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This is a follow up to commit c4781dc3d1cf ("Kbuild: enable
-fms-extensions") but in a separate change due to being substantially
different from the initial submission.
There are many places within the kernel that use their own CFLAGS
instead of the main KBUILD_CFLAGS, meaning code written with the main
kernel's use of '-fms-extensions' in mind that may be tangentially
included in these areas will result in "error: declaration does not
declare anything" messages from the compiler.
Add '-fms-extensions' to all these areas to ensure consistency, along
with -Wno-microsoft-anon-tag to silence clang's warning about use of the
extension that the kernel cares about using. parisc does not build with
clang so it does not need this warning flag. LoongArch does not need it
either because -W flags from KBUILD_FLAGS are pulled into cflags-vdso.
Reported-by: Christian Brauner <brauner@kernel.org>
Closes: https://lore.kernel.org/20251030-meerjungfrau-getrocknet-7b46eacc215d@brauner/
Reviewed-by: Christian Brauner <brauner@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
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Recent EFI x86 systems are more strict when it comes to mapping boot
images, and require that mappings are either read-write or read-execute.
Now that the boot code is being cleaned up and refactored, most of it is
being moved into .init.text [where it arguably belongs] but that implies
that when booting on such strict EFI firmware, we need to take care to
map .init.text (and the .altinstr_aux section that follows it)
read-execute as well.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-44-ardb+git@google.com
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Similar to zboot architectures, implement support for embedding SBAT data
for x86. Put '.sbat' section in between '.data' and '.text' as the former
also covers '.bss' and '.pgtable' and thus must be the last one in the
file.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/20250603091951.57775-1-vkuznets@redhat.com
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As a first step towards disentangling the SEV #VC handling code -which
is shared between the decompressor and the core kernel- from the SEV
startup code, move the decompressor's copy of the instruction decoder
into a separate source file.
Code movement only - no functional change intended.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250504095230.2932860-30-ardb+git@google.com
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Move the early GDT/IDT setup code that runs long before the kernel
virtual mapping is up into arch/x86/boot/startup/, and build it in a way
that ensures that the code tolerates being called from the 1:1 mapping
of memory. The code itself is left unchanged by this patch.
Also tweak the sed symbol matching pattern in the decompressor to match
on lower case 't' or 'b', as these will be emitted by Clang for symbols
with hidden linkage.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250410134117.3713574-15-ardb+git@google.com
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The 5-level paging trampoline is used by both the EFI stub and the
traditional decompressor. Move it out of the decompressor sources into
the newly minted arch/x86/boot/startup/ sub-directory which will hold
startup code that may be shared between the decompressor, the EFI stub
and the kernel proper, and needs to tolerate being called during early
boot, before the kernel virtual mapping has been created.
This will allow the 5-level paging trampoline to be used by EFI boot
images such as zboot that omit the traditional decompressor entirely.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250401133416.1436741-10-ardb+git@google.com
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git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Improve performance in gendwarfksyms
- Remove deprecated EXTRA_*FLAGS and KBUILD_ENABLE_EXTRA_GCC_CHECKS
- Support CONFIG_HEADERS_INSTALL for ARCH=um
- Use more relative paths to sources files for better reproducibility
- Support the loong64 Debian architecture
- Add Kbuild bash completion
- Introduce intermediate vmlinux.unstripped for architectures that need
static relocations to be stripped from the final vmlinux
- Fix versioning in Debian packages for -rc releases
- Treat missing MODULE_DESCRIPTION() as an error
- Convert Nios2 Makefiles to use the generic rule for built-in DTB
- Add debuginfo support to the RPM package
* tag 'kbuild-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (40 commits)
kbuild: rpm-pkg: build a debuginfo RPM
kconfig: merge_config: use an empty file as initfile
nios2: migrate to the generic rule for built-in DTB
rust: kbuild: skip `--remap-path-prefix` for `rustdoc`
kbuild: pacman-pkg: hardcode module installation path
kbuild: deb-pkg: don't set KBUILD_BUILD_VERSION unconditionally
modpost: require a MODULE_DESCRIPTION()
kbuild: make all file references relative to source root
x86: drop unnecessary prefix map configuration
kbuild: deb-pkg: add comment about future removal of KDEB_COMPRESS
kbuild: Add a help message for "headers"
kbuild: deb-pkg: remove "version" variable in mkdebian
kbuild: deb-pkg: fix versioning for -rc releases
Documentation/kbuild: Fix indentation in modules.rst example
x86: Get rid of Makefile.postlink
kbuild: Create intermediate vmlinux build with relocations preserved
kbuild: Introduce Kconfig symbol for linking vmlinux with relocations
kbuild: link-vmlinux.sh: Make output file name configurable
kbuild: do not generate .tmp_vmlinux*.map when CONFIG_VMLINUX_MAP=y
Revert "kheaders: Ignore silly-rename files"
...
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git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi
Pull EFI updates from Ard Biesheuvel:
- Decouple mixed mode startup code from the traditional x86
decompressor
- Revert zero-length file hack in efivarfs
- Prevent EFI zboot from using the CopyMem/SetMem boot services after
ExitBootServices()
- Update EFI zboot to use the ZLIB/ZSTD library interfaces directly
* tag 'efi-next-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efi/libstub: Avoid legacy decompressor zlib/zstd wrappers
efi/libstub: Avoid CopyMem/SetMem EFI services after ExitBootServices
efi: efibc: change kmalloc(size * count, ...) to kmalloc_array()
efivarfs: Revert "allow creation of zero length files"
x86/efi/mixed: Move mixed mode startup code into libstub
x86/efi/mixed: Simplify and document thunking logic
x86/efi/mixed: Remove dependency on legacy startup_32 code
x86/efi/mixed: Set up 1:1 mapping of lower 4GiB in the stub
x86/efi/mixed: Factor out and clean up long mode entry
x86/efi/mixed: Check CPU compatibility without relying on verify_cpu()
x86/efistub: Merge PE and handover entrypoints
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The toplevel Makefile already provides -fmacro-prefix-map as part of
KBUILD_CPPFLAGS. In contrast to the KBUILD_CFLAGS and KBUILD_AFLAGS
variables, KBUILD_CPPFLAGS is not redefined in the architecture specific
Makefiles. Therefore the toplevel KBUILD_CPPFLAGS do apply just fine, to
both C and ASM sources.
The custom configuration was necessary when it was added in
commit 9e2276fa6eb3 ("arch/x86/boot: Use prefix map to avoid embedded
paths") but has since become unnecessary in commit a716bd743210
("kbuild: use -fmacro-prefix-map for .S sources").
Drop the now unnecessary custom prefix map configuration.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Instead of generating the vmlinux.relocs file (needed by the
decompressor build to construct the KASLR relocation tables) as a
vmlinux postlink step, which is dubious because it depends on data that
is stripped from vmlinux before the build completes, generate it from
vmlinux.unstripped, which has been introduced specifically for this
purpose.
This ensures that each artifact is rebuilt as needed, rather than as a
side effect of another build rule.
This effectively reverts commit
9d9173e9ceb6 ("x86/build: Avoid relocation information in final vmlinux")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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To permit the EFI stub to call this code even when building the kernel
without the legacy decompressor, move the trampoline out of the latter's
startup code.
This is part of an ongoing WIP effort on my part to make the existing,
generic EFI zboot format work on x86 as well.
No functional change intended.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250313120324.1095968-2-ardb+git@google.com
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The EFI mixed mode code has been decoupled from the legacy decompressor,
in order to be able to reuse it with generic EFI zboot images for x86.
Move the source file into the libstub source directory to facilitate
this.
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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GCC 15 changed the default C standard version to C23, which should not
have impacted the kernel because it requests the gnu11 standard via
'-std=' in the main Makefile. However, the x86 compressed boot Makefile
uses its own set of KBUILD_CFLAGS without a '-std=' value (i.e., using
the default), resulting in errors from the kernel's definitions of bool,
true, and false in stddef.h, which are reserved keywords under C23.
./include/linux/stddef.h:11:9: error: expected identifier before ‘false’
11 | false = 0,
./include/linux/types.h:35:33: error: two or more data types in declaration specifiers
35 | typedef _Bool bool;
Set '-std=gnu11' in the x86 compressed boot Makefile to resolve the
error and consistently use the same C standard version for the entire
kernel.
Closes: https://lore.kernel.org/4OAhbllK7x4QJGpZjkYjtBYNLd_2whHx9oFiuZcGwtVR4hIzvduultkgfAIRZI3vQpZylu7Gl929HaYFRGeMEalWCpeMzCIIhLxxRhq4U-Y=@protonmail.com/
Closes: https://lore.kernel.org/Z4467umXR2PZ0M1H@tucnak/
Reported-by: Kostadin Shishmanov <kostadinshishmanov@protonmail.com>
Reported-by: Jakub Jelinek <jakub@redhat.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250121-x86-use-std-consistently-gcc-15-v1-1-8ab0acf645cb%40kernel.org
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This is a re-commit of
da05b143a308 ("x86/boot: Don't add the EFI stub to targets")
after the tagged patch incorrectly reverted it.
vmlinux-objs-y is added to targets, with an assumption that they are all
relative to $(obj); adding a $(objtree)/drivers/... path causes the
build to incorrectly create a useless
arch/x86/boot/compressed/drivers/... directory tree.
Fix this just by using a different make variable for the EFI stub.
Fixes: cb8bda8ad443 ("x86/boot/compressed: Rename efi_thunk_64.S to efi-mixed.S")
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: stable@vger.kernel.org # v6.1+
Link: https://lore.kernel.org/r/xm267ceukksz.fsf@bsegall.svl.corp.google.com
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Now Kbuild provides reasonable defaults for objtool, sanitizers, and
profilers.
Remove redundant variables.
Note:
This commit changes the coverage for some objects:
- include arch/mips/vdso/vdso-image.o into UBSAN, GCOV, KCOV
- include arch/sparc/vdso/vdso-image-*.o into UBSAN
- include arch/sparc/vdso/vma.o into UBSAN
- include arch/x86/entry/vdso/extable.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
- include arch/x86/entry/vdso/vdso-image-*.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
- include arch/x86/entry/vdso/vdso32-setup.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
- include arch/x86/entry/vdso/vma.o into GCOV, KCOV
- include arch/x86/um/vdso/vma.o into KASAN, GCOV, KCOV
I believe these are positive effects because all of them are kernel
space objects.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Roberto Sassu <roberto.sassu@huawei.com>
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Currently, the EFI stub invokes the EFI memory attributes protocol to
strip any NX restrictions from the entire loaded kernel, resulting in
all code and data being mapped read-write-execute.
The point of the EFI memory attributes protocol is to remove the need
for all memory allocations to be mapped with both write and execute
permissions by default, and make it the OS loader's responsibility to
transition data mappings to code mappings where appropriate.
Even though the UEFI specification does not appear to leave room for
denying memory attribute changes based on security policy, let's be
cautious and avoid relying on the ability to create read-write-execute
mappings. This is trivially achievable, given that the amount of kernel
code executing via the firmware's 1:1 mapping is rather small and
limited to the .head.text region. So let's drop the NX restrictions only
on that subregion, but not before remapping it as read-only first.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Fix typos, most reported by "codespell arch/x86". Only touches comments,
no code changes.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org
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The bare metal decompressor code was never really intended to run in a
hosted environment such as the EFI boot services, and does a few things
that are becoming problematic in the context of EFI boot now that the
logo requirements are getting tighter: EFI executables will no longer be
allowed to consist of a single executable section that is mapped with
read, write and execute permissions if they are intended for use in a
context where Secure Boot is enabled (and where Microsoft's set of
certificates is used, i.e., every x86 PC built to run Windows).
To avoid stepping on reserved memory before having inspected the E820
tables, and to ensure the correct placement when running a kernel build
that is non-relocatable, the bare metal decompressor moves its own
executable image to the end of the allocation that was reserved for it,
in order to perform the decompression in place. This means the region in
question requires both write and execute permissions, which either need
to be given upfront (which EFI will no longer permit), or need to be
applied on demand using the existing page fault handling framework.
However, the physical placement of the kernel is usually randomized
anyway, and even if it isn't, a dedicated decompression output buffer
can be allocated anywhere in memory using EFI APIs when still running in
the boot services, given that EFI support already implies a relocatable
kernel. This means that decompression in place is never necessary, nor
is moving the compressed image from one end to the other.
Since EFI already maps all of memory 1:1, it is also unnecessary to
create new page tables or handle page faults when decompressing the
kernel. That means there is also no need to replace the special
exception handlers for SEV. Generally, there is little need to do
any of the things that the decompressor does beyond
- initialize SEV encryption, if needed,
- perform the 4/5 level paging switch, if needed,
- decompress the kernel
- relocate the kernel
So do all of this from the EFI stub code, and avoid the bare metal
decompressor altogether.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-24-ardb@kernel.org
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 confidential computing update from Borislav Petkov:
- Add support for unaccepted memory as specified in the UEFI spec v2.9.
The gist of it all is that Intel TDX and AMD SEV-SNP confidential
computing guests define the notion of accepting memory before using
it and thus preventing a whole set of attacks against such guests
like memory replay and the like.
There are a couple of strategies of how memory should be accepted -
the current implementation does an on-demand way of accepting.
* tag 'x86_cc_for_v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
virt: sevguest: Add CONFIG_CRYPTO dependency
x86/efi: Safely enable unaccepted memory in UEFI
x86/sev: Add SNP-specific unaccepted memory support
x86/sev: Use large PSC requests if applicable
x86/sev: Allow for use of the early boot GHCB for PSC requests
x86/sev: Put PSC struct on the stack in prep for unaccepted memory support
x86/sev: Fix calculation of end address based on number of pages
x86/tdx: Add unaccepted memory support
x86/tdx: Refactor try_accept_one()
x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub
efi/unaccepted: Avoid load_unaligned_zeropad() stepping into unaccepted memory
efi: Add unaccepted memory support
x86/boot/compressed: Handle unaccepted memory
efi/libstub: Implement support for unaccepted memory
efi/x86: Get full memory map in allocate_e820()
mm: Add support for unaccepted memory
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The Linux build process on x86 roughly consists of compiling all input
files, statically linking them into a vmlinux ELF file, and then taking
and turning this file into an actual bzImage bootable file.
vmlinux has in this process two main purposes:
1) It is an intermediate build target on the way to produce the final
bootable image.
2) It is a file that is expected to be used by debuggers and standard
ELF tooling to work with the built kernel.
For the second purpose, a vmlinux file is typically collected by various
package build recipes, such as distribution spec files, including the
kernel's own tar-pkg target.
When building a kernel supporting KASLR with CONFIG_X86_NEED_RELOCS,
vmlinux contains also relocation information produced by using the
--emit-relocs linker option. This is utilized by subsequent build steps
to create vmlinux.relocs and produce a relocatable image. However, the
information is not needed by debuggers and other standard ELF tooling.
The issue is then that the collected vmlinux file and hence distribution
packages end up unnecessarily large because of this extra data. The
following is a size comparison of vmlinux v6.0 with and without the
relocation information:
| Configuration | With relocs | Stripped relocs |
| x86_64_defconfig | 70 MB | 43 MB |
| +CONFIG_DEBUG_INFO | 818 MB | 367 MB |
Optimize a resulting vmlinux by adding a postlink step that splits the
relocation information into vmlinux.relocs and then strips it from the
vmlinux binary.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20220927084632.14531-1-petr.pavlu@suse.com
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Hookup TDX-specific code to accept memory.
Accepting the memory is done with ACCEPT_PAGE module call on every page
in the range. MAP_GPA hypercall is not required as the unaccepted memory
is considered private already.
Extract the part of tdx_enc_status_changed() that does memory acceptance
in a new helper. Move the helper tdx-shared.c. It is going to be used by
both main kernel and decompressor.
[ bp: Fix the INTEL_TDX_GUEST=y, KVM_GUEST=n build. ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230606142637.5171-10-kirill.shutemov@linux.intel.com
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UEFI Specification version 2.9 introduces the concept of memory
acceptance: Some Virtual Machine platforms, such as Intel TDX or AMD
SEV-SNP, requiring memory to be accepted before it can be used by the
guest. Accepting happens via a protocol specific for the Virtual
Machine platform.
Accepting memory is costly and it makes VMM allocate memory for the
accepted guest physical address range. It's better to postpone memory
acceptance until memory is needed. It lowers boot time and reduces
memory overhead.
The kernel needs to know what memory has been accepted. Firmware
communicates this information via memory map: a new memory type --
EFI_UNACCEPTED_MEMORY -- indicates such memory.
Range-based tracking works fine for firmware, but it gets bulky for
the kernel: e820 (or whatever the arch uses) has to be modified on every
page acceptance. It leads to table fragmentation and there's a limited
number of entries in the e820 table.
Another option is to mark such memory as usable in e820 and track if the
range has been accepted in a bitmap. One bit in the bitmap represents a
naturally aligned power-2-sized region of address space -- unit.
For x86, unit size is 2MiB: 4k of the bitmap is enough to track 64GiB or
physical address space.
In the worst-case scenario -- a huge hole in the middle of the
address space -- It needs 256MiB to handle 4PiB of the address
space.
Any unaccepted memory that is not aligned to unit_size gets accepted
upfront.
The bitmap is allocated and constructed in the EFI stub and passed down
to the kernel via EFI configuration table. allocate_e820() allocates the
bitmap if unaccepted memory is present, according to the size of
unaccepted region.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20230606142637.5171-4-kirill.shutemov@linux.intel.com
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as-option tests new options using KBUILD_CFLAGS, which causes problems
when using as-option to update KBUILD_AFLAGS because many compiler
options are not valid assembler options.
This will be fixed in a follow up patch. Before doing so, move the
assembler test for -Wa,-mrelax-relocations=no from using as-option to
cc-option.
Link: https://lore.kernel.org/llvm/CAK7LNATcHt7GcXZ=jMszyH=+M_LC9Qr6yeAGRCBbE6xriLxtUQ@mail.gmail.com/
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull kernel hardening updates from Kees Cook:
- Convert flexible array members, fix -Wstringop-overflow warnings, and
fix KCFI function type mismatches that went ignored by maintainers
(Gustavo A. R. Silva, Nathan Chancellor, Kees Cook)
- Remove the remaining side-effect users of ksize() by converting
dma-buf, btrfs, and coredump to using kmalloc_size_roundup(), add
more __alloc_size attributes, and introduce full testing of all
allocator functions. Finally remove the ksize() side-effect so that
each allocation-aware checker can finally behave without exceptions
- Introduce oops_limit (default 10,000) and warn_limit (default off) to
provide greater granularity of control for panic_on_oops and
panic_on_warn (Jann Horn, Kees Cook)
- Introduce overflows_type() and castable_to_type() helpers for cleaner
overflow checking
- Improve code generation for strscpy() and update str*() kern-doc
- Convert strscpy and sigphash tests to KUnit, and expand memcpy tests
- Always use a non-NULL argument for prepare_kernel_cred()
- Disable structleak plugin in FORTIFY KUnit test (Anders Roxell)
- Adjust orphan linker section checking to respect CONFIG_WERROR (Xin
Li)
- Make sure siginfo is cleared for forced SIGKILL (haifeng.xu)
- Fix um vs FORTIFY warnings for always-NULL arguments
* tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (31 commits)
ksmbd: replace one-element arrays with flexible-array members
hpet: Replace one-element array with flexible-array member
um: virt-pci: Avoid GCC non-NULL warning
signal: Initialize the info in ksignal
lib: fortify_kunit: build without structleak plugin
panic: Expose "warn_count" to sysfs
panic: Introduce warn_limit
panic: Consolidate open-coded panic_on_warn checks
exit: Allow oops_limit to be disabled
exit: Expose "oops_count" to sysfs
exit: Put an upper limit on how often we can oops
panic: Separate sysctl logic from CONFIG_SMP
mm/pgtable: Fix multiple -Wstringop-overflow warnings
mm: Make ksize() a reporting-only function
kunit/fortify: Validate __alloc_size attribute results
drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()
drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()
driver core: Add __alloc_size hint to devm allocators
overflow: Introduce overflows_type() and castable_to_type()
coredump: Proactively round up to kmalloc bucket size
...
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Avoid building the mem_encrypt.o object if memory encryption support is
not enabled to begin with.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221122161017.2426828-17-ardb@kernel.org
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In preparation for moving the mixed mode specific code out of head_64.S,
rename the existing file to clarify that it contains more than just the
mixed mode thunk.
While at it, clean up the Makefile rules that add it to the build.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221122161017.2426828-2-ardb@kernel.org
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Andrew Cooper suggested upgrading the orphan section warning to a hard link
error. However Nathan Chancellor said outright turning the warning into an
error with no escape hatch might be too aggressive, as we have had these
warnings triggered by new compiler generated sections, and suggested turning
orphan sections into an error only if CONFIG_WERROR is set. Kees Cook echoed
and emphasized that the mandate from Linus is that we should avoid breaking
builds. It wrecks bisection, it causes problems across compiler versions, etc.
Thus upgrade the orphan section warning to a hard link error only if
CONFIG_WERROR is set.
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Xin Li <xin3.li@intel.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221025073023.16137-2-xin3.li@intel.com
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Instrumenting some files with KMSAN will result in kernel being unable to
link, boot or crashing at runtime for various reasons (e.g. infinite
recursion caused by instrumentation hooks calling instrumented code
again).
Completely omit KMSAN instrumentation in the following places:
- arch/x86/boot and arch/x86/realmode/rm, as KMSAN doesn't work for i386;
- arch/x86/entry/vdso, which isn't linked with KMSAN runtime;
- three files in arch/x86/kernel - boot problems;
- arch/x86/mm/cpu_entry_area.c - recursion.
Link: https://lkml.kernel.org/r/20220915150417.722975-33-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Users of GNU ld (BFD) from binutils 2.39+ will observe multiple
instances of a new warning when linking kernels in the form:
ld: warning: arch/x86/boot/pmjump.o: missing .note.GNU-stack section implies executable stack
ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
ld: warning: arch/x86/boot/compressed/vmlinux has a LOAD segment with RWX permissions
Generally, we would like to avoid the stack being executable. Because
there could be a need for the stack to be executable, assembler sources
have to opt-in to this security feature via explicit creation of the
.note.GNU-stack feature (which compilers create by default) or command
line flag --noexecstack. Or we can simply tell the linker the
production of such sections is irrelevant and to link the stack as
--noexecstack.
LLVM's LLD linker defaults to -z noexecstack, so this flag isn't
strictly necessary when linking with LLD, only BFD, but it doesn't hurt
to be explicit here for all linkers IMO. --no-warn-rwx-segments is
currently BFD specific and only available in the current latest release,
so it's wrapped in an ld-option check.
While the kernel makes extensive usage of ELF sections, it doesn't use
permissions from ELF segments.
Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
Link: https://github.com/llvm/llvm-project/issues/57009
Reported-and-tested-by: Jens Axboe <axboe@kernel.dk>
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull Intel TDX support from Borislav Petkov:
"Intel Trust Domain Extensions (TDX) support.
This is the Intel version of a confidential computing solution called
Trust Domain Extensions (TDX). This series adds support to run the
kernel as part of a TDX guest. It provides similar guest protections
to AMD's SEV-SNP like guest memory and register state encryption,
memory integrity protection and a lot more.
Design-wise, it differs from AMD's solution considerably: it uses a
software module which runs in a special CPU mode called (Secure
Arbitration Mode) SEAM. As the name suggests, this module serves as
sort of an arbiter which the confidential guest calls for services it
needs during its lifetime.
Just like AMD's SNP set, this series reworks and streamlines certain
parts of x86 arch code so that this feature can be properly
accomodated"
* tag 'x86_tdx_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
x86/tdx: Fix RETs in TDX asm
x86/tdx: Annotate a noreturn function
x86/mm: Fix spacing within memory encryption features message
x86/kaslr: Fix build warning in KASLR code in boot stub
Documentation/x86: Document TDX kernel architecture
ACPICA: Avoid cache flush inside virtual machines
x86/tdx/ioapic: Add shared bit for IOAPIC base address
x86/mm: Make DMA memory shared for TD guest
x86/mm/cpa: Add support for TDX shared memory
x86/tdx: Make pages shared in ioremap()
x86/topology: Disable CPU online/offline control for TDX guests
x86/boot: Avoid #VE during boot for TDX platforms
x86/boot: Set CR0.NE early and keep it set during the boot
x86/acpi/x86/boot: Add multiprocessor wake-up support
x86/boot: Add a trampoline for booting APs via firmware handoff
x86/tdx: Wire up KVM hypercalls
x86/tdx: Port I/O: Add early boot support
x86/tdx: Port I/O: Add runtime hypercalls
x86/boot: Port I/O: Add decompression-time support for TDX
x86/boot: Port I/O: Allow to hook up alternative helpers
...
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Port I/O instructions trigger #VE in the TDX environment. In response to
the exception, kernel emulates these instructions using hypercalls.
But during early boot, on the decompression stage, it is cumbersome to
deal with #VE. It is cleaner to go to hypercalls directly, bypassing #VE
handling.
Hook up TDX-specific port I/O helpers if booting in TDX environment.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220405232939.73860-17-kirill.shutemov@linux.intel.com
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The early decompression code does port I/O for its console output. But,
handling the decompression-time port I/O demands a different approach
from normal runtime because the IDT required to support #VE based port
I/O emulation is not yet set up. Paravirtualizing I/O calls during
the decompression step is acceptable because the decompression code
doesn't have a lot of call sites to IO instruction.
To support port I/O in decompression code, TDX must be detected before
the decompression code might do port I/O. Detect whether the kernel runs
in a TDX guest.
Add an early_is_tdx_guest() interface to query the cached TDX guest
status in the decompression code.
TDX is detected with CPUID. Make cpuid_count() accessible outside
boot/cpuflags.c.
TDX detection in the main kernel is very similar. Move common bits
into <asm/shared/tdx.h>.
The actual port I/O paravirtualization will come later in the series.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220405232939.73860-13-kirill.shutemov@linux.intel.com
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Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.
First, carve out the functionality which determines the EFI environment
type the machine is booting on.
[ bp: Massage commit message. ]
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-25-brijesh.singh@amd.com
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git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Add new kconfig target 'make mod2noconfig', which will be useful to
speed up the build and test iteration.
- Raise the minimum supported version of LLVM to 11.0.0
- Refactor certs/Makefile
- Change the format of include/config/auto.conf to stop double-quoting
string type CONFIG options.
- Fix ARCH=sh builds in dash
- Separate compression macros for general purposes (cmd_bzip2 etc.) and
the ones for decompressors (cmd_bzip2_with_size etc.)
- Misc Makefile cleanups
* tag 'kbuild-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits)
kbuild: add cmd_file_size
arch: decompressor: remove useless vmlinux.bin.all-y
kbuild: rename cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22}
kbuild: drop $(size_append) from cmd_zstd
sh: rename suffix-y to suffix_y
doc: kbuild: fix default in `imply` table
microblaze: use built-in function to get CPU_{MAJOR,MINOR,REV}
certs: move scripts/extract-cert to certs/
kbuild: do not quote string values in include/config/auto.conf
kbuild: do not include include/config/auto.conf from shell scripts
certs: simplify $(srctree)/ handling and remove config_filename macro
kbuild: stop using config_filename in scripts/Makefile.modsign
certs: remove misleading comments about GCC PR
certs: refactor file cleaning
certs: remove unneeded -I$(srctree) option for system_certificates.o
certs: unify duplicated cmd_extract_certs and improve the log
certs: use $< and $@ to simplify the key generation rule
kbuild: remove headers_check stub
kbuild: move headers_check.pl to usr/include/
certs: use if_changed to re-generate the key when the key type is changed
...
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GZIP-compressed files end with 4 byte data that represents the size
of the original input. The decompressors (the self-extracting kernel)
exploit it to know the vmlinux size beforehand. To mimic the GZIP's
trailer, Kbuild provides cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22}.
Unfortunately these macros are used everywhere despite the appended
size data is only useful for the decompressors.
There is no guarantee that such hand-crafted trailers are safely ignored.
In fact, the kernel refuses compressed initramdfs with the garbage data.
That is why usr/Makefile overrides size_append to make it no-op.
To limit the use of such broken compressed files, this commit renames
the existing macros as follows:
cmd_bzip2 --> cmd_bzip2_with_size
cmd_lzma --> cmd_lzma_with_size
cmd_lzo --> cmd_lzo_with_size
cmd_lz4 --> cmd_lz4_with_size
cmd_xzkern --> cmd_xzkern_with_size
cmd_zstd22 --> cmd_zstd22_with_size
To keep the decompressors working, I updated the following Makefiles
accordingly:
arch/arm/boot/compressed/Makefile
arch/h8300/boot/compressed/Makefile
arch/mips/boot/compressed/Makefile
arch/parisc/boot/compressed/Makefile
arch/s390/boot/compressed/Makefile
arch/sh/boot/compressed/Makefile
arch/x86/boot/compressed/Makefile
I reused the current macro names for the normal usecases; they produce
the compressed data in the proper format.
I did not touch the following:
arch/arc/boot/Makefile
arch/arm64/boot/Makefile
arch/csky/boot/Makefile
arch/mips/boot/Makefile
arch/riscv/boot/Makefile
arch/sh/boot/Makefile
kernel/Makefile
This means those Makefiles will stop appending the size data.
I dropped the 'override size_append' hack from usr/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
|
|
When cross compiling i386_defconfig on an arm64 host with clang, there
are a few instances of '-Waddress-of-packed-member' and
'-Wgnu-variable-sized-type-not-at-end' in arch/x86/boot/compressed/,
which should both be disabled with the cc-disable-warning calls in that
directory's Makefile, which indicates that cc-disable-warning is failing
at the point of testing these flags.
The cc-disable-warning calls fail because at the point that the flags
are tested, KBUILD_CFLAGS has '-march=i386' without $(CLANG_FLAGS),
which has the '--target=' flag to tell clang what architecture it is
targeting. Without the '--target=' flag, the host architecture (arm64)
is used and i386 is not a valid value for '-march=' in that case. This
error can be seen by adding some logging to try-run:
clang-14: error: the clang compiler does not support '-march=i386'
Invoking the compiler has to succeed prior to calling cc-option or
cc-disable-warning in order to accurately test whether or not the flag
is supported; if it doesn't, the requested flag can never be added to
the compiler flags. Move $(CLANG_FLAGS) to the beginning of KBUILD_FLAGS
so that any new flags that might be added in the future can be
accurately tested.
Fixes: d5cbd80e302d ("x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211222163040.1961481-1-nathan@kernel.org
|
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A discussion around -Wundef showed that there were still a few boolean
Kconfigs where #if was used rather than #ifdef to guard different code.
Kconfig doesn't define boolean configs, which can result in -Wundef
warnings.
arch/x86/boot/compressed/Makefile resets the CFLAGS used for this
directory, and doesn't re-enable -Wundef as the top level Makefile does.
If re-added, with RANDOMIZE_BASE and X86_NEED_RELOCS disabled, the
following warnings are visible.
arch/x86/boot/compressed/misc.h:82:5: warning: 'CONFIG_RANDOMIZE_BASE'
is not defined, evaluates to 0 [-Wundef]
^
arch/x86/boot/compressed/misc.c:175:5: warning: 'CONFIG_X86_NEED_RELOCS'
is not defined, evaluates to 0 [-Wundef]
^
Simply fix these and re-enable this warning for this directory.
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20210422190450.3903999-1-ndesaulniers@google.com
|
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SEV-SNP builds upon the SEV-ES functionality while adding new hardware
protection. Version 2 of the GHCB specification adds new NAE events that
are SEV-SNP specific. Rename the sev-es.{ch} to sev.{ch} so that all
SEV* functionality can be consolidated in one place.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20210427111636.1207-2-brijesh.singh@amd.com
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When cross compiling x86 on an ARM machine with clang, there are several
errors along the lines of:
arch/x86/include/asm/string_64.h:27:10: error: invalid output constraint '=&c' in asm
This happens because the compressed boot Makefile reassigns KBUILD_CFLAGS
and drops the clang flags that set the target architecture ('--target=')
and the path to the GNU cross tools ('--prefix='), meaning that the host
architecture is targeted.
These flags are available as $(CLANG_FLAGS) from the main Makefile so
add them to the compressed boot folder's KBUILD_CFLAGS so that cross
compiling works as expected.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lkml.kernel.org/r/20210326000435.4785-3-nathan@kernel.org
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull EFI updates from Borislav Petkov:
"These got delayed due to a last minute ia64 build issue which got
fixed in the meantime.
EFI updates collected by Ard Biesheuvel:
- Don't move BSS section around pointlessly in the x86 decompressor
- Refactor helper for discovering the EFI secure boot mode
- Wire up EFI secure boot to IMA for arm64
- Some fixes for the capsule loader
- Expose the RT_PROP table via the EFI test module
- Relax DT and kernel placement restrictions on ARM
with a few followup fixes:
- fix the build breakage on IA64 caused by recent capsule loader
changes
- suppress a type mismatch build warning in the expansion of
EFI_PHYS_ALIGN on ARM"
* tag 'efi_updates_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
efi: arm: force use of unsigned type for EFI_PHYS_ALIGN
efi: ia64: disable the capsule loader
efi: stub: get rid of efi_get_max_fdt_addr()
efi/efi_test: read RuntimeServicesSupported
efi: arm: reduce minimum alignment of uncompressed kernel
efi: capsule: clean scatter-gather entries from the D-cache
efi: capsule: use atomic kmap for transient sglist mappings
efi: x86/xen: switch to efi_get_secureboot_mode helper
arm64/ima: add ima_arch support
ima: generalize x86/EFI arch glue for other EFI architectures
efi: generalize efi_get_secureboot
efi/libstub: EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER should not default to yes
efi/x86: Only copy the compressed kernel image in efi_relocate_kernel()
efi/libstub/x86: simplify efi_is_native()
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Currently, '--orphan-handling=warn' is spread out across four different
architectures in their respective Makefiles, which makes it a little
unruly to deal with in case it needs to be disabled for a specific
linker version (in this case, ld.lld 10.0.1).
To make it easier to control this, hoist this warning into Kconfig and
the main Makefile so that disabling it is simpler, as the warning will
only be enabled in a couple places (main Makefile and a couple of
compressed boot folders that blow away LDFLAGS_vmlinx) and making it
conditional is easier due to Kconfig syntax. One small additional
benefit of this is saving a call to ld-option on incremental builds
because we will have already evaluated it for CONFIG_LD_ORPHAN_WARN.
To keep the list of supported architectures the same, introduce
CONFIG_ARCH_WANT_LD_ORPHAN_WARN, which an architecture can select to
gain this automatically after all of the sections are specified and size
asserted. A special thanks to Kees Cook for the help text on this
config.
Link: https://github.com/ClangBuiltLinux/linux/issues/1187
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Generalize the efi_get_secureboot() function so not only efistub but also
other subsystems can use it.
Note that the MokSbState handling is not factored out: the variable is
boot time only, and so it cannot be parameterized as easily. Also, the
IMA code will switch to this version in a future patch, and it does not
incorporate the MokSbState exception in the first place.
Note that the new efi_get_secureboot_mode() helper treats any failures
to read SetupMode as setup mode being disabled.
Co-developed-by: Chester Lin <clin@suse.com>
Signed-off-by: Chester Lin <clin@suse.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV-ES support from Borislav Petkov:
"SEV-ES enhances the current guest memory encryption support called SEV
by also encrypting the guest register state, making the registers
inaccessible to the hypervisor by en-/decrypting them on world
switches. Thus, it adds additional protection to Linux guests against
exfiltration, control flow and rollback attacks.
With SEV-ES, the guest is in full control of what registers the
hypervisor can access. This is provided by a guest-host exchange
mechanism based on a new exception vector called VMM Communication
Exception (#VC), a new instruction called VMGEXIT and a shared
Guest-Host Communication Block which is a decrypted page shared
between the guest and the hypervisor.
Intercepts to the hypervisor become #VC exceptions in an SEV-ES guest
so in order for that exception mechanism to work, the early x86 init
code needed to be made able to handle exceptions, which, in itself,
brings a bunch of very nice cleanups and improvements to the early
boot code like an early page fault handler, allowing for on-demand
building of the identity mapping. With that, !KASLR configurations do
not use the EFI page table anymore but switch to a kernel-controlled
one.
The main part of this series adds the support for that new exchange
mechanism. The goal has been to keep this as much as possibly separate
from the core x86 code by concentrating the machinery in two
SEV-ES-specific files:
arch/x86/kernel/sev-es-shared.c
arch/x86/kernel/sev-es.c
Other interaction with core x86 code has been kept at minimum and
behind static keys to minimize the performance impact on !SEV-ES
setups.
Work by Joerg Roedel and Thomas Lendacky and others"
* tag 'x86_seves_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (73 commits)
x86/sev-es: Use GHCB accessor for setting the MMIO scratch buffer
x86/sev-es: Check required CPU features for SEV-ES
x86/efi: Add GHCB mappings when SEV-ES is active
x86/sev-es: Handle NMI State
x86/sev-es: Support CPU offline/online
x86/head/64: Don't call verify_cpu() on starting APs
x86/smpboot: Load TSS and getcpu GDT entry before loading IDT
x86/realmode: Setup AP jump table
x86/realmode: Add SEV-ES specific trampoline entry point
x86/vmware: Add VMware-specific handling for VMMCALL under SEV-ES
x86/kvm: Add KVM-specific VMMCALL handling under SEV-ES
x86/paravirt: Allow hypervisor-specific VMMCALL handling under SEV-ES
x86/sev-es: Handle #DB Events
x86/sev-es: Handle #AC Events
x86/sev-es: Handle VMMCALL Events
x86/sev-es: Handle MWAIT/MWAITX Events
x86/sev-es: Handle MONITOR/MONITORX Events
x86/sev-es: Handle INVD Events
x86/sev-es: Handle RDPMC Events
x86/sev-es: Handle RDTSC(P) Events
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull orphan section checking from Ingo Molnar:
"Orphan link sections were a long-standing source of obscure bugs,
because the heuristics that various linkers & compilers use to handle
them (include these bits into the output image vs discarding them
silently) are both highly idiosyncratic and also version dependent.
Instead of this historically problematic mess, this tree by Kees Cook
(et al) adds build time asserts and build time warnings if there's any
orphan section in the kernel or if a section is not sized as expected.
And because we relied on so many silent assumptions in this area, fix
a metric ton of dependencies and some outright bugs related to this,
before we can finally enable the checks on the x86, ARM and ARM64
platforms"
* tag 'core-build-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
x86/boot/compressed: Warn on orphan section placement
x86/build: Warn on orphan section placement
arm/boot: Warn on orphan section placement
arm/build: Warn on orphan section placement
arm64/build: Warn on orphan section placement
x86/boot/compressed: Add missing debugging sections to output
x86/boot/compressed: Remove, discard, or assert for unwanted sections
x86/boot/compressed: Reorganize zero-size section asserts
x86/build: Add asserts for unwanted sections
x86/build: Enforce an empty .got.plt section
x86/asm: Avoid generating unused kprobe sections
arm/boot: Handle all sections explicitly
arm/build: Assert for unwanted sections
arm/build: Add missing sections
arm/build: Explicitly keep .ARM.attributes sections
arm/build: Refactor linker script headers
arm64/build: Assert for unwanted sections
arm64/build: Add missing DWARF sections
arm64/build: Use common DISCARDS in linker script
arm64/build: Remove .eh_frame* sections due to unwind tables
...
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The x86-64 psABI [0] specifies special relocation types
(R_X86_64_[REX_]GOTPCRELX) for indirection through the Global Offset
Table, semantically equivalent to R_X86_64_GOTPCREL, which the linker
can take advantage of for optimization (relaxation) at link time. This
is supported by LLD and binutils versions 2.26 onwards.
The compressed kernel is position-independent code, however, when using
LLD or binutils versions before 2.27, it must be linked without the -pie
option. In this case, the linker may optimize certain instructions into
a non-position-independent form, by converting foo@GOTPCREL(%rip) to $foo.
This potential issue has been present with LLD and binutils-2.26 for a
long time, but it has never manifested itself before now:
- LLD and binutils-2.26 only relax
movq foo@GOTPCREL(%rip), %reg
to
leaq foo(%rip), %reg
which is still position-independent, rather than
mov $foo, %reg
which is permitted by the psABI when -pie is not enabled.
- GCC happens to only generate GOTPCREL relocations on mov instructions.
- CLang does generate GOTPCREL relocations on non-mov instructions, but
when building the compressed kernel, it uses its integrated assembler
(due to the redefinition of KBUILD_CFLAGS dropping -no-integrated-as),
which has so far defaulted to not generating the GOTPCRELX
relocations.
Nick Desaulniers reports [1,2]:
"A recent change [3] to a default value of configuration variable
(ENABLE_X86_RELAX_RELOCATIONS OFF -> ON) in LLVM now causes Clang's
integrated assembler to emit R_X86_64_GOTPCRELX/R_X86_64_REX_GOTPCRELX
relocations. LLD will relax instructions with these relocations based
on whether the image is being linked as position independent or not.
When not, then LLD will relax these instructions to use absolute
addressing mode (R_RELAX_GOT_PC_NOPIC). This causes kernels built with
Clang and linked with LLD to fail to boot."
Patch series [4] is a solution to allow the compressed kernel to be
linked with -pie unconditionally, but even if merged is unlikely to be
backported. As a simple solution that can be applied to stable as well,
prevent the assembler from generating the relaxed relocation types using
the -mrelax-relocations=no option. For ease of backporting, do this
unconditionally.
[0] https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/linker-optimization.tex#L65
[1] https://lore.kernel.org/lkml/20200807194100.3570838-1-ndesaulniers@google.com/
[2] https://github.com/ClangBuiltLinux/linux/issues/1121
[3] https://reviews.llvm.org/rGc41a18cf61790fc898dcda1055c3efbf442c14c0
[4] https://lore.kernel.org/lkml/20200731202738.2577854-1-nivedita@alum.mit.edu/
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200812004308.1448603-1-nivedita@alum.mit.edu
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Install an exception handler for #VC exception that uses a GHCB. Also
add the infrastructure for handling different exit-codes by decoding
the instruction that caused the exception and error handling.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-24-joro@8bytes.org
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Add the first handler for #VC exceptions. At stage 1 there is no GHCB
yet because the kernel might still be running on the EFI page table.
The stage 1 handler is limited to the MSR-based protocol to talk to the
hypervisor and can only support CPUID exit-codes, but that is enough to
get to stage 2.
[ bp: Zap superfluous newlines after rd/wrmsr instruction mnemonics. ]
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-20-joro@8bytes.org
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The file contains only code related to identity-mapped page tables.
Rename the file and compile it always in.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-15-joro@8bytes.org
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Add code needed to setup an IDT in the early pre-decompression
boot-code. The IDT is loaded first in startup_64, which is after
EfiExitBootServices() has been called, and later reloaded when the
kernel image has been relocated to the end of the decompression area.
This allows to setup different IDT handlers before and after the
relocation.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-14-joro@8bytes.org
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