linux-stable.git/arch/alpha/include, branch linux-6.18.y

alpha: fix ieee_swcr_to_fpcr setting FPCR_DNOD unconditionally

2026-09-07T15:22:20+00:00

commit 49672d026cc4773608e1222b69b29fd70f41336b upstream.

ieee_swcr_to_fpcr() converts the software IEEE trap-enable and status
bits kept in thread_info.ieee_state into the hardware FPCR format.  It
contained:

	fp |= (~sw & IEEE_TRAP_ENABLE_DNO) << 41;

FPCR_DNOD (bit 47) disables denormal operand traps: with it set the
hardware handles a denormal operand itself, treating it as zero, instead
of trapping for software completion.  The intent was to set DNOD when the
user has not asked for SIGFPE on denormal operands, but
IEEE_TRAP_ENABLE_DNO is clear by default, so ieee_swcr_to_fpcr(0) always
set DNOD.

Instructions built with the software completion suffix therefore never
trapped on a denormal operand.  The hardware silently substituted zero
and produced wrong results, affecting every program compiled with -mieee
and default FPU settings, glibc included.

Set FPCR_DNOD only when IEEE_MAP_DMZ is requested, which is exactly the
case where flushing denormal inputs to zero is what the user asked for.
DNOD then encodes MAP_DMZ, which ieee_fpcr_to_swcr() already recovers
from FPCR_DNZ, so drop its attempt to recover IEEE_TRAP_ENABLE_DNO from
DNOD; the DNO trap enable lives solely in ieee_state.

Both functions are in a uapi header, so the encoding change is visible to
userspace, but nothing outside the kernel is known to depend on DNOD
carrying the DNO trap enable, and the kernel is the only writer of the
FPCR.

This must not be backported on its own.  Re-enabling denormal operand
traps exposes a second bug, fixed in the following patch: those traps
usually find an exact result, and for an exact result the emulator did
not write the FPCR back, leaving hardware-fabricated exception bits
visible to user space.  Taken alone this change would make spurious
exception flags more common.

The bug predates the git history, so there is no commit to reference in a
Fixes tag.

Cc: stable@vger.kernel.org # 5.15+
Signed-off-by: Matt Turner 
Reviewed-by: Magnus Lindholm 
Tested-by: Magnus Lindholm 
Link: https://lore.kernel.org/r/20260803-alpha-fp-exceptions-v1-1-c99d75608e60@gmail.com
Signed-off-by: Magnus Lindholm 
Signed-off-by: Greg Kroah-Hartman

ring-buffer: Flush and stop persistent ring buffer on panic

2026-06-01T15:50:44+00:00

commit a494d3c8d5392bcdff83c2a593df0c160ff9f322 upstream.

On real hardware, panic and machine reboot may not flush hardware cache
to memory. This means the persistent ring buffer, which relies on a
coherent state of memory, may not have its events written to the buffer
and they may be lost. Moreover, there may be inconsistency with the
counters which are used for validation of the integrity of the
persistent ring buffer which may cause all data to be discarded.

To avoid this issue, stop recording of the ring buffer on panic and
flush the cache of the ring buffer's memory.

Fixes: e645535a954a ("tracing: Add option to use memmapped memory for trace boot instance")
Cc: stable@vger.kernel.org
Cc: Will Deacon 
Cc: Mathieu Desnoyers 
Cc: Ian Rogers 
Link: https://patch.msgid.link/177751969602.2136606.12031934362587643488.stgit@mhiramat.tok.corp.google.com
Signed-off-by: Masami Hiramatsu (Google) 
Acked-by: Catalin Marinas 
Acked-by: Geert Uytterhoeven 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

alpha: fix user-space corruption during memory compaction

2026-03-04T12:19:36+00:00

[ Upstream commit dd5712f3379cfe760267cdd28ff957d9ab4e51c7 ]

Alpha systems can suffer sporadic user-space crashes and heap
corruption when memory compaction is enabled.

Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned
tcache chunk"), and compiler internal errors. The failures disappear
when compaction is disabled or when using global TLB invalidation.

The root cause is insufficient TLB shootdown during page migration.
Alpha relies on ASN-based MM context rollover for instruction cache
coherency, but this alone is not sufficient to prevent stale data or
instruction translations from surviving migration.

Fix this by introducing a migration-specific helper that combines:
  - MM context invalidation (ASN rollover),
  - immediate per-CPU TLB invalidation (TBI),
  - synchronous cross-CPU shootdown when required.

The helper is used only by migration/compaction paths to avoid changing
global TLB semantics.

Additionally, update flush_tlb_other(), pte_clear(), to use
READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering.

This fixes observed crashes on both UP and SMP Alpha systems.

Reviewed-by: Ivan Kokshaysky 
Tested-by: Matoro Mahri 
Tested-by: Michael Cree 
Signed-off-by: Magnus Lindholm 
Link: https://lore.kernel.org/r/20260102173603.18247-2-linmag7@gmail.com
Signed-off-by: Magnus Lindholm 
Signed-off-by: Sasha Levin

alpha: don't reference obsolete termio struct for TC* constants

2026-01-17T15:35:16+00:00

[ Upstream commit 9aeed9041929812a10a6d693af050846942a1d16 ]

Similar in nature to ab107276607af90b13a5994997e19b7b9731e251. glibc-2.42
drops the legacy termio struct, but the ioctls.h header still defines some
TC* constants in terms of termio (via sizeof). Hardcode the values instead.

This fixes building Python for example, which falls over like:
  ./Modules/termios.c:1119:16: error: invalid application of 'sizeof' to incomplete type 'struct termio'

Link: https://bugs.gentoo.org/961769
Link: https://bugs.gentoo.org/962600
Signed-off-by: Sam James 
Reviewed-by: Magnus Lindholm 
Link: https://lore.kernel.org/r/6ebd3451908785cad53b50ca6bc46cfe9d6bc03c.1764922497.git.sam@gentoo.org
Signed-off-by: Magnus Lindholm 
Signed-off-by: Sasha Levin

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

2025-10-03T18:37:50+00:00

Pull misc non-vfs updates from Al Viro:
 "Assorted dead code removal around asm/pgtable.h"

* tag 'pull-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  alpha: unobfuscate _PAGE_P() definition
  kill FIRST_USER_PGD_NR
  alpha: get rid of the remnants of BAD_PAGE and friends
  SET_PAGE_DIR() users had been gone since 2.3.12pre1
  PAGE_PTR() had been last used outside of arch/* in 1.1.94
  csky: remove BS check for FAULT_FLAG_ALLOW_RETRY

Merge tag 'for-6.18/block-20250929' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux

2025-10-02T17:16:56+00:00

Pull block updates from Jens Axboe:

 - NVMe pull request via Keith:
     - FC target fixes (Daniel)
     - Authentication fixes and updates (Martin, Chris)
     - Admin controller handling (Kamaljit)
     - Target lockdep assertions (Max)
     - Keep-alive updates for discovery (Alastair)
     - Suspend quirk (Georg)

 - MD pull request via Yu:
     - Add support for a lockless bitmap.

       A key feature for the new bitmap are that the IO fastpath is
       lockless. If a user issues lots of write IO to the same bitmap
       bit in a short time, only the first write has additional overhead
       to update bitmap bit, no additional overhead for the following
       writes.

       By supporting only resync or recover written data, means in the
       case creating new array or replacing with a new disk, there is no
       need to do a full disk resync/recovery.

 - Switch ->getgeo() and ->bios_param() to using struct gendisk rather
   than struct block_device.

 - Rust block changes via Andreas. This series adds configuration via
   configfs and remote completion to the rnull driver. The series also
   includes a set of changes to the rust block device driver API: a few
   cleanup patches, and a few features supporting the rnull changes.

   The series removes the raw buffer formatting logic from
   `kernel::block` and improves the logic available in `kernel::string`
   to support the same use as the removed logic.

 - floppy arch cleanups

 - Reduce the number of dereferencing needed for ublk commands

 - Restrict supported sockets for nbd. Mostly done to eliminate a class
   of issues perpetually reported by syzbot, by using nonsensical socket
   setups.

 - A few s390 dasd block fixes

 - Fix a few issues around atomic writes

 - Improve DMA interation for integrity requests

 - Improve how iovecs are treated with regards to O_DIRECT aligment
   constraints.

   We used to require each segment to adhere to the constraints, now
   only the request as a whole needs to.

 - Clean up and improve p2p support, enabling use of p2p for metadata
   payloads

 - Improve locking of request lookup, using SRCU where appropriate

 - Use page references properly for brd, avoiding very long RCU sections

 - Fix ordering of recursively submitted IOs

 - Clean up and improve updating nr_requests for a live device

 - Various fixes and cleanups

* tag 'for-6.18/block-20250929' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux: (164 commits)
  s390/dasd: enforce dma_alignment to ensure proper buffer validation
  s390/dasd: Return BLK_STS_INVAL for EINVAL from do_dasd_request
  ublk: remove redundant zone op check in ublk_setup_iod()
  nvme: Use non zero KATO for persistent discovery connections
  nvmet: add safety check for subsys lock
  nvme-core: use nvme_is_io_ctrl() for I/O controller check
  nvme-core: do ioccsz/iorcsz validation only for I/O controllers
  nvme-core: add method to check for an I/O controller
  blk-cgroup: fix possible deadlock while configuring policy
  blk-mq: fix null-ptr-deref in blk_mq_free_tags() from error path
  blk-mq: Fix more tag iteration function documentation
  selftests: ublk: fix behavior when fio is not installed
  ublk: don't access ublk_queue in ublk_unmap_io()
  ublk: pass ublk_io to __ublk_complete_rq()
  ublk: don't access ublk_queue in ublk_need_complete_req()
  ublk: don't access ublk_queue in ublk_check_commit_and_fetch()
  ublk: don't pass ublk_queue to ublk_fetch()
  ublk: don't access ublk_queue in ublk_config_io_buf()
  ublk: don't access ublk_queue in ublk_check_fetch_buf()
  ublk: pass q_id and tag to __ublk_check_and_get_req()
  ...

alpha: unobfuscate _PAGE_P() definition

2025-09-16T01:12:05+00:00

Way, way back it used to be
	_PAGE_NORMAL((x) | ((x & _PAGE_FOW) ? 0 : _PAGE_FOW | _PAGE_COW))
Then (in 1.3.54) _PAGE_COW had died.  Result:
	_PAGE_NORMAL((x) | ((x & _PAGE_FOW) ? 0 : _PAGE_FOW))
which is somewhat... obscure.  What it does is simply
	_PAGE_NORMAL((x) | _PAGE_FOW)
and IMO that's easier to follow.

Signed-off-by: Al Viro

alpha: get rid of the remnants of BAD_PAGE and friends

2025-09-13T19:15:08+00:00

unused since 2.4 times...

Signed-off-by: Al Viro

PAGE_PTR() had been last used outside of arch/* in 1.1.94

2025-09-13T19:15:07+00:00

.. and in arch/* - circa 2.2.7.

Reviewed-by: Geert Uytterhoeven  # m68k
Acked-by: Geert Uytterhoeven  # m68k
Signed-off-by: Al Viro

alpha: Add __attribute_const__ to ffs()-family implementations

2025-09-08T21:58:51+00:00

While tracking down a problem where constant expressions used by
BUILD_BUG_ON() suddenly stopped working[1], we found that an added static
initializer was convincing the compiler that it couldn't track the state
of the prior statically initialized value. Tracing this down found that
ffs() was used in the initializer macro, but since it wasn't marked with
__attribute__const__, the compiler had to assume the function might
change variable states as a side-effect (which is not true for ffs(),
which provides deterministic math results).

Add missing __attribute_const__ annotations to Alpha's implementations
of __ffs(), ffs(), fls64(), __fls(), fls(), and ffz() functions. These
are pure mathematical functions that always return the same result for
the same input with no side effects, making them eligible for compiler
optimization.

Build tested ARCH=alpha defconfig with GCC alpha-linux-gnu 14.2.0.

Link: https://github.com/KSPP/linux/issues/364 [1]
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250804164417.1612371-7-kees@kernel.org
Signed-off-by: Kees Cook