them was causing some grief due to code growth. There's also a problem with using __noendbr in code compiled without -fcf-protection=branch. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20220308154317.519875203@infradead.org

x86: Add straight-line-speculation mitigation

2021-12-09T12:32:25Z

Make use of an upcoming GCC feature to mitigate straight-line-speculation for x86: https://gcc.gnu.org/g:53a643f8568067d7700a9f2facc8ba39974973d3 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952 https://bugs.llvm.org/show_bug.cgi?id=52323 It's built tested on x86_64-allyesconfig using GCC-12 and GCC-11. Maintenance overhead of this should be fairly low due to objtool validation. Size overhead of all these additional int3 instructions comes to: text data bss dec hex filename 22267751 6933356 2011368 31212475 1dc43bb defconfig-build/vmlinux 22804126 6933356 1470696 31208178 1dc32f2 defconfig-build/vmlinux.sls Or roughly 2.4% additional text. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20211204134908.140103474@infradead.org

x86: Use -mindirect-branch-cs-prefix for RETPOLINE builds

2021-12-08T10:57:04Z

In order to further enable commit: bbe2df3f6b6d ("x86/alternative: Try inline spectre_v2=retpoline,amd") add the new GCC flag -mindirect-branch-cs-prefix: https://gcc.gnu.org/g:2196a681d7810ad8b227bf983f38ba716620545e https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952 https://bugs.llvm.org/show_bug.cgi?id=52323 to RETPOLINE=y builds. This should allow fully inlining retpoline,amd for GCC builds. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Kees Cook Acked-by: Nick Desaulniers Link: https://lkml.kernel.org/r/20211119165630.276205624@infradead.org