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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/arch/arm/vfp/vfpmodule.c
  *
  *  Copyright (C) 2004 ARM Limited.
  *  Written by Deep Blue Solutions Limited.
  */
 #include <linux/types.h>
 #include <linux/cpu.h>
 #include <linux/cpu_pm.h>
 #include <linux/hardirq.h>
 #include <linux/kernel.h>
 #include <linux/notifier.h>
 #include <linux/signal.h>
 #include <linux/sched/signal.h>
 #include <linux/smp.h>
 #include <linux/init.h>
 #include <linux/uaccess.h>
 #include <linux/user.h>
 #include <linux/export.h>
 
 #include <asm/cp15.h>
 #include <asm/cputype.h>
 #include <asm/system_info.h>
 #include <asm/thread_notify.h>
 #include <asm/traps.h>
 #include <asm/vfp.h>
 
 #include "vfpinstr.h"
 #include "vfp.h"
 
 /*
  * Our undef handlers (in entry.S)
  */
 asmlinkage void vfp_support_entry(void);
 asmlinkage void vfp_null_entry(void);
 
 asmlinkage void (*vfp_vector)(void) = vfp_null_entry;
 
 /*
  * Dual-use variable.
  * Used in startup: set to non-zero if VFP checks fail
  * After startup, holds VFP architecture
  */
 static unsigned int __initdata VFP_arch;
 
 /*
  * The pointer to the vfpstate structure of the thread which currently
  * owns the context held in the VFP hardware, or NULL if the hardware
  * context is invalid.
  *
  * For UP, this is sufficient to tell which thread owns the VFP context.
  * However, for SMP, we also need to check the CPU number stored in the
  * saved state too to catch migrations.
  */
 union vfp_state *vfp_current_hw_state[NR_CPUS];
 
 /*
  * Is 'thread's most up to date state stored in this CPUs hardware?
  * Must be called from non-preemptible context.
  */
 static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread)
 {
 #ifdef CONFIG_SMP
     if (thread->vfpstate.hard.cpu != cpu)
         return false;
 #endif
     return vfp_current_hw_state[cpu] == &thread->vfpstate;
 }
 
 /*
  * Force a reload of the VFP context from the thread structure.  We do
  * this by ensuring that access to the VFP hardware is disabled, and
  * clear vfp_current_hw_state.  Must be called from non-preemptible context.
  */
 static void vfp_force_reload(unsigned int cpu, struct thread_info *thread)
 {
     if (vfp_state_in_hw(cpu, thread)) {
         fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
         vfp_current_hw_state[cpu] = NULL;
     }
 #ifdef CONFIG_SMP
     thread->vfpstate.hard.cpu = NR_CPUS;
 #endif
 }
 
 /*
  * Per-thread VFP initialization.
  */
 static void vfp_thread_flush(struct thread_info *thread)
 {
     union vfp_state *vfp = &thread->vfpstate;
     unsigned int cpu;
 
     /*
      * Disable VFP to ensure we initialize it first.  We must ensure
      * that the modification of vfp_current_hw_state[] and hardware
      * disable are done for the same CPU and without preemption.
      *
      * Do this first to ensure that preemption won't overwrite our
      * state saving should access to the VFP be enabled at this point.
      */
     cpu = get_cpu();
     if (vfp_current_hw_state[cpu] == vfp)
         vfp_current_hw_state[cpu] = NULL;
     fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
     put_cpu();
 
     memset(vfp, 0, sizeof(union vfp_state));
 
     vfp->hard.fpexc = FPEXC_EN;
     vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
 #ifdef CONFIG_SMP
     vfp->hard.cpu = NR_CPUS;
 #endif
 }
 
 static void vfp_thread_exit(struct thread_info *thread)
 {
     /* release case: Per-thread VFP cleanup. */
     union vfp_state *vfp = &thread->vfpstate;
     unsigned int cpu = get_cpu();
 
     if (vfp_current_hw_state[cpu] == vfp)
         vfp_current_hw_state[cpu] = NULL;
     put_cpu();
 }
 
 static void vfp_thread_copy(struct thread_info *thread)
 {
     struct thread_info *parent = current_thread_info();
 
     vfp_sync_hwstate(parent);
     thread->vfpstate = parent->vfpstate;
 #ifdef CONFIG_SMP
     thread->vfpstate.hard.cpu = NR_CPUS;
 #endif
 }
 
 /*
  * When this function is called with the following 'cmd's, the following
  * is true while this function is being run:
  *  THREAD_NOFTIFY_SWTICH:
  *   - the previously running thread will not be scheduled onto another CPU.
  *   - the next thread to be run (v) will not be running on another CPU.
  *   - thread->cpu is the local CPU number
  *   - not preemptible as we're called in the middle of a thread switch
  *  THREAD_NOTIFY_FLUSH:
  *   - the thread (v) will be running on the local CPU, so
  *  v === current_thread_info()
  *   - thread->cpu is the local CPU number at the time it is accessed,
  *  but may change at any time.
  *   - we could be preempted if tree preempt rcu is enabled, so
  *  it is unsafe to use thread->cpu.
  *  THREAD_NOTIFY_EXIT
  *   - we could be preempted if tree preempt rcu is enabled, so
  *  it is unsafe to use thread->cpu.
  */
 static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
 {
     struct thread_info *thread = v;
     u32 fpexc;
 #ifdef CONFIG_SMP
     unsigned int cpu;
 #endif
 
     switch (cmd) {
     case THREAD_NOTIFY_SWITCH:
         fpexc = fmrx(FPEXC);
 
 #ifdef CONFIG_SMP
         cpu = thread->cpu;
 
         /*
          * On SMP, if VFP is enabled, save the old state in
          * case the thread migrates to a different CPU. The
          * restoring is done lazily.
          */
         if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu])
             vfp_save_state(vfp_current_hw_state[cpu], fpexc);
 #endif
 
         /*
          * Always disable VFP so we can lazily save/restore the
          * old state.
          */
         fmxr(FPEXC, fpexc & ~FPEXC_EN);
         break;
 
     case THREAD_NOTIFY_FLUSH:
         vfp_thread_flush(thread);
         break;
 
     case THREAD_NOTIFY_EXIT:
         vfp_thread_exit(thread);
         break;
 
     case THREAD_NOTIFY_COPY:
         vfp_thread_copy(thread);
         break;
     }
 
     return NOTIFY_DONE;
 }
 
 static struct notifier_block vfp_notifier_block = {
     .notifier_call  = vfp_notifier,
 };
 
 /*
  * Raise a SIGFPE for the current process.
  * sicode describes the signal being raised.
  */
 static void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
 {
     /*
      * This is the same as NWFPE, because it's not clear what
      * this is used for
      */
     current->thread.error_code = 0;
     current->thread.trap_no = 6;
 
     send_sig_fault(SIGFPE, sicode,
                (void __user *)(instruction_pointer(regs) - 4),
                current);
 }
 
 static void vfp_panic(char *reason, u32 inst)
 {
     int i;
 
     pr_err("VFP: Error: %s\n", reason);
     pr_err("VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n",
         fmrx(FPEXC), fmrx(FPSCR), inst);
     for (i = 0; i < 32; i += 2)
         pr_err("VFP: s%2u: 0x%08x s%2u: 0x%08x\n",
                i, vfp_get_float(i), i+1, vfp_get_float(i+1));
 }
 
 /*
  * Process bitmask of exception conditions.
  */
 static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
 {
     int si_code = 0;
 
     pr_debug("VFP: raising exceptions %08x\n", exceptions);
 
     if (exceptions == VFP_EXCEPTION_ERROR) {
         vfp_panic("unhandled bounce", inst);
         vfp_raise_sigfpe(FPE_FLTINV, regs);
         return;
     }
 
     /*
      * If any of the status flags are set, update the FPSCR.
      * Comparison instructions always return at least one of
      * these flags set.
      */
     if (exceptions & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V))
         fpscr &= ~(FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V);
 
     fpscr |= exceptions;
 
     fmxr(FPSCR, fpscr);
 
 #define RAISE(stat,en,sig)              \
     if (exceptions & stat && fpscr & en)        \
         si_code = sig;
 
     /*
      * These are arranged in priority order, least to highest.
      */
     RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV);
     RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES);
     RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND);
     RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
     RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);
 
     if (si_code)
         vfp_raise_sigfpe(si_code, regs);
 }
 
 /*
  * Emulate a VFP instruction.
  */
 static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
 {
     u32 exceptions = VFP_EXCEPTION_ERROR;
 
     pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);
 
     if (INST_CPRTDO(inst)) {
         if (!INST_CPRT(inst)) {
             /*
              * CPDO
              */
             if (vfp_single(inst)) {
                 exceptions = vfp_single_cpdo(inst, fpscr);
             } else {
                 exceptions = vfp_double_cpdo(inst, fpscr);
             }
         } else {
             /*
              * A CPRT instruction can not appear in FPINST2, nor
              * can it cause an exception.  Therefore, we do not
              * have to emulate it.
              */
         }
     } else {
         /*
          * A CPDT instruction can not appear in FPINST2, nor can
          * it cause an exception.  Therefore, we do not have to
          * emulate it.
          */
     }
     return exceptions & ~VFP_NAN_FLAG;
 }
 
 /*
  * Package up a bounce condition.
  */
 void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
 {
     u32 fpscr, orig_fpscr, fpsid, exceptions;
 
     pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);
 
     /*
      * At this point, FPEXC can have the following configuration:
      *
      *  EX DEX IXE
      *  0   1   x   - synchronous exception
      *  1   x   0   - asynchronous exception
      *  1   x   1   - sychronous on VFP subarch 1 and asynchronous on later
      *  0   0   1   - synchronous on VFP9 (non-standard subarch 1
      *                implementation), undefined otherwise
      *
      * Clear various bits and enable access to the VFP so we can
      * handle the bounce.
      */
     fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));
 
     fpsid = fmrx(FPSID);
     orig_fpscr = fpscr = fmrx(FPSCR);
 
     /*
      * Check for the special VFP subarch 1 and FPSCR.IXE bit case
      */
     if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT)
         && (fpscr & FPSCR_IXE)) {
         /*
          * Synchronous exception, emulate the trigger instruction
          */
         goto emulate;
     }
 
     if (fpexc & FPEXC_EX) {
 #ifndef CONFIG_CPU_FEROCEON
         /*
          * Asynchronous exception. The instruction is read from FPINST
          * and the interrupted instruction has to be restarted.
          */
         trigger = fmrx(FPINST);
         regs->ARM_pc -= 4;
 #endif
     } else if (!(fpexc & FPEXC_DEX)) {
         /*
          * Illegal combination of bits. It can be caused by an
          * unallocated VFP instruction but with FPSCR.IXE set and not
          * on VFP subarch 1.
          */
          vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
         goto exit;
     }
 
     /*
      * Modify fpscr to indicate the number of iterations remaining.
      * If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates
      * whether FPEXC.VECITR or FPSCR.LEN is used.
      */
     if (fpexc & (FPEXC_EX | FPEXC_VV)) {
         u32 len;
 
         len = fpexc + (1 << FPEXC_LENGTH_BIT);
 
         fpscr &= ~FPSCR_LENGTH_MASK;
         fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT);
     }
 
     /*
      * Handle the first FP instruction.  We used to take note of the
      * FPEXC bounce reason, but this appears to be unreliable.
      * Emulate the bounced instruction instead.
      */
     exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
     if (exceptions)
         vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
 
     /*
      * If there isn't a second FP instruction, exit now. Note that
      * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1.
      */
     if ((fpexc & (FPEXC_EX | FPEXC_FP2V)) != (FPEXC_EX | FPEXC_FP2V))
         goto exit;
 
     /*
      * The barrier() here prevents fpinst2 being read
      * before the condition above.
      */
     barrier();
     trigger = fmrx(FPINST2);
 
  emulate:
     exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
     if (exceptions)
         vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
  exit:
     preempt_enable();
 }
 
 static void vfp_enable(void *unused)
 {
     u32 access;
 
     BUG_ON(preemptible());
     access = get_copro_access();
 
     /*
      * Enable full access to VFP (cp10 and cp11)
      */
     set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
 }
 
 /* Called by platforms on which we want to disable VFP because it may not be
  * present on all CPUs within a SMP complex. Needs to be called prior to
  * vfp_init().
  */
 void __init vfp_disable(void)
 {
     if (VFP_arch) {
         pr_debug("%s: should be called prior to vfp_init\n", __func__);
         return;
     }
     VFP_arch = 1;
 }
 
 #ifdef CONFIG_CPU_PM
 static int vfp_pm_suspend(void)
 {
     struct thread_info *ti = current_thread_info();
     u32 fpexc = fmrx(FPEXC);
 
     /* if vfp is on, then save state for resumption */
     if (fpexc & FPEXC_EN) {
         pr_debug("%s: saving vfp state\n", __func__);
         vfp_save_state(&ti->vfpstate, fpexc);
 
         /* disable, just in case */
         fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
     } else if (vfp_current_hw_state[ti->cpu]) {
 #ifndef CONFIG_SMP
         fmxr(FPEXC, fpexc | FPEXC_EN);
         vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);
         fmxr(FPEXC, fpexc);
 #endif
     }
 
     /* clear any information we had about last context state */
     vfp_current_hw_state[ti->cpu] = NULL;
 
     return 0;
 }
 
 static void vfp_pm_resume(void)
 {
     /* ensure we have access to the vfp */
     vfp_enable(NULL);
 
     /* and disable it to ensure the next usage restores the state */
     fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
 }
 
 static int vfp_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd,
     void *v)
 {
     switch (cmd) {
     case CPU_PM_ENTER:
         vfp_pm_suspend();
         break;
     case CPU_PM_ENTER_FAILED:
     case CPU_PM_EXIT:
         vfp_pm_resume();
         break;
     }
     return NOTIFY_OK;
 }
 
 static struct notifier_block vfp_cpu_pm_notifier_block = {
     .notifier_call = vfp_cpu_pm_notifier,
 };
 
 static void vfp_pm_init(void)
 {
     cpu_pm_register_notifier(&vfp_cpu_pm_notifier_block);
 }
 
 #else
 static inline void vfp_pm_init(void) { }
 #endif /* CONFIG_CPU_PM */
 
 /*
  * Ensure that the VFP state stored in 'thread->vfpstate' is up to date
  * with the hardware state.
  */
 void vfp_sync_hwstate(struct thread_info *thread)
 {
     unsigned int cpu = get_cpu();
 
     if (vfp_state_in_hw(cpu, thread)) {
         u32 fpexc = fmrx(FPEXC);
 
         /*
          * Save the last VFP state on this CPU.
          */
         fmxr(FPEXC, fpexc | FPEXC_EN);
         vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
         fmxr(FPEXC, fpexc);
     }
 
     put_cpu();
 }
 
 /* Ensure that the thread reloads the hardware VFP state on the next use. */
 void vfp_flush_hwstate(struct thread_info *thread)
 {
     unsigned int cpu = get_cpu();
 
     vfp_force_reload(cpu, thread);
 
     put_cpu();
 }
 
 /*
  * Save the current VFP state into the provided structures and prepare
  * for entry into a new function (signal handler).
  */
 int vfp_preserve_user_clear_hwstate(struct user_vfp *ufp,
                     struct user_vfp_exc *ufp_exc)
 {
     struct thread_info *thread = current_thread_info();
     struct vfp_hard_struct *hwstate = &thread->vfpstate.hard;
 
     /* Ensure that the saved hwstate is up-to-date. */
     vfp_sync_hwstate(thread);
 
     /*
      * Copy the floating point registers. There can be unused
      * registers see asm/hwcap.h for details.
      */
     memcpy(&ufp->fpregs, &hwstate->fpregs, sizeof(hwstate->fpregs));
 
     /*
      * Copy the status and control register.
      */
     ufp->fpscr = hwstate->fpscr;
 
     /*
      * Copy the exception registers.
      */
     ufp_exc->fpexc = hwstate->fpexc;
     ufp_exc->fpinst = hwstate->fpinst;
     ufp_exc->fpinst2 = hwstate->fpinst2;
 
     /* Ensure that VFP is disabled. */
     vfp_flush_hwstate(thread);
 
     /*
      * As per the PCS, clear the length and stride bits for function
      * entry.
      */
     hwstate->fpscr &= ~(FPSCR_LENGTH_MASK | FPSCR_STRIDE_MASK);
     return 0;
 }
 
 /* Sanitise and restore the current VFP state from the provided structures. */
 int vfp_restore_user_hwstate(struct user_vfp *ufp, struct user_vfp_exc *ufp_exc)
 {
     struct thread_info *thread = current_thread_info();
     struct vfp_hard_struct *hwstate = &thread->vfpstate.hard;
     unsigned long fpexc;
 
     /* Disable VFP to avoid corrupting the new thread state. */
     vfp_flush_hwstate(thread);
 
     /*
      * Copy the floating point registers. There can be unused
      * registers see asm/hwcap.h for details.
      */
     memcpy(&hwstate->fpregs, &ufp->fpregs, sizeof(hwstate->fpregs));
     /*
      * Copy the status and control register.
      */
     hwstate->fpscr = ufp->fpscr;
 
     /*
      * Sanitise and restore the exception registers.
      */
     fpexc = ufp_exc->fpexc;
 
     /* Ensure the VFP is enabled. */
     fpexc |= FPEXC_EN;
 
     /* Ensure FPINST2 is invalid and the exception flag is cleared. */
     fpexc &= ~(FPEXC_EX | FPEXC_FP2V);
     hwstate->fpexc = fpexc;
 
     hwstate->fpinst = ufp_exc->fpinst;
     hwstate->fpinst2 = ufp_exc->fpinst2;
 
     return 0;
 }
 
 /*
  * VFP hardware can lose all context when a CPU goes offline.
  * As we will be running in SMP mode with CPU hotplug, we will save the
  * hardware state at every thread switch.  We clear our held state when
  * a CPU has been killed, indicating that the VFP hardware doesn't contain
  * a threads VFP state.  When a CPU starts up, we re-enable access to the
  * VFP hardware. The callbacks below are called on the CPU which
  * is being offlined/onlined.
  */
 static int vfp_dying_cpu(unsigned int cpu)
 {
     vfp_current_hw_state[cpu] = NULL;
     return 0;
 }
 
 static int vfp_starting_cpu(unsigned int unused)
 {
     vfp_enable(NULL);
     return 0;
 }
 
 #ifdef CONFIG_KERNEL_MODE_NEON
 
 static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr)
 {
     /*
      * If we reach this point, a floating point exception has been raised
      * while running in kernel mode. If the NEON/VFP unit was enabled at the
      * time, it means a VFP instruction has been issued that requires
      * software assistance to complete, something which is not currently
      * supported in kernel mode.
      * If the NEON/VFP unit was disabled, and the location pointed to below
      * is properly preceded by a call to kernel_neon_begin(), something has
      * caused the task to be scheduled out and back in again. In this case,
      * rebuilding and running with CONFIG_DEBUG_ATOMIC_SLEEP enabled should
      * be helpful in localizing the problem.
      */
     if (fmrx(FPEXC) & FPEXC_EN)
         pr_crit("BUG: unsupported FP instruction in kernel mode\n");
     else
         pr_crit("BUG: FP instruction issued in kernel mode with FP unit disabled\n");
     pr_crit("FPEXC == 0x%08x\n", fmrx(FPEXC));
     return 1;
 }
 
 static struct undef_hook vfp_kmode_exception_hook[] = {{
     .instr_mask = 0xfe000000,
     .instr_val  = 0xf2000000,
     .cpsr_mask  = MODE_MASK | PSR_T_BIT,
     .cpsr_val   = SVC_MODE,
     .fn     = vfp_kmode_exception,
 }, {
     .instr_mask = 0xff100000,
     .instr_val  = 0xf4000000,
     .cpsr_mask  = MODE_MASK | PSR_T_BIT,
     .cpsr_val   = SVC_MODE,
     .fn     = vfp_kmode_exception,
 }, {
     .instr_mask = 0xef000000,
     .instr_val  = 0xef000000,
     .cpsr_mask  = MODE_MASK | PSR_T_BIT,
     .cpsr_val   = SVC_MODE | PSR_T_BIT,
     .fn     = vfp_kmode_exception,
 }, {
     .instr_mask = 0xff100000,
     .instr_val  = 0xf9000000,
     .cpsr_mask  = MODE_MASK | PSR_T_BIT,
     .cpsr_val   = SVC_MODE | PSR_T_BIT,
     .fn     = vfp_kmode_exception,
 }, {
     .instr_mask = 0x0c000e00,
     .instr_val  = 0x0c000a00,
     .cpsr_mask  = MODE_MASK,
     .cpsr_val   = SVC_MODE,
     .fn     = vfp_kmode_exception,
 }};
 
 static int __init vfp_kmode_exception_hook_init(void)
 {
     int i;
 
     for (i = 0; i < ARRAY_SIZE(vfp_kmode_exception_hook); i++)
         register_undef_hook(&vfp_kmode_exception_hook[i]);
     return 0;
 }
 subsys_initcall(vfp_kmode_exception_hook_init);
 
 /*
  * Kernel-side NEON support functions
  */
 void kernel_neon_begin(void)
 {
     struct thread_info *thread = current_thread_info();
     unsigned int cpu;
     u32 fpexc;
 
     /*
      * Kernel mode NEON is only allowed outside of interrupt context
      * with preemption disabled. This will make sure that the kernel
      * mode NEON register contents never need to be preserved.
      */
     BUG_ON(in_interrupt());
     cpu = get_cpu();
 
     fpexc = fmrx(FPEXC) | FPEXC_EN;
     fmxr(FPEXC, fpexc);
 
     /*
      * Save the userland NEON/VFP state. Under UP,
      * the owner could be a task other than 'current'
      */
     if (vfp_state_in_hw(cpu, thread))
         vfp_save_state(&thread->vfpstate, fpexc);
 #ifndef CONFIG_SMP
     else if (vfp_current_hw_state[cpu] != NULL)
         vfp_save_state(vfp_current_hw_state[cpu], fpexc);
 #endif
     vfp_current_hw_state[cpu] = NULL;
 }
 EXPORT_SYMBOL(kernel_neon_begin);
 
 void kernel_neon_end(void)
 {
     /* Disable the NEON/VFP unit. */
     fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
     put_cpu();
 }
 EXPORT_SYMBOL(kernel_neon_end);
 
 #endif /* CONFIG_KERNEL_MODE_NEON */
 
 static int __init vfp_detect(struct pt_regs *regs, unsigned int instr)
 {
     VFP_arch = UINT_MAX;    /* mark as not present */
     regs->ARM_pc += 4;
     return 0;
 }
 
 static struct undef_hook vfp_detect_hook __initdata = {
     .instr_mask = 0x0c000e00,
     .instr_val  = 0x0c000a00,
     .cpsr_mask  = MODE_MASK,
     .cpsr_val   = SVC_MODE,
     .fn     = vfp_detect,
 };
 
 /*
  * VFP support code initialisation.
  */
 static int __init vfp_init(void)
 {
     unsigned int vfpsid;
     unsigned int cpu_arch = cpu_architecture();
 
     /*
      * Enable the access to the VFP on all online CPUs so the
      * following test on FPSID will succeed.
      */
     if (cpu_arch >= CPU_ARCH_ARMv6)
         on_each_cpu(vfp_enable, NULL, 1);
 
     /*
      * First check that there is a VFP that we can use.
      * The handler is already setup to just log calls, so
      * we just need to read the VFPSID register.
      */
     register_undef_hook(&vfp_detect_hook);
     barrier();
     vfpsid = fmrx(FPSID);
     barrier();
     unregister_undef_hook(&vfp_detect_hook);
     vfp_vector = vfp_null_entry;
 
     pr_info("VFP support v0.3: ");
     if (VFP_arch) {
         pr_cont("not present\n");
         return 0;
     /* Extract the architecture on CPUID scheme */
     } else if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {
         VFP_arch = vfpsid & FPSID_CPUID_ARCH_MASK;
         VFP_arch >>= FPSID_ARCH_BIT;
         /*
          * Check for the presence of the Advanced SIMD
          * load/store instructions, integer and single
          * precision floating point operations. Only check
          * for NEON if the hardware has the MVFR registers.
          */
         if (IS_ENABLED(CONFIG_NEON) &&
            (fmrx(MVFR1) & 0x000fff00) == 0x00011100)
             elf_hwcap |= HWCAP_NEON;
 
         if (IS_ENABLED(CONFIG_VFPv3)) {
             u32 mvfr0 = fmrx(MVFR0);
             if (((mvfr0 & MVFR0_DP_MASK) >> MVFR0_DP_BIT) == 0x2 ||
                 ((mvfr0 & MVFR0_SP_MASK) >> MVFR0_SP_BIT) == 0x2) {
                 elf_hwcap |= HWCAP_VFPv3;
                 /*
                  * Check for VFPv3 D16 and VFPv4 D16.  CPUs in
                  * this configuration only have 16 x 64bit
                  * registers.
                  */
                 if ((mvfr0 & MVFR0_A_SIMD_MASK) == 1)
                     /* also v4-D16 */
                     elf_hwcap |= HWCAP_VFPv3D16;
                 else
                     elf_hwcap |= HWCAP_VFPD32;
             }
 
             if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000)
                 elf_hwcap |= HWCAP_VFPv4;
         }
     /* Extract the architecture version on pre-cpuid scheme */
     } else {
         if (vfpsid & FPSID_NODOUBLE) {
             pr_cont("no double precision support\n");
             return 0;
         }
 
         VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;
     }
 
     cpuhp_setup_state_nocalls(CPUHP_AP_ARM_VFP_STARTING,
                   "arm/vfp:starting", vfp_starting_cpu,
                   vfp_dying_cpu);
 
     vfp_vector = vfp_support_entry;
 
     thread_register_notifier(&vfp_notifier_block);
     vfp_pm_init();
 
     /*
      * We detected VFP, and the support code is
      * in place; report VFP support to userspace.
      */
     elf_hwcap |= HWCAP_VFP;
 
     pr_cont("implementor %02x architecture %d part %02x variant %x rev %x\n",
         (vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,
         VFP_arch,
         (vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,
         (vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,
         (vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);
 
     return 0;
 }
 
 core_initcall(vfp_init);

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