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