linux.git/arch/loongarch/kernel/process.c, branch master

LoongArch: Add THREAD_INFO_IN_TASK implementation

2026-06-25T05:03:47+00:00

Like other architectures such as x86, arm64, riscv, powerpc and s390, select THREAD_INFO_IN_TASK for LoongArch to move thread_info off the stack into task_struct. This follows modern kernel standards and also makes the system more secure. With this patch, thread_info is included in task_struct at an offset of 0 instead of being placed at the bottom of the kernel stack. Thus, the $tp register points to both thread_info and task_struct. To support this, introduce a per-CPU variable cpu_tasks to store the pointer to the current task_struct. This decouples the recovery of the $tp register from the stack pointer during exception entry. Then initialize cpu_tasks for the primary and secondary CPUs during arch-specific setup and SMP boot paths. To eliminate the dangerous windows during the early initialization where the cpu_tasks remains uninitialized, set_current() is invoked as early as possible in both setup_arch() and start_secondary(). This ensures the $tp recovery barrier is armed in case any early boot exceptions or kernel panics occur. Modify SAVE_SOME and handle_syscall to restore the $tp register from cpu_tasks, and also use the la_abs absolute addressing for cpu_tasks access in assembly to bypass the relocation limits within exception handling sections. By advancing the preservation of u0 in SAVE_SOME, we reuse the PERCPU_BASE_KS value in u0 for the cpu_tasks calculation, effectively eliminating a duplicate csrrd instruction execution on SMP platforms. Update and to fully support the CONFIG_THREAD_INFO_IN_TASK feature. Remove the obsolete next_ti argument from __switch_to(), which shifts the remaining arguments ahead in the calling convention (sched_ra from a3 to a2, and sched_cfa from a4 to a3). Under the new configuration, __switch_to() now directly derives the thread pointer ($tp) from the next task_struct pointer in a1. To preserve the optimal and clean "move tp, a1" path for 64-bit kernels, the thread pointer ($tp) is assigned directly from a1 in the core path. For 32-bit kernels, where a1 carries a 2000-byte structural pointer bias at entry, an explicit adjustment "PTR_ADDI tp, tp, -TASK_STRUCT_OFFSET" is introduced at the function exit. In the context of __switch_to(), local interrupts are disabled, and the kernel is in a critical switching phase where handling any synchronous exception is practically impossible and prohibited. If any synchronous exception or watchpoint does trigger in this narrow window, it constitutes a fatal double fault and the kernel is expected to die/panic immediately anyway. Therefore, the temporary biased value in $tp is safe and acceptable here. Additionally, evaluate the stack lookup as a single load instruction "LONG_LPTR t0, a1, (TASK_STACK - TASK_STRUCT_OFFSET)", this perfectly satisfies both 32-bit and 64-bit kernels. Using the "next" pointer in a1 as the base register, rather than $tp, effectively unchains the data dependency (RAW hazard) from the preceding move instruction, maximizing the instruction-level parallelism and superscalar execution efficiency while naturally adapting the structural shift. With CONFIG_THREAD_INFO_IN_TASK enabled, the kernel stack life cycle is decoupled from task_struct and can be freed concurrently. Currently, show_stacktrace() reads raw stack data via __get_addr() and subsequently calls show_backtrace() to unwind the frame, without holding any reference to the target task's stack. If show_stacktrace() is called on a concurrently exiting task, it could attempt to read from a freed or reallocated kernel stack. This introduces a severe use-after-free (UAF) read risk or kernel panics. Wrap the entire stack inspection process inside show_stacktrace() with a try_get_task_stack() and put_task_stack() pair. This ensures the task stack remains pinned safely during both the raw stack data dump loop and the subsequent stack unwinding phase. Also, ensure that the task pointer is initialized to "current" early if it is NULL, so that try_get_task_stack() always operates on a valid task reference. Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen

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