gdb/alphanbsd-tdep.c

/* Target-dependent code for NetBSD/alpha.

   Copyright (C) 2002, 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011
   Free Software Foundation, Inc.

   Contributed by Wasabi Systems, 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 3 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, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "frame.h"
#include "gdbcore.h"
#include "osabi.h"
#include "regcache.h"
#include "regset.h"
#include "value.h"

#include "gdb_assert.h"
#include "gdb_string.h"

#include "alpha-tdep.h"
#include "alphabsd-tdep.h"
#include "nbsd-tdep.h"
#include "solib-svr4.h"
#include "target.h"

/* Core file support.  */

/* Even though NetBSD/alpha used ELF since day one, it used the
   traditional a.out-style core dump format before NetBSD 1.6.  */

/* Sizeof `struct reg' in <machine/reg.h>.  */
#define ALPHANBSD_SIZEOF_GREGS	(32 * 8)

/* Sizeof `struct fpreg' in <machine/reg.h.  */
#define ALPHANBSD_SIZEOF_FPREGS	((32 * 8) + 8)

/* Supply register REGNUM from the buffer specified by FPREGS and LEN
   in the floating-point register set REGSET to register cache
   REGCACHE.  If REGNUM is -1, do this for all registers in REGSET.  */

static void
alphanbsd_supply_fpregset (const struct regset *regset,
			   struct regcache *regcache,
			   int regnum, const void *fpregs, size_t len)
{
  const gdb_byte *regs = fpregs;
  int i;

  gdb_assert (len >= ALPHANBSD_SIZEOF_FPREGS);

  for (i = ALPHA_FP0_REGNUM; i < ALPHA_FP0_REGNUM + 31; i++)
    {
      if (regnum == i || regnum == -1)
	regcache_raw_supply (regcache, i, regs + (i - ALPHA_FP0_REGNUM) * 8);
    }

  if (regnum == ALPHA_FPCR_REGNUM || regnum == -1)
    regcache_raw_supply (regcache, ALPHA_FPCR_REGNUM, regs + 32 * 8);
}

/* Supply register REGNUM from the buffer specified by GREGS and LEN
   in the general-purpose register set REGSET to register cache
   REGCACHE.  If REGNUM is -1, do this for all registers in REGSET.  */

static void
alphanbsd_supply_gregset (const struct regset *regset,
			  struct regcache *regcache,
			  int regnum, const void *gregs, size_t len)
{
  const gdb_byte *regs = gregs;
  int i;

  gdb_assert (len >= ALPHANBSD_SIZEOF_GREGS);

  for (i = 0; i < ALPHA_ZERO_REGNUM; i++)
    {
      if (regnum == i || regnum == -1)
	regcache_raw_supply (regcache, i, regs + i * 8);
    }

  if (regnum == ALPHA_PC_REGNUM || regnum == -1)
    regcache_raw_supply (regcache, ALPHA_PC_REGNUM, regs + 31 * 8);
}

/* Supply register REGNUM from the buffer specified by GREGS and LEN
   in the general-purpose register set REGSET to register cache
   REGCACHE.  If REGNUM is -1, do this for all registers in REGSET.  */

static void
alphanbsd_aout_supply_gregset (const struct regset *regset,
			       struct regcache *regcache,
			       int regnum, const void *gregs, size_t len)
{
  const gdb_byte *regs = gregs;
  int i;

  /* Table to map a GDB register number to a trapframe register index.  */
  static const int regmap[] =
  {
     0,   1,   2,   3,
     4,   5,   6,   7,
     8,   9,  10,  11,
    12,  13,  14,  15, 
    30,  31,  32,  16, 
    17,  18,  19,  20,
    21,  22,  23,  24,
    25,  29,  26
  };

  gdb_assert (len >= ALPHANBSD_SIZEOF_GREGS);

  for (i = 0; i < ARRAY_SIZE(regmap); i++)
    {
      if (regnum == i || regnum == -1)
	regcache_raw_supply (regcache, i, regs + regmap[i] * 8);
    }

  if (regnum == ALPHA_PC_REGNUM || regnum == -1)
    regcache_raw_supply (regcache, ALPHA_PC_REGNUM, regs + 31 * 8);

  if (len >= ALPHANBSD_SIZEOF_GREGS + ALPHANBSD_SIZEOF_FPREGS)
    {
      regs += ALPHANBSD_SIZEOF_GREGS;
      len -= ALPHANBSD_SIZEOF_GREGS;
      alphanbsd_supply_fpregset (regset, regcache, regnum, regs, len);
    }
}

/* NetBSD/alpha register sets.  */

static struct regset alphanbsd_gregset =
{
  NULL,
  alphanbsd_supply_gregset
};

static struct regset alphanbsd_fpregset =
{
  NULL,
  alphanbsd_supply_fpregset
};

static struct regset alphanbsd_aout_gregset =
{
  NULL,
  alphanbsd_aout_supply_gregset
};

/* Return the appropriate register set for the core section identified
   by SECT_NAME and SECT_SIZE.  */

const struct regset *
alphanbsd_regset_from_core_section (struct gdbarch *gdbarch,
				    const char *sect_name, size_t sect_size)
{
  if (strcmp (sect_name, ".reg") == 0 && sect_size >= ALPHANBSD_SIZEOF_GREGS)
    {
      if (sect_size >= ALPHANBSD_SIZEOF_GREGS + ALPHANBSD_SIZEOF_FPREGS)
	return &alphanbsd_aout_gregset;
      else
	return &alphanbsd_gregset;
    }

  if (strcmp (sect_name, ".reg2") == 0 && sect_size >= ALPHANBSD_SIZEOF_FPREGS)
    return &alphanbsd_fpregset;

  return NULL;
}


/* Signal trampolines.  */

/* Under NetBSD/alpha, signal handler invocations can be identified by the
   designated code sequence that is used to return from a signal handler.
   In particular, the return address of a signal handler points to the
   following code sequence:

	ldq	a0, 0(sp)
	lda	sp, 16(sp)
	lda	v0, 295(zero)	# __sigreturn14
	call_pal callsys

   Each instruction has a unique encoding, so we simply attempt to match
   the instruction the PC is pointing to with any of the above instructions.
   If there is a hit, we know the offset to the start of the designated
   sequence and can then check whether we really are executing in the
   signal trampoline.  If not, -1 is returned, otherwise the offset from the
   start of the return sequence is returned.  */
static const unsigned char sigtramp_retcode[] =
{
  0x00, 0x00, 0x1e, 0xa6,	/* ldq a0, 0(sp) */
  0x10, 0x00, 0xde, 0x23,	/* lda sp, 16(sp) */
  0x27, 0x01, 0x1f, 0x20,	/* lda v0, 295(zero) */
  0x83, 0x00, 0x00, 0x00,	/* call_pal callsys */
};
#define RETCODE_NWORDS		4
#define RETCODE_SIZE		(RETCODE_NWORDS * 4)

static LONGEST
alphanbsd_sigtramp_offset (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  unsigned char ret[RETCODE_SIZE], w[4];
  LONGEST off;
  int i;

  if (target_read_memory (pc, (char *) w, 4) != 0)
    return -1;

  for (i = 0; i < RETCODE_NWORDS; i++)
    {
      if (memcmp (w, sigtramp_retcode + (i * 4), 4) == 0)
	break;
    }
  if (i == RETCODE_NWORDS)
    return (-1);

  off = i * 4;
  pc -= off;

  if (target_read_memory (pc, (char *) ret, sizeof (ret)) != 0)
    return -1;

  if (memcmp (ret, sigtramp_retcode, RETCODE_SIZE) == 0)
    return off;

  return -1;
}

static int
alphanbsd_pc_in_sigtramp (struct gdbarch *gdbarch,
		 	  CORE_ADDR pc, char *func_name)
{
  return (nbsd_pc_in_sigtramp (pc, func_name)
	  || alphanbsd_sigtramp_offset (gdbarch, pc) >= 0);
}

static CORE_ADDR
alphanbsd_sigcontext_addr (struct frame_info *frame)
{
  /* FIXME: This is not correct for all versions of NetBSD/alpha.
     We will probably need to disassemble the trampoline to figure
     out which trampoline frame type we have.  */
  if (!get_next_frame (frame))
    return 0;
  return get_frame_base (get_next_frame (frame));
}


static void
alphanbsd_init_abi (struct gdbarch_info info,
                    struct gdbarch *gdbarch)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* Hook into the DWARF CFI frame unwinder.  */
  alpha_dwarf2_init_abi (info, gdbarch);

  /* Hook into the MDEBUG frame unwinder.  */
  alpha_mdebug_init_abi (info, gdbarch);

  /* NetBSD/alpha does not provide single step support via ptrace(2); we
     must use software single-stepping.  */
  set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);

  /* NetBSD/alpha has SVR4-style shared libraries.  */
  set_solib_svr4_fetch_link_map_offsets
    (gdbarch, svr4_lp64_fetch_link_map_offsets);

  tdep->dynamic_sigtramp_offset = alphanbsd_sigtramp_offset;
  tdep->pc_in_sigtramp = alphanbsd_pc_in_sigtramp;
  tdep->sigcontext_addr = alphanbsd_sigcontext_addr;

  tdep->jb_pc = 2;
  tdep->jb_elt_size = 8;

  set_gdbarch_regset_from_core_section
    (gdbarch, alphanbsd_regset_from_core_section);
}


static enum gdb_osabi
alphanbsd_core_osabi_sniffer (bfd *abfd)
{
  if (strcmp (bfd_get_target (abfd), "netbsd-core") == 0)
    return GDB_OSABI_NETBSD_ELF;

  return GDB_OSABI_UNKNOWN;
}


/* Provide a prototype to silence -Wmissing-prototypes.  */
void _initialize_alphanbsd_tdep (void);

void
_initialize_alphanbsd_tdep (void)
{
  /* BFD doesn't set a flavour for NetBSD style a.out core files.  */
  gdbarch_register_osabi_sniffer (bfd_arch_alpha, bfd_target_unknown_flavour,
                                  alphanbsd_core_osabi_sniffer);

  gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_NETBSD_ELF,
                          alphanbsd_init_abi);
}