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unwind_decoder.c

/*
 * Copyright (C) 2000 Hewlett-Packard Co
 * Copyright (C) 2000 David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * Generic IA-64 unwind info decoder.
 *
 * This file is used both by the Linux kernel and objdump.  Please keep
 * the two copies of this file in sync.
 *
 * You need to customize the decoder by defining the following
 * macros/constants before including this file:
 *
 *  Types:
 *    unw_word    Unsigned integer type with at least 64 bits 
 *
 *  Register names:
 *    UNW_REG_BSP
 *    UNW_REG_BSPSTORE
 *    UNW_REG_FPSR
 *    UNW_REG_LC
 *    UNW_REG_PFS
 *    UNW_REG_PR
 *    UNW_REG_RNAT
 *    UNW_REG_PSP
 *    UNW_REG_RP
 *    UNW_REG_UNAT
 *
 *  Decoder action macros:
 *    UNW_DEC_BAD_CODE(code)
 *    UNW_DEC_ABI(fmt,abi,context,arg)
 *    UNW_DEC_BR_GR(fmt,brmask,gr,arg)
 *    UNW_DEC_BR_MEM(fmt,brmask,arg)
 *    UNW_DEC_COPY_STATE(fmt,label,arg)
 *    UNW_DEC_EPILOGUE(fmt,t,ecount,arg)
 *    UNW_DEC_FRGR_MEM(fmt,grmask,frmask,arg)
 *    UNW_DEC_FR_MEM(fmt,frmask,arg)
 *    UNW_DEC_GR_GR(fmt,grmask,gr,arg)
 *    UNW_DEC_GR_MEM(fmt,grmask,arg)
 *    UNW_DEC_LABEL_STATE(fmt,label,arg)
 *    UNW_DEC_MEM_STACK_F(fmt,t,size,arg)
 *    UNW_DEC_MEM_STACK_V(fmt,t,arg)
 *    UNW_DEC_PRIUNAT_GR(fmt,r,arg)
 *    UNW_DEC_PRIUNAT_WHEN_GR(fmt,t,arg)
 *    UNW_DEC_PRIUNAT_WHEN_MEM(fmt,t,arg)
 *    UNW_DEC_PRIUNAT_WHEN_PSPREL(fmt,pspoff,arg)
 *    UNW_DEC_PRIUNAT_WHEN_SPREL(fmt,spoff,arg)
 *    UNW_DEC_PROLOGUE(fmt,body,rlen,arg)
 *    UNW_DEC_PROLOGUE_GR(fmt,rlen,mask,grsave,arg)
 *    UNW_DEC_REG_PSPREL(fmt,reg,pspoff,arg)
 *    UNW_DEC_REG_REG(fmt,src,dst,arg)
 *    UNW_DEC_REG_SPREL(fmt,reg,spoff,arg)
 *    UNW_DEC_REG_WHEN(fmt,reg,t,arg)
 *    UNW_DEC_RESTORE(fmt,t,abreg,arg)
 *    UNW_DEC_RESTORE_P(fmt,qp,t,abreg,arg)
 *    UNW_DEC_SPILL_BASE(fmt,pspoff,arg)
 *    UNW_DEC_SPILL_MASK(fmt,imaskp,arg)
 *    UNW_DEC_SPILL_PSPREL(fmt,t,abreg,pspoff,arg)
 *    UNW_DEC_SPILL_PSPREL_P(fmt,qp,t,abreg,pspoff,arg)
 *    UNW_DEC_SPILL_REG(fmt,t,abreg,x,ytreg,arg)
 *    UNW_DEC_SPILL_REG_P(fmt,qp,t,abreg,x,ytreg,arg)
 *    UNW_DEC_SPILL_SPREL(fmt,t,abreg,spoff,arg)
 *    UNW_DEC_SPILL_SPREL_P(fmt,qp,t,abreg,pspoff,arg)
 */

static unw_word
unw_decode_uleb128 (unsigned char **dpp)
{
  unsigned shift = 0;
  unw_word byte, result = 0;
  unsigned char *bp = *dpp;

  while (1)
    {
      byte = *bp++;
      result |= (byte & 0x7f) << shift;
      if ((byte & 0x80) == 0)
      break;
      shift += 7;
    }
  *dpp = bp;
  return result;
}

static unsigned char *
unw_decode_x1 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char byte1, abreg;
  unw_word t, off;

  byte1 = *dp++;
  t = unw_decode_uleb128 (&dp);
  off = unw_decode_uleb128 (&dp);
  abreg = (byte1 & 0x7f);
  if (byte1 & 0x80)
        UNW_DEC_SPILL_SPREL(X1, t, abreg, off, arg);
  else
        UNW_DEC_SPILL_PSPREL(X1, t, abreg, off, arg);
  return dp;
}

static unsigned char *
unw_decode_x2 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char byte1, byte2, abreg, x, ytreg;
  unw_word t;

  byte1 = *dp++; byte2 = *dp++;
  t = unw_decode_uleb128 (&dp);
  abreg = (byte1 & 0x7f);
  ytreg = byte2;
  x = (byte1 >> 7) & 1;
  if ((byte1 & 0x80) == 0 && ytreg == 0)
    UNW_DEC_RESTORE(X2, t, abreg, arg);
  else
    UNW_DEC_SPILL_REG(X2, t, abreg, x, ytreg, arg);
  return dp;
}

static unsigned char *
unw_decode_x3 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char byte1, byte2, abreg, qp;
  unw_word t, off;

  byte1 = *dp++; byte2 = *dp++;
  t = unw_decode_uleb128 (&dp);
  off = unw_decode_uleb128 (&dp);

  qp = (byte1 & 0x3f);
  abreg = (byte2 & 0x7f);

  if (byte1 & 0x80)
    UNW_DEC_SPILL_SPREL_P(X3, qp, t, abreg, off, arg);
  else
    UNW_DEC_SPILL_PSPREL_P(X3, qp, t, abreg, off, arg);
  return dp;
}

static unsigned char *
unw_decode_x4 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char byte1, byte2, byte3, qp, abreg, x, ytreg;
  unw_word t;

  byte1 = *dp++; byte2 = *dp++; byte3 = *dp++;
  t = unw_decode_uleb128 (&dp);

  qp = (byte1 & 0x3f);
  abreg = (byte2 & 0x7f);
  x = (byte2 >> 7) & 1;
  ytreg = byte3;

  if ((byte2 & 0x80) == 0 && byte3 == 0)
    UNW_DEC_RESTORE_P(X4, qp, t, abreg, arg);
  else
    UNW_DEC_SPILL_REG_P(X4, qp, t, abreg, x, ytreg, arg);
  return dp;
}

static unsigned char *
unw_decode_r1 (unsigned char *dp, unsigned char code, void *arg)
{
  int body = (code & 0x20) != 0;
  unw_word rlen;

  rlen = (code & 0x1f);
  UNW_DEC_PROLOGUE(R1, body, rlen, arg);
  return dp;
}

static unsigned char *
unw_decode_r2 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char byte1, mask, grsave;
  unw_word rlen;

  byte1 = *dp++;

  mask = ((code & 0x7) << 1) | ((byte1 >> 7) & 1);
  grsave = (byte1 & 0x7f);
  rlen = unw_decode_uleb128 (&dp);
  UNW_DEC_PROLOGUE_GR(R2, rlen, mask, grsave, arg);
  return dp;
}

static unsigned char *
unw_decode_r3 (unsigned char *dp, unsigned char code, void *arg)
{
  unw_word rlen;

  rlen = unw_decode_uleb128 (&dp);
  UNW_DEC_PROLOGUE(R3, ((code & 0x3) == 1), rlen, arg);
  return dp;
}

static unsigned char *
unw_decode_p1 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char brmask = (code & 0x1f);

  UNW_DEC_BR_MEM(P1, brmask, arg);
  return dp;
}

static unsigned char *
unw_decode_p2_p5 (unsigned char *dp, unsigned char code, void *arg)
{
  if ((code & 0x10) == 0)
    {
      unsigned char byte1 = *dp++;

      UNW_DEC_BR_GR(P2, ((code & 0xf) << 1) | ((byte1 >> 7) & 1),
                (byte1 & 0x7f), arg);
    }
  else if ((code & 0x08) == 0)
    {
      unsigned char byte1 = *dp++, r, dst;

      r = ((code & 0x7) << 1) | ((byte1 >> 7) & 1);
      dst = (byte1 & 0x7f);
      switch (r)
      {
      case 0: UNW_DEC_REG_GR(P3, UNW_REG_PSP, dst, arg); break;
      case 1: UNW_DEC_REG_GR(P3, UNW_REG_RP, dst, arg); break;
      case 2: UNW_DEC_REG_GR(P3, UNW_REG_PFS, dst, arg); break;
      case 3: UNW_DEC_REG_GR(P3, UNW_REG_PR, dst, arg); break;
      case 4: UNW_DEC_REG_GR(P3, UNW_REG_UNAT, dst, arg); break;
      case 5: UNW_DEC_REG_GR(P3, UNW_REG_LC, dst, arg); break;
      case 6: UNW_DEC_RP_BR(P3, dst, arg); break;
      case 7: UNW_DEC_REG_GR(P3, UNW_REG_RNAT, dst, arg); break;
      case 8: UNW_DEC_REG_GR(P3, UNW_REG_BSP, dst, arg); break;
      case 9: UNW_DEC_REG_GR(P3, UNW_REG_BSPSTORE, dst, arg); break;
      case 10: UNW_DEC_REG_GR(P3, UNW_REG_FPSR, dst, arg); break;
      case 11: UNW_DEC_PRIUNAT_GR(P3, dst, arg); break;
      default: UNW_DEC_BAD_CODE(r); break;
      }
    }
  else if ((code & 0x7) == 0)
    UNW_DEC_SPILL_MASK(P4, dp, arg);
  else if ((code & 0x7) == 1)
    {
      unw_word grmask, frmask, byte1, byte2, byte3;

      byte1 = *dp++; byte2 = *dp++; byte3 = *dp++;
      grmask = ((byte1 >> 4) & 0xf);
      frmask = ((byte1 & 0xf) << 16) | (byte2 << 8) | byte3;
      UNW_DEC_FRGR_MEM(P5, grmask, frmask, arg);
    }
  else
    UNW_DEC_BAD_CODE(code);
  return dp;
}

static unsigned char *
unw_decode_p6 (unsigned char *dp, unsigned char code, void *arg)
{
  int gregs = (code & 0x10) != 0;
  unsigned char mask = (code & 0x0f);

  if (gregs)
    UNW_DEC_GR_MEM(P6, mask, arg);
  else
    UNW_DEC_FR_MEM(P6, mask, arg);
  return dp;
}

static unsigned char *
unw_decode_p7_p10 (unsigned char *dp, unsigned char code, void *arg)
{
  unsigned char r, byte1, byte2;
  unw_word t, size;

  if ((code & 0x10) == 0)
    {
      r = (code & 0xf);
      t = unw_decode_uleb128 (&dp);
      switch (r)
      {
      case 0:
        size = unw_decode_uleb128 (&dp);
        UNW_DEC_MEM_STACK_F(P7, t, size, arg);
        break;

      case 1: UNW_DEC_MEM_STACK_V(P7, t, arg); break;
      case 2: UNW_DEC_SPILL_BASE(P7, t, arg); break;
      case 3: UNW_DEC_REG_SPREL(P7, UNW_REG_PSP, t, arg); break;
      case 4: UNW_DEC_REG_WHEN(P7, UNW_REG_RP, t, arg); break;
      case 5: UNW_DEC_REG_PSPREL(P7, UNW_REG_RP, t, arg); break;
      case 6: UNW_DEC_REG_WHEN(P7, UNW_REG_PFS, t, arg); break;
      case 7: UNW_DEC_REG_PSPREL(P7, UNW_REG_PFS, t, arg); break;
      case 8: UNW_DEC_REG_WHEN(P7, UNW_REG_PR, t, arg); break;
      case 9: UNW_DEC_REG_PSPREL(P7, UNW_REG_PR, t, arg); break;
      case 10: UNW_DEC_REG_WHEN(P7, UNW_REG_LC, t, arg); break;
      case 11: UNW_DEC_REG_PSPREL(P7, UNW_REG_LC, t, arg); break;
      case 12: UNW_DEC_REG_WHEN(P7, UNW_REG_UNAT, t, arg); break;
      case 13: UNW_DEC_REG_PSPREL(P7, UNW_REG_UNAT, t, arg); break;
      case 14: UNW_DEC_REG_WHEN(P7, UNW_REG_FPSR, t, arg); break;
      case 15: UNW_DEC_REG_PSPREL(P7, UNW_REG_FPSR, t, arg); break;
      default: UNW_DEC_BAD_CODE(r); break;
      }
    }
  else
    {
      switch (code & 0xf)
      {
      case 0x0: /* p8 */
        {
          r = *dp++;
          t = unw_decode_uleb128 (&dp);
          switch (r)
            {
            case  1: UNW_DEC_REG_SPREL(P8, UNW_REG_RP, t, arg); break;
            case  2: UNW_DEC_REG_SPREL(P8, UNW_REG_PFS, t, arg); break;
            case  3: UNW_DEC_REG_SPREL(P8, UNW_REG_PR, t, arg); break;
            case  4: UNW_DEC_REG_SPREL(P8, UNW_REG_LC, t, arg); break;
            case  5: UNW_DEC_REG_SPREL(P8, UNW_REG_UNAT, t, arg); break;
            case  6: UNW_DEC_REG_SPREL(P8, UNW_REG_FPSR, t, arg); break;
            case  7: UNW_DEC_REG_WHEN(P8, UNW_REG_BSP, t, arg); break;
            case  8: UNW_DEC_REG_PSPREL(P8, UNW_REG_BSP, t, arg); break;
            case  9: UNW_DEC_REG_SPREL(P8, UNW_REG_BSP, t, arg); break;
            case 10: UNW_DEC_REG_WHEN(P8, UNW_REG_BSPSTORE, t, arg); break;
            case 11: UNW_DEC_REG_PSPREL(P8, UNW_REG_BSPSTORE, t, arg); break;
            case 12: UNW_DEC_REG_SPREL(P8, UNW_REG_BSPSTORE, t, arg); break;
            case 13: UNW_DEC_REG_WHEN(P8, UNW_REG_RNAT, t, arg); break;
            case 14: UNW_DEC_REG_PSPREL(P8, UNW_REG_RNAT, t, arg); break;
            case 15: UNW_DEC_REG_SPREL(P8, UNW_REG_RNAT, t, arg); break;
            case 16: UNW_DEC_PRIUNAT_WHEN_GR(P8, t, arg); break;
            case 17: UNW_DEC_PRIUNAT_PSPREL(P8, t, arg); break;
            case 18: UNW_DEC_PRIUNAT_SPREL(P8, t, arg); break;
            case 19: UNW_DEC_PRIUNAT_WHEN_MEM(P8, t, arg); break;
            default: UNW_DEC_BAD_CODE(r); break;
          }
        }
        break;

      case 0x1:
        byte1 = *dp++; byte2 = *dp++;
        UNW_DEC_GR_GR(P9, (byte1 & 0xf), (byte2 & 0x7f), arg);
        break;

      case 0xf: /* p10 */
        byte1 = *dp++; byte2 = *dp++;
        UNW_DEC_ABI(P10, byte1, byte2, arg);
        break;

      case 0x9:
        return unw_decode_x1 (dp, code, arg);

      case 0xa:
        return unw_decode_x2 (dp, code, arg);

      case 0xb:
        return unw_decode_x3 (dp, code, arg);

      case 0xc:
        return unw_decode_x4 (dp, code, arg);

      default:
        UNW_DEC_BAD_CODE(code);
        break;
      }
    }
  return dp;
}

static unsigned char *
unw_decode_b1 (unsigned char *dp, unsigned char code, void *arg)
{
  unw_word label = (code & 0x1f);

  if ((code & 0x20) != 0)
    UNW_DEC_COPY_STATE(B1, label, arg);
  else
    UNW_DEC_LABEL_STATE(B1, label, arg);
  return dp;
}

static unsigned char *
unw_decode_b2 (unsigned char *dp, unsigned char code, void *arg)
{
  unw_word t;

  t = unw_decode_uleb128 (&dp);
  UNW_DEC_EPILOGUE(B2, t, (code & 0x1f), arg);
  return dp;
}

static unsigned char *
unw_decode_b3_x4 (unsigned char *dp, unsigned char code, void *arg)
{
  unw_word t, ecount, label;

  if ((code & 0x10) == 0)
    {
      t = unw_decode_uleb128 (&dp);
      ecount = unw_decode_uleb128 (&dp);
      UNW_DEC_EPILOGUE(B3, t, ecount, arg);
    }
  else if ((code & 0x07) == 0)
    {
      label = unw_decode_uleb128 (&dp);
      if ((code & 0x08) != 0)
      UNW_DEC_COPY_STATE(B4, label, arg);
      else
      UNW_DEC_LABEL_STATE(B4, label, arg);
    }
  else
    switch (code & 0x7)
      {
      case 1: return unw_decode_x1 (dp, code, arg);
      case 2: return unw_decode_x2 (dp, code, arg);
      case 3: return unw_decode_x3 (dp, code, arg);
      case 4: return unw_decode_x4 (dp, code, arg);
      default: UNW_DEC_BAD_CODE(code); break;
      }
  return dp;
}

typedef unsigned char *(*unw_decoder) (unsigned char *, unsigned char, void *);

static unw_decoder unw_decode_table[2][8] =
{
  /* prologue table: */
  {
    unw_decode_r1,      /* 0 */
    unw_decode_r1,
    unw_decode_r2,
    unw_decode_r3,
    unw_decode_p1,      /* 4 */
    unw_decode_p2_p5,
    unw_decode_p6,
    unw_decode_p7_p10
  },
  {
    unw_decode_r1,      /* 0 */
    unw_decode_r1,
    unw_decode_r2,
    unw_decode_r3,
    unw_decode_b1,      /* 4 */
    unw_decode_b1,
    unw_decode_b2,
    unw_decode_b3_x4
  }
};

/*
 * Decode one descriptor and return address of next descriptor.
 */
static inline unsigned char *
unw_decode (unsigned char *dp, int inside_body, void *arg)
{
  unw_decoder decoder;
  unsigned char code;

  code = *dp++;
  decoder = unw_decode_table[inside_body][code >> 5];
  dp = (*decoder) (dp, code, arg);
  return dp;
}

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