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unaligned.c

/* unaligned.c: unalignment fixup handler for CPUs on which it is supported (FR451 only)
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/user.h>
#include <linux/string.h>
#include <linux/linkage.h>
#include <linux/init.h>

#include <asm/setup.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#if 0
#define kdebug(fmt, ...) printk("FDPIC "fmt"\n" ,##__VA_ARGS__ )
#else
#define kdebug(fmt, ...) do {} while(0)
#endif

#define _MA_SIGNED      0x01
#define _MA_HALF  0x02
#define _MA_WORD  0x04
#define _MA_DWORD 0x08
#define _MA_SZ_MASK     0x0e
#define _MA_LOAD  0x10
#define _MA_STORE 0x20
#define _MA_UPDATE      0x40
#define _MA_IMM         0x80

#define _MA_LDxU  _MA_LOAD | _MA_UPDATE
#define _MA_LDxI  _MA_LOAD | _MA_IMM
#define _MA_STxU  _MA_STORE | _MA_UPDATE
#define _MA_STxI  _MA_STORE | _MA_IMM

static const uint8_t tbl_LDGRk_reg[0x40] = {
      [0x02] = _MA_LOAD | _MA_HALF | _MA_SIGNED,      /* LDSH  @(GRi,GRj),GRk */
      [0x03] = _MA_LOAD | _MA_HALF,             /* LDUH  @(GRi,GRj),GRk */
      [0x04] = _MA_LOAD | _MA_WORD,             /* LD  @(GRi,GRj),GRk */
      [0x05] = _MA_LOAD | _MA_DWORD,                  /* LDD       @(GRi,GRj),GRk */
      [0x12] = _MA_LDxU | _MA_HALF | _MA_SIGNED,      /* LDSHU @(GRi,GRj),GRk */
      [0x13] = _MA_LDxU | _MA_HALF,             /* LDUHU @(GRi,GRj),GRk */
      [0x14] = _MA_LDxU | _MA_WORD,             /* LDU       @(GRi,GRj),GRk */
      [0x15] = _MA_LDxU | _MA_DWORD,                  /* LDDU      @(GRi,GRj),GRk */
};

static const uint8_t tbl_STGRk_reg[0x40] = {
      [0x01] = _MA_STORE | _MA_HALF,                  /* STH   @(GRi,GRj),GRk */
      [0x02] = _MA_STORE | _MA_WORD,                  /* ST  @(GRi,GRj),GRk */
      [0x03] = _MA_STORE | _MA_DWORD,                 /* STD       @(GRi,GRj),GRk */
      [0x11] = _MA_STxU  | _MA_HALF,                  /* STHU  @(GRi,GRj),GRk */
      [0x12] = _MA_STxU  | _MA_WORD,                  /* STU       @(GRi,GRj),GRk */
      [0x13] = _MA_STxU  | _MA_DWORD,                 /* STDU      @(GRi,GRj),GRk */
};

static const uint8_t tbl_LDSTGRk_imm[0x80] = {
      [0x31] = _MA_LDxI | _MA_HALF | _MA_SIGNED,      /* LDSHI @(GRi,d12),GRk */
      [0x32] = _MA_LDxI | _MA_WORD,             /* LDI   @(GRi,d12),GRk */
      [0x33] = _MA_LDxI | _MA_DWORD,                  /* LDDI  @(GRi,d12),GRk */
      [0x36] = _MA_LDxI | _MA_HALF,             /* LDUHI @(GRi,d12),GRk */
      [0x51] = _MA_STxI | _MA_HALF,             /* STHI  @(GRi,d12),GRk */
      [0x52] = _MA_STxI | _MA_WORD,             /* STI   @(GRi,d12),GRk */
      [0x53] = _MA_STxI | _MA_DWORD,                  /* STDI  @(GRi,d12),GRk */
};


/*****************************************************************************/
/*
 * see if we can handle the exception by fixing up a misaligned memory access
 */
int handle_misalignment(unsigned long esr0, unsigned long ear0, unsigned long epcr0)
{
      unsigned long insn, addr, *greg;
      int GRi, GRj, GRk, D12, op;

      union {
            uint64_t _64;
            uint32_t _32[2];
            uint16_t _16;
            uint8_t _8[8];
      } x;

      if (!(esr0 & ESR0_EAV) || !(epcr0 & EPCR0_V) || !(ear0 & 7))
            return -EAGAIN;

      epcr0 &= EPCR0_PC;

      if (__frame->pc != epcr0) {
            kdebug("MISALIGN: Execution not halted on excepting instruction\n");
            BUG();
      }

      if (__get_user(insn, (unsigned long *) epcr0) < 0)
            return -EFAULT;

      /* determine the instruction type first */
      switch ((insn >> 18) & 0x7f) {
      case 0x2:
            /* LDx @(GRi,GRj),GRk */
            op = tbl_LDGRk_reg[(insn >> 6) & 0x3f];
            break;

      case 0x3:
            /* STx GRk,@(GRi,GRj) */
            op = tbl_STGRk_reg[(insn >> 6) & 0x3f];
            break;

      default:
            op = tbl_LDSTGRk_imm[(insn >> 18) & 0x7f];
            break;
      }

      if (!op)
            return -EAGAIN;

      kdebug("MISALIGN: pc=%08lx insn=%08lx ad=%08lx op=%02x\n", epcr0, insn, ear0, op);

      memset(&x, 0xba, 8);

      /* validate the instruction parameters */
      greg = (unsigned long *) &__frame->tbr;

      GRi = (insn >> 12) & 0x3f;
      GRk = (insn >> 25) & 0x3f;

      if (GRi > 31 || GRk > 31)
            return -ENOENT;

      if (op & _MA_DWORD && GRk & 1)
            return -EINVAL;

      if (op & _MA_IMM) {
            D12 = insn & 0xfff;
            asm ("slli %0,#20,%0 ! srai %0,#20,%0" : "=r"(D12) : "0"(D12)); /* sign extend */
            addr = (GRi ? greg[GRi] : 0) + D12;
      }
      else {
            GRj = (insn >>  0) & 0x3f;
            if (GRj > 31)
                  return -ENOENT;
            addr = (GRi ? greg[GRi] : 0) + (GRj ? greg[GRj] : 0);
      }

      if (addr != ear0) {
            kdebug("MISALIGN: Calculated addr (%08lx) does not match EAR0 (%08lx)\n",
                   addr, ear0);
            return -EFAULT;
      }

      /* check the address is okay */
      if (user_mode(__frame) && ___range_ok(ear0, 8) < 0)
            return -EFAULT;

      /* perform the memory op */
      if (op & _MA_STORE) {
            /* perform a store */
            x._32[0] = 0;
            if (GRk != 0) {
                  if (op & _MA_HALF) {
                        x._16 = greg[GRk];
                  }
                  else {
                        x._32[0] = greg[GRk];
                  }
            }
            if (op & _MA_DWORD)
                  x._32[1] = greg[GRk + 1];

            kdebug("MISALIGN: Store GR%d { %08x:%08x } -> %08lx (%dB)\n",
                   GRk, x._32[1], x._32[0], addr, op & _MA_SZ_MASK);

            if (__memcpy_user((void *) addr, &x, op & _MA_SZ_MASK) != 0)
                  return -EFAULT;
      }
      else {
            /* perform a load */
            if (__memcpy_user(&x, (void *) addr, op & _MA_SZ_MASK) != 0)
                  return -EFAULT;

            if (op & _MA_HALF) {
                  if (op & _MA_SIGNED)
                        asm ("slli %0,#16,%0 ! srai %0,#16,%0"
                             : "=r"(x._32[0]) : "0"(x._16));
                  else
                        asm ("sethi #0,%0"
                             : "=r"(x._32[0]) : "0"(x._16));
            }

            kdebug("MISALIGN: Load %08lx (%dB) -> GR%d, { %08x:%08x }\n",
                   addr, op & _MA_SZ_MASK, GRk, x._32[1], x._32[0]);

            if (GRk != 0)
                  greg[GRk] = x._32[0];
            if (op & _MA_DWORD)
                  greg[GRk + 1] = x._32[1];
      }

      /* update the base pointer if required */
      if (op & _MA_UPDATE)
            greg[GRi] = addr;

      /* well... we've done that insn */
      __frame->pc = __frame->pc + 4;

      return 0;
} /* end handle_misalignment() */

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