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   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
  16 struct task_struct *fpu_state_owner;
  17
  18 /*
  19  * handle an exception due to the FPU being disabled
  20  */
  21 asmlinkage void fpu_disabled(struct pt_regs *regs, enum exception_code code)
  22 {
  23         struct task_struct *tsk = current;
  24
  25         if (!user_mode(regs))
  26                 die_if_no_fixup("An FPU Disabled exception happened in"
  27                                 " kernel space\n",
  28                                 regs, code);
  29
  30 #ifdef CONFIG_FPU
  31         preempt_disable();
  32
  33         /* transfer the last process's FPU state to memory */
  34         if (fpu_state_owner) {
  35                 fpu_save(&fpu_state_owner->thread.fpu_state);
  36                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
  37         }
  38
  39         /* the current process now owns the FPU state */
  40         fpu_state_owner = tsk;
  41         regs->epsw |= EPSW_FE;
  42
  43         /* load the FPU with the current process's FPU state or invent a new
  44          * clean one if the process doesn't have one */
  45         if (is_using_fpu(tsk)) {
  46                 fpu_restore(&tsk->thread.fpu_state);
  47         } else {
  48                 fpu_init_state();
  49                 set_using_fpu(tsk);
  50         }
  51
  52         preempt_enable();
  53 #else
  54         {
  55                 siginfo_t info;
  56
  57                 info.si_signo = SIGFPE;
  58                 info.si_errno = 0;
  59                 info.si_addr = (void *) tsk->thread.uregs->pc;
  60                 info.si_code = FPE_FLTINV;
  61
  62                 force_sig_info(SIGFPE, &info, tsk);
  63         }
  64 #endif  /* CONFIG_FPU */
  65 }
  66
  67 /*
  68  * handle an FPU operational exception
  69  * - there's a possibility that if the FPU is asynchronous, the signal might
  70  *   be meant for a process other than the current one
  71  */
  72 asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
  73 {
  74         struct task_struct *tsk = fpu_state_owner;
  75         siginfo_t info;
  76
  77         if (!user_mode(regs))
  78                 die_if_no_fixup("An FPU Operation exception happened in"
  79                                 " kernel space\n",
  80                                 regs, code);
  81
  82         if (!tsk)
  83                 die_if_no_fixup("An FPU Operation exception happened,"
  84                                 " but the FPU is not in use",
  85                                 regs, code);
  86
  87         info.si_signo = SIGFPE;
  88         info.si_errno = 0;
  89         info.si_addr = (void *) tsk->thread.uregs->pc;
  90         info.si_code = FPE_FLTINV;
  91
  92 #ifdef CONFIG_FPU
  93         {
  94                 u32 fpcr;
  95
  96                 /* get FPCR (we need to enable the FPU whilst we do this) */
  97                 asm volatile("  or      %1,epsw         \n"
  98 #ifdef CONFIG_MN10300_PROC_MN103E010
  99                              "  nop                     \n"
 100                              "  nop                     \n"
 101                              "  nop                     \n"
 102 #endif
 103                              "  fmov    fpcr,%0         \n"
 104 #ifdef CONFIG_MN10300_PROC_MN103E010
 105                              "  nop                     \n"
 106                              "  nop                     \n"
 107                              "  nop                     \n"
 108 #endif
 109                              "  and     %2,epsw         \n"
 110                              : "=&d"(fpcr)
 111                              : "i"(EPSW_FE), "i"(~EPSW_FE)
 112                              );
 113
 114                 if (fpcr & FPCR_EC_Z)
 115                         info.si_code = FPE_FLTDIV;
 116                 else if (fpcr & FPCR_EC_O)
 117                         info.si_code = FPE_FLTOVF;
 118                 else if (fpcr & FPCR_EC_U)
 119                         info.si_code = FPE_FLTUND;
 120                 else if (fpcr & FPCR_EC_I)
 121                         info.si_code = FPE_FLTRES;
 122         }
 123 #endif
 124
 125         force_sig_info(SIGFPE, &info, tsk);
 126 }
 127
 128 /*
 129  * save the FPU state to a signal context
 130  */
 131 int fpu_setup_sigcontext(struct fpucontext *fpucontext)
 132 {
 133 #ifdef CONFIG_FPU
 134         struct task_struct *tsk = current;
 135
 136         if (!is_using_fpu(tsk))
 137                 return 0;
 138
 139         /* transfer the current FPU state to memory and cause fpu_init() to be
 140          * triggered by the next attempted FPU operation by the current
 141          * process.
 142          */
 143         preempt_disable();
 144
 145         if (fpu_state_owner == tsk) {
 146                 fpu_save(&tsk->thread.fpu_state);
 147                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
 148                 fpu_state_owner = NULL;
 149         }
 150
 151         preempt_enable();
 152
 153         /* we no longer have a valid current FPU state */
 154         clear_using_fpu(tsk);
 155
 156         /* transfer the saved FPU state onto the userspace stack */
 157         if (copy_to_user(fpucontext,
 158                          &tsk->thread.fpu_state,
 159                          min(sizeof(struct fpu_state_struct),
 160                              sizeof(struct fpucontext))))
 161                 return -1;
 162
 163         return 1;
 164 #else
 165         return 0;
 166 #endif
 167 }
 168
 169 /*
 170  * kill a process's FPU state during restoration after signal handling
 171  */
 172 void fpu_kill_state(struct task_struct *tsk)
 173 {
 174 #ifdef CONFIG_FPU
 175         /* disown anything left in the FPU */
 176         preempt_disable();
 177
 178         if (fpu_state_owner == tsk) {
 179                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
 180                 fpu_state_owner = NULL;
 181         }
 182
 183         preempt_enable();
 184 #endif
 185         /* we no longer have a valid current FPU state */
 186         clear_using_fpu(tsk);
 187 }
 188
 189 /*
 190  * restore the FPU state from a signal context
 191  */
 192 int fpu_restore_sigcontext(struct fpucontext *fpucontext)
 193 {
 194         struct task_struct *tsk = current;
 195         int ret;
 196
 197         /* load up the old FPU state */
 198         ret = copy_from_user(&tsk->thread.fpu_state,
 199                              fpucontext,
 200                              min(sizeof(struct fpu_state_struct),
 201                                  sizeof(struct fpucontext)));
 202         if (!ret)
 203                 set_using_fpu(tsk);
 204
 205         return ret;
 206 }
 207
 208 /*
 209  * fill in the FPU structure for a core dump
 210  */
 211 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpreg)
 212 {
 213         struct task_struct *tsk = current;
 214         int fpvalid;
 215
 216         fpvalid = is_using_fpu(tsk);
 217         if (fpvalid) {
 218                 unlazy_fpu(tsk);
 219                 memcpy(fpreg, &tsk->thread.fpu_state, sizeof(*fpreg));
 220         }
 221
 222         return fpvalid;
 223 }