linux-stable.git/arch/loongarch/kernel/process.c, branch linux-rolling-stable

Merge tag 'loongarch-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson

2026-04-24T16:54:45+00:00

Pull LoongArch updates from Huacai Chen:

 - Adjust build infrastructure for 32BIT/64BIT

 - Add HIGHMEM (PKMAP and FIX_KMAP) support

 - Show and handle CPU vulnerabilites correctly

 - Batch the icache maintenance for jump_label

 - Add more atomic instructions support for BPF JIT

 - Add more features (e.g. fsession) support for BPF trampoline

 - Some bug fixes and other small changes

* tag 'loongarch-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson: (21 commits)
  selftests/bpf: Enable CAN_USE_LOAD_ACQ_STORE_REL for LoongArch
  LoongArch: BPF: Add fsession support for trampolines
  LoongArch: BPF: Introduce emit_store_stack_imm64() helper
  LoongArch: BPF: Support up to 12 function arguments for trampoline
  LoongArch: BPF: Support small struct arguments for trampoline
  LoongArch: BPF: Open code and remove invoke_bpf_mod_ret()
  LoongArch: BPF: Support load-acquire and store-release instructions
  LoongArch: BPF: Support 8 and 16 bit read-modify-write instructions
  LoongArch: BPF: Add the default case in emit_atomic() and rename it
  LoongArch: Define instruction formats for AM{SWAP/ADD}.{B/H} and DBAR
  LoongArch: Batch the icache maintenance for jump_label
  LoongArch: Add flush_icache_all()/local_flush_icache_all()
  LoongArch: Add spectre boundry for syscall dispatch table
  LoongArch: Show CPU vulnerabilites correctly
  LoongArch: Make arch_irq_work_has_interrupt() true only if IPI HW exist
  LoongArch: Use get_random_canary() for stack canary init
  LoongArch: Improve the logging of disabling KASLR
  LoongArch: Align FPU register state to 32 bytes
  LoongArch: Handle CONFIG_32BIT in syscall_get_arch()
  LoongArch: Add HIGHMEM (PKMAP and FIX_KMAP) support
  ...

LoongArch: Align FPU register state to 32 bytes

2026-04-22T07:45:11+00:00

Move fpr to the beginning of struct loongarch_fpu so it is naturally
aligned to FPU_ALIGN (32 bytes), improving 256-bit SIMD (LASX) context
switch performance.

Also adjust process.c and fpu.S to work well with the new loongarch_fpu
layout.

Signed-off-by: Lisa Robinson 
Signed-off-by: Huacai Chen

LoongArch: vDSO: Explicitly include asm/vdso/vdso.h

2026-03-11T14:12:41+00:00

The usage of 'struct old_timespec32' requires asm/vdso/vdso.h. Currently
this header is included transitively, but that transitive inclusion is
about to go away.

Explicitly include the header.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://patch.msgid.link/20260227-vdso-header-cleanups-v2-6-35d60acf7410@linutronix.de

LoongArch: Adjust process management for 32BIT/64BIT

2025-12-08T10:09:17+00:00

Adjust process management for both 32BIT and 64BIT, including: CPU
context switching, FPU loading/restoring, process dumping and process
tracing routines.

Q: Why modify switch.S?
A: LoongArch32 has no ldptr.d/stptr.d instructions, and asm offsets of
   thead_struct members are too large to be filled in the 12b immediate
   field of ld.w/st.w.

Reviewed-by: Arnd Bergmann 
Signed-off-by: Jiaxun Yang 
Signed-off-by: Huacai Chen

LoongArch: Fix arch_dup_task_struct() for CONFIG_RANDSTRUCT

2025-12-06T02:39:48+00:00

Now the optimized version of arch_dup_task_struct() for LoongArch
assumes 'thread' is the last member of 'task_struct'. But this is
not true if CONFIG_RANDSTRUCT is enabled after Linux-6.16.

So fix the arch_dup_task_struct() function for CONFIG_RANDSTRUCT by
copying the whole 'task_struct'.

Cc: stable@vger.kernel.org   # 6.16+
Signed-off-by: Huacai Chen

arch: copy_thread: pass clone_flags as u64

2025-09-01T13:31:34+00:00

With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.

While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.

Thus, this commit fixes all relevant interfaces of the copy_thread
function that is called from copy_process to consistently pass
clone_flags as u64, so that no truncation to 32-bit integers occurs on
32-bit architectures.

Signed-off-by: Simon Schuster 
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-3-53fcf5577d57@siemens-energy.com
Fixes: c5febea0956fd387 ("fork: Pass struct kernel_clone_args into copy_thread")
Acked-by: Guo Ren (Alibaba Damo Academy) 
Acked-by: Andreas Larsson  # sparc
Acked-by: David Hildenbrand 
Acked-by: Geert Uytterhoeven  # m68k
Reviewed-by: Arnd Bergmann 
Signed-off-by: Christian Brauner

LoongArch: entry: Fix include order

2025-05-07T09:05:57+00:00

Reorder some introduced include headers to keep alphabetical order.

Fixes: 7ace1602abf2 ("LoongArch: entry: Migrate ret_from_fork() to C")
Signed-off-by: Charlie Jenkins 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250507-loongarch_include_order-v1-1-e8aada6a3da8@rivosinc.com

LoongArch: entry: Migrate ret_from_fork() to C

2025-04-29T06:27:10+00:00

LoongArch is the only architecture that calls syscall_exit_to_user_mode()
from assembly.

Move the call into C so that this function can be inlined across all
architectures.

Signed-off-by: Charlie Jenkins 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250320-riscv_optimize_entry-v6-3-63e187e26041@rivosinc.com

LoongArch: Don't crash in stack_top() for tasks without vDSO

2024-10-21T14:11:19+00:00

Not all tasks have a vDSO mapped, for example kthreads never do. If such
a task ever ends up calling stack_top(), it will derefence the NULL vdso
pointer and crash.

This can for example happen when using kunit:

	[<9000000000203874>] stack_top+0x58/0xa8
	[<90000000002956cc>] arch_pick_mmap_layout+0x164/0x220
	[<90000000003c284c>] kunit_vm_mmap_init+0x108/0x12c
	[<90000000003c1fbc>] __kunit_add_resource+0x38/0x8c
	[<90000000003c2704>] kunit_vm_mmap+0x88/0xc8
	[<9000000000410b14>] usercopy_test_init+0xbc/0x25c
	[<90000000003c1db4>] kunit_try_run_case+0x5c/0x184
	[<90000000003c3d54>] kunit_generic_run_threadfn_adapter+0x24/0x48
	[<900000000022e4bc>] kthread+0xc8/0xd4
	[<9000000000200ce8>] ret_from_kernel_thread+0xc/0xa4

Fixes: 803b0fc5c3f2 ("LoongArch: Add process management")
Signed-off-by: Thomas Weißschuh 
Signed-off-by: Huacai Chen

LoongArch: Fix and simplify fcsr initialization on execve()

2024-01-17T04:43:08+00:00

There has been a lingering bug in LoongArch Linux systems causing some
GCC tests to intermittently fail (see Closes link).  I've made a minimal
reproducer:

    zsh% cat measure.s
    .align 4
    .globl _start
    _start:
        movfcsr2gr  $a0, $fcsr0
        bstrpick.w  $a0, $a0, 16, 16
        beqz        $a0, .ok
        break       0
    .ok:
        li.w        $a7, 93
        syscall     0
    zsh% cc mesaure.s -o measure -nostdlib
    zsh% echo $((1.0/3))
    0.33333333333333331
    zsh% while ./measure; do ; done

This while loop should not stop as POSIX is clear that execve must set
fenv to the default, where FCSR should be zero.  But in fact it will
just stop after running for a while (normally less than 30 seconds).
Note that "$((1.0/3))" is needed to reproduce this issue because it
raises FE_INVALID and makes fcsr0 non-zero.

The problem is we are currently relying on SET_PERSONALITY2() to reset
current->thread.fpu.fcsr.  But SET_PERSONALITY2() is executed before
start_thread which calls lose_fpu(0).  We can see if kernel preempt is
enabled, we may switch to another thread after SET_PERSONALITY2() but
before lose_fpu(0).  Then bad thing happens: during the thread switch
the value of the fcsr0 register is stored into current->thread.fpu.fcsr,
making it dirty again.

The issue can be fixed by setting current->thread.fpu.fcsr after
lose_fpu(0) because lose_fpu() clears TIF_USEDFPU, then the thread
switch won't touch current->thread.fpu.fcsr.

The only other architecture setting FCSR in SET_PERSONALITY2() is MIPS.
I've ran a similar test on MIPS with mainline kernel and it turns out
MIPS is buggy, too.  Anyway MIPS do this for supporting different FP
flavors (NaN encodings, etc.) which do not exist on LoongArch.  So for
LoongArch, we can simply remove the current->thread.fpu.fcsr setting
from SET_PERSONALITY2() and do it in start_thread(), after lose_fpu(0).

The while loop failing with the mainline kernel has survived one hour
after this change on LoongArch.

Fixes: 803b0fc5c3f2baa ("LoongArch: Add process management")
Closes: https://github.com/loongson-community/discussions/issues/7
Link: https://lore.kernel.org/linux-mips/7a6aa1bbdbbe2e63ae96ff163fab0349f58f1b9e.camel@xry111.site/
Cc: stable@vger.kernel.org
Signed-off-by: Xi Ruoyao 
Signed-off-by: Huacai Chen