linux.git/arch/alpha/kernel/traps.c, branch v7.3-rc2

alpha: read $gp and $sp explicitly for clang

2026-08-16T14:00:00+00:00

clang honors a local `register unsigned long x __asm__("$N")` variable
only where it appears as an inline-asm operand; merely reading it does
not produce the contents of that register.  So trap_init() passed an
undefined global pointer to PAL_wrkgp, and load_PCB() stored an undefined
stack pointer into the PCB that swpctx then loaded.  Either one wedges an
early boot.

Read the registers explicitly instead: an inline mov for $gp in
trap_init(), and the file-scope current_stack_pointer for $sp in
load_PCB().  A file-scope register-asm variable is the form clang does
support.

Signed-off-by: Matt Turner 
Reviewed-by: Maciej W. Rozycki 
Reviewed-by: Magnus Lindholm 
Tested-by: Magnus Lindholm 
Link: https://lore.kernel.org/r/20260803-alpha-clang-v1-2-1c4ba5ba7a64@gmail.com
Signed-off-by: Magnus Lindholm

alpha: don't leak hardware-fabricated FP exception bits to user space

2026-08-11T21:07:54+00:00

On EV6 and later the hardware records exception status bits in the FPCR
before delivering a software completion trap, and those bits can be wrong
for the instruction that trapped.  Converting a double that is exactly
representable as a subnormal float sets FPCR_UNF even though the result
is exact, and an underflow trap additionally sets FPCR_INE even when the
emulated operation turns out to be exact.

alpha_fp_emul() only wrote the FPCR when soft-fp raised an exception, so
whenever it determined that the instruction was exact the fabricated bits
stayed in the FPCR and were reported to user space by fetestexcept().

Pass the exception summary register down from do_entArith() so the
handler can tell which exceptions the hardware attributed to the trapping
instruction, and always write the FPCR.  Clear the exceptions that the
trap reported but that soft-fp did not raise.  EXC_SUM reports only the
underflow or overflow when the hardware also set INE, so treat INE as a
candidate in that case, and treat a trap with no reported exception as a
denormal operand trap, for which the hardware can fabricate INE and UNF
as well.  Bits that software has already confirmed in ieee_state belong
to this or an earlier instruction and are never cleared.

The imprecise path passes no summary.  There the trap was taken somewhere
in the trap shadow, so EXC_SUM is not attribution for the instruction
being re-executed -- and only EV6, which traps precisely and so never
takes that path, has fabricated bits to clear.  For the same reason the
clearing is guarded by implver(), matching swcr_update_status().

On an UP1500 (EV68) this takes the glibc math testsuite from 831 failures
to 28, the remainder being unrelated to exception status.

This belongs with the preceding fix to ieee_swcr_to_fpcr(), and should
not be backported without it -- nor it without this.  That fix stops
FPCR_DNOD being set unconditionally, so denormal operand traps start
firing again.  Those traps very often find an exact result, which is
precisely the case where the old code left the FPCR unwritten and the
fabricated bits visible.  Applied alone it would make spurious exception
flags more common, not less.

One case cannot be resolved here: an inexact instruction without the
software completion suffix never traps, so its INE reaches the FPCR
without being recorded anywhere else.  Such a bit is indistinguishable
from an INE the hardware fabricated for a trapping instruction, and is
lost if an underflow or overflow trap with an exact result follows it.
The FPCR is the only record of those instructions and it carries no
attribution.

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-v1-2-c99d75608e60@gmail.com
Signed-off-by: Magnus Lindholm

alpha: enable regset-based ptrace and core dumps

2026-07-19T11:15:40+00:00

Add a user_regset_view for Alpha and switch ELF core dumping to
CORE_DUMP_USE_REGSET.  General-purpose registers are exported in
ELF gregs layout, including callee-saved registers and a correct
user stack pointer.

The user stack pointer is not preserved in pt_regs on Alpha, so expose
it from the PCB, or via rdusp() for the current task, when building the
ELF register image.  This makes the user stack pointer consistent for
core dumps, ptrace regsets, and PTRACE_GET_SYSCALL_INFO.

Implement regset get/set callbacks for both NT_PRSTATUS and NT_PRFPREG.
The callbacks translate between Alpha's pt_regs/thread state and the
ELF-visible register layouts, while the common ptrace regset code handles
PTRACE_GETREGSET and PTRACE_SETREGSET iovec semantics.  This avoids
duplicating subtle short-buffer and oversized-buffer behavior in
arch_ptrace().

With these changes Alpha satisfies the requirements for
HAVE_ARCH_TRACEHOOK and selects it, enabling generic tracehook and
ptrace syscall-info code paths without changing the existing syscall
entry ABI.

Reviewed-by: Matt Turner 
Tested-by: Matt Turner 
Signed-off-by: Magnus Lindholm 
Link: https://lore.kernel.org/r/20260706170019.2941459-2-linmag7@gmail.com
Signed-off-by: Magnus Lindholm

alpha: align stack for page fault and user unaligned trap handlers

2025-02-14T19:06:04+00:00

do_page_fault() and do_entUna() are special because they use
non-standard stack frame layout. Fix them manually.

Cc: stable@vger.kernel.org
Tested-by: Maciej W. Rozycki 
Tested-by: Magnus Lindholm 
Tested-by: Matt Turner 
Reviewed-by: Maciej W. Rozycki 
Suggested-by: Maciej W. Rozycki 
Signed-off-by: Ivan Kokshaysky 
Signed-off-by: Matt Turner

move asm/unaligned.h to linux/unaligned.h

2024-10-02T21:23:23+00:00

asm/unaligned.h is always an include of asm-generic/unaligned.h;
might as well move that thing to linux/unaligned.h and include
that - there's nothing arch-specific in that header.

auto-generated by the following:

for i in `git grep -l -w asm/unaligned.h`; do
	sed -i -e "s/asm\/unaligned.h/linux\/unaligned.h/" $i
done
for i in `git grep -l -w asm-generic/unaligned.h`; do
	sed -i -e "s/asm-generic\/unaligned.h/linux\/unaligned.h/" $i
done
git mv include/asm-generic/unaligned.h include/linux/unaligned.h
git mv tools/include/asm-generic/unaligned.h tools/include/linux/unaligned.h
sed -i -e "/unaligned.h/d" include/asm-generic/Kbuild
sed -i -e "s/__ASM_GENERIC/__LINUX/" include/linux/unaligned.h tools/include/linux/unaligned.h

alpha: drop pre-EV56 support

2024-05-06T10:05:00+00:00

All EV4 machines are already gone, and the remaining EV5 based machines
all support the slightly more modern EV56 generation as well.
Debian only supports EV56 and later.

Drop both of these and build kernels optimized for EV56 and higher
when the "generic" options is selected, tuning for an out-of-order
EV6 pipeline, same as Debian userspace.

Since this was the only supported architecture without 8-bit and
16-bit stores, common kernel code no longer has to worry about
aligning struct members, and existing workarounds from the block
and tty layers can be removed.

The alpha memory management code no longer needs an abstraction
for the differences between EV4 and EV5+.

Link: https://lists.debian.org/debian-alpha/2023/05/msg00009.html
Acked-by: Paul E. McKenney 
Acked-by: Matt Turner 
Signed-off-by: Arnd Bergmann

arch: include linux/cpu.h for trap_init() prototype

2023-11-23T10:32:31+00:00

some architectures run into a -Wmissing-prototypes warning
for trap_init()

arch/microblaze/kernel/traps.c:21:6: warning: no previous prototype for 'trap_init' [-Wmissing-prototypes]

Include the right header to avoid this consistently, removing
the extra declarations on m68k and x86 that were added as local
workarounds already.

Signed-off-by: Arnd Bergmann

alpha: fix FEN fault handling

2023-01-11T20:34:43+00:00

Type 3 instruction fault (FPU insn with FPU disabled) is handled
by quietly enabling FPU and returning.  Which is fine, except that
we need to do that both for fault in userland and in the kernel;
the latter *can* legitimately happen - all it takes is this:

.global _start
_start:
        call_pal 0xae
	lda $0, 0
	ldq $0, 0($0)

- call_pal CLRFEN to clear "FPU enabled" flag and arrange for
a signal delivery (SIGSEGV in this case).

Fixed by moving the handling of type 3 into the common part of
do_entIF(), before we check for kernel vs. user mode.

Incidentally, the check for kernel mode is unidiomatic; the normal
way to do that is !user_mode(regs).  The difference is that
the open-coded variant treats any of bits 63..3 of regs->ps being
set as "it's user mode" while the normal approach is to check just
the bit 3.  PS is a 4-bit register and regs->ps always will have
bits 63..4 clear, so the open-coded variant here is actually equivalent
to !user_mode(regs).  Harder to follow, though...

Cc: stable@vger.kernel.org
Reviewed-by: Richard Henderson 
Signed-off-by: Al Viro

exit: Add and use make_task_dead.

2021-12-13T18:04:45+00:00

There are two big uses of do_exit.  The first is it's design use to be
the guts of the exit(2) system call.  The second use is to terminate
a task after something catastrophic has happened like a NULL pointer
in kernel code.

Add a function make_task_dead that is initialy exactly the same as
do_exit to cover the cases where do_exit is called to handle
catastrophic failure.  In time this can probably be reduced to just a
light wrapper around do_task_dead. For now keep it exactly the same so
that there will be no behavioral differences introducing this new
concept.

Replace all of the uses of do_exit that use it for catastraphic
task cleanup with make_task_dead to make it clear what the code
is doing.

As part of this rename rewind_stack_do_exit
rewind_stack_and_make_dead.

Signed-off-by: "Eric W. Biederman"

alpha: use is_kernel_text() helper

2021-11-09T18:02:51+00:00

Use is_kernel_text() helper to simplify code.

Link: https://lkml.kernel.org/r/20210930071143.63410-12-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang 
Reviewed-by: Sergey Senozhatsky 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: Alexander Potapenko 
Cc: Alexei Starovoitov 
Cc: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Arnd Bergmann 
Cc: Benjamin Herrenschmidt 
Cc: Borislav Petkov 
Cc: Christophe Leroy 
Cc: "David S. Miller" 
Cc: Dmitry Vyukov 
Cc: Ingo Molnar 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Paul Mackerras 
Cc: Petr Mladek 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds