arch/arm64/kernel/fpsimd.c

   1 /*
   2  * FP/SIMD context switching and fault handling
   3  *
   4  * Copyright (C) 2012 ARM Ltd.
   5  * Author: Catalin Marinas <catalin.marinas@arm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/cpu_pm.h>
  21 #include <linux/kernel.h>
  22 #include <linux/init.h>
  23 #include <linux/sched.h>
  24 #include <linux/signal.h>
  25 #include <linux/hardirq.h>
  26
  27 #include <asm/fpsimd.h>
  28 #include <asm/cputype.h>
  29
  30 #define FPEXC_IOF       (1 << 0)
  31 #define FPEXC_DZF       (1 << 1)
  32 #define FPEXC_OFF       (1 << 2)
  33 #define FPEXC_UFF       (1 << 3)
  34 #define FPEXC_IXF       (1 << 4)
  35 #define FPEXC_IDF       (1 << 7)
  36
  37 /*
  38  * Trapped FP/ASIMD access.
  39  */
  40 void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
  41 {
  42         /* TODO: implement lazy context saving/restoring */
  43         WARN_ON(1);
  44 }
  45
  46 /*
  47  * Raise a SIGFPE for the current process.
  48  */
  49 void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
  50 {
  51         siginfo_t info;
  52         unsigned int si_code = 0;
  53
  54         if (esr & FPEXC_IOF)
  55                 si_code = FPE_FLTINV;
  56         else if (esr & FPEXC_DZF)
  57                 si_code = FPE_FLTDIV;
  58         else if (esr & FPEXC_OFF)
  59                 si_code = FPE_FLTOVF;
  60         else if (esr & FPEXC_UFF)
  61                 si_code = FPE_FLTUND;
  62         else if (esr & FPEXC_IXF)
  63                 si_code = FPE_FLTRES;
  64
  65         memset(&info, 0, sizeof(info));
  66         info.si_signo = SIGFPE;
  67         info.si_code = si_code;
  68         info.si_addr = (void __user *)instruction_pointer(regs);
  69
  70         send_sig_info(SIGFPE, &info, current);
  71 }
  72
  73 void fpsimd_thread_switch(struct task_struct *next)
  74 {
  75         /* check if not kernel threads */
  76         if (current->mm)
  77                 fpsimd_save_state(&current->thread.fpsimd_state);
  78         if (next->mm)
  79                 fpsimd_load_state(&next->thread.fpsimd_state);
  80 }
  81
  82 void fpsimd_flush_thread(void)
  83 {
  84         preempt_disable();
  85         memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
  86         fpsimd_load_state(&current->thread.fpsimd_state);
  87         preempt_enable();
  88 }
  89
  90 /*
  91  * Save the userland FPSIMD state of 'current' to memory
  92  */
  93 void fpsimd_preserve_current_state(void)
  94 {
  95         preempt_disable();
  96         fpsimd_save_state(&current->thread.fpsimd_state);
  97         preempt_enable();
  98 }
  99
 100 /*
 101  * Load an updated userland FPSIMD state for 'current' from memory
 102  */
 103 void fpsimd_update_current_state(struct fpsimd_state *state)
 104 {
 105         preempt_disable();
 106         fpsimd_load_state(state);
 107         preempt_enable();
 108 }
 109
 110 #ifdef CONFIG_KERNEL_MODE_NEON
 111
 112 /*
 113  * Kernel-side NEON support functions
 114  */
 115 void kernel_neon_begin(void)
 116 {
 117         /* Avoid using the NEON in interrupt context */
 118         BUG_ON(in_interrupt());
 119         preempt_disable();
 120
 121         if (current->mm)
 122                 fpsimd_save_state(&current->thread.fpsimd_state);
 123 }
 124 EXPORT_SYMBOL(kernel_neon_begin);
 125
 126 void kernel_neon_end(void)
 127 {
 128         if (current->mm)
 129                 fpsimd_load_state(&current->thread.fpsimd_state);
 130
 131         preempt_enable();
 132 }
 133 EXPORT_SYMBOL(kernel_neon_end);
 134
 135 #endif /* CONFIG_KERNEL_MODE_NEON */
 136
 137 #ifdef CONFIG_CPU_PM
 138 static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
 139                                   unsigned long cmd, void *v)
 140 {
 141         switch (cmd) {
 142         case CPU_PM_ENTER:
 143                 if (current->mm)
 144                         fpsimd_save_state(&current->thread.fpsimd_state);
 145                 break;
 146         case CPU_PM_EXIT:
 147                 if (current->mm)
 148                         fpsimd_load_state(&current->thread.fpsimd_state);
 149                 break;
 150         case CPU_PM_ENTER_FAILED:
 151         default:
 152                 return NOTIFY_DONE;
 153         }
 154         return NOTIFY_OK;
 155 }
 156
 157 static struct notifier_block fpsimd_cpu_pm_notifier_block = {
 158         .notifier_call = fpsimd_cpu_pm_notifier,
 159 };
 160
 161 static void fpsimd_pm_init(void)
 162 {
 163         cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);
 164 }
 165
 166 #else
 167 static inline void fpsimd_pm_init(void) { }
 168 #endif /* CONFIG_CPU_PM */
 169
 170 /*
 171  * FP/SIMD support code initialisation.
 172  */
 173 static int __init fpsimd_init(void)
 174 {
 175         u64 pfr = read_cpuid(ID_AA64PFR0_EL1);
 176
 177         if (pfr & (0xf << 16)) {
 178                 pr_notice("Floating-point is not implemented\n");
 179                 return 0;
 180         }
 181         elf_hwcap |= HWCAP_FP;
 182
 183         if (pfr & (0xf << 20))
 184                 pr_notice("Advanced SIMD is not implemented\n");
 185         else
 186                 elf_hwcap |= HWCAP_ASIMD;
 187
 188         fpsimd_pm_init();
 189
 190         return 0;
 191 }
 192 late_initcall(fpsimd_init);