kbuild: Consolidate C dialect options

Introduce CC_FLAGS_DIALECT to make it easier to update the various
places in the tree that rely on the GNU C standard and Microsoft
extensions flags atomically.

kbuild: Consolidate C dialect options

Introduce CC_FLAGS_DIALECT to make it easier to update the various
places in the tree that rely on the GNU C standard and Microsoft
extensions flags atomically. All remaining uses of '-std=gnu11' and
'-fms-extensions' are in the tools directory (which has its own build
system) and other standalone Makefiles. This will allow the kernel to
use a narrower option to enable the Microsoft anonymous tagged structure
extension in a simpler manner. Place the CC_FLAGS_DIALECT block after
the configuration include (so that a future change can move the
selection of the flag to Kconfig) but before the
arch/$(SRCARCH)/Makefile include (so that CC_FLAGS_DIALECT is available
for use in those Makefiles).

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Link: https://patch.msgid.link/20260223-fms-anonymous-structs-v1-1-8ee406d3c36c@kernel.org
Signed-off-by: Nicolas Schier <nsc@kernel.org>

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x86/entry/vdso: Update the object paths for "make vdso_install"

The location of the vdso binary files in the object tree has changed;
update "make vdso_install" to match.

Closes: https://lore.kerne

x86/entry/vdso: Update the object paths for "make vdso_install"

The location of the vdso binary files in the object tree has changed;
update "make vdso_install" to match.

Closes: https://lore.kernel.org/16ea64d1-2a9b-46f9-9fcc-42958f599eb6@leemhuis.info
Fixes: 693c819fedcd ("x86/entry/vdso: Refactor the vdso build")
Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260116204057.386268-2-hpa@zytor.com

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x86/entry/vdso: Move vdso2c to arch/x86/tools

It is generally better to build tools in arch/x86/tools to keep host
cflags proliferation down, and to reduce makefile sequencing issues.
Move the vdso

x86/entry/vdso: Move vdso2c to arch/x86/tools

It is generally better to build tools in arch/x86/tools to keep host
cflags proliferation down, and to reduce makefile sequencing issues.
Move the vdso build tool vdso2c into arch/x86/tools in preparation for
refactoring the vdso makefiles.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20251216212606.1325678-3-hpa@zytor.com

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Merge tag 'vfs-6.19-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull misc vfs updates from Christian Brauner:
"Features:

- Cheaper MAY_EXEC handling for path lookup. This

Merge tag 'vfs-6.19-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull misc vfs updates from Christian Brauner:
"Features:

- Cheaper MAY_EXEC handling for path lookup. This elides MAY_WRITE
permission checks during path lookup and adds the
IOP_FASTPERM_MAY_EXEC flag so filesystems like btrfs can avoid
expensive permission work.

- Hide dentry_cache behind runtime const machinery.

- Add German Maglione as virtiofs co-maintainer.

Cleanups:

- Tidy up and inline step_into() and walk_component() for improved
code generation.

- Re-enable IOCB_NOWAIT writes to files. This refactors file
timestamp update logic, fixing a layering bypass in btrfs when
updating timestamps on device files and improving FMODE_NOCMTIME
handling in VFS now that nfsd started using it.

- Path lookup optimizations extracting slowpaths into dedicated
routines and adding branch prediction hints for mntput_no_expire(),
fd_install(), lookup_slow(), and various other hot paths.

- Enable clang's -fms-extensions flag, requiring a JFS rename to
avoid conflicts.

- Remove spurious exports in fs/file_attr.c.

- Stop duplicating union pipe_index declaration. This depends on the
shared kbuild branch that brings in -fms-extensions support which
is merged into this branch.

- Use MD5 library instead of crypto_shash in ecryptfs.

- Use largest_zero_folio() in iomap_dio_zero().

- Replace simple_strtol/strtoul with kstrtoint/kstrtouint in init and
initrd code.

- Various typo fixes.

Fixes:

- Fix emergency sync for btrfs. Btrfs requires an explicit sync_fs()
call with wait == 1 to commit super blocks. The emergency sync path
never passed this, leaving btrfs data uncommitted during emergency
sync.

- Use local kmap in watch_queue's post_one_notification().

- Add hint prints in sb_set_blocksize() for LBS dependency on THP"

* tag 'vfs-6.19-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (35 commits)
MAINTAINERS: add German Maglione as virtiofs co-maintainer
fs: inline step_into() and walk_component()
fs: tidy up step_into() & friends before inlining
orangefs: use inode_update_timestamps directly
btrfs: fix the comment on btrfs_update_time
btrfs: use vfs_utimes to update file timestamps
fs: export vfs_utimes
fs: lift the FMODE_NOCMTIME check into file_update_time_flags
fs: refactor file timestamp update logic
include/linux/fs.h: trivial fix: regualr -> regular
fs/splice.c: trivial fix: pipes -> pipe's
fs: mark lookup_slow() as noinline
fs: add predicts based on nd->depth
fs: move mntput_no_expire() slowpath into a dedicated routine
fs: remove spurious exports in fs/file_attr.c
watch_queue: Use local kmap in post_one_notification()
fs: touch up predicts in path lookup
fs: move fd_install() slowpath into a dedicated routine and provide commentary
fs: hide dentry_cache behind runtime const machinery
fs: touch predicts in do_dentry_open()
...

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rust: kbuild: support `-Cjump-tables=n` for Rust 1.93.0

Rust 1.93.0 (expected 2026-01-22) is stabilizing `-Zno-jump-tables`
[1][2] as `-Cjump-tables=n` [3].

Without this change, one would eventuall

rust: kbuild: support `-Cjump-tables=n` for Rust 1.93.0

Rust 1.93.0 (expected 2026-01-22) is stabilizing `-Zno-jump-tables`
[1][2] as `-Cjump-tables=n` [3].

Without this change, one would eventually see:

RUSTC L rust/core.o
error: unknown unstable option: `no-jump-tables`

Thus support the upcoming version.

Link: https://github.com/rust-lang/rust/issues/116592 [1]
Link: https://github.com/rust-lang/rust/pull/105812 [2]
Link: https://github.com/rust-lang/rust/pull/145974 [3]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251101094011.1024534-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

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kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

This is a follow up to commit c4781dc3d1cf ("Kbuild: enable
-fms-extensions") but in a separate change due to being substantially
differe

kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

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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x86/build: Disable SSE4a

Leyvi Rose reported that his X86_NATIVE_CPU=y build is failing because our
instruction decoder doesn't support SSE4a and the AMDGPU code seems to be
generating those with hi

x86/build: Disable SSE4a

Leyvi Rose reported that his X86_NATIVE_CPU=y build is failing because our
instruction decoder doesn't support SSE4a and the AMDGPU code seems to be
generating those with his compiler of choice (CLANG+LTO).

Now, our normal build flags disable SSE MMX SSE2 3DNOW AVX, but then
CC_FLAGS_FPU re-enable SSE SSE2.

Since nothing mentions SSE3 or SSE4, I'm assuming that -msse (or its negative)
control all SSE variants -- but why then explicitly enumerate SSE2 ?

Anyway, until the instruction decoder gets fixed, explicitly disallow SSE4a
(an AMD specific SSE4 extension).

Fixes: ea1dcca1de12 ("x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Arisu Tachibana <arisu.tachibana@miraclelinux.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Cc: <stable@kernel.org>

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Merge tag 'x86_apic_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SEV and apic updates from Borislav Petkov:

- Add functionality to provide runtime firmware upda

Merge tag 'x86_apic_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SEV and apic updates from Borislav Petkov:

- Add functionality to provide runtime firmware updates for the non-x86
parts of an AMD platform like the security processor (ASP) firmware,
modules etc, for example. The intent being that these updates are
interim, live fixups before a proper BIOS update can be attempted

- Add guest support for AMD's Secure AVIC feature which gives encrypted
guests the needed protection against a malicious hypervisor
generating unexpected interrupts and injecting them into such guest,
thus interfering with its operation in an unexpected and negative
manner.

The advantage of this scheme is that the guest determines which
interrupts and when to accept them vs leaving that to the benevolence
(or not) of the hypervisor

- Strictly separate the startup code from the rest of the kernel where
former is executed from the initial 1:1 mapping of memory.

The problem was that the toolchain-generated version of the code was
being executed from a different mapping of memory than what was
"assumed" during code generation, needing an ever-growing pile of
fixups for absolute memory references which are invalid in the early,
1:1 memory mapping during boot.

The major advantage of this is that there's no need to check the 1:1
mapping portion of the code for absolute relocations anymore and get
rid of the RIP_REL_REF() macro sprinkling all over the place.

For more info, see Ard's very detailed writeup on this [1]

- The usual cleanups and fixes

Link: https://lore.kernel.org/r/CAMj1kXEzKEuePEiHB%2BHxvfQbFz0sTiHdn4B%2B%2BzVBJ2mhkPkQ4Q@mail.gmail.com [1]

* tag 'x86_apic_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits)
x86/boot: Drop erroneous __init annotation from early_set_pages_state()
crypto: ccp - Add AMD Seamless Firmware Servicing (SFS) driver
crypto: ccp - Add new HV-Fixed page allocation/free API
x86/sev: Add new dump_rmp parameter to snp_leak_pages() API
x86/startup/sev: Document the CPUID flow in the boot #VC handler
objtool: Ignore __pi___cfi_ prefixed symbols
x86/sev: Zap snp_abort()
x86/apic/savic: Do not use snp_abort()
x86/boot: Get rid of the .head.text section
x86/boot: Move startup code out of __head section
efistub/x86: Remap inittext read-execute when needed
x86/boot: Create a confined code area for startup code
x86/kbuild: Incorporate boot/startup/ via Kbuild makefile
x86/boot: Revert "Reject absolute references in .head.text"
x86/boot: Check startup code for absence of absolute relocations
objtool: Add action to check for absence of absolute relocations
x86/sev: Export startup routines for later use
x86/sev: Move __sev_[get|put]_ghcb() into separate noinstr object
x86/sev: Provide PIC aliases for SEV related data objects
x86/boot: Provide PIC aliases for 5-level paging related constants
...

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x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

Using core-y is not the correct way to get kbuild to descend into
arch/x86/boot/startup. For instance, building an individual object does
no

x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

Using core-y is not the correct way to get kbuild to descend into
arch/x86/boot/startup. For instance, building an individual object does
not work as expected when the pattern rule is local to the Makefile

$ make arch/x86/boot/startup/map_kernel.pi.o
GEN Makefile
CALL /home/ardb/linux/scripts/checksyscalls.sh
DESCEND objtool
INSTALL libsubcmd_headers
make[3]: *** No rule to make target 'arch/x86/boot/startup/map_kernel.pi.o'. Stop.
make[2]: *** [/home/ardb/linux/scripts/Makefile.build:461: arch/x86] Error 2
make[1]: *** [/home/ardb/linux/Makefile:2011: .] Error 2
make: *** [/home/ardb/linux/Makefile:248: __sub-make] Error 2

So use obj-y from arch.x86/Kbuild instead, which makes things work as
expected.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-42-ardb+git@google.com

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x86/build: Remove cc-option from -mskip-rax-setup

This has been supported in GCC since 5.1 and clang since 14.0. Now that x86
requires LLVM 15 or newer since

7861640aac52 ("x86/build: Raise the m

x86/build: Remove cc-option from -mskip-rax-setup

This has been supported in GCC since 5.1 and clang since 14.0. Now that x86
requires LLVM 15 or newer since

7861640aac52 ("x86/build: Raise the minimum LLVM version to 15.0.0"),

this flag can be unconditionally added, saving a compiler invocation.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=fbe575b652f5bdcc459f447a0e6f0e059996d4ef
Link: https://github.com/llvm/llvm-project/commit/a9fba2be35db674971382e38b99a31403444d9bf
Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-5-ff7f19457523@kernel.org

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x86/build: Remove cc-option from -mno-fp-ret-in-387

This has been supported in GCC for forever and clang gained support for it as
an alias of '-mno-x87' in LLVM 14. Now that x86 requires LLVM 15 or

x86/build: Remove cc-option from -mno-fp-ret-in-387

This has been supported in GCC for forever and clang gained support for it as
an alias of '-mno-x87' in LLVM 14. Now that x86 requires LLVM 15 or newer
since

7861640aac52 ("x86/build: Raise the minimum LLVM version to 15.0.0"),

this flag can be unconditionally added, saving a compiler invocation.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://github.com/llvm/llvm-project/commit/a9fba2be35db674971382e38b99a31403444d9bf
Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-4-ff7f19457523@kernel.org

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x86/build: Clean up stack alignment flags in CC_FLAGS_FPU

The minimum supported version of GCC to build the x86 kernel was bumped
to GCC 8.1 in

a3e8fe814ad1 ("x86/build: Raise the minimum GCC ver

x86/build: Clean up stack alignment flags in CC_FLAGS_FPU

The minimum supported version of GCC to build the x86 kernel was bumped
to GCC 8.1 in

a3e8fe814ad1 ("x86/build: Raise the minimum GCC version to 8.1").

Prior to GCC 7.1, '-mpreferred-stack-boundary=3' was not allowed with
'-msse', so areas of the kernel that needed floating point had a
different alignment. Now that GCC > 7.1 is mandatory, there is no need
to have a different value of '-mpreferred-stack-boundary' from the rest
of the kernel, so remove this handling from CC_FLAGS_FPU.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=34fac449e121be97dd073c5428cc855367b2872c
Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-3-ff7f19457523@kernel.org

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x86/build: Remove cc-option from stack alignment flags

'-mpreferred-stack-boundary' (the GCC option) and '-mstack-alignment'
(the clang option) have been supported in their respective compilers for

x86/build: Remove cc-option from stack alignment flags

'-mpreferred-stack-boundary' (the GCC option) and '-mstack-alignment'
(the clang option) have been supported in their respective compilers for
some time, so it is unnecessary to check for support for them via
cc-option. '-mpreferred-stack-boundary=3' had a restriction on
'-mno-sse' until GCC 7.1 but that is irrelevant for most of the kernel,
which includes '-mno-sse'.

Move to simple Kconfig checks to avoid querying the compiler for the
flags that it supports.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-2-ff7f19457523@kernel.org

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x86/build: Remove cc-option for GCC retpoline flags

The minimum supported version of GCC to build the x86 kernel was bumped
to GCC 8.1 in

a3e8fe814ad1 ("x86/build: Raise the minimum GCC version t

x86/build: Remove cc-option for GCC retpoline flags

The minimum supported version of GCC to build the x86 kernel was bumped
to GCC 8.1 in

a3e8fe814ad1 ("x86/build: Raise the minimum GCC version to 8.1").

'-mindirect-branch' and '-mindirect-branch-register' were first supported in
GCC 8.1, so there is no need to call cc-option to inquire if it is supported.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=da99fd4a3ca06b43b08ba8d96dab84e83ac90aa7
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=d543c04b795f8af4ebe5b3d5f38156ef4e5734f1
Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-1-ff7f19457523@kernel.org

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Merge tag 'x86-build-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Ingo Molnar:
"Add the CONFIG_X86_NATIVE_CPU=y build option to locally optimize

Merge tag 'x86-build-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Ingo Molnar:
"Add the CONFIG_X86_NATIVE_CPU=y build option to locally optimize the
kernel build with '-march=native'"

* tag 'x86-build-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/kbuild/64: Restrict clang versions that can use '-march=native'
x86/kbuild/64: Test for the availability of the -mtune=native compiler flag
x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'

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x86/boot: Move the 5-level paging trampoline into /startup

The 5-level paging trampoline is used by both the EFI stub and the
traditional decompressor. Move it out of the decompressor sources into
t

x86/boot: Move the 5-level paging trampoline into /startup

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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Merge tag 'kbuild-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

- Improve performance in gendwarfksyms

- Remove depreca

Merge tag 'kbuild-v6.15' of 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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x86: don't re-generate cpufeaturemasks.h so eagerly

It turns out the code to generate the x86 cpufeaturemasks.h header was
way too aggressive, and would re-generate it whenever the timestamp on
the

x86: don't re-generate cpufeaturemasks.h so eagerly

It turns out the code to generate the x86 cpufeaturemasks.h header was
way too aggressive, and would re-generate it whenever the timestamp on
the kernel config file changed.

Now, the regular 'make *config' tools are fairly careful to not rewrite
the kernel config file unless the contents change, but other usecases
aren't that careful.

Michael Kelley reports that 'make-kpkg' ends up doing "make syncconfig"
multiple times in prepping to build, and will modify the config file in
the process (and then modify it back, but by then the timestamps have
changed).

Jakub Kicinski reports that the netdev CI does something similar in how
it generates the config file in multiple steps.

In both cases, the config file timestamp updates then cause the
cpufeaturemasks.h file to be regenerated, and that in turn then causes
lots of unnecessary rebuilds due to all the normal dependencies.

Fix it by using our 'filechk' infrastructure in the Makefile to generate
the header file. That will only write a new version of the file if the
contents of the file have actually changed.

Fixes: 841326332bcb ("x86/cpufeatures: Generate the <asm/cpufeaturemasks.h> header based on build config")
Reported-by: Michael Kelley <mhklinux@outlook.com>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/all/SN6PR02MB415756D1829740F6E8AC11D1D4D82@SN6PR02MB4157.namprd02.prod.outlook.com/
Link: https://lore.kernel.org/all/20250328162311.08134fa6@kernel.org/
Cc: Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'

Add a 'native' option that allows users to build an optimized kernel for
their local machine (

x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'

Add a 'native' option that allows users to build an optimized kernel for
their local machine (i.e. the machine which is used to build the kernel)
by passing '-march=native' to CFLAGS.

The idea comes from Linus' reply to Arnd's initial proposal:

https://lore.kernel.org/all/CAHk-=wji1sV93yKbc==Z7OSSHBiDE=LAdG_d5Y-zPBrnSs0k2A@mail.gmail.com/

Here are some numbers comparing 'generic' to 'native' on a Skylake dual-core
laptop (generic --> native):

- vmlinux and compressed modules size:
125'907'744 bytes --> 125'595'280 bytes (-0.248 %)
18'810 kilobytes --> 18'770 kilobytes (-0.213 %)

- phoronix, average of 3 runs:
ffmpeg:
130.99 --> 131.15 (+0.122 %)
nginx:
10'650 --> 10'725 (+0.704 %)
hackbench (lower is better):
102.27 --> 99.50 (-2.709 %)

- xz compression of firefox tarball (lower is better):
319.57 seconds --> 317.34 seconds (-0.698 %)

- stress-ng, bogoops, average of 3 15-second runs:
fork:
111'744 --> 115'509 (+3.397 %)
bsearch:
7'211 --> 7'436 (+3.120 %)
memfd:
3'591 --> 3'604 (+0.362 %)
mmapfork:
630 --> 629 (-0.159 %)
schedmix:
42'715 --> 43'251 (+1.255 %)
epoll:
2'443'767 --> 2'454'413 (+0.436 %)
vm:
1'442'256 --> 1'486'615 (+3.076 %)

- schbench (two message threads), 30-second runs:
304 rps --> 305 rps (+0.329 %)

There is little difference both in terms of size and of performance, however
the native build comes out on top ever so slightly.

[ mingo: Renamed the option to CONFIG_X86_NATIVE_CPU, expanded the help text
and added Linus's Suggested-by tag. ]

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Tor Vic <torvic9@mailbox.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250321142859.13889-1-torvic9@mailbox.org

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Merge tag 'x86-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core x86 updates from Ingo Molnar:
"x86 CPU features support:
- Generate the <asm/cpufeaturemasks.h>

Merge tag 'x86-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core x86 updates from Ingo Molnar:
"x86 CPU features support:
- Generate the <asm/cpufeaturemasks.h> header based on build config
(H. Peter Anvin, Xin Li)
- x86 CPUID parsing updates and fixes (Ahmed S. Darwish)
- Introduce the 'setcpuid=' boot parameter (Brendan Jackman)
- Enable modifying CPU bug flags with '{clear,set}puid=' (Brendan
Jackman)
- Utilize CPU-type for CPU matching (Pawan Gupta)
- Warn about unmet CPU feature dependencies (Sohil Mehta)
- Prepare for new Intel Family numbers (Sohil Mehta)

Percpu code:
- Standardize & reorganize the x86 percpu layout and related cleanups
(Brian Gerst)
- Convert the stackprotector canary to a regular percpu variable
(Brian Gerst)
- Add a percpu subsection for cache hot data (Brian Gerst)
- Unify __pcpu_op{1,2}_N() macros to __pcpu_op_N() (Uros Bizjak)
- Construct __percpu_seg_override from __percpu_seg (Uros Bizjak)

MM:
- Add support for broadcast TLB invalidation using AMD's INVLPGB
instruction (Rik van Riel)
- Rework ROX cache to avoid writable copy (Mike Rapoport)
- PAT: restore large ROX pages after fragmentation (Kirill A.
Shutemov, Mike Rapoport)
- Make memremap(MEMREMAP_WB) map memory as encrypted by default
(Kirill A. Shutemov)
- Robustify page table initialization (Kirill A. Shutemov)
- Fix flush_tlb_range() when used for zapping normal PMDs (Jann Horn)
- Clear _PAGE_DIRTY for kernel mappings when we clear _PAGE_RW
(Matthew Wilcox)

KASLR:
- x86/kaslr: Reduce KASLR entropy on most x86 systems, to support PCI
BAR space beyond the 10TiB region (CONFIG_PCI_P2PDMA=y) (Balbir
Singh)

CPU bugs:
- Implement FineIBT-BHI mitigation (Peter Zijlstra)
- speculation: Simplify and make CALL_NOSPEC consistent (Pawan Gupta)
- speculation: Add a conditional CS prefix to CALL_NOSPEC (Pawan
Gupta)
- RFDS: Exclude P-only parts from the RFDS affected list (Pawan
Gupta)

System calls:
- Break up entry/common.c (Brian Gerst)
- Move sysctls into arch/x86 (Joel Granados)

Intel LAM support updates: (Maciej Wieczor-Retman)
- selftests/lam: Move cpu_has_la57() to use cpuinfo flag
- selftests/lam: Skip test if LAM is disabled
- selftests/lam: Test get_user() LAM pointer handling

AMD SMN access updates:
- Add SMN offsets to exclusive region access (Mario Limonciello)
- Add support for debugfs access to SMN registers (Mario Limonciello)
- Have HSMP use SMN through AMD_NODE (Yazen Ghannam)

Power management updates: (Patryk Wlazlyn)
- Allow calling mwait_play_dead with an arbitrary hint
- ACPI/processor_idle: Add FFH state handling
- intel_idle: Provide the default enter_dead() handler
- Eliminate mwait_play_dead_cpuid_hint()

Build system:
- Raise the minimum GCC version to 8.1 (Brian Gerst)
- Raise the minimum LLVM version to 15.0.0 (Nathan Chancellor)

Kconfig: (Arnd Bergmann)
- Add cmpxchg8b support back to Geode CPUs
- Drop 32-bit "bigsmp" machine support
- Rework CONFIG_GENERIC_CPU compiler flags
- Drop configuration options for early 64-bit CPUs
- Remove CONFIG_HIGHMEM64G support
- Drop CONFIG_SWIOTLB for PAE
- Drop support for CONFIG_HIGHPTE
- Document CONFIG_X86_INTEL_MID as 64-bit-only
- Remove old STA2x11 support
- Only allow CONFIG_EISA for 32-bit

Headers:
- Replace __ASSEMBLY__ with __ASSEMBLER__ in UAPI and non-UAPI
headers (Thomas Huth)

Assembly code & machine code patching:
- x86/alternatives: Simplify alternative_call() interface (Josh
Poimboeuf)
- x86/alternatives: Simplify callthunk patching (Peter Zijlstra)
- KVM: VMX: Use named operands in inline asm (Josh Poimboeuf)
- x86/hyperv: Use named operands in inline asm (Josh Poimboeuf)
- x86/traps: Cleanup and robustify decode_bug() (Peter Zijlstra)
- x86/kexec: Merge x86_32 and x86_64 code using macros from
<asm/asm.h> (Uros Bizjak)
- Use named operands in inline asm (Uros Bizjak)
- Improve performance by using asm_inline() for atomic locking
instructions (Uros Bizjak)

Earlyprintk:
- Harden early_serial (Peter Zijlstra)

NMI handler:
- Add an emergency handler in nmi_desc & use it in
nmi_shootdown_cpus() (Waiman Long)

Miscellaneous fixes and cleanups:
- by Ahmed S. Darwish, Andy Shevchenko, Ard Biesheuvel, Artem
Bityutskiy, Borislav Petkov, Brendan Jackman, Brian Gerst, Dan
Carpenter, Dr. David Alan Gilbert, H. Peter Anvin, Ingo Molnar,
Josh Poimboeuf, Kevin Brodsky, Mike Rapoport, Lukas Bulwahn, Maciej
Wieczor-Retman, Max Grobecker, Patryk Wlazlyn, Pawan Gupta, Peter
Zijlstra, Philip Redkin, Qasim Ijaz, Rik van Riel, Thomas Gleixner,
Thorsten Blum, Tom Lendacky, Tony Luck, Uros Bizjak, Vitaly
Kuznetsov, Xin Li, liuye"

* tag 'x86-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (211 commits)
zstd: Increase DYNAMIC_BMI2 GCC version cutoff from 4.8 to 11.0 to work around compiler segfault
x86/asm: Make asm export of __ref_stack_chk_guard unconditional
x86/mm: Only do broadcast flush from reclaim if pages were unmapped
perf/x86/intel, x86/cpu: Replace Pentium 4 model checks with VFM ones
perf/x86/intel, x86/cpu: Simplify Intel PMU initialization
x86/headers: Replace __ASSEMBLY__ with __ASSEMBLER__ in non-UAPI headers
x86/headers: Replace __ASSEMBLY__ with __ASSEMBLER__ in UAPI headers
x86/locking/atomic: Improve performance by using asm_inline() for atomic locking instructions
x86/asm: Use asm_inline() instead of asm() in clwb()
x86/asm: Use CLFLUSHOPT and CLWB mnemonics in <asm/special_insns.h>
x86/hweight: Use asm_inline() instead of asm()
x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()
x86/hweight: Use named operands in inline asm()
x86/stackprotector/64: Only export __ref_stack_chk_guard on CONFIG_SMP
x86/head/64: Avoid Clang < 17 stack protector in startup code
x86/kexec: Merge x86_32 and x86_64 code using macros from <asm/asm.h>
x86/runtime-const: Add the RUNTIME_CONST_PTR assembly macro
x86/cpu/intel: Limit the non-architectural constant_tsc model checks
x86/mm/pat: Replace Intel x86_model checks with VFM ones
x86/cpu/intel: Fix fast string initialization for extended Families
...

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x86/cpufeatures: Generate the <asm/cpufeaturemasks.h> header based on build config

Introduce an AWK script to auto-generate the <asm/cpufeaturemasks.h> header
with required and disabled feature mask

x86/cpufeatures: Generate the <asm/cpufeaturemasks.h> header based on build config

Introduce an AWK script to auto-generate the <asm/cpufeaturemasks.h> header
with required and disabled feature masks based on <asm/cpufeatures.h>
and the current build config.

Thus for any CPU feature with a build config, e.g., X86_FRED, simply add:

config X86_DISABLED_FEATURE_FRED
def_bool y
depends on !X86_FRED

to arch/x86/Kconfig.cpufeatures, instead of adding a conditional CPU
feature disable flag, e.g., DISABLE_FRED.

Lastly, the generated required and disabled feature masks will be added to
their corresponding feature masks for this particular compile-time
configuration.

[ Xin: build integration improvements ]
[ mingo: Improved changelog and comments ]

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250305184725.3341760-3-xin@zytor.com

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kbuild: Introduce Kconfig symbol for linking vmlinux with relocations

Some architectures build vmlinux with static relocations preserved, but
strip them again from the final vmlinux image. Arch spec

kbuild: Introduce Kconfig symbol for linking vmlinux with relocations

Some architectures build vmlinux with static relocations preserved, but
strip them again from the final vmlinux image. Arch specific tools
consume these static relocations in order to construct relocation tables
for KASLR.

The fact that vmlinux is created, consumed and subsequently updated goes
against the typical, declarative paradigm used by Make, which is based
on rules and dependencies. So as a first step towards cleaning this up,
introduce a Kconfig symbol to declare that the arch wants to consume the
static relocations emitted into vmlinux. This will be wired up further
in subsequent patches.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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hardening: Enable i386 FORTIFY_SOURCE on Clang 16+

The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed
in Clang 16[1].

Link: https://github.com/llvm/llvm-project/commit/c167c0a4dc

hardening: Enable i386 FORTIFY_SOURCE on Clang 16+

The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed
in Clang 16[1].

Link: https://github.com/llvm/llvm-project/commit/c167c0a4dcdb998affb2756ce76903a12f7d8ca5 [1]
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250308042929.1753543-2-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

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x86/build: Remove -ffreestanding on i386 with GCC

The use of -ffreestanding is a leftover that is only needed for certain
versions of Clang. Adjust this to be Clang-only. A later patch will make
thi

x86/build: Remove -ffreestanding on i386 with GCC

The use of -ffreestanding is a leftover that is only needed for certain
versions of Clang. Adjust this to be Clang-only. A later patch will make
this a versioned check.

Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250308042929.1753543-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

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Merge branch 'x86/cpu' into x86/asm, to pick up dependent commits

Signed-off-by: Ingo Molnar <mingo@kernel.org>