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 <linux/sched/signal.h>
  13
  14 #include <asm/fpu.h>
  15 #include <asm/elf.h>
  16 #include <asm/exceptions.h>
  17
  18 #ifdef CONFIG_LAZY_SAVE_FPU
  19 struct task_struct *fpu_state_owner;
  20 #endif
  21
  22 /*
  23  * error functions in FPU disabled exception
  24  */
  25 asmlinkage void fpu_disabled_in_kernel(struct pt_regs *regs)
  26 {
  27         die_if_no_fixup("An FPU Disabled exception happened in kernel space\n",
  28                         regs, EXCEP_FPU_DISABLED);
  29 }
  30
  31 /*
  32  * handle an FPU operational exception
  33  * - there's a possibility that if the FPU is asynchronous, the signal might
  34  *   be meant for a process other than the current one
  35  */
  36 asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
  37 {
  38         struct task_struct *tsk = current;
  39         siginfo_t info;
  40         u32 fpcr;
  41
  42         if (!user_mode(regs))
  43                 die_if_no_fixup("An FPU Operation exception happened in"
  44                                 " kernel space\n",
  45                                 regs, code);
  46
  47         if (!is_using_fpu(tsk))
  48                 die_if_no_fixup("An FPU Operation exception happened,"
  49                                 " but the FPU is not in use",
  50                                 regs, code);
  51
  52         info.si_signo = SIGFPE;
  53         info.si_errno = 0;
  54         info.si_addr = (void *) tsk->thread.uregs->pc;
  55         info.si_code = FPE_FLTINV;
  56
  57         unlazy_fpu(tsk);
  58
  59         fpcr = tsk->thread.fpu_state.fpcr;
  60
  61         if (fpcr & FPCR_EC_Z)
  62                 info.si_code = FPE_FLTDIV;
  63         else if (fpcr & FPCR_EC_O)
  64                 info.si_code = FPE_FLTOVF;
  65         else if (fpcr & FPCR_EC_U)
  66                 info.si_code = FPE_FLTUND;
  67         else if (fpcr & FPCR_EC_I)
  68                 info.si_code = FPE_FLTRES;
  69
  70         force_sig_info(SIGFPE, &info, tsk);
  71 }
  72
  73 /*
  74  * save the FPU state to a signal context
  75  */
  76 int fpu_setup_sigcontext(struct fpucontext *fpucontext)
  77 {
  78         struct task_struct *tsk = current;
  79
  80         if (!is_using_fpu(tsk))
  81                 return 0;
  82
  83         /* transfer the current FPU state to memory and cause fpu_init() to be
  84          * triggered by the next attempted FPU operation by the current
  85          * process.
  86          */
  87         preempt_disable();
  88
  89 #ifndef CONFIG_LAZY_SAVE_FPU
  90         if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
  91                 fpu_save(&tsk->thread.fpu_state);
  92                 tsk->thread.uregs->epsw &= ~EPSW_FE;
  93                 tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
  94         }
  95 #else /* !CONFIG_LAZY_SAVE_FPU */
  96         if (fpu_state_owner == tsk) {
  97                 fpu_save(&tsk->thread.fpu_state);
  98                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
  99                 fpu_state_owner = NULL;
 100         }
 101 #endif /* !CONFIG_LAZY_SAVE_FPU */
 102
 103         preempt_enable();
 104
 105         /* we no longer have a valid current FPU state */
 106         clear_using_fpu(tsk);
 107
 108         /* transfer the saved FPU state onto the userspace stack */
 109         if (copy_to_user(fpucontext,
 110                          &tsk->thread.fpu_state,
 111                          min(sizeof(struct fpu_state_struct),
 112                              sizeof(struct fpucontext))))
 113                 return -1;
 114
 115         return 1;
 116 }
 117
 118 /*
 119  * kill a process's FPU state during restoration after signal handling
 120  */
 121 void fpu_kill_state(struct task_struct *tsk)
 122 {
 123         /* disown anything left in the FPU */
 124         preempt_disable();
 125
 126 #ifndef CONFIG_LAZY_SAVE_FPU
 127         if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
 128                 tsk->thread.uregs->epsw &= ~EPSW_FE;
 129                 tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
 130         }
 131 #else /* !CONFIG_LAZY_SAVE_FPU */
 132         if (fpu_state_owner == tsk) {
 133                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
 134                 fpu_state_owner = NULL;
 135         }
 136 #endif /* !CONFIG_LAZY_SAVE_FPU */
 137
 138         preempt_enable();
 139
 140         /* we no longer have a valid current FPU state */
 141         clear_using_fpu(tsk);
 142 }
 143
 144 /*
 145  * restore the FPU state from a signal context
 146  */
 147 int fpu_restore_sigcontext(struct fpucontext *fpucontext)
 148 {
 149         struct task_struct *tsk = current;
 150         int ret;
 151
 152         /* load up the old FPU state */
 153         ret = copy_from_user(&tsk->thread.fpu_state, fpucontext,
 154                              min(sizeof(struct fpu_state_struct),
 155                                  sizeof(struct fpucontext)));
 156         if (!ret)
 157                 set_using_fpu(tsk);
 158
 159         return ret;
 160 }
 161
 162 /*
 163  * fill in the FPU structure for a core dump
 164  */
 165 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpreg)
 166 {
 167         struct task_struct *tsk = current;
 168         int fpvalid;
 169
 170         fpvalid = is_using_fpu(tsk);
 171         if (fpvalid) {
 172                 unlazy_fpu(tsk);
 173                 memcpy(fpreg, &tsk->thread.fpu_state, sizeof(*fpreg));
 174         }
 175
 176         return fpvalid;
 177 }