In preparation for strtomem*() checking that its destination is a
__nonstring, annotate "nonstring" and "nonstring_small" variables
accordingly.
Signed-off-by: Kees Cook <kees@kernel.org>
Replace X86_CMPXCHG64 with X86_CX8, as CX8 is the name of the CPUID
flag, thus to make it consistent with X86_FEATURE_CX8 defined in
<asm/cpufeatures.h>.
No functional change intended.
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>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250228082338.73859-2-xin@zytor.com
Introduce free_pages_nolock() that can free pages without taking locks.
It relies on trylock and can be called from any context.
Since spin_trylock() cannot be used in PREEMPT_RT from hard IRQ or NMI
it uses lockless link list to stash the pages which will be freed
by subsequent free_pages() from good context.
Do not use llist unconditionally. BPF maps continuously
allocate/free, so we cannot unconditionally delay the freeing to
llist. When the memory becomes free make it available to the
kernel and BPF users right away if possible, and fallback to
llist as the last resort.
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20250222024427.30294-4-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tracing BPF programs execute from tracepoints and kprobes where
running context is unknown, but they need to request additional
memory. The prior workarounds were using pre-allocated memory and
BPF specific freelists to satisfy such allocation requests.
Instead, introduce gfpflags_allow_spinning() condition that signals
to the allocator that running context is unknown.
Then rely on percpu free list of pages to allocate a page.
try_alloc_pages() -> get_page_from_freelist() -> rmqueue() ->
rmqueue_pcplist() will spin_trylock to grab the page from percpu
free list. If it fails (due to re-entrancy or list being empty)
then rmqueue_bulk()/rmqueue_buddy() will attempt to
spin_trylock zone->lock and grab the page from there.
spin_trylock() is not safe in PREEMPT_RT when in NMI or in hard IRQ.
Bailout early in such case.
The support for gfpflags_allow_spinning() mode for free_page and memcg
comes in the next patches.
This is a first step towards supporting BPF requirements in SLUB
and getting rid of bpf_mem_alloc.
That goal was discussed at LSFMM: https://lwn.net/Articles/974138/
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20250222024427.30294-3-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
A common task for most drivers is to remember the user-set CPU affinity
to its IRQs. On each netdev reset, the driver should re-assign the user's
settings to the IRQs. Unify this task across all drivers by moving the CPU
affinity to napi->config.
However, to move the CPU affinity to core, we also need to move aRFS
rmap management since aRFS uses its own IRQ notifiers.
For the aRFS, add a new netdev flag "rx_cpu_rmap_auto". Drivers supporting
aRFS should set the flag via netif_enable_cpu_rmap() and core will allocate
and manage the aRFS rmaps. Freeing the rmap is also done by core when the
netdev is freed. For better IRQ affinity management, move the IRQ rmap
notifier inside the napi_struct and add new notify.notify and
notify.release functions: netif_irq_cpu_rmap_notify() and
netif_napi_affinity_release().
Now we have the aRFS rmap management in core, add CPU affinity mask to
napi_config. To delegate the CPU affinity management to the core, drivers
must:
1 - set the new netdev flag "irq_affinity_auto":
netif_enable_irq_affinity(netdev)
2 - create the napi with persistent config:
netif_napi_add_config()
3 - bind an IRQ to the napi instance: netif_napi_set_irq()
the core will then make sure to use re-assign affinity to the napi's
IRQ.
The default IRQ mask is set to one cpu starting from the closest NUMA.
Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Link: https://patch.msgid.link/20250224232228.990783-2-ahmed.zaki@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now that we have cpumask_next_wrap() wired to generic find_next_bit_wrap(),
the old implementation is not needed.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Now that cpumask_next{_and}_wrap() is wired to generic
find_next_bit_wrap(), we can use it in cpumask_any{_and}_distribute().
This automatically makes the cpumask_*_distribute() functions to use
small_cpumask_bits instead of nr_cpumask_bits, which itself is a good
optimization.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
The next patch aligns implementation of cpumask_next_wrap() with the
find_next_bit_wrap(), and it changes function signature.
To make the transition smooth, this patch deprecates current
implementation by adding an _old suffix. The following patches switch
current users to the new implementation one by one.
No functional changes were intended.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
The HAVE_ARCH Kconfig options in lib/crypto try to solve the
modular versus built-in problem, but it still fails when the
the LIB option (e.g., CRYPTO_LIB_CURVE25519) is selected externally.
Fix this by introducing a level of indirection with ARCH_MAY_HAVE
Kconfig options, these then go on to select the ARCH_HAVE options
if the ARCH Kconfig options matches that of the LIB option.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501230223.ikroNDr1-lkp@intel.com/
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
All users of the time releated parts of the vDSO are now using the generic
storage implementation. Remove the therefore unnecessary compatibility
accessor functions and symbols.
Co-developed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-18-13a4669dfc8c@linutronix.de
Some architectures need to expose architecture-specific data to the vDSO.
Enable the generic vDSO storage mechanism to both store and map this
data. Some architectures require more than a single page, like LoongArch,
so prepare for that usecase, too.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-7-13a4669dfc8c@linutronix.de
Extend the generic vDSO data storage with a page for the random state data.
The random state data is stored in a dedicated page, as the existing
storage page is only meant for time-related, time-namespace-aware data.
This simplifies to access logic to not need to handle time namespaces
anymore and also frees up more space in the time-related page.
In case further generic vDSO data store is required it can be added to
the random state page.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-6-13a4669dfc8c@linutronix.de
Historically each architecture defined their own way to store the vDSO
data page. Add a generic mechanism to provide storage for that page.
Furthermore this generic storage will be extended to also provide
uniform storage for *non*-time-related data, like the random state or
architecture-specific data. These will have their own pages and data
structures, so rename 'vdso_data' into 'vdso_time_data' to make that
split clear from the name.
Also introduce a new consistent naming scheme for the symbols related to
the vDSO, which makes it clear if the symbol is accessible from
userspace or kernel space and the type of data behind the symbol.
The generic fault handler contains an optimization to prefault the vvar
page when the timens page is accessed. This was lifted from s390 and x86.
Co-developed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-5-13a4669dfc8c@linutronix.de
As the Makefile is included into other Makefiles it can not be used to
define objects to be built from the current source directory.
However the generic datastore will introduce such a local source file.
Rename the included Makefile so it is clear how it is to be used and to
make room for a regular Makefile in lib/vdso/.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-4-13a4669dfc8c@linutronix.de
Describe that it tests the miscdevice API and include the usual disclaimer
about KUnit not being fit for production kernels.
While at it, also fix KUnit capitalization.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://lore.kernel.org/r/20250123123249.4081674-2-cascardo@igalia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This has been unused since commit 3aa56885e5 ("bitmap: replace
bitmap_{from,to}_u32array") in 2018.
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
hrtimer_setup() takes the callback function pointer as argument and
initializes the timer completely.
Replace hrtimer_init() and the open coded initialization of
hrtimer::function with the new setup mechanism.
Patch was created by using Coccinelle.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/edc46fbf290b280ebe67bb0d21599c4c30716b68.1738746821.git.namcao@linutronix.de
In case CONFIG_XARRAY_MULTI is not defined, xa_store_order can store a
multi-index entry but xas_for_each can't tell sbiling entry from valid
entry. So the check_pause failed when we store a multi-index entry and
wish xas_for_each can handle it normally. Avoid to store multi-index
entry when CONFIG_XARRAY_MULTI is disabled to fix the failure.
Link: https://lkml.kernel.org/r/20250213163659.414309-1-shikemeng@huaweicloud.com
Fixes: c9ba5249ef ("Xarray: move forward index correctly in xas_pause()")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/r/CAMuHMdU_bfadUO=0OZ=AoQ9EAmQPA4wsLCBqohXR+QCeCKRn4A@mail.gmail.com
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
import_iovec() says that it should always be fine to kfree the iovec
returned in @iovp regardless of the error code. __import_iovec_ubuf()
never reallocates it and thus should clear the pointer even in cases when
copy_iovec_*() fail.
Link: https://lkml.kernel.org/r/378ae26923ffc20fd5e41b4360d673bf47b1775b.1738332461.git.asml.silence@gmail.com
Fixes: 3b2deb0e46 ("iov_iter: import single vector iovecs as ITER_UBUF")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Extract a private header and convert the prime_numbers self-test to a
KUnit test. I considered parameterizing the test using
`KUNIT_CASE_PARAM` but didn't see how it was possible since the test
logic is entangled with the test parameter generation logic.
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250208-prime_numbers-kunit-convert-v5-2-b0cb82ae7c7d@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>
Add a KUnit test suite for the gcd() function.
This test suite verifies the correctness of gcd() across various
scenarios, including edge cases.
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Link: https://lore.kernel.org/r/20250203075400.3431330-1-eleanor15x@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>
This commit introduces KUnit tests for the intlog2 and intlog10
functions, which compute logarithms in base 2 and base 10, respectively.
The tests cover a range of inputs to ensure the correctness of these
functions across common and edge cases.
Signed-off-by: Bruno Sobreira França <brunofrancadevsec@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Link: https://lore.kernel.org/r/20241202075545.3648096-3-davidgow@google.com
Signed-off-by: Kees Cook <kees@kernel.org>
The static code analysis tool "Coverity Scan" pointed the following
implementation details out for further development considerations:
CID 1309755: Unused value
In sw842_compress: A value assigned to a variable is never used. (CWE-563)
returned_value: Assigning value from add_repeat_template(p, repeat_count)
to ret here, but that stored value is overwritten before it can be used.
Conclusion:
Add error handling for the return value from an add_repeat_template()
call.
Fixes: 2da572c959 ("lib: add software 842 compression/decompression")
Signed-off-by: Tanya Agarwal <tanyaagarwal25699@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Following the standardization on crc32c() as the lib entry point for the
Castagnoli CRC32 instead of the previous mix of crc32c(), crc32c_le(),
and __crc32c_le(), make the same change to the underlying base and arch
functions that implement it.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-7-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Since the Castagnoli CRC32 is now always just crc32c(), rename
__crc32c_le_combine() and __crc32c_le_shift() accordingly.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Drop the use of __pure and __attribute_const__ from the CRC32 library
functions that had them. Both of these are unusual optimizations that
don't help properly written code. They seem more likely to cause
problems than have any real benefit.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Add support for architecture-optimized implementations of the CRC64
library functions, following the approach taken for the CRC32 and
CRC-T10DIF library functions.
Also take the opportunity to tweak the function prototypes:
- Use 'const void *' for the lib entry points (since this is easier for
users) but 'const u8 *' for the underlying arch and generic functions
(since this is easier for the implementations of these functions).
- Don't bother with __pure. It's an unusual optimization that doesn't
help properly written code. It's a weird quirk we can do without.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20250130035130.180676-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Wire up crc64_nvme() to the new CRC unit test and benchmark.
This replaces and improves on the test coverage that was lost by
removing this CRC variant from the crypto API.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20250130035130.180676-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This CRC64 variant comes from the NVME NVM Command Set Specification
(https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0e-2024.07.29-Ratified.pdf).
The "Rocksoft Model CRC Algorithm", published in 1993 and available at
https://www.zlib.net/crc_v3.txt, is a generalized CRC algorithm that can
calculate any variant of CRC, given a list of parameters such as
polynomial, bit order, etc. It is not a CRC variant.
The NVME NVM Command Set Specification has a table that gives the
"Rocksoft Model Parameters" for the CRC variant it uses. When support
for this CRC variant was added to Linux, this table seems to have been
misinterpreted as naming the CRC variant the "Rocksoft" CRC. In fact,
the table names the CRC variant as the "NVM Express 64b CRC".
Most implementations of this CRC variant outside Linux have been calling
it CRC64-NVME. Therefore, update Linux to match.
While at it, remove the superfluous "update" from the function name, so
crc64_rocksoft_update() is now just crc64_nvme(), matching most of the
other CRC library functions.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20250130035130.180676-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Following what was done for the CRC32 and CRC-T10DIF library functions,
get rid of the pointless use of the crypto API and make
crc64_rocksoft_update() call into the library directly. This is faster
and simpler.
Remove crc64_rocksoft() (the version of the function that did not take a
'crc' argument) since it is unused.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20250130035130.180676-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
- Fix stackinit KUnit regression on m68k
- Use ARRAY_SIZE() for memtostr*()/strtomem*()
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Merge tag 'hardening-v6.14-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening fixes from Kees Cook:
"Address a KUnit stack initialization regression that got tickled on
m68k, and solve a Clang(v14 and earlier) bug found by 0day:
- Fix stackinit KUnit regression on m68k
- Use ARRAY_SIZE() for memtostr*()/strtomem*()"
* tag 'hardening-v6.14-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
string.h: Use ARRAY_SIZE() for memtostr*()/strtomem*()
compiler.h: Introduce __must_be_byte_array()
compiler.h: Move C string helpers into C-only kernel section
stackinit: Fix comment for test_small_end
stackinit: Keep selftest union size small on m68k
13 are for MM and 8 are for non-MM. All are singletons, please see the
changelogs for details.
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Merge tag 'mm-hotfixes-stable-2025-02-01-03-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton:
"21 hotfixes. 8 are cc:stable and the remainder address post-6.13
issues. 13 are for MM and 8 are for non-MM.
All are singletons, please see the changelogs for details"
* tag 'mm-hotfixes-stable-2025-02-01-03-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (21 commits)
MAINTAINERS: include linux-mm for xarray maintenance
revert "xarray: port tests to kunit"
MAINTAINERS: add lib/test_xarray.c
mailmap, MAINTAINERS, docs: update Carlos's email address
mm/hugetlb: fix hugepage allocation for interleaved memory nodes
mm: gup: fix infinite loop within __get_longterm_locked
mm, swap: fix reclaim offset calculation error during allocation
.mailmap: update email address for Christopher Obbard
kfence: skip __GFP_THISNODE allocations on NUMA systems
nilfs2: fix possible int overflows in nilfs_fiemap()
mm: compaction: use the proper flag to determine watermarks
kernel: be more careful about dup_mmap() failures and uprobe registering
mm/fake-numa: handle cases with no SRAT info
mm: kmemleak: fix upper boundary check for physical address objects
mailmap: add an entry for Hamza Mahfooz
MAINTAINERS: mailmap: update Yosry Ahmed's email address
scripts/gdb: fix aarch64 userspace detection in get_current_task
mm/vmscan: accumulate nr_demoted for accurate demotion statistics
ocfs2: fix incorrect CPU endianness conversion causing mount failure
mm/zsmalloc: add __maybe_unused attribute for is_first_zpdesc()
...
Revert c7bb5cf9fc ("xarray: port tests to kunit"). It broke the build
when compiing the xarray userspace test harness code.
Reported-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Closes: https://lkml.kernel.org/r/07cf896e-adf8-414f-a629-a808fc26014a@oracle.com
Cc: David Gow <davidgow@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Tamir Duberstein <tamird@gmail.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
- Fix regression in GCC 15's initialization of union members
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Merge tag 'hardening-v6.14-rc1-fix1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening fixes from Kees Cook:
"This is a fix for the soon to be released GCC 15 which has regressed
its initialization of unions when performing explicit initialization
(i.e. a general problem, not specifically a hardening problem; we're
just carrying the fix).
Details in the final patch, Acked by Masahiro, with updated selftests
to validate the fix"
* tag 'hardening-v6.14-rc1-fix1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
kbuild: Use -fzero-init-padding-bits=all
stackinit: Add union initialization to selftests
stackinit: Add old-style zero-init syntax to struct tests
The stack initialization selftests were checking scalars, strings,
and structs, but not unions. Add union tests (which are mostly identical
setup to structs). This catches the recent union initialization behavioral
changes seen in GCC 15. Before GCC 15, this new test passes:
ok 18 test_small_start_old_zero
With GCC 15, it fails:
not ok 18 test_small_start_old_zero
Specifically, a union with a larger member where a smaller member is
initialized with the older "= { 0 }" syntax:
union test_small_start {
char one:1;
char two;
short three;
unsigned long four;
struct big_struct {
unsigned long array[8];
} big;
};
This is a regression in compiler behavior that Linux has depended on.
GCC does not seem likely to fix it, instead suggesting that affected
projects start using -fzero-init-padding-bits=unions:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118403
Link: https://lore.kernel.org/r/20250127191031.245214-2-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
Simplify the kconfig options for controlling which CRC implementations
are built into the kernel, as was requested by Linus. This means making
the option to disable the arch code visible only when CONFIG_EXPERT=y,
and standardizing on a single generic implementation of CRC32.
This has been in linux-next since last Friday. The late rebase was just
to add review tags.
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Merge tag 'crc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux
Pull CRC cleanups from Eric Biggers:
"Simplify the kconfig options for controlling which CRC implementations
are built into the kernel, as was requested by Linus.
This means making the option to disable the arch code visible only
when CONFIG_EXPERT=y, and standardizing on a single generic
implementation of CRC32"
* tag 'crc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
lib/crc32: remove other generic implementations
lib/crc: simplify the kconfig options for CRC implementations
All ctl_table declared outside of functions and that remain unmodified after
initialization are const qualified. This prevents unintended modifications to
proc_handler function pointers by placing them in the .rodata section. This is
a continuation of the tree-wide effort started a few releases ago with the
constification of the ctl_table struct arguments in the sysctl API done in
78eb4ea25c ("sysctl: treewide: constify the ctl_table argument of
proc_handlers")
Testing:
Testing was done on 0-day and sysctl selftests in x86_64. The linux-next
branch was not used for such a big change in order to avoid unnecessary merge
conflicts
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Merge tag 'constfy-sysctl-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl
Pull sysctl table constification from Joel Granados:
"All ctl_table declared outside of functions and that remain unmodified
after initialization are const qualified.
This prevents unintended modifications to proc_handler function
pointers by placing them in the .rodata section.
This is a continuation of the tree-wide effort started a few releases
ago with the constification of the ctl_table struct arguments in the
sysctl API done in 78eb4ea25c ("sysctl: treewide: constify the
ctl_table argument of proc_handlers")"
* tag 'constfy-sysctl-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
treewide: const qualify ctl_tables where applicable
Now that we've standardized on the byte-by-byte implementation of CRC32
as the only generic implementation (see previous commit for the
rationale), remove the code for the other implementations.
Tested with crc_kunit.
Link: https://lore.kernel.org/r/20250123212904.118683-3-ebiggers@kernel.org
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Make the following simplifications to the kconfig options for choosing
CRC implementations for CRC32 and CRC_T10DIF:
1. Make the option to disable the arch-optimized code be visible only
when CONFIG_EXPERT=y.
2. Make a single option control the inclusion of the arch-optimized code
for all enabled CRC variants.
3. Make CRC32_SARWATE (a.k.a. slice-by-1 or byte-by-byte) be the only
generic CRC32 implementation.
The result is there is now just one option, CRC_OPTIMIZATIONS, which is
default y and can be disabled only when CONFIG_EXPERT=y.
Rationale:
1. Enabling the arch-optimized code is nearly always the right choice.
However, people trying to build the tiniest kernel possible would
find some use in disabling it. Anything we add to CRC32 is de facto
unconditional, given that CRC32 gets selected by something in nearly
all kernels. And unfortunately enabling the arch CRC code does not
eliminate the need to build the generic CRC code into the kernel too,
due to CPU feature dependencies. The size of the arch CRC code will
also increase slightly over time as more CRC variants get added and
more implementations targeting different instruction set extensions
get added. Thus, it seems worthwhile to still provide an option to
disable it, but it should be considered an expert-level tweak.
2. Considering the use case described in (1), there doesn't seem to be
sufficient value in making the arch-optimized CRC code be
independently configurable for different CRC variants. Note also
that multiple variants were already grouped together, e.g.
CONFIG_CRC32 actually enables three different variants of CRC32.
3. The bit-by-bit implementation is uselessly slow, whereas slice-by-n
for n=4 and n=8 use tables that are inconveniently large: 4096 bytes
and 8192 bytes respectively, compared to 1024 bytes for n=1. Higher
n gives higher instruction-level parallelism, so higher n easily wins
on traditional microbenchmarks on most CPUs. However, the larger
tables, which are accessed randomly, can be harmful in real-world
situations where the dcache may be cold or useful data may need be
evicted from the dcache. Meanwhile, today most architectures have
much faster CRC32 implementations using dedicated CRC32 instructions
or carryless multiplication instructions anyway, which make the
generic code obsolete in most cases especially on long messages.
Another reason for going with n=1 is that this is already what is
used by all the other CRC variants in the kernel. CRC32 was unique
in having support for larger tables. But as per the above this can
be considered an outdated optimization.
The standardization on slice-by-1 a.k.a. CRC32_SARWATE makes much of
the code in lib/crc32.c unused. A later patch will clean that up.
Link: https://lore.kernel.org/r/20250123212904.118683-2-ebiggers@kernel.org
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
