binutils-gdb/gdb/ppc-linux-nat.c

/* PPC GNU/Linux native support.

   Copyright 1988, 1989, 1991, 1992, 1994, 1996, 2000, 2001, 2002,
   2003 Free Software Foundation, Inc.

   This file is part of GDB.

   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.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdb_string.h"
#include "frame.h"
#include "inferior.h"
#include "gdbcore.h"
#include "regcache.h"
#include "gdb_assert.h"

#include <sys/types.h>
#include <sys/param.h>
#include <signal.h>
#include <sys/user.h>
#include <sys/ioctl.h>
#include "gdb_wait.h"
#include <fcntl.h>
#include <sys/procfs.h>
#include <sys/ptrace.h>

/* Prototypes for supply_gregset etc. */
#include "gregset.h"
#include "ppc-tdep.h"

#ifndef PT_READ_U
#define PT_READ_U PTRACE_PEEKUSR
#endif
#ifndef PT_WRITE_U
#define PT_WRITE_U PTRACE_POKEUSR
#endif

/* Default the type of the ptrace transfer to int.  */
#ifndef PTRACE_XFER_TYPE
#define PTRACE_XFER_TYPE int
#endif

/* Glibc's headers don't define PTRACE_GETVRREGS so we cannot use a
   configure time check.  Some older glibc's (for instance 2.2.1)
   don't have a specific powerpc version of ptrace.h, and fall back on
   a generic one.  In such cases, sys/ptrace.h defines
   PTRACE_GETFPXREGS and PTRACE_SETFPXREGS to the same numbers that
   ppc kernel's asm/ptrace.h defines PTRACE_GETVRREGS and
   PTRACE_SETVRREGS to be.  This also makes a configury check pretty
   much useless.  */

/* These definitions should really come from the glibc header files,
   but Glibc doesn't know about the vrregs yet.  */
#ifndef PTRACE_GETVRREGS
#define PTRACE_GETVRREGS 18
#define PTRACE_SETVRREGS 19
#endif


/* Similarly for the ptrace requests for getting / setting the SPE
   registers (ev0 -- ev31, acc, and spefscr).  See the description of
   gdb_evrregset_t for details.  */
#ifndef PTRACE_GETEVRREGS
#define PTRACE_GETEVRREGS 20
#define PTRACE_SETEVRREGS 21
#endif


/* This oddity is because the Linux kernel defines elf_vrregset_t as
   an array of 33 16 bytes long elements.  I.e. it leaves out vrsave.
   However the PTRACE_GETVRREGS and PTRACE_SETVRREGS requests return
   the vrsave as an extra 4 bytes at the end.  I opted for creating a
   flat array of chars, so that it is easier to manipulate for gdb.

   There are 32 vector registers 16 bytes longs, plus a VSCR register
   which is only 4 bytes long, but is fetched as a 16 bytes
   quantity. Up to here we have the elf_vrregset_t structure.
   Appended to this there is space for the VRSAVE register: 4 bytes.
   Even though this vrsave register is not included in the regset
   typedef, it is handled by the ptrace requests.

   Note that GNU/Linux doesn't support little endian PPC hardware,
   therefore the offset at which the real value of the VSCR register
   is located will be always 12 bytes.

   The layout is like this (where x is the actual value of the vscr reg): */

/* *INDENT-OFF* */
/*
   |.|.|.|.|.....|.|.|.|.||.|.|.|x||.|
   <------->     <-------><-------><->
     VR0           VR31     VSCR    VRSAVE
*/
/* *INDENT-ON* */

#define SIZEOF_VRREGS 33*16+4

typedef char gdb_vrregset_t[SIZEOF_VRREGS];


/* On PPC processors that support the the Signal Processing Extension
   (SPE) APU, the general-purpose registers are 64 bits long.
   However, the ordinary Linux kernel PTRACE_PEEKUSR / PTRACE_POKEUSR
   / PT_READ_U / PT_WRITE_U ptrace calls only access the lower half of
   each register, to allow them to behave the same way they do on
   non-SPE systems.  There's a separate pair of calls,
   PTRACE_GETEVRREGS / PTRACE_SETEVRREGS, that read and write the top
   halves of all the general-purpose registers at once, along with
   some SPE-specific registers.

   GDB itself continues to claim the general-purpose registers are 32
   bits long; the full 64-bit registers are called 'ev0' -- 'ev31'.
   The ev registers are raw registers, and the GPR's are pseudo-
   registers mapped onto their lower halves.  This means that reading
   and writing ev registers involves a mix of regset-at-once
   PTRACE_{GET,SET}EVRREGS calls and register-at-a-time
   PTRACE_{PEEK,POKE}USR calls.

   This is the structure filled in by PTRACE_GETEVRREGS and written to
   the inferior's registers by PTRACE_SETEVRREGS.  */
struct gdb_evrregset_t
{
  unsigned long evr[32];
  unsigned long long acc;
  unsigned long spefscr;
};


/* Non-zero if our kernel may support the PTRACE_GETVRREGS and
   PTRACE_SETVRREGS requests, for reading and writing the Altivec
   registers.  Zero if we've tried one of them and gotten an
   error.  */
int have_ptrace_getvrregs = 1;


/* Non-zero if our kernel may support the PTRACE_GETEVRREGS and
   PTRACE_SETEVRREGS requests, for reading and writing the SPE
   registers.  Zero if we've tried one of them and gotten an
   error.  */
int have_ptrace_getsetevrregs = 1;


int
kernel_u_size (void)
{
  return (sizeof (struct user));
}

/* *INDENT-OFF* */
/* registers layout, as presented by the ptrace interface:
PT_R0, PT_R1, PT_R2, PT_R3, PT_R4, PT_R5, PT_R6, PT_R7,
PT_R8, PT_R9, PT_R10, PT_R11, PT_R12, PT_R13, PT_R14, PT_R15,
PT_R16, PT_R17, PT_R18, PT_R19, PT_R20, PT_R21, PT_R22, PT_R23,
PT_R24, PT_R25, PT_R26, PT_R27, PT_R28, PT_R29, PT_R30, PT_R31,
PT_FPR0, PT_FPR0 + 2, PT_FPR0 + 4, PT_FPR0 + 6, PT_FPR0 + 8, PT_FPR0 + 10, PT_FPR0 + 12, PT_FPR0 + 14,
PT_FPR0 + 16, PT_FPR0 + 18, PT_FPR0 + 20, PT_FPR0 + 22, PT_FPR0 + 24, PT_FPR0 + 26, PT_FPR0 + 28, PT_FPR0 + 30,
PT_FPR0 + 32, PT_FPR0 + 34, PT_FPR0 + 36, PT_FPR0 + 38, PT_FPR0 + 40, PT_FPR0 + 42, PT_FPR0 + 44, PT_FPR0 + 46,
PT_FPR0 + 48, PT_FPR0 + 50, PT_FPR0 + 52, PT_FPR0 + 54, PT_FPR0 + 56, PT_FPR0 + 58, PT_FPR0 + 60, PT_FPR0 + 62,
PT_NIP, PT_MSR, PT_CCR, PT_LNK, PT_CTR, PT_XER, PT_MQ */
/* *INDENT_ON * */

static int
ppc_register_u_addr (int regno)
{
  int u_addr = -1;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  /* NOTE: cagney/2003-11-25: This is the word size used by the ptrace
     interface, and not the wordsize of the program's ABI.  */
  int wordsize = sizeof (PTRACE_XFER_TYPE);

  /* General purpose registers occupy 1 slot each in the buffer */
  if (regno >= tdep->ppc_gp0_regnum 
      && regno < tdep->ppc_gp0_regnum + ppc_num_gprs)
    u_addr = ((regno - tdep->ppc_gp0_regnum + PT_R0) * wordsize);

  /* Floating point regs: eight bytes each in both 32- and 64-bit
     ptrace interfaces.  Thus, two slots each in 32-bit interface, one
     slot each in 64-bit interface.  */
  if (tdep->ppc_fp0_regnum >= 0
      && regno >= tdep->ppc_fp0_regnum
      && regno < tdep->ppc_fp0_regnum + ppc_num_fprs)
    u_addr = (PT_FPR0 * wordsize) + ((regno - tdep->ppc_fp0_regnum) * 8);

  /* UISA special purpose registers: 1 slot each */
  if (regno == PC_REGNUM)
    u_addr = PT_NIP * wordsize;
  if (regno == tdep->ppc_lr_regnum)
    u_addr = PT_LNK * wordsize;
  if (regno == tdep->ppc_cr_regnum)
    u_addr = PT_CCR * wordsize;
  if (regno == tdep->ppc_xer_regnum)
    u_addr = PT_XER * wordsize;
  if (regno == tdep->ppc_ctr_regnum)
    u_addr = PT_CTR * wordsize;
#ifdef PT_MQ
  if (regno == tdep->ppc_mq_regnum)
    u_addr = PT_MQ * wordsize;
#endif
  if (regno == tdep->ppc_ps_regnum)
    u_addr = PT_MSR * wordsize;
  if (tdep->ppc_fpscr_regnum >= 0
      && regno == tdep->ppc_fpscr_regnum)
    u_addr = PT_FPSCR * wordsize;

  return u_addr;
}

/* The Linux kernel ptrace interface for AltiVec registers uses the
   registers set mechanism, as opposed to the interface for all the
   other registers, that stores/fetches each register individually.  */
static void
fetch_altivec_register (int tid, int regno)
{
  int ret;
  int offset = 0;
  gdb_vrregset_t regs;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  int vrregsize = register_size (current_gdbarch, tdep->ppc_vr0_regnum);

  ret = ptrace (PTRACE_GETVRREGS, tid, 0, &regs);
  if (ret < 0)
    {
      if (errno == EIO)
        {
          have_ptrace_getvrregs = 0;
          return;
        }
      perror_with_name ("Unable to fetch AltiVec register");
    }
 
  /* VSCR is fetched as a 16 bytes quantity, but it is really 4 bytes
     long on the hardware.  We deal only with the lower 4 bytes of the
     vector.  VRSAVE is at the end of the array in a 4 bytes slot, so
     there is no need to define an offset for it.  */
  if (regno == (tdep->ppc_vrsave_regnum - 1))
    offset = vrregsize - register_size (current_gdbarch, tdep->ppc_vrsave_regnum);
  
  regcache_raw_supply (current_regcache, regno,
		       regs + (regno - tdep->ppc_vr0_regnum) * vrregsize + offset);
}

/* Fetch the top 32 bits of TID's general-purpose registers and the
   SPE-specific registers, and place the results in EVRREGSET.  If we
   don't support PTRACE_GETEVRREGS, then just fill EVRREGSET with
   zeros.

   All the logic to deal with whether or not the PTRACE_GETEVRREGS and
   PTRACE_SETEVRREGS requests are supported is isolated here, and in
   set_spe_registers.  */
static void
get_spe_registers (int tid, struct gdb_evrregset_t *evrregset)
{
  if (have_ptrace_getsetevrregs)
    {
      if (ptrace (PTRACE_GETEVRREGS, tid, 0, evrregset) >= 0)
        return;
      else
        {
          /* EIO means that the PTRACE_GETEVRREGS request isn't supported;
             we just return zeros.  */
          if (errno == EIO)
            have_ptrace_getsetevrregs = 0;
          else
            /* Anything else needs to be reported.  */
            perror_with_name ("Unable to fetch SPE registers");
        }
    }

  memset (evrregset, 0, sizeof (*evrregset));
}

/* Assuming TID refers to an SPE process, store the full 64-bit value
   of TID's ev register EV_REGNUM in DEST, getting the high bits from
   EVRREGS and the low bits from the kernel via ptrace.  */
static void
read_spliced_spe_reg (int tid, int ev_regnum,
                      struct gdb_evrregset_t *evrregs,
                      char *dest)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  /* Make sure we're trying to read an EV register; that's all we
     handle.  */
  gdb_assert (tdep->ppc_ev0_regnum <= ev_regnum
              && ev_regnum <= tdep->ppc_ev31_regnum);

  /* Make sure the sizes for the splicing add up.  */
  gdb_assert (sizeof (evrregs->evr[0]) + sizeof (PTRACE_XFER_TYPE)
              == register_size (current_gdbarch, ev_regnum));

  {
    /* The index of ev_regnum in evrregs->evr[].  */
    int ev_index = ev_regnum - tdep->ppc_ev0_regnum;

    /* The number of the corresponding general-purpose register, which
       holds the lower 32 bits of the EV register.  */
    int gpr_regnum = tdep->ppc_gp0_regnum + ev_index;

    /* The offset of gpr_regnum in the process's uarea.  */
    CORE_ADDR gpr_uoffset = ppc_register_u_addr (gpr_regnum);

    /* The low word of the EV register's value.  */
    PTRACE_XFER_TYPE low_word;

    /* The PTRACE_PEEKUSR / PT_READ_U ptrace requests need to be able
       to return arbitrary register values, so they can't return -1 to
       indicate an error.  So we clear errno, and then check it after
       the call.  */
    errno = 0;
    low_word = ptrace (PT_READ_U, tid, (PTRACE_ARG3_TYPE) gpr_uoffset, 0);
  
    if (errno != 0)
      {
        char message[128];
        sprintf (message, "reading register %s (#%d)",
                 REGISTER_NAME (ev_regnum), ev_regnum);
        perror_with_name (message);
      }

    if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
      {
        memcpy (dest, &evrregs->evr[ev_index],
                sizeof (evrregs->evr[ev_index]));
        * (PTRACE_XFER_TYPE *) (dest + sizeof (evrregs->evr[ev_index]))
          = low_word;
      }
    else if (TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE)
      {
        * (PTRACE_XFER_TYPE *) dest = low_word;
        memcpy (dest + sizeof (PTRACE_XFER_TYPE),
                &evrregs->evr[ev_index], sizeof (evrregs->evr[ev_index]));
      }
    else
      gdb_assert (0);
  }
}


/* On SPE machines, supply the full value of the SPE register REGNO
   from TID.  This handles ev0 -- ev31 and acc, which are 64 bits
   long, and spefscr, which is 32 bits long.  */
static void
fetch_spe_register (int tid, int regno)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  struct gdb_evrregset_t evrregs;

  get_spe_registers (tid, &evrregs);

  if (tdep->ppc_ev0_regnum <= regno
      && regno <= tdep->ppc_ev31_regnum)
    {
      char buf[MAX_REGISTER_SIZE];
      read_spliced_spe_reg (tid, regno, &evrregs, buf);
      regcache_raw_supply (current_regcache, regno, buf);
    }
  else if (regno == tdep->ppc_acc_regnum)
    {
      gdb_assert (sizeof (evrregs.acc)
                  == register_size (current_gdbarch, regno));
      regcache_raw_supply (current_regcache, regno, &evrregs.acc);
    }
  else if (regno == tdep->ppc_spefscr_regnum)
    {
      gdb_assert (sizeof (evrregs.spefscr)
                  == register_size (current_gdbarch, regno));
      regcache_raw_supply (current_regcache, regno, &evrregs.spefscr);
    }
  else
    gdb_assert (0);
}

static void
fetch_register (int tid, int regno)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  /* This isn't really an address.  But ptrace thinks of it as one.  */
  CORE_ADDR regaddr = ppc_register_u_addr (regno);
  int bytes_transferred;
  unsigned int offset;         /* Offset of registers within the u area. */
  char buf[MAX_REGISTER_SIZE];

  /* Sanity check: this function should only be called to fetch raw
     registers' values, never pseudoregisters' values.  */
  if (tdep->ppc_gp0_regnum <= regno
      && regno < tdep->ppc_gp0_regnum + ppc_num_gprs)
    gdb_assert (! tdep->ppc_gprs_pseudo_p);

  if (altivec_register_p (regno))
    {
      /* If this is the first time through, or if it is not the first
         time through, and we have comfirmed that there is kernel
         support for such a ptrace request, then go and fetch the
         register.  */
      if (have_ptrace_getvrregs)
       {
         fetch_altivec_register (tid, regno);
         return;
       }
     /* If we have discovered that there is no ptrace support for
        AltiVec registers, fall through and return zeroes, because
        regaddr will be -1 in this case.  */
    }
  else if (spe_register_p (regno))
    {
      fetch_spe_register (tid, regno);
      return;
    }

  if (regaddr == -1)
    {
      memset (buf, '\0', register_size (current_gdbarch, regno));   /* Supply zeroes */
      regcache_raw_supply (current_regcache, regno, buf);
      return;
    }

  /* Read the raw register using PTRACE_XFER_TYPE sized chunks.  On a
     32-bit platform, 64-bit floating-point registers will require two
     transfers.  */
  for (bytes_transferred = 0;
       bytes_transferred < register_size (current_gdbarch, regno);
       bytes_transferred += sizeof (PTRACE_XFER_TYPE))
    {
      errno = 0;
      *(PTRACE_XFER_TYPE *) & buf[bytes_transferred]
        = ptrace (PT_READ_U, tid, (PTRACE_ARG3_TYPE) regaddr, 0);
      regaddr += sizeof (PTRACE_XFER_TYPE);
      if (errno != 0)
	{
          char message[128];
	  sprintf (message, "reading register %s (#%d)", 
		   REGISTER_NAME (regno), regno);
	  perror_with_name (message);
	}
    }

  /* Now supply the register.  Keep in mind that the regcache's idea
     of the register's size may not be a multiple of sizeof
     (PTRACE_XFER_TYPE).  */
  if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_LITTLE)
    {
      /* Little-endian values are always found at the left end of the
         bytes transferred.  */
      regcache_raw_supply (current_regcache, regno, buf);
    }
  else if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
    {
      /* Big-endian values are found at the right end of the bytes
         transferred.  */
      size_t padding = (bytes_transferred
                        - register_size (current_gdbarch, regno));
      regcache_raw_supply (current_regcache, regno, buf + padding);
    }
  else 
    gdb_assert (0);
}

static void
supply_vrregset (gdb_vrregset_t *vrregsetp)
{
  int i;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  int num_of_vrregs = tdep->ppc_vrsave_regnum - tdep->ppc_vr0_regnum + 1;
  int vrregsize = register_size (current_gdbarch, tdep->ppc_vr0_regnum);
  int offset = vrregsize - register_size (current_gdbarch, tdep->ppc_vrsave_regnum);

  for (i = 0; i < num_of_vrregs; i++)
    {
      /* The last 2 registers of this set are only 32 bit long, not
         128.  However an offset is necessary only for VSCR because it
         occupies a whole vector, while VRSAVE occupies a full 4 bytes
         slot.  */
      if (i == (num_of_vrregs - 2))
        regcache_raw_supply (current_regcache, tdep->ppc_vr0_regnum + i,
			     *vrregsetp + i * vrregsize + offset);
      else
        regcache_raw_supply (current_regcache, tdep->ppc_vr0_regnum + i,
			     *vrregsetp + i * vrregsize);
    }
}

static void
fetch_altivec_registers (int tid)
{
  int ret;
  gdb_vrregset_t regs;
  
  ret = ptrace (PTRACE_GETVRREGS, tid, 0, &regs);
  if (ret < 0)
    {
      if (errno == EIO)
	{
          have_ptrace_getvrregs = 0;
	  return;
	}
      perror_with_name ("Unable to fetch AltiVec registers");
    }
  supply_vrregset (&regs);
}

/* On SPE machines, fetch the full 64 bits of all the general-purpose
   registers, as well as the SPE-specific registers 'acc' and
   'spefscr'.  */
static void
fetch_spe_registers (int tid)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  struct gdb_evrregset_t evrregs;
  int i;

  get_spe_registers (tid, &evrregs);

  /* Splice and supply each of the EV registers.  */
  for (i = 0; i < ppc_num_gprs; i++)
    {
      char buf[MAX_REGISTER_SIZE];

      read_spliced_spe_reg (tid, tdep->ppc_ev0_regnum + i, &evrregs, buf);
      regcache_raw_supply (current_regcache, tdep->ppc_ev0_regnum + i, buf);
    }

  /* Supply the SPE-specific registers.  */
  regcache_raw_supply (current_regcache, tdep->ppc_acc_regnum, &evrregs.acc);
  regcache_raw_supply (current_regcache, tdep->ppc_spefscr_regnum,
		       &evrregs.spefscr);
}

static void 
fetch_ppc_registers (int tid)
{
  int i;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (! tdep->ppc_gprs_pseudo_p)
    for (i = 0; i < ppc_num_gprs; i++)
      fetch_register (tid, tdep->ppc_gp0_regnum + i);
  if (tdep->ppc_fp0_regnum >= 0)
    for (i = 0; i < ppc_num_fprs; i++)
      fetch_register (tid, tdep->ppc_fp0_regnum + i);
  fetch_register (tid, PC_REGNUM);
  if (tdep->ppc_ps_regnum != -1)
    fetch_register (tid, tdep->ppc_ps_regnum);
  if (tdep->ppc_cr_regnum != -1)
    fetch_register (tid, tdep->ppc_cr_regnum);
  if (tdep->ppc_lr_regnum != -1)
    fetch_register (tid, tdep->ppc_lr_regnum);
  if (tdep->ppc_ctr_regnum != -1)
    fetch_register (tid, tdep->ppc_ctr_regnum);
  if (tdep->ppc_xer_regnum != -1)
    fetch_register (tid, tdep->ppc_xer_regnum);
  if (tdep->ppc_mq_regnum != -1)
    fetch_register (tid, tdep->ppc_mq_regnum);
  if (tdep->ppc_fpscr_regnum != -1)
    fetch_register (tid, tdep->ppc_fpscr_regnum);
  if (have_ptrace_getvrregs)
    if (tdep->ppc_vr0_regnum != -1 && tdep->ppc_vrsave_regnum != -1)
      fetch_altivec_registers (tid);
  if (tdep->ppc_ev0_regnum >= 0)
    fetch_spe_registers (tid);
}

/* Fetch registers from the child process.  Fetch all registers if
   regno == -1, otherwise fetch all general registers or all floating
   point registers depending upon the value of regno.  */
void
fetch_inferior_registers (int regno)
{
  /* Overload thread id onto process id */
  int tid = TIDGET (inferior_ptid);

  /* No thread id, just use process id */
  if (tid == 0)
    tid = PIDGET (inferior_ptid);

  if (regno == -1)
    fetch_ppc_registers (tid);
  else 
    fetch_register (tid, regno);
}

/* Store one register. */
static void
store_altivec_register (int tid, int regno)
{
  int ret;
  int offset = 0;
  gdb_vrregset_t regs;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  int vrregsize = register_size (current_gdbarch, tdep->ppc_vr0_regnum);

  ret = ptrace (PTRACE_GETVRREGS, tid, 0, &regs);
  if (ret < 0)
    {
      if (errno == EIO)
        {
          have_ptrace_getvrregs = 0;
          return;
        }
      perror_with_name ("Unable to fetch AltiVec register");
    }

  /* VSCR is fetched as a 16 bytes quantity, but it is really 4 bytes
     long on the hardware.  */
  if (regno == (tdep->ppc_vrsave_regnum - 1))
    offset = vrregsize - register_size (current_gdbarch, tdep->ppc_vrsave_regnum);

  regcache_raw_collect (current_regcache, regno,
			regs + (regno - tdep->ppc_vr0_regnum) * vrregsize + offset);

  ret = ptrace (PTRACE_SETVRREGS, tid, 0, &regs);
  if (ret < 0)
    perror_with_name ("Unable to store AltiVec register");
}

/* Assuming TID referrs to an SPE process, set the top halves of TID's
   general-purpose registers and its SPE-specific registers to the
   values in EVRREGSET.  If we don't support PTRACE_SETEVRREGS, do
   nothing.

   All the logic to deal with whether or not the PTRACE_GETEVRREGS and
   PTRACE_SETEVRREGS requests are supported is isolated here, and in
   get_spe_registers.  */
static void
set_spe_registers (int tid, struct gdb_evrregset_t *evrregset)
{
  if (have_ptrace_getsetevrregs)
    {
      if (ptrace (PTRACE_SETEVRREGS, tid, 0, evrregset) >= 0)
        return;
      else
        {
          /* EIO means that the PTRACE_SETEVRREGS request isn't
             supported; we fail silently, and don't try the call
             again.  */
          if (errno == EIO)
            have_ptrace_getsetevrregs = 0;
          else
            /* Anything else needs to be reported.  */
            perror_with_name ("Unable to set SPE registers");
        }
    }
}

/* Store the bytes at SRC as the contents of TID's EV register EV_REGNUM.
   Write the less significant word to TID using ptrace, and copy the
   more significant word to the appropriate slot in EVRREGS.  */
static void
write_spliced_spe_reg (int tid, int ev_regnum,
                       struct gdb_evrregset_t *evrregs,
                       char *src)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  /* Make sure we're trying to write an EV register; that's all we
     handle.  */
  gdb_assert (tdep->ppc_ev0_regnum <= ev_regnum
              && ev_regnum <= tdep->ppc_ev31_regnum);

  /* Make sure the sizes for the splicing add up.  */
  gdb_assert (sizeof (evrregs->evr[0]) + sizeof (PTRACE_XFER_TYPE)
              == register_size (current_gdbarch, ev_regnum));

  {
    int ev_index = ev_regnum - tdep->ppc_ev0_regnum;

    /* The number of the corresponding general-purpose register, which
       holds the lower 32 bits of the EV register.  */
    int gpr_regnum = tdep->ppc_gp0_regnum + ev_index;

    /* The offset of gpr_regnum in the process's uarea.  */
    CORE_ADDR gpr_uoffset = ppc_register_u_addr (gpr_regnum);

    /* The PTRACE_POKEUSR / PT_WRITE_U ptrace requests need to be able
       to return arbitrary register values, so they can't return -1 to
       indicate an error.  So we clear errno, and check it again
       afterwards.  */
    errno = 0;

    if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
      {
        memcpy (&evrregs->evr[ev_index], src, sizeof (evrregs->evr[ev_index]));
        ptrace (PT_WRITE_U, tid, (PTRACE_ARG3_TYPE) gpr_uoffset,
                * (PTRACE_XFER_TYPE *) (src + sizeof (evrregs->evr[0])));
      }
    else if (TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE)
      {
        ptrace (PT_WRITE_U, tid, (PTRACE_ARG3_TYPE) gpr_uoffset,
                * (PTRACE_XFER_TYPE *) src);
        memcpy (&evrregs->evr[ev_index], src + sizeof (PTRACE_XFER_TYPE),
                sizeof (evrregs->evr[ev_index]));
      }
    else 
      gdb_assert (0);

    if (errno != 0)
      {
        char message[128];
        sprintf (message, "writing register %s (#%d)", 
                 REGISTER_NAME (ev_regnum), ev_regnum);
        perror_with_name (message);
      }
  }
}

/* Write GDB's value for the SPE register REGNO to TID.  */
static void
store_spe_register (int tid, int regno)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  struct gdb_evrregset_t evrregs;

  /* We can only read and write the entire EVR register set at a time,
     so to write just a single register, we do a read-modify-write
     maneuver.  */
  get_spe_registers (tid, &evrregs);

  if (tdep->ppc_ev0_regnum >= 0
      && tdep->ppc_ev0_regnum <= regno && regno <= tdep->ppc_ev31_regnum)
    {
      char buf[MAX_REGISTER_SIZE];
      regcache_raw_collect (current_regcache, regno, buf);
      write_spliced_spe_reg (tid, regno, &evrregs, buf);
    }
  else if (tdep->ppc_acc_regnum >= 0
           && regno == tdep->ppc_acc_regnum)
    {
      gdb_assert (sizeof (evrregs.acc)
                  == register_size (current_gdbarch, regno));
      regcache_raw_collect (current_regcache, regno, &evrregs.acc);
    }
  else if (tdep->ppc_spefscr_regnum >= 0
           && regno == tdep->ppc_spefscr_regnum)
    {
      gdb_assert (sizeof (evrregs.spefscr)
                  == register_size (current_gdbarch, regno));
      regcache_raw_collect (current_regcache, regno, &evrregs.spefscr);
    }
  else
    gdb_assert (0);

  /* Write back the modified register set.  */
  set_spe_registers (tid, &evrregs);
}

static void
store_register (int tid, int regno)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  /* This isn't really an address.  But ptrace thinks of it as one.  */
  CORE_ADDR regaddr = ppc_register_u_addr (regno);
  int i;
  size_t bytes_to_transfer;
  char buf[MAX_REGISTER_SIZE];

  /* Sanity check: this function should only be called to store raw
     registers' values, never pseudoregisters' values.  */
  if (tdep->ppc_gp0_regnum <= regno
      && regno < tdep->ppc_gp0_regnum + ppc_num_gprs)
    gdb_assert (! tdep->ppc_gprs_pseudo_p);

  if (altivec_register_p (regno))
    {
      store_altivec_register (tid, regno);
      return;
    }
  else if (spe_register_p (regno))
    {
      store_spe_register (tid, regno);
      return;
    }

  if (regaddr == -1)
    return;

  /* First collect the register.  Keep in mind that the regcache's
     idea of the register's size may not be a multiple of sizeof
     (PTRACE_XFER_TYPE).  */
  memset (buf, 0, sizeof buf);
  bytes_to_transfer = align_up (register_size (current_gdbarch, regno),
                                sizeof (PTRACE_XFER_TYPE));
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE)
    {
      /* Little-endian values always sit at the left end of the buffer.  */
      regcache_raw_collect (current_regcache, regno, buf);
    }
  else if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      /* Big-endian values sit at the right end of the buffer.  */
      size_t padding = (bytes_to_transfer
                        - register_size (current_gdbarch, regno));
      regcache_raw_collect (current_regcache, regno, buf + padding);
    }

  for (i = 0; i < bytes_to_transfer; i += sizeof (PTRACE_XFER_TYPE))
    {
      errno = 0;
      ptrace (PT_WRITE_U, tid, (PTRACE_ARG3_TYPE) regaddr,
	      *(PTRACE_XFER_TYPE *) & buf[i]);
      regaddr += sizeof (PTRACE_XFER_TYPE);

      if (errno == EIO 
          && regno == tdep->ppc_fpscr_regnum)
	{
	  /* Some older kernel versions don't allow fpscr to be written.  */
	  continue;
	}

      if (errno != 0)
	{
          char message[128];
	  sprintf (message, "writing register %s (#%d)", 
		   REGISTER_NAME (regno), regno);
	  perror_with_name (message);
	}
    }
}

static void
fill_vrregset (gdb_vrregset_t *vrregsetp)
{
  int i;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  int num_of_vrregs = tdep->ppc_vrsave_regnum - tdep->ppc_vr0_regnum + 1;
  int vrregsize = register_size (current_gdbarch, tdep->ppc_vr0_regnum);
  int offset = vrregsize - register_size (current_gdbarch, tdep->ppc_vrsave_regnum);

  for (i = 0; i < num_of_vrregs; i++)
    {
      /* The last 2 registers of this set are only 32 bit long, not
         128, but only VSCR is fetched as a 16 bytes quantity.  */
      if (i == (num_of_vrregs - 2))
        regcache_raw_collect (current_regcache, tdep->ppc_vr0_regnum + i,
			      *vrregsetp + i * vrregsize + offset);
      else
        regcache_raw_collect (current_regcache, tdep->ppc_vr0_regnum + i,
			      *vrregsetp + i * vrregsize);
    }
}

static void
store_altivec_registers (int tid)
{
  int ret;
  gdb_vrregset_t regs;

  ret = ptrace (PTRACE_GETVRREGS, tid, 0, &regs);
  if (ret < 0)
    {
      if (errno == EIO)
        {
          have_ptrace_getvrregs = 0;
          return;
        }
      perror_with_name ("Couldn't get AltiVec registers");
    }

  fill_vrregset (&regs);
  
  if (ptrace (PTRACE_SETVRREGS, tid, 0, &regs) < 0)
    perror_with_name ("Couldn't write AltiVec registers");
}

static void
store_spe_registers (int tid)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  struct gdb_evrregset_t evrregs;
  int i;

  /* The code below should store to every field of evrregs; if that
     doesn't happen, make it obvious by initializing it with
     suspicious values.  */
  memset (&evrregs, 42, sizeof (evrregs));

  for (i = 0; i < ppc_num_gprs; i++)
    {
      char buf[MAX_REGISTER_SIZE];

      regcache_raw_collect (current_regcache, tdep->ppc_ev0_regnum + i, buf);
      write_spliced_spe_reg (tid, tdep->ppc_ev0_regnum + i, &evrregs, buf);
    }

  gdb_assert (sizeof (evrregs.acc)
              == register_size (current_gdbarch, tdep->ppc_acc_regnum));
  regcache_raw_collect (current_regcache, tdep->ppc_acc_regnum, &evrregs.acc);
  gdb_assert (sizeof (evrregs.spefscr)
              == register_size (current_gdbarch, tdep->ppc_spefscr_regnum));
  regcache_raw_collect (current_regcache, tdep->ppc_acc_regnum, &evrregs.spefscr);

  set_spe_registers (tid, &evrregs);
}

static void
store_ppc_registers (int tid)
{
  int i;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  
  if (! tdep->ppc_gprs_pseudo_p)
    for (i = 0; i < ppc_num_gprs; i++)
      store_register (tid, tdep->ppc_gp0_regnum + i);
  if (tdep->ppc_fp0_regnum >= 0)
    for (i = 0; i < ppc_num_fprs; i++)
      store_register (tid, tdep->ppc_fp0_regnum + i);
  store_register (tid, PC_REGNUM);
  if (tdep->ppc_ps_regnum != -1)
    store_register (tid, tdep->ppc_ps_regnum);
  if (tdep->ppc_cr_regnum != -1)
    store_register (tid, tdep->ppc_cr_regnum);
  if (tdep->ppc_lr_regnum != -1)
    store_register (tid, tdep->ppc_lr_regnum);
  if (tdep->ppc_ctr_regnum != -1)
    store_register (tid, tdep->ppc_ctr_regnum);
  if (tdep->ppc_xer_regnum != -1)
    store_register (tid, tdep->ppc_xer_regnum);
  if (tdep->ppc_mq_regnum != -1)
    store_register (tid, tdep->ppc_mq_regnum);
  if (tdep->ppc_fpscr_regnum != -1)
    store_register (tid, tdep->ppc_fpscr_regnum);
  if (have_ptrace_getvrregs)
    if (tdep->ppc_vr0_regnum != -1 && tdep->ppc_vrsave_regnum != -1)
      store_altivec_registers (tid);
  if (tdep->ppc_ev0_regnum >= 0)
    store_spe_registers (tid);
}

void
store_inferior_registers (int regno)
{
  /* Overload thread id onto process id */
  int tid = TIDGET (inferior_ptid);

  /* No thread id, just use process id */
  if (tid == 0)
    tid = PIDGET (inferior_ptid);

  if (regno >= 0)
    store_register (tid, regno);
  else
    store_ppc_registers (tid);
}

void
supply_gregset (gdb_gregset_t *gregsetp)
{
  /* NOTE: cagney/2003-11-25: This is the word size used by the ptrace
     interface, and not the wordsize of the program's ABI.  */
  int wordsize = sizeof (PTRACE_XFER_TYPE);
  ppc_linux_supply_gregset (current_regcache, -1, gregsetp,
			    sizeof (gdb_gregset_t), wordsize);
}

static void
right_fill_reg (int regnum, void *reg)
{
  /* NOTE: cagney/2003-11-25: This is the word size used by the ptrace
     interface, and not the wordsize of the program's ABI.  */
  int wordsize = sizeof (PTRACE_XFER_TYPE);
  /* Right fill the register.  */
  regcache_raw_collect (current_regcache, regnum,
			((bfd_byte *) reg
			 + wordsize
			 - register_size (current_gdbarch, regnum)));
}

void
fill_gregset (gdb_gregset_t *gregsetp, int regno)
{
  int regi;
  elf_greg_t *regp = (elf_greg_t *) gregsetp;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch); 
  const int elf_ngreg = 48;


  /* Start with zeros.  */
  memset (regp, 0, elf_ngreg * sizeof (*regp));

  for (regi = 0; regi < ppc_num_gprs; regi++)
    {
      if ((regno == -1) || regno == tdep->ppc_gp0_regnum + regi)
	right_fill_reg (tdep->ppc_gp0_regnum + regi, (regp + PT_R0 + regi));
    }

  if ((regno == -1) || regno == PC_REGNUM)
    right_fill_reg (PC_REGNUM, regp + PT_NIP);
  if ((regno == -1) || regno == tdep->ppc_lr_regnum)
    right_fill_reg (tdep->ppc_lr_regnum, regp + PT_LNK);
  if ((regno == -1) || regno == tdep->ppc_cr_regnum)
    regcache_raw_collect (current_regcache, tdep->ppc_cr_regnum,
			  regp + PT_CCR);
  if ((regno == -1) || regno == tdep->ppc_xer_regnum)
    regcache_raw_collect (current_regcache, tdep->ppc_xer_regnum,
			  regp + PT_XER);
  if ((regno == -1) || regno == tdep->ppc_ctr_regnum)
    right_fill_reg (tdep->ppc_ctr_regnum, regp + PT_CTR);
#ifdef PT_MQ
  if (((regno == -1) || regno == tdep->ppc_mq_regnum)
      && (tdep->ppc_mq_regnum != -1))
    right_fill_reg (tdep->ppc_mq_regnum, regp + PT_MQ);
#endif
  if ((regno == -1) || regno == tdep->ppc_ps_regnum)
    right_fill_reg (tdep->ppc_ps_regnum, regp + PT_MSR);
}

void
supply_fpregset (gdb_fpregset_t * fpregsetp)
{
  ppc_linux_supply_fpregset (NULL, current_regcache, -1, fpregsetp,
			     sizeof (gdb_fpregset_t));
}

/* Given a pointer to a floating point register set in /proc format
   (fpregset_t *), update the register specified by REGNO from gdb's
   idea of the current floating point register set.  If REGNO is -1,
   update them all.  */
void
fill_fpregset (gdb_fpregset_t *fpregsetp, int regno)
{
  int regi;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch); 
  bfd_byte *fpp = (void *) fpregsetp;
  
  if (ppc_floating_point_unit_p (current_gdbarch))
    {
      for (regi = 0; regi < ppc_num_fprs; regi++)
        {
          if ((regno == -1) || (regno == tdep->ppc_fp0_regnum + regi))
            regcache_raw_collect (current_regcache, tdep->ppc_fp0_regnum + regi,
				  fpp + 8 * regi);
        }
      if (regno == -1 || regno == tdep->ppc_fpscr_regnum)
        right_fill_reg (tdep->ppc_fpscr_regnum, (fpp + 8 * 32));
    }
}