// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/cpu.h>
#include <linux/prctl.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/idle.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/pm.h>
#include <linux/tick.h>
#include <linux/random.h>
#include <linux/user-return-notifier.h>
#include <linux/dmi.h>
#include <linux/utsname.h>
#include <linux/stackprotector.h>
#include <linux/cpuidle.h>
#include <linux/acpi.h>
#include <linux/elf-randomize.h>
#include <linux/static_call.h>
#include <trace/events/power.h>
#include <linux/hw_breakpoint.h>
#include <linux/entry-common.h>
#include <asm/cpu.h>
#include <asm/cpuid/api.h>
#include <asm/apic.h>
#include <linux/uaccess.h>
#include <asm/mwait.h>
#include <asm/fpu/api.h>
#include <asm/fpu/sched.h>
#include <asm/fpu/xstate.h>
#include <asm/debugreg.h>
#include <asm/nmi.h>
#include <asm/tlbflush.h>
#include <asm/mce.h>
#include <asm/vm86.h>
#include <asm/switch_to.h>
#include <asm/desc.h>
#include <asm/prctl.h>
#include <asm/spec-ctrl.h>
#include <asm/io_bitmap.h>
#include <asm/proto.h>
#include <asm/frame.h>
#include <asm/unwind.h>
#include <asm/tdx.h>
#include <asm/mmu_context.h>
#include <asm/msr.h>
#include <asm/shstk.h>

#include "process.h"

/*
 * per-CPU TSS segments. Threads are completely 'soft' on Linux,
 * no more per-task TSS's. The TSS size is kept cacheline-aligned
 * so they are allowed to end up in the .data..cacheline_aligned
 * section. Since TSS's are completely CPU-local, we want them
 * on exact cacheline boundaries, to eliminate cacheline ping-pong.
 */
__visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = {
        .x86_tss = {
                /*
                 * .sp0 is only used when entering ring 0 from a lower
                 * privilege level.  Since the init task never runs anything
                 * but ring 0 code, there is no need for a valid value here.
                 * Poison it.
                 */
                .sp0 = (1UL << (BITS_PER_LONG-1)) + 1,

#ifdef CONFIG_X86_32
                .sp1 = TOP_OF_INIT_STACK,

                .ss0 = __KERNEL_DS,
                .ss1 = __KERNEL_CS,
#endif
                .io_bitmap_base = IO_BITMAP_OFFSET_INVALID,
         },
};
EXPORT_PER_CPU_SYMBOL(cpu_tss_rw);

DEFINE_PER_CPU(bool, __tss_limit_invalid);
EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);

/*
 * The cache may be in an incoherent state and needs flushing during kexec.
 * E.g., on SME/TDX platforms, dirty cacheline aliases with and without
 * encryption bit(s) can coexist and the cache needs to be flushed before
 * booting to the new kernel to avoid the silent memory corruption due to
 * dirty cachelines with different encryption property being written back
 * to the memory.
 */
DEFINE_PER_CPU(bool, cache_state_incoherent);

/*
 * this gets called so that we can store lazy state into memory and copy the
 * current task into the new thread.
 */
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
        /* fpu_clone() will initialize the "dst_fpu" memory */
        memcpy_and_pad(dst, arch_task_struct_size, src, sizeof(*dst), 0);

#ifdef CONFIG_VM86
        dst->thread.vm86 = NULL;
#endif

        return 0;
}

#ifdef CONFIG_X86_64
void arch_release_task_struct(struct task_struct *tsk)
{
        if (fpu_state_size_dynamic() && !(tsk->flags & (PF_KTHREAD | PF_USER_WORKER)))
                fpstate_free(x86_task_fpu(tsk));
}
#endif

/*
 * Free thread data structures etc..
 */
void exit_thread(struct task_struct *tsk)
{
        struct thread_struct *t = &tsk->thread;

        if (test_thread_flag(TIF_IO_BITMAP))
                io_bitmap_exit(tsk);

        free_vm86(t);

        shstk_free(tsk);
        fpu__drop(tsk);
}

static int set_new_tls(struct task_struct *p, unsigned long tls)
{
        struct user_desc __user *utls = (struct user_desc __user *)tls;

        if (in_ia32_syscall())
                return do_set_thread_area(p, -1, utls, 0);
        else
                return do_set_thread_area_64(p, ARCH_SET_FS, tls);
}

__visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs,
                                     int (*fn)(void *), void *fn_arg)
{
        schedule_tail(prev);

        /* Is this a kernel thread? */
        if (unlikely(fn)) {
                fn(fn_arg);
                /*
                 * A kernel thread is allowed to return here after successfully
                 * calling kernel_execve().  Exit to userspace to complete the
                 * execve() syscall.
                 */
                regs->ax = 0;
        }

        syscall_exit_to_user_mode(regs);
}

int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
        u64 clone_flags = args->flags;
        unsigned long sp = args->stack;
        unsigned long tls = args->tls;
        struct inactive_task_frame *frame;
        struct fork_frame *fork_frame;
        struct pt_regs *childregs;
        unsigned long new_ssp;
        int ret = 0;

        childregs = task_pt_regs(p);
        fork_frame = container_of(childregs, struct fork_frame, regs);
        frame = &fork_frame->frame;

        frame->bp = encode_frame_pointer(childregs);
        frame->ret_addr = (unsigned long) ret_from_fork_asm;
        p->thread.sp = (unsigned long) fork_frame;
        p->thread.io_bitmap = NULL;
        clear_tsk_thread_flag(p, TIF_IO_BITMAP);
        p->thread.iopl_warn = 0;
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));

#ifdef CONFIG_X86_64
        current_save_fsgs();
        p->thread.fsindex = current->thread.fsindex;
        p->thread.fsbase = current->thread.fsbase;
        p->thread.gsindex = current->thread.gsindex;
        p->thread.gsbase = current->thread.gsbase;

        savesegment(es, p->thread.es);
        savesegment(ds, p->thread.ds);

        if (p->mm && (clone_flags & (CLONE_VM | CLONE_VFORK)) == CLONE_VM)
                set_bit(MM_CONTEXT_LOCK_LAM, &p->mm->context.flags);
#else
        p->thread.sp0 = (unsigned long) (childregs + 1);
        savesegment(gs, p->thread.gs);
        /*
         * Clear all status flags including IF and set fixed bit. 64bit
         * does not have this initialization as the frame does not contain
         * flags. The flags consistency (especially vs. AC) is there
         * ensured via objtool, which lacks 32bit support.
         */
        frame->flags = X86_EFLAGS_FIXED;
#endif

        /*
         * Allocate a new shadow stack for thread if needed. If shadow stack,
         * is disabled, new_ssp will remain 0, and fpu_clone() will know not to
         * update it.
         */
        new_ssp = shstk_alloc_thread_stack(p, clone_flags, args->stack_size);
        if (IS_ERR_VALUE(new_ssp))
                return PTR_ERR((void *)new_ssp);

        fpu_clone(p, clone_flags, args->fn, new_ssp);

        /* Kernel thread ? */
        if (unlikely(p->flags & PF_KTHREAD)) {
                p->thread.pkru = pkru_get_init_value();
                memset(childregs, 0, sizeof(struct pt_regs));
                kthread_frame_init(frame, args->fn, args->fn_arg);
                return 0;
        }

        /*
         * Clone current's PKRU value from hardware. tsk->thread.pkru
         * is only valid when scheduled out.
         */
        p->thread.pkru = read_pkru();

        frame->bx = 0;
        *childregs = *current_pt_regs();
        childregs->ax = 0;
        if (sp)
                childregs->sp = sp;

        if (unlikely(args->fn)) {
                /*
                 * A user space thread, but it doesn't return to
                 * ret_after_fork().
                 *
                 * In order to indicate that to tools like gdb,
                 * we reset the stack and instruction pointers.
                 *
                 * It does the same kernel frame setup to return to a kernel
                 * function that a kernel thread does.
                 */
                childregs->sp = 0;
                childregs->ip = 0;
                kthread_frame_init(frame, args->fn, args->fn_arg);
                return 0;
        }

        /* Set a new TLS for the child thread? */
        if (clone_flags & CLONE_SETTLS)
                ret = set_new_tls(p, tls);

        if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
                io_bitmap_share(p);

        return ret;
}

static void pkru_flush_thread(void)
{
        /*
         * If PKRU is enabled the default PKRU value has to be loaded into
         * the hardware right here (similar to context switch).
         */
        pkru_write_default();
}

void flush_thread(void)
{
        struct task_struct *tsk = current;

        flush_ptrace_hw_breakpoint(tsk);
        memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));

        fpu_flush_thread();
        pkru_flush_thread();
}

void disable_TSC(void)
{
        preempt_disable();
        if (!test_and_set_thread_flag(TIF_NOTSC))
                /*
                 * Must flip the CPU state synchronously with
                 * TIF_NOTSC in the current running context.
                 */
                cr4_set_bits(X86_CR4_TSD);
        preempt_enable();
}

static void enable_TSC(void)
{
        preempt_disable();
        if (test_and_clear_thread_flag(TIF_NOTSC))
                /*
                 * Must flip the CPU state synchronously with
                 * TIF_NOTSC in the current running context.
                 */
                cr4_clear_bits(X86_CR4_TSD);
        preempt_enable();
}

int get_tsc_mode(unsigned long adr)
{
        unsigned int val;

        if (test_thread_flag(TIF_NOTSC))
                val = PR_TSC_SIGSEGV;
        else
                val = PR_TSC_ENABLE;

        return put_user(val, (unsigned int __user *)adr);
}

int set_tsc_mode(unsigned int val)
{
        if (val == PR_TSC_SIGSEGV)
                disable_TSC();
        else if (val == PR_TSC_ENABLE)
                enable_TSC();
        else
                return -EINVAL;

        return 0;
}

DEFINE_PER_CPU(u64, msr_misc_features_shadow);

static void set_cpuid_faulting(bool on)
{

        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
                u64 msrval;

                msrval = this_cpu_read(msr_misc_features_shadow);
                msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
                msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT);
                this_cpu_write(msr_misc_features_shadow, msrval);
                wrmsrq(MSR_MISC_FEATURES_ENABLES, msrval);
        } else if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
                if (on)
                        msr_set_bit(MSR_K7_HWCR, MSR_K7_HWCR_CPUID_USER_DIS_BIT);
                else
                        msr_clear_bit(MSR_K7_HWCR, MSR_K7_HWCR_CPUID_USER_DIS_BIT);
        }
}

static void disable_cpuid(void)
{
        preempt_disable();
        if (!test_and_set_thread_flag(TIF_NOCPUID)) {
                /*
                 * Must flip the CPU state synchronously with
                 * TIF_NOCPUID in the current running context.
                 */
                set_cpuid_faulting(true);
        }
        preempt_enable();
}

static void enable_cpuid(void)
{
        preempt_disable();
        if (test_and_clear_thread_flag(TIF_NOCPUID)) {
                /*
                 * Must flip the CPU state synchronously with
                 * TIF_NOCPUID in the current running context.
                 */
                set_cpuid_faulting(false);
        }
        preempt_enable();
}

static int get_cpuid_mode(void)
{
        return !test_thread_flag(TIF_NOCPUID);
}

static int set_cpuid_mode(unsigned long cpuid_enabled)
{
        if (!boot_cpu_has(X86_FEATURE_CPUID_FAULT))
                return -ENODEV;

        if (cpuid_enabled)
                enable_cpuid();
        else
                disable_cpuid();

        return 0;
}

/*
 * Called immediately after a successful exec.
 */
void arch_setup_new_exec(void)
{
        /* If cpuid was previously disabled for this task, re-enable it. */
        if (test_thread_flag(TIF_NOCPUID))
                enable_cpuid();

        /*
         * Don't inherit TIF_SSBD across exec boundary when
         * PR_SPEC_DISABLE_NOEXEC is used.
         */
        if (test_thread_flag(TIF_SSBD) &&
            task_spec_ssb_noexec(current)) {
                clear_thread_flag(TIF_SSBD);
                task_clear_spec_ssb_disable(current);
                task_clear_spec_ssb_noexec(current);
                speculation_ctrl_update(read_thread_flags());
        }

        mm_reset_untag_mask(current->mm);
}

#ifdef CONFIG_X86_IOPL_IOPERM
static inline void switch_to_bitmap(unsigned long tifp)
{
        /*
         * Invalidate I/O bitmap if the previous task used it. This prevents
         * any possible leakage of an active I/O bitmap.
         *
         * If the next task has an I/O bitmap it will handle it on exit to
         * user mode.
         */
        if (tifp & _TIF_IO_BITMAP)
                tss_invalidate_io_bitmap();
}

static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
{
        /*
         * Copy at least the byte range of the incoming tasks bitmap which
         * covers the permitted I/O ports.
         *
         * If the previous task which used an I/O bitmap had more bits
         * permitted, then the copy needs to cover those as well so they
         * get turned off.
         */
        memcpy(tss->io_bitmap.bitmap, iobm->bitmap,
               max(tss->io_bitmap.prev_max, iobm->max));

        /*
         * Store the new max and the sequence number of this bitmap
         * and a pointer to the bitmap itself.
         */
        tss->io_bitmap.prev_max = iobm->max;
        tss->io_bitmap.prev_sequence = iobm->sequence;
}

/**
 * native_tss_update_io_bitmap - Update I/O bitmap before exiting to user mode
 */
void native_tss_update_io_bitmap(void)
{
        struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
        struct thread_struct *t = &current->thread;
        u16 *base = &tss->x86_tss.io_bitmap_base;

        if (!test_thread_flag(TIF_IO_BITMAP)) {
                native_tss_invalidate_io_bitmap();
                return;
        }

        if (IS_ENABLED(CONFIG_X86_IOPL_IOPERM) && t->iopl_emul == 3) {
                *base = IO_BITMAP_OFFSET_VALID_ALL;
        } else {
                struct io_bitmap *iobm = t->io_bitmap;

                if (WARN_ON_ONCE(!iobm)) {
                        clear_thread_flag(TIF_IO_BITMAP);
                        native_tss_invalidate_io_bitmap();
                }

                /*
                 * Only copy bitmap data when the sequence number differs. The
                 * update time is accounted to the incoming task.
                 */
                if (tss->io_bitmap.prev_sequence != iobm->sequence)
                        tss_copy_io_bitmap(tss, iobm);

                /* Enable the bitmap */
                *base = IO_BITMAP_OFFSET_VALID_MAP;
        }

        /*
         * Make sure that the TSS limit is covering the IO bitmap. It might have
         * been cut down by a VMEXIT to 0x67 which would cause a subsequent I/O
         * access from user space to trigger a #GP because the bitmap is outside
         * the TSS limit.
         */
        refresh_tss_limit();
}
#else /* CONFIG_X86_IOPL_IOPERM */
static inline void switch_to_bitmap(unsigned long tifp) { }
#endif

#ifdef CONFIG_SMP

struct ssb_state {
        struct ssb_state        *shared_state;
        raw_spinlock_t          lock;
        unsigned int            disable_state;
        unsigned long           local_state;
};

#define LSTATE_SSB      0

static DEFINE_PER_CPU(struct ssb_state, ssb_state);

void speculative_store_bypass_ht_init(void)
{
        struct ssb_state *st = this_cpu_ptr(&ssb_state);
        unsigned int this_cpu = smp_processor_id();
        unsigned int cpu;

        st->local_state = 0;

        /*
         * Shared state setup happens once on the first bringup
         * of the CPU. It's not destroyed on CPU hotunplug.
         */
        if (st->shared_state)
                return;

        raw_spin_lock_init(&st->lock);

        /*
         * Go over HT siblings and check whether one of them has set up the
         * shared state pointer already.
         */
        for_each_cpu(cpu, topology_sibling_cpumask(this_cpu)) {
                if (cpu == this_cpu)
                        continue;

                if (!per_cpu(ssb_state, cpu).shared_state)
                        continue;

                /* Link it to the state of the sibling: */
                st->shared_state = per_cpu(ssb_state, cpu).shared_state;
                return;
        }

        /*
         * First HT sibling to come up on the core.  Link shared state of
         * the first HT sibling to itself. The siblings on the same core
         * which come up later will see the shared state pointer and link
         * themselves to the state of this CPU.
         */
        st->shared_state = st;
}

/*
 * Logic is: First HT sibling enables SSBD for both siblings in the core
 * and last sibling to disable it, disables it for the whole core. This how
 * MSR_SPEC_CTRL works in "hardware":
 *
 *  CORE_SPEC_CTRL = THREAD0_SPEC_CTRL | THREAD1_SPEC_CTRL
 */
static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
{
        struct ssb_state *st = this_cpu_ptr(&ssb_state);
        u64 msr = x86_amd_ls_cfg_base;

        if (!static_cpu_has(X86_FEATURE_ZEN)) {
                msr |= ssbd_tif_to_amd_ls_cfg(tifn);
                wrmsrq(MSR_AMD64_LS_CFG, msr);
                return;
        }

        if (tifn & _TIF_SSBD) {
                /*
                 * Since this can race with prctl(), block reentry on the
                 * same CPU.
                 */
                if (__test_and_set_bit(LSTATE_SSB, &st->local_state))
                        return;

                msr |= x86_amd_ls_cfg_ssbd_mask;

                raw_spin_lock(&st->shared_state->lock);
                /* First sibling enables SSBD: */
                if (!st->shared_state->disable_state)
                        wrmsrq(MSR_AMD64_LS_CFG, msr);
                st->shared_state->disable_state++;
                raw_spin_unlock(&st->shared_state->lock);
        } else {
                if (!__test_and_clear_bit(LSTATE_SSB, &st->local_state))
                        return;

                raw_spin_lock(&st->shared_state->lock);
                st->shared_state->disable_state--;
                if (!st->shared_state->disable_state)
                        wrmsrq(MSR_AMD64_LS_CFG, msr);
                raw_spin_unlock(&st->shared_state->lock);
        }
}
#else
static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
{
        u64 msr = x86_amd_ls_cfg_base | ssbd_tif_to_amd_ls_cfg(tifn);

        wrmsrq(MSR_AMD64_LS_CFG, msr);
}
#endif

static __always_inline void amd_set_ssb_virt_state(unsigned long tifn)
{
        /*
         * SSBD has the same definition in SPEC_CTRL and VIRT_SPEC_CTRL,
         * so ssbd_tif_to_spec_ctrl() just works.
         */
        wrmsrq(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn));
}

/*
 * Update the MSRs managing speculation control, during context switch.
 *
 * tifp: Previous task's thread flags
 * tifn: Next task's thread flags
 */
static __always_inline void __speculation_ctrl_update(unsigned long tifp,
                                                      unsigned long tifn)
{
        unsigned long tif_diff = tifp ^ tifn;
        u64 msr = x86_spec_ctrl_base;
        bool updmsr = false;

        lockdep_assert_irqs_disabled();

        /* Handle change of TIF_SSBD depending on the mitigation method. */
        if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) {
                if (tif_diff & _TIF_SSBD)
                        amd_set_ssb_virt_state(tifn);
        } else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) {
                if (tif_diff & _TIF_SSBD)
                        amd_set_core_ssb_state(tifn);
        } else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
                   static_cpu_has(X86_FEATURE_AMD_SSBD)) {
                updmsr |= !!(tif_diff & _TIF_SSBD);
                msr |= ssbd_tif_to_spec_ctrl(tifn);
        }

        /* Only evaluate TIF_SPEC_IB if conditional STIBP is enabled. */
        if (IS_ENABLED(CONFIG_SMP) &&
            static_branch_unlikely(&switch_to_cond_stibp)) {
                updmsr |= !!(tif_diff & _TIF_SPEC_IB);
                msr |= stibp_tif_to_spec_ctrl(tifn);
        }

        if (updmsr)
                update_spec_ctrl_cond(msr);
}

static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
{
        if (test_and_clear_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE)) {
                if (task_spec_ssb_disable(tsk))
                        set_tsk_thread_flag(tsk, TIF_SSBD);
                else
                        clear_tsk_thread_flag(tsk, TIF_SSBD);

                if (task_spec_ib_disable(tsk))
                        set_tsk_thread_flag(tsk, TIF_SPEC_IB);
                else
                        clear_tsk_thread_flag(tsk, TIF_SPEC_IB);
        }
        /* Return the updated threadinfo flags*/
        return read_task_thread_flags(tsk);
}

void speculation_ctrl_update(unsigned long tif)
{
        unsigned long flags;

        /* Forced update. Make sure all relevant TIF flags are different */
        local_irq_save(flags);
        __speculation_ctrl_update(~tif, tif);
        local_irq_restore(flags);
}

/* Called from seccomp/prctl update */
void speculation_ctrl_update_current(void)
{
        preempt_disable();
        speculation_ctrl_update(speculation_ctrl_update_tif(current));
        preempt_enable();
}

static inline void cr4_toggle_bits_irqsoff(unsigned long mask)
{
        unsigned long newval, cr4 = this_cpu_read(cpu_tlbstate.cr4);

        newval = cr4 ^ mask;
        if (newval != cr4) {
                this_cpu_write(cpu_tlbstate.cr4, newval);
                __write_cr4(newval);
        }
}

void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
{
        unsigned long tifp, tifn;

        tifn = read_task_thread_flags(next_p);
        tifp = read_task_thread_flags(prev_p);

        switch_to_bitmap(tifp);

        propagate_user_return_notify(prev_p, next_p);

        if ((tifp & _TIF_BLOCKSTEP || tifn & _TIF_BLOCKSTEP) &&
            arch_has_block_step()) {
                unsigned long debugctl, msk;

                rdmsrq(MSR_IA32_DEBUGCTLMSR, debugctl);
                debugctl &= ~DEBUGCTLMSR_BTF;
                msk = tifn & _TIF_BLOCKSTEP;
                debugctl |= (msk >> TIF_BLOCKSTEP) << DEBUGCTLMSR_BTF_SHIFT;
                wrmsrq(MSR_IA32_DEBUGCTLMSR, debugctl);
        }

        if ((tifp ^ tifn) & _TIF_NOTSC)
                cr4_toggle_bits_irqsoff(X86_CR4_TSD);

        if ((tifp ^ tifn) & _TIF_NOCPUID)
                set_cpuid_faulting(!!(tifn & _TIF_NOCPUID));

        if (likely(!((tifp | tifn) & _TIF_SPEC_FORCE_UPDATE))) {
                __speculation_ctrl_update(tifp, tifn);
        } else {
                speculation_ctrl_update_tif(prev_p);
                tifn = speculation_ctrl_update_tif(next_p);

                /* Enforce MSR update to ensure consistent state */
                __speculation_ctrl_update(~tifn, tifn);
        }
}

/*
 * Idle related variables and functions
 */
unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
EXPORT_SYMBOL(boot_option_idle_override);

/*
 * We use this if we don't have any better idle routine..
 */
void __cpuidle default_idle(void)
{
        raw_safe_halt();
        raw_local_irq_disable();
}
#if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
EXPORT_SYMBOL(default_idle);
#endif

DEFINE_STATIC_CALL_NULL(x86_idle, default_idle);

static bool x86_idle_set(void)
{
        return !!static_call_query(x86_idle);
}

#ifndef CONFIG_SMP
static inline void __noreturn play_dead(void)
{
        BUG();
}
#endif

void arch_cpu_idle_enter(void)
{
        tsc_verify_tsc_adjust(false);
        local_touch_nmi();
}

void __noreturn arch_cpu_idle_dead(void)
{
        play_dead();
}

/*
 * Called from the generic idle code.
 */
void __cpuidle arch_cpu_idle(void)
{
        static_call(x86_idle)();
}
EXPORT_SYMBOL_GPL(arch_cpu_idle);

#ifdef CONFIG_XEN
bool xen_set_default_idle(void)
{
        bool ret = x86_idle_set();

        static_call_update(x86_idle, default_idle);

        return ret;
}
#endif

struct cpumask cpus_stop_mask;

void __noreturn stop_this_cpu(void *dummy)
{
        struct cpuinfo_x86 *c = this_cpu_ptr(&cpu_info);
        unsigned int cpu = smp_processor_id();

        local_irq_disable();

        /*
         * Remove this CPU from the online mask and disable it
         * unconditionally. This might be redundant in case that the reboot
         * vector was handled late and stop_other_cpus() sent an NMI.
         *
         * According to SDM and APM NMIs can be accepted even after soft
         * disabling the local APIC.
         */
        set_cpu_online(cpu, false);
        disable_local_APIC();
        mcheck_cpu_clear(c);

        if (this_cpu_read(cache_state_incoherent))
                wbinvd();

        /*
         * This brings a cache line back and dirties it, but
         * native_stop_other_cpus() will overwrite cpus_stop_mask after it
         * observed that all CPUs reported stop. This write will invalidate
         * the related cache line on this CPU.
         */
        cpumask_clear_cpu(cpu, &cpus_stop_mask);

#ifdef CONFIG_SMP
        if (smp_ops.stop_this_cpu) {
                smp_ops.stop_this_cpu();
                BUG();
        }
#endif

        for (;;) {
                /*
                 * Use native_halt() so that memory contents don't change
                 * (stack usage and variables) after possibly issuing the
                 * wbinvd() above.
                 */
                native_halt();
        }
}

/*
 * Prefer MWAIT over HALT if MWAIT is supported, MWAIT_CPUID leaf
 * exists and whenever MONITOR/MWAIT extensions are present there is at
 * least one C1 substate.
 *
 * Do not prefer MWAIT if MONITOR instruction has a bug or idle=nomwait
 * is passed to kernel commandline parameter.
 */
static __init bool prefer_mwait_c1_over_halt(void)
{
        const struct cpuinfo_x86 *c = &boot_cpu_data;
        u32 eax, ebx, ecx, edx;

        /* If override is enforced on the command line, fall back to HALT. */
        if (boot_option_idle_override != IDLE_NO_OVERRIDE)
                return false;

        /* MWAIT is not supported on this platform. Fallback to HALT */
        if (!cpu_has(c, X86_FEATURE_MWAIT))
                return false;

        /* Monitor has a bug or APIC stops in C1E. Fallback to HALT */
        if (boot_cpu_has_bug(X86_BUG_MONITOR) || boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E))
                return false;

        cpuid(CPUID_LEAF_MWAIT, &eax, &ebx, &ecx, &edx);

        /*
         * If MWAIT extensions are not available, it is safe to use MWAIT
         * with EAX=0, ECX=0.
         */
        if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED))
                return true;

        /*
         * If MWAIT extensions are available, there should be at least one
         * MWAIT C1 substate present.
         */
        return !!(edx & MWAIT_C1_SUBSTATE_MASK);
}

/*
 * MONITOR/MWAIT with no hints, used for default C1 state. This invokes MWAIT
 * with interrupts enabled and no flags, which is backwards compatible with the
 * original MWAIT implementation.
 */
static __cpuidle void mwait_idle(void)
{
        if (need_resched())
                return;

        x86_idle_clear_cpu_buffers();

        if (!current_set_polling_and_test()) {
                const void *addr = &current_thread_info()->flags;

                alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [addr] "a" (addr));
                __monitor(addr, 0, 0);
                if (need_resched())
                        goto out;

                __sti_mwait(0, 0);
                raw_local_irq_disable();
        }

out:
        __current_clr_polling();
}

void __init select_idle_routine(void)
{
        if (boot_option_idle_override == IDLE_POLL) {
                if (IS_ENABLED(CONFIG_SMP) && __max_threads_per_core > 1)
                        pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
                return;
        }

        /* Required to guard against xen_set_default_idle() */
        if (x86_idle_set())
                return;

        if (prefer_mwait_c1_over_halt()) {
                pr_info("using mwait in idle threads\n");
                static_call_update(x86_idle, mwait_idle);
        } else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
                pr_info("using TDX aware idle routine\n");
                static_call_update(x86_idle, tdx_halt);
        } else {
                static_call_update(x86_idle, default_idle);
        }
}

void amd_e400_c1e_apic_setup(void)
{
        if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
                pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id());
                local_irq_disable();
                tick_broadcast_force();
                local_irq_enable();
        }
}

void __init arch_post_acpi_subsys_init(void)
{
        u32 lo, hi;

        if (!boot_cpu_has_bug(X86_BUG_AMD_E400))
                return;

        /*
         * AMD E400 detection needs to happen after ACPI has been enabled. If
         * the machine is affected K8_INTP_C1E_ACTIVE_MASK bits are set in
         * MSR_K8_INT_PENDING_MSG.
         */
        rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
        if (!(lo & K8_INTP_C1E_ACTIVE_MASK))
                return;

        boot_cpu_set_bug(X86_BUG_AMD_APIC_C1E);

        if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
                mark_tsc_unstable("TSC halt in AMD C1E");

        if (IS_ENABLED(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST_IDLE))
                static_branch_enable(&arch_needs_tick_broadcast);
        pr_info("System has AMD C1E erratum E400. Workaround enabled.\n");
}

static int __init idle_setup(char *str)
{
        if (!str)
                return -EINVAL;

        if (!strcmp(str, "poll")) {
                pr_info("using polling idle threads\n");
                boot_option_idle_override = IDLE_POLL;
                cpu_idle_poll_ctrl(true);
        } else if (!strcmp(str, "halt")) {
                /* 'idle=halt' HALT for idle. C-states are disabled. */
                boot_option_idle_override = IDLE_HALT;
        } else if (!strcmp(str, "nomwait")) {
                /* 'idle=nomwait' disables MWAIT for idle */
                boot_option_idle_override = IDLE_NOMWAIT;
        } else {
                return -EINVAL;
        }

        return 0;
}
early_param("idle", idle_setup);

unsigned long arch_align_stack(unsigned long sp)
{
        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
                sp -= get_random_u32_below(8192);
        return sp & ~0xf;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
        if (mmap_is_ia32())
                return randomize_page(mm->brk, SZ_32M);

        return randomize_page(mm->brk, SZ_1G);
}

/*
 * Called from fs/proc with a reference on @p to find the function
 * which called into schedule(). This needs to be done carefully
 * because the task might wake up and we might look at a stack
 * changing under us.
 */
unsigned long __get_wchan(struct task_struct *p)
{
        struct unwind_state state;
        unsigned long addr = 0;

        if (!try_get_task_stack(p))
                return 0;

        for (unwind_start(&state, p, NULL, NULL); !unwind_done(&state);
             unwind_next_frame(&state)) {
                addr = unwind_get_return_address(&state);
                if (!addr)
                        break;
                if (in_sched_functions(addr))
                        continue;
                break;
        }

        put_task_stack(p);

        return addr;
}

SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
{
        switch (option) {
        case ARCH_GET_CPUID:
                return get_cpuid_mode();
        case ARCH_SET_CPUID:
                return set_cpuid_mode(arg2);
        case ARCH_GET_XCOMP_SUPP:
        case ARCH_GET_XCOMP_PERM:
        case ARCH_REQ_XCOMP_PERM:
        case ARCH_GET_XCOMP_GUEST_PERM:
        case ARCH_REQ_XCOMP_GUEST_PERM:
                return fpu_xstate_prctl(option, arg2);
        }

        if (!in_ia32_syscall())
                return do_arch_prctl_64(current, option, arg2);

        return -EINVAL;
}

SYSCALL_DEFINE0(ni_syscall)
{
        return -ENOSYS;
}