gdb/i386-linux-nat.c

/* Native-dependent code for Linux running on i386's, for GDB.

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 "inferior.h"
#include "gdbcore.h"

/* For i386_linux_skip_solib_resolver */
#include "symtab.h"
#include "frame.h"
#include "symfile.h"
#include "objfiles.h"

#include <sys/ptrace.h>
#include <sys/user.h>
#include <sys/procfs.h>

#ifdef HAVE_SYS_REG_H
#include <sys/reg.h>
#endif

/*
 * Some systems (Linux) may have threads implemented as pseudo-processes, 
 * in which case we may be tracing more than one process at a time.
 * In that case, inferior_pid will contain the main process ID and the 
 * individual thread (process) id mashed together.  These macros are 
 * used to separate them out.  The definitions may be overridden in tm.h
 */

#if !defined (PIDGET)	/* Default definition for PIDGET/TIDGET.  */
#define PIDGET(PID)	PID
#define TIDGET(PID)	0
#endif

/* This is a duplicate of the table in i386-xdep.c. */

static int regmap[] = 
{
  EAX, ECX, EDX, EBX,
  UESP, EBP, ESI, EDI,
  EIP, EFL, CS, SS,
  DS, ES, FS, GS,
};


/* Which ptrace request retrieves which registers?
   These apply to the corresponding SET requests as well.  */
#define GETREGS_SUPPLIES(regno) \
  (0 <= (regno) && (regno) <= 15)
#define GETFPREGS_SUPPLIES(regno) \
  (FP0_REGNUM <= (regno) && (regno) <= LAST_FPU_CTRL_REGNUM)
#define GETXFPREGS_SUPPLIES(regno) \
  (FP0_REGNUM <= (regno) && (regno) <= MXCSR_REGNUM)

/* Does the current host support the GETXFPREGS request?  The header
   file may or may not define it, and even if it is defined, the
   kernel will return EIO if it's running on a pre-SSE processor.

   PTRACE_GETXFPREGS is a Cygnus invention, since we wrote our own
   Linux kernel patch for SSE support.  That patch may or may not
   actually make it into the official distribution.  If you find that
   years have gone by since this stuff was added, and Linux isn't
   using PTRACE_GETXFPREGS, that means that our patch didn't make it,
   and you can delete this, and the related code.

   My instinct is to attach this to some architecture- or
   target-specific data structure, but really, a particular GDB
   process can only run on top of one kernel at a time.  So it's okay
   for this to be a simple variable.  */
int have_ptrace_getxfpregs =
#ifdef HAVE_PTRACE_GETXFPREGS
  1
#else
  0
#endif
;



/* Transfering the general registers between GDB, inferiors and core files.  */

/* Given a pointer to a general register set in struct user format
   (gregset_t *), unpack the register contents and supply them as
   gdb's idea of the current register values. */
void
supply_gregset (gregsetp)
     gregset_t *gregsetp;
{
  register int regi;
  register greg_t *regp = (greg_t *) gregsetp;

  for (regi = 0; regi < NUM_GREGS; regi++)
    {
      supply_register (regi, (char *) (regp + regmap[regi]));
    }
}


/* Fill in a gregset_t object with selected data from a gdb-format
   register file.
   - GREGSETP points to the gregset_t object to be filled.
   - GDB_REGS points to the GDB-style register file providing the data.
   - VALID is an array indicating which registers in GDB_REGS are
     valid; the parts of *GREGSETP that would hold registers marked
     invalid in GDB_REGS are left unchanged.  If VALID is zero, all
     registers are assumed to be valid.  */
void
convert_to_gregset (gregset_t *gregsetp,
		    char *gdb_regs,
		    signed char *valid)
{
  int regi;
  register greg_t *regp = (greg_t *) gregsetp;

  for (regi = 0; regi < NUM_GREGS; regi++)
    if (! valid || valid[regi])
      *(regp + regmap[regi]) = * (int *) &registers[REGISTER_BYTE (regi)];
}


/* Store GDB's value for REGNO in *GREGSETP.  If REGNO is -1, do all
   of them.  */
void
fill_gregset (gregset_t *gregsetp,
	      int regno)
{
  if (regno == -1)
    convert_to_gregset (gregsetp, registers, 0);
  else if (regno >= 0 && regno < NUM_GREGS)
    {
      signed char valid[NUM_GREGS];
      memset (valid, 0, sizeof (valid));
      valid[regno] = 1;
      convert_to_gregset (gregsetp, registers, valid);
    }
}


/* Read the general registers from the process, and store them
   in registers[].  */
static void
fetch_regs (int tid)
{
  int ret, regno;
  gregset_t buf;

  ret = ptrace (PTRACE_GETREGS, tid, 0, (int) &buf);
  if (ret < 0)
    {
      warning ("Couldn't get registers");
      return;
    }

  supply_gregset (&buf);
}


/* Set the inferior's general registers to the values in registers[]
   --- but only those registers marked as valid.  */
static void
store_regs (int tid)
{
  int ret, regno;
  gregset_t buf;

  ret = ptrace (PTRACE_GETREGS, tid, 0, (int) &buf);
  if (ret < 0)
    {
      warning ("Couldn't get registers");
      return;
    }

  convert_to_gregset (&buf, registers, register_valid);

  ret = ptrace (PTRACE_SETREGS, tid, 0, (int)buf);
  if (ret < 0)
    {
      warning ("Couldn't write registers");
      return;
    }
}



/* Transfering floating-point registers between GDB, inferiors and cores.  */

/* What is the address of st(N) within the fpregset_t structure F?  */
#define FPREGSET_T_FPREG_ADDR(f, n) \
  ((char *) &(f)->st_space + (n) * 10)

/* Fill GDB's register file with the floating-point register values in
   *FPREGSETP.  */
void 
supply_fpregset (fpregset_t *fpregsetp)
{
  int i;

  /* Supply the floating-point registers.  */
  for (i = 0; i < 8; i++)
    supply_register (FP0_REGNUM + i, FPREGSET_T_FPREG_ADDR (fpregsetp, i));

  supply_register (FCTRL_REGNUM, (char *) &fpregsetp->cwd);
  supply_register (FSTAT_REGNUM, (char *) &fpregsetp->swd);
  supply_register (FTAG_REGNUM,  (char *) &fpregsetp->twd);
  supply_register (FCOFF_REGNUM, (char *) &fpregsetp->fip);
  supply_register (FDS_REGNUM,   (char *) &fpregsetp->fos);
  supply_register (FDOFF_REGNUM, (char *) &fpregsetp->foo);
  
  /* Extract the code segment and opcode from the  "fcs" member.  */
  {
    long l;

    l = fpregsetp->fcs & 0xffff;
    supply_register (FCS_REGNUM, (char *) &l);

    l = (fpregsetp->fcs >> 16) & ((1 << 11) - 1);
    supply_register (FOP_REGNUM, (char *) &l);
  }
}


/* Fill in an fpregset_t structure with selected data from a
   gdb-format register file.
   - FPREGSETP points to the structure to be filled. 
   - GDB_REGS points to the GDB-style register file providing the data.
   - VALID is an array indicating which registers in GDB_REGS are
     valid; the parts of *FPREGSETP that would hold registers marked
     invalid in GDB_REGS are left unchanged.  If VALID is zero, all
     registers are assumed to be valid.  */
void
convert_to_fpregset (fpregset_t *fpregsetp,
		     char *gdb_regs,
		     signed char *valid)
{
  int i;

  /* Fill in the floating-point registers.  */
  for (i = 0; i < 8; i++)
    if (!valid || valid[i])
      memcpy (FPREGSET_T_FPREG_ADDR (fpregsetp, i),
	      &registers[REGISTER_BYTE (FP0_REGNUM + i)],
	      REGISTER_RAW_SIZE(FP0_REGNUM + i));

#define fill(MEMBER, REGNO)						\
  if (! valid || valid[(REGNO)])					\
    memcpy (&fpregsetp->MEMBER, &registers[REGISTER_BYTE (REGNO)],	\
	    sizeof (fpregsetp->MEMBER))

  fill (cwd, FCTRL_REGNUM);
  fill (swd, FSTAT_REGNUM);
  fill (twd, FTAG_REGNUM);
  fill (fip, FCOFF_REGNUM);
  fill (foo, FDOFF_REGNUM);
  fill (fos, FDS_REGNUM);

#undef fill

  if (! valid || valid[FCS_REGNUM])
    fpregsetp->fcs
      = ((fpregsetp->fcs & ~0xffff)
	 | (* (int *) &registers[REGISTER_BYTE (FCS_REGNUM)] & 0xffff));

  if (! valid || valid[FOP_REGNUM])
    fpregsetp->fcs
      = ((fpregsetp->fcs & 0xffff)
	 | ((*(int *) &registers[REGISTER_BYTE (FOP_REGNUM)] & ((1 << 11) - 1))
	    << 16));
}


/* Given a pointer to a floating point register set in (fpregset_t *)
   format, update all of the registers from gdb's idea of the current
   floating point register set.  */

void
fill_fpregset (fpregset_t *fpregsetp,
	       int regno)
{
  convert_to_fpregset (fpregsetp, registers, 0);
}


/* Get the whole floating point state of the process and store the
   floating point stack into registers[].  */
static void
fetch_fpregs (int tid)
{
  int ret, regno;
  fpregset_t buf;

  ret = ptrace (PTRACE_GETFPREGS, tid, 0, (int) &buf);
  if (ret < 0)
    {
      warning ("Couldn't get floating point status");
      return;
    }

  /* ptrace fills an fpregset_t, so we can use the same function we do
     for core files.  */
  supply_fpregset (&buf);
}


/* Set the inferior's floating-point registers to the values in
   registers[] --- but only those registers marked valid.  */
static void
store_fpregs (int tid)
{
  int ret;
  fpregset_t buf;

  ret = ptrace (PTRACE_GETFPREGS, tid, 0, (int) &buf);
  if (ret < 0)
    {
      warning ("Couldn't get floating point status");
      return;
    }

  convert_to_fpregset (&buf, registers, register_valid);

  ret = ptrace (PTRACE_SETFPREGS, tid, 0, (int) &buf);
  if (ret < 0)
    {
      warning ("Couldn't write floating point status");
      return;
    }
}


/* Transfering floating-point and SSE registers to and from GDB.  */


/* PTRACE_GETXFPREGS is a Cygnus invention, since we wrote our own
   Linux kernel patch for SSE support.  That patch may or may not
   actually make it into the official distribution.  If you find that
   years have gone by since this code was added, and Linux isn't using
   PTRACE_GETXFPREGS, that means that our patch didn't make it, and
   you can delete this code.  */

#ifdef HAVE_PTRACE_GETXFPREGS
static void
supply_xfpregset (struct user_xfpregs_struct *xfpregs)
{
  int reg;

  /* Supply the floating-point registers.  */
  for (reg = 0; reg < 8; reg++)
    supply_register (FP0_REGNUM + reg, (char *) &xfpregs->st_space[reg]);

  {
    supply_register (FCTRL_REGNUM, (char *) &xfpregs->cwd);
    supply_register (FSTAT_REGNUM, (char *) &xfpregs->swd);
    supply_register (FTAG_REGNUM,  (char *) &xfpregs->twd);
    supply_register (FCOFF_REGNUM, (char *) &xfpregs->fip);
    supply_register (FDS_REGNUM,   (char *) &xfpregs->fos);
    supply_register (FDOFF_REGNUM, (char *) &xfpregs->foo);
  
    /* Extract the code segment and opcode from the  "fcs" member.  */
    {
      long l;
      
      l = xfpregs->fcs & 0xffff;
      supply_register (FCS_REGNUM, (char *) &l);

      l = (xfpregs->fcs >> 16) & ((1 << 11) - 1);
      supply_register (FOP_REGNUM, (char *) &l);
    }
  }

  /* Supply the SSE registers.  */
  for (reg = 0; reg < 8; reg++)
    supply_register (XMM0_REGNUM + reg, (char *) &xfpregs->xmm_space[reg]);
  supply_register (MXCSR_REGNUM, (char *) &xfpregs->mxcsr);
}


static void
convert_to_xfpregset (struct user_xfpregs_struct *xfpregs,
		      char *gdb_regs,
		      signed char *valid)
{
  int reg;

  /* Fill in the floating-point registers.  */
  for (reg = 0; reg < 8; reg++)
    if (!valid || valid[reg])
      memcpy (&xfpregs->st_space[reg],
	      &registers[REGISTER_BYTE (FP0_REGNUM + reg)],
	      REGISTER_RAW_SIZE(FP0_REGNUM + reg));

#define fill(MEMBER, REGNO)						\
  if (! valid || valid[(REGNO)])					\
    memcpy (&xfpregs->MEMBER, &registers[REGISTER_BYTE (REGNO)],	\
	    sizeof (xfpregs->MEMBER))

  fill (cwd, FCTRL_REGNUM);
  fill (swd, FSTAT_REGNUM);
  fill (twd, FTAG_REGNUM);
  fill (fip, FCOFF_REGNUM);
  fill (foo, FDOFF_REGNUM);
  fill (fos, FDS_REGNUM);

#undef fill

  if (! valid || valid[FCS_REGNUM])
    xfpregs->fcs
      = ((xfpregs->fcs & ~0xffff)
	 | (* (int *) &registers[REGISTER_BYTE (FCS_REGNUM)] & 0xffff));

  if (! valid || valid[FOP_REGNUM])
    xfpregs->fcs
      = ((xfpregs->fcs & 0xffff)
	 | ((*(int *) &registers[REGISTER_BYTE (FOP_REGNUM)] & ((1 << 11) - 1))
	    << 16));

  /* Fill in the XMM registers.  */
  for (reg = 0; reg < 8; reg++)
    if (! valid || valid[reg])
      memcpy (&xfpregs->xmm_space[reg],
	      &registers[REGISTER_BYTE (XMM0_REGNUM + reg)],
	      REGISTER_RAW_SIZE (XMM0_REGNUM + reg));
}


/* Make a PTRACE_GETXFPREGS request, and supply all the register
   values that yields to GDB.  */
static int
fetch_xfpregs (int tid)
{
  int ret;
  struct user_xfpregs_struct xfpregs;

  if (! have_ptrace_getxfpregs) 
    return 0;

  ret = ptrace (PTRACE_GETXFPREGS, tid, 0, &xfpregs);
  if (ret == -1)
    {
      if (errno == EIO)
	{
	  have_ptrace_getxfpregs = 0;
	  return 0;
	}

      warning ("couldn't read floating-point and SSE registers.");
      return 0;
    }

  supply_xfpregset (&xfpregs);
  return 1;
}


/* Send all the valid register values in GDB's register file covered
   by the PTRACE_SETXFPREGS request to the inferior.  */
static int
store_xfpregs (int tid)
{
  int ret;
  struct user_xfpregs_struct xfpregs;

  if (! have_ptrace_getxfpregs)
    return 0;

  ret = ptrace (PTRACE_GETXFPREGS, tid, 0, &xfpregs);
  if (ret == -1)
    {
      if (errno == EIO)
	{
	  have_ptrace_getxfpregs = 0;
	  return 0;
	}

      warning ("couldn't read floating-point and SSE registers.");
      return 0;
    }

  convert_to_xfpregset (&xfpregs, registers, register_valid);

  if (ptrace (PTRACE_SETXFPREGS, tid, 0, &xfpregs) < 0)
    {
      warning ("Couldn't write floating-point and SSE registers.");
      return 0;
    }

  return 1;
}


/* Fill the XMM registers in the register file with dummy values.  For
   cases where we don't have access to the XMM registers.  I think
   this is cleaner than printing a warning.  For a cleaner solution,
   we should gdbarchify the i386 family.  */
static void
dummy_sse_values ()
{
  /* C doesn't have a syntax for NaN's, so write it out as an array of
     longs.  */
  static long dummy[4] = { 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff };
  static long mxcsr = 0x1f80;
  int reg;

  for (reg = 0; reg < 8; reg++)
    supply_register (XMM0_REGNUM + reg, (char *) dummy);
  supply_register (MXCSR_REGNUM, (char *) &mxcsr);
}

#else

/* Stub versions of the above routines, for systems that don't have
   PTRACE_GETXFPREGS.  */
static int store_xfpregs (int tid) { return 0; }
static int fetch_xfpregs (int tid) { return 0; }
static void dummy_sse_values () {}

#endif


/* Transferring arbitrary registers between GDB and inferior.  */

/* Fetch registers from the child process.
   Fetch all if regno == -1, otherwise fetch all ordinary
   registers or all floating point registers depending
   upon the value of regno. */

void
fetch_inferior_registers (int regno)
{
  /* linux lwp id's are process id's */
  int tid;

  if ((tid = TIDGET (inferior_pid)) == 0)
    tid = inferior_pid;		/* not a threaded program */

  /* Use the xfpregs requests whenever possible, since they transfer
     more registers in one system call, and we'll cache the results.
     But remember that fetch_xfpregs can fail, and return zero.  */
  if (regno == -1)
    {
      fetch_regs (tid);
      if (fetch_xfpregs (tid))
	return;
      fetch_fpregs (tid);
      return;
    }

  if (GETREGS_SUPPLIES (regno))
    {
      fetch_regs (tid);
      return;
    }

  if (GETXFPREGS_SUPPLIES (regno))
    {
      if (fetch_xfpregs (tid))
	return;

      /* Either our processor or our kernel doesn't support the SSE
	 registers, so read the FP registers in the traditional way,
	 and fill the SSE registers with dummy values.  It would be
	 more graceful to handle differences in the register set using
	 gdbarch.  Until then, this will at least make things work
	 plausibly.  */
      fetch_fpregs (tid);
      dummy_sse_values ();
      return;
    }

  internal_error ("i386-linux-nat.c (fetch_inferior_registers): "
		  "got request for bad register number %d", regno);
}


/* Store our register values back into the inferior.
   If REGNO is -1, do this for all registers.
   Otherwise, REGNO specifies which register, which
   then determines whether we store all ordinary
   registers or all of the floating point registers. */

void
store_inferior_registers (regno)
     int regno;
{
  /* linux lwp id's are process id's */
  int tid;

  if ((tid = TIDGET (inferior_pid)) == 0)
    tid = inferior_pid;		/* not a threaded program */

  /* Use the xfpregs requests whenever possible, since they transfer
     more registers in one system call.  But remember that
     store_xfpregs can fail, and return zero.  */
  if (regno == -1)
    {
      store_regs (tid);
      if (store_xfpregs (tid))
	return;
      store_fpregs (tid);
      return;
    }

  if (GETREGS_SUPPLIES (regno))
    {
      store_regs (tid);
      return;
    }

  if (GETXFPREGS_SUPPLIES (regno))
    {
      if (store_xfpregs (tid))
	return;

      /* Either our processor or our kernel doesn't support the SSE
	 registers, so just write the FP registers in the traditional way.  */
      store_fpregs (tid);
      return;
    }

  internal_error ("i386-linux-nat.c (store_inferior_registers): "
		  "got request to store bad register number %d", regno);
}



/* Interpreting register set info found in core files.  */

/* Provide registers to GDB from a core file.

   (We can't use the generic version of this function in
   core-regset.c, because Linux has *three* different kinds of
   register set notes.  core-regset.c would have to call
   supply_xfpregset, which most platforms don't have.)

   CORE_REG_SECT points to an array of bytes, which are the contents
   of a `note' from a core file which BFD thinks might contain
   register contents.  CORE_REG_SIZE is its size.

   WHICH says which register set corelow suspects this is:
   0 --- the general register set, in gregset format
   2 --- the floating-point register set, in fpregset format
   3 --- the extended floating-point register set, in struct
         user_xfpregs_struct format

   DUMMY isn't used on Linux.  */
static void
i386_linux_fetch_core_registers (char *core_reg_sect,
				 unsigned core_reg_size,
				 int which,
				 CORE_ADDR dummy)
{
  gregset_t gregset;
  fpregset_t fpregset;

  switch (which)
    {
    case 0:
      if (core_reg_size != sizeof (gregset))
	warning ("wrong size gregset struct in core file");
      else
	{
	  memcpy (&gregset, core_reg_sect, sizeof (gregset));
	  supply_gregset (&gregset);
	}
      break;

    case 2:
      if (core_reg_size != sizeof (fpregset))
	warning ("wrong size fpregset struct in core file");
      else
	{
	  memcpy (&fpregset, core_reg_sect, sizeof (fpregset));
	  supply_fpregset (&fpregset);
	}
      break;

#ifdef HAVE_PTRACE_GETXFPREGS
      {
	struct user_xfpregs_struct xfpregset;
      case 3:
	if (core_reg_size != sizeof (struct user_xfpregs_struct))
	  warning ("wrong size user_xfpregs_struct in core file");
	else
	  {
	    memcpy (&xfpregset, core_reg_sect, sizeof (xfpregset));
	    supply_xfpregset (&xfpregset);
	  }
	break;
      }
#endif

    default:
      /* We've covered all the kinds of registers we know about here,
         so this must be something we wouldn't know what to do with
         anyway.  Just ignore it.  */
      break;
    }
}


static struct core_fns i386_linux_nat_core_fns =
{
  bfd_target_elf_flavour,		/* core_flavour */
  default_check_format,			/* check_format */
  default_core_sniffer,			/* core_sniffer */
  i386_linux_fetch_core_registers,	/* core_read_registers */
  NULL					/* next */
};


/* Calling functions in shared libraries.  */

/* Find the minimal symbol named NAME, and return both the minsym
   struct and its objfile.  This probably ought to be in minsym.c, but
   everything there is trying to deal with things like C++ and
   SOFUN_ADDRESS_MAYBE_TURQUOISE, ...  Since this is so simple, it may
   be considered too special-purpose for general consumption.  */

static struct minimal_symbol *
find_minsym_and_objfile (char *name, struct objfile **objfile_p)
{
  struct objfile *objfile;

  ALL_OBJFILES (objfile)
    {
      struct minimal_symbol *msym;

      ALL_OBJFILE_MSYMBOLS (objfile, msym)
	{
	  if (SYMBOL_NAME (msym)
	      && STREQ (SYMBOL_NAME (msym), name))
	    {
	      *objfile_p = objfile;
	      return msym;
	    }
	}
    }

  return 0;
}


static CORE_ADDR
skip_hurd_resolver (CORE_ADDR pc)
{
  /* The HURD dynamic linker is part of the GNU C library, so many
     GNU/Linux distributions use it.  (All ELF versions, as far as I
     know.)  An unresolved PLT entry points to "_dl_runtime_resolve",
     which calls "fixup" to patch the PLT, and then passes control to
     the function.

     We look for the symbol `_dl_runtime_resolve', and find `fixup' in
     the same objfile.  If we are at the entry point of `fixup', then
     we set a breakpoint at the return address (at the top of the
     stack), and continue.
  
     It's kind of gross to do all these checks every time we're
     called, since they don't change once the executable has gotten
     started.  But this is only a temporary hack --- upcoming versions
     of Linux will provide a portable, efficient interface for
     debugging programs that use shared libraries.  */

  struct objfile *objfile;
  struct minimal_symbol *resolver 
    = find_minsym_and_objfile ("_dl_runtime_resolve", &objfile);

  if (resolver)
    {
      struct minimal_symbol *fixup
	= lookup_minimal_symbol ("fixup", 0, objfile);

      if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc)
	return (SAVED_PC_AFTER_CALL (get_current_frame ()));
    }

  return 0;
}      


/* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c.
   This function:
   1) decides whether a PLT has sent us into the linker to resolve
      a function reference, and 
   2) if so, tells us where to set a temporary breakpoint that will
      trigger when the dynamic linker is done.  */

CORE_ADDR
i386_linux_skip_solib_resolver (CORE_ADDR pc)
{
  CORE_ADDR result;

  /* Plug in functions for other kinds of resolvers here.  */
  result = skip_hurd_resolver (pc);
  if (result)
    return result;

  return 0;
}



/* Module initialization.  */

void
_initialize_i386_linux_nat ()
{
  add_core_fns (&i386_linux_nat_core_fns);
}