arch/mn10300/kernel/fpu.c

   1 /* MN10300 FPU management
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <asm/uaccess.h>
  12 #include <asm/fpu.h>
  13 #include <asm/elf.h>
  14 #include <asm/exceptions.h>
  15 #include <asm/system.h>
  16
  17 #ifdef CONFIG_LAZY_SAVE_FPU
  18 struct task_struct *fpu_state_owner;
  19 #endif
  20
  21 /*
  22  * error functions in FPU disabled exception
  23  */
  24 asmlinkage void fpu_disabled_in_kernel(struct pt_regs *regs)
  25 {
  26         die_if_no_fixup("An FPU Disabled exception happened in kernel space\n",
  27                         regs, EXCEP_FPU_DISABLED);
  28 }
  29
  30 /*
  31  * handle an FPU operational exception
  32  * - there's a possibility that if the FPU is asynchronous, the signal might
  33  *   be meant for a process other than the current one
  34  */
  35 asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
  36 {
  37         struct task_struct *tsk = current;
  38         siginfo_t info;
  39         u32 fpcr;
  40
  41         if (!user_mode(regs))
  42                 die_if_no_fixup("An FPU Operation exception happened in"
  43                                 " kernel space\n",
  44                                 regs, code);
  45
  46         if (!is_using_fpu(tsk))
  47                 die_if_no_fixup("An FPU Operation exception happened,"
  48                                 " but the FPU is not in use",
  49                                 regs, code);
  50
  51         info.si_signo = SIGFPE;
  52         info.si_errno = 0;
  53         info.si_addr = (void *) tsk->thread.uregs->pc;
  54         info.si_code = FPE_FLTINV;
  55
  56         unlazy_fpu(tsk);
  57
  58         fpcr = tsk->thread.fpu_state.fpcr;
  59
  60         if (fpcr & FPCR_EC_Z)
  61                 info.si_code = FPE_FLTDIV;
  62         else if (fpcr & FPCR_EC_O)
  63                 info.si_code = FPE_FLTOVF;
  64         else if (fpcr & FPCR_EC_U)
  65                 info.si_code = FPE_FLTUND;
  66         else if (fpcr & FPCR_EC_I)
  67                 info.si_code = FPE_FLTRES;
  68
  69         force_sig_info(SIGFPE, &info, tsk);
  70 }
  71
  72 /*
  73  * save the FPU state to a signal context
  74  */
  75 int fpu_setup_sigcontext(struct fpucontext *fpucontext)
  76 {
  77         struct task_struct *tsk = current;
  78
  79         if (!is_using_fpu(tsk))
  80                 return 0;
  81
  82         /* transfer the current FPU state to memory and cause fpu_init() to be
  83          * triggered by the next attempted FPU operation by the current
  84          * process.
  85          */
  86         preempt_disable();
  87
  88 #ifndef CONFIG_LAZY_SAVE_FPU
  89         if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
  90                 fpu_save(&tsk->thread.fpu_state);
  91                 tsk->thread.uregs->epsw &= ~EPSW_FE;
  92                 tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
  93         }
  94 #else /* !CONFIG_LAZY_SAVE_FPU */
  95         if (fpu_state_owner == tsk) {
  96                 fpu_save(&tsk->thread.fpu_state);
  97                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
  98                 fpu_state_owner = NULL;
  99         }
 100 #endif /* !CONFIG_LAZY_SAVE_FPU */
 101
 102         preempt_enable();
 103
 104         /* we no longer have a valid current FPU state */
 105         clear_using_fpu(tsk);
 106
 107         /* transfer the saved FPU state onto the userspace stack */
 108         if (copy_to_user(fpucontext,
 109                          &tsk->thread.fpu_state,
 110                          min(sizeof(struct fpu_state_struct),
 111                              sizeof(struct fpucontext))))
 112                 return -1;
 113
 114         return 1;
 115 }
 116
 117 /*
 118  * kill a process's FPU state during restoration after signal handling
 119  */
 120 void fpu_kill_state(struct task_struct *tsk)
 121 {
 122         /* disown anything left in the FPU */
 123         preempt_disable();
 124
 125 #ifndef CONFIG_LAZY_SAVE_FPU
 126         if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
 127                 tsk->thread.uregs->epsw &= ~EPSW_FE;
 128                 tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
 129         }
 130 #else /* !CONFIG_LAZY_SAVE_FPU */
 131         if (fpu_state_owner == tsk) {
 132                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
 133                 fpu_state_owner = NULL;
 134         }
 135 #endif /* !CONFIG_LAZY_SAVE_FPU */
 136
 137         preempt_enable();
 138
 139         /* we no longer have a valid current FPU state */
 140         clear_using_fpu(tsk);
 141 }
 142
 143 /*
 144  * restore the FPU state from a signal context
 145  */
 146 int fpu_restore_sigcontext(struct fpucontext *fpucontext)
 147 {
 148         struct task_struct *tsk = current;
 149         int ret;
 150
 151         /* load up the old FPU state */
 152         ret = copy_from_user(&tsk->thread.fpu_state, fpucontext,
 153                              min(sizeof(struct fpu_state_struct),
 154                                  sizeof(struct fpucontext)));
 155         if (!ret)
 156                 set_using_fpu(tsk);
 157
 158         return ret;
 159 }
 160
 161 /*
 162  * fill in the FPU structure for a core dump
 163  */
 164 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpreg)
 165 {
 166         struct task_struct *tsk = current;
 167         int fpvalid;
 168
 169         fpvalid = is_using_fpu(tsk);
 170         if (fpvalid) {
 171                 unlazy_fpu(tsk);
 172                 memcpy(fpreg, &tsk->thread.fpu_state, sizeof(*fpreg));
 173         }
 174
 175         return fpvalid;
 176 }