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softemu8xx.c

/*
 * Software emulation of some PPC instructions for the 8xx core.
 *
 * Copyright (C) 1998 Dan Malek (dmalek@jlc.net)
 *
 * Software floating emuation for the MPC8xx processor.  I did this mostly
 * because it was easier than trying to get the libraries compiled for
 * software floating point.  The goal is still to get the libraries done,
 * but I lost patience and needed some hacks to at least get init and
 * shells running.  The first problem is the setjmp/longjmp that save
 * and restore the floating point registers.
 *
 * For this emulation, our working registers are found on the register
 * save area.
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/interrupt.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>

/* Eventually we may need a look-up table, but this works for now.
*/
#define LFS 48
#define LFD 50
#define LFDU      51
#define STFD      54
#define STFDU     55
#define FMR 63

void print_8xx_pte(struct mm_struct *mm, unsigned long addr)
{
      pgd_t *pgd;
      pmd_t *pmd;
      pte_t *pte;

      printk(" pte @ 0x%8lx: ", addr);
      pgd = pgd_offset(mm, addr & PAGE_MASK);
      if (pgd) {
            pmd = pmd_offset(pud_offset(pgd, addr & PAGE_MASK),
                             addr & PAGE_MASK);
            if (pmd && pmd_present(*pmd)) {
                  pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
                  if (pte) {
                        printk(" (0x%08lx)->(0x%08lx)->0x%08lx\n",
                                (long)pgd, (long)pte, (long)pte_val(*pte));
#define pp ((long)pte_val(*pte))
                        printk(" RPN: %05lx PP: %lx SPS: %lx SH: %lx "
                               "CI: %lx v: %lx\n",
                               pp>>12,    /* rpn */
                               (pp>>10)&3, /* pp */
                               (pp>>3)&1, /* small */
                               (pp>>2)&1, /* shared */
                               (pp>>1)&1, /* cache inhibit */
                               pp&1       /* valid */
                               );
#undef pp
                  }
                  else {
                        printk("no pte\n");
                  }
            }
            else {
                  printk("no pmd\n");
            }
      }
      else {
            printk("no pgd\n");
      }
}

int get_8xx_pte(struct mm_struct *mm, unsigned long addr)
{
      pgd_t *pgd;
      pmd_t *pmd;
      pte_t *pte;
      int retval = 0;

      pgd = pgd_offset(mm, addr & PAGE_MASK);
      if (pgd) {
            pmd = pmd_offset(pud_offset(pgd, addr & PAGE_MASK),
                             addr & PAGE_MASK);
            if (pmd && pmd_present(*pmd)) {
                  pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
                  if (pte) {
                        retval = (int)pte_val(*pte);
                  }
            }
      }
      return retval;
}

/*
 * We return 0 on success, 1 on unimplemented instruction, and EFAULT
 * if a load/store faulted.
 */
int Soft_emulate_8xx(struct pt_regs *regs)
{
      u32 inst, instword;
      u32 flreg, idxreg, disp;
      int retval;
      s16 sdisp;
      u32 *ea, *ip;

      retval = 0;

      instword = *((u32 *)regs->nip);
      inst = instword >> 26;

      flreg = (instword >> 21) & 0x1f;
      idxreg = (instword >> 16) & 0x1f;
      disp = instword & 0xffff;

      ea = (u32 *)(regs->gpr[idxreg] + disp);
      ip = (u32 *)&current->thread.TS_FPR(flreg);

      switch ( inst )
      {
      case LFD:
            /* this is a 16 bit quantity that is sign extended
             * so use a signed short here -- Cort
             */
            sdisp = (instword & 0xffff);
            ea = (u32 *)(regs->gpr[idxreg] + sdisp);
            if (copy_from_user(ip, ea, sizeof(double)))
                  retval = -EFAULT;
            break;

      case LFDU:
            if (copy_from_user(ip, ea, sizeof(double)))
                  retval = -EFAULT;
            else
                  regs->gpr[idxreg] = (u32)ea;
            break;
      case LFS:
            sdisp = (instword & 0xffff);
            ea = (u32 *)(regs->gpr[idxreg] + sdisp);
            if (copy_from_user(ip, ea, sizeof(float)))
                  retval = -EFAULT;
            break;
      case STFD:
            /* this is a 16 bit quantity that is sign extended
             * so use a signed short here -- Cort
             */
            sdisp = (instword & 0xffff);
            ea = (u32 *)(regs->gpr[idxreg] + sdisp);
            if (copy_to_user(ea, ip, sizeof(double)))
                  retval = -EFAULT;
            break;

      case STFDU:
            if (copy_to_user(ea, ip, sizeof(double)))
                  retval = -EFAULT;
            else
                  regs->gpr[idxreg] = (u32)ea;
            break;
      case FMR:
            /* assume this is a fp move -- Cort */
            memcpy(ip, &current->thread.TS_FPR((instword>>11)&0x1f),
                   sizeof(double));
            break;
      default:
            retval = 1;
            printk("Bad emulation %s/%d\n"
                   " NIP: %08lx instruction: %08x opcode: %x "
                   "A: %x B: %x C: %x code: %x rc: %x\n",
                   current->comm,current->pid,
                   regs->nip,
                   instword,inst,
                   (instword>>16)&0x1f,
                   (instword>>11)&0x1f,
                   (instword>>6)&0x1f,
                   (instword>>1)&0x3ff,
                   instword&1);
            {
                  int pa;
                  print_8xx_pte(current->mm,regs->nip);
                  pa = get_8xx_pte(current->mm,regs->nip) & PAGE_MASK;
                  pa |= (regs->nip & ~PAGE_MASK);
                  pa = (unsigned long)__va(pa);
                  printk("Kernel VA for NIP %x ", pa);
                  print_8xx_pte(current->mm,pa);
            }
      }

      if (retval == 0)
            regs->nip += 4;

      return retval;
}

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