xref: /netbsd-src/external/gpl3/gdb.old/dist/gdb/go32-nat.c (revision f0fde9902fd4d72ded2807793acc7bfaa1ebf243)
1 /* Native debugging support for Intel x86 running DJGPP.
2    Copyright (C) 1997-2019 Free Software Foundation, Inc.
3    Written by Robert Hoehne.
4 
5    This file is part of GDB.
6 
7    This program is free software; you can redistribute it and/or modify
8    it under the terms of the GNU General Public License as published by
9    the Free Software Foundation; either version 3 of the License, or
10    (at your option) any later version.
11 
12    This program is distributed in the hope that it will be useful,
13    but WITHOUT ANY WARRANTY; without even the implied warranty of
14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15    GNU General Public License for more details.
16 
17    You should have received a copy of the GNU General Public License
18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
19 
20 /* To whomever it may concern, here's a general description of how
21    debugging in DJGPP works, and the special quirks GDB does to
22    support that.
23 
24    When the DJGPP port of GDB is debugging a DJGPP program natively,
25    there aren't 2 separate processes, the debuggee and GDB itself, as
26    on other systems.  (This is DOS, where there can only be one active
27    process at any given time, remember?)  Instead, GDB and the
28    debuggee live in the same process.  So when GDB calls
29    go32_create_inferior below, and that function calls edi_init from
30    the DJGPP debug support library libdbg.a, we load the debuggee's
31    executable file into GDB's address space, set it up for execution
32    as the stub loader (a short real-mode program prepended to each
33    DJGPP executable) normally would, and do a lot of preparations for
34    swapping between GDB's and debuggee's internal state, primarily wrt
35    the exception handlers.  This swapping happens every time we resume
36    the debuggee or switch back to GDB's code, and it includes:
37 
38     . swapping all the segment registers
39     . swapping the PSP (the Program Segment Prefix)
40     . swapping the signal handlers
41     . swapping the exception handlers
42     . swapping the FPU status
43     . swapping the 3 standard file handles (more about this below)
44 
45    Then running the debuggee simply means longjmp into it where its PC
46    is and let it run until it stops for some reason.  When it stops,
47    GDB catches the exception that stopped it and longjmp's back into
48    its own code.  All the possible exit points of the debuggee are
49    watched; for example, the normal exit point is recognized because a
50    DOS program issues a special system call to exit.  If one of those
51    exit points is hit, we mourn the inferior and clean up after it.
52    Cleaning up is very important, even if the process exits normally,
53    because otherwise we might leave behind traces of previous
54    execution, and in several cases GDB itself might be left hosed,
55    because all the exception handlers were not restored.
56 
57    Swapping of the standard handles (in redir_to_child and
58    redir_to_debugger) is needed because, since both GDB and the
59    debuggee live in the same process, as far as the OS is concerned,
60    the share the same file table.  This means that the standard
61    handles 0, 1, and 2 point to the same file table entries, and thus
62    are connected to the same devices.  Therefore, if the debugger
63    redirects its standard output, the standard output of the debuggee
64    is also automagically redirected to the same file/device!
65    Similarly, if the debuggee redirects its stdout to a file, you
66    won't be able to see debugger's output (it will go to the same file
67    where the debuggee has its output); and if the debuggee closes its
68    standard input, you will lose the ability to talk to debugger!
69 
70    For this reason, every time the debuggee is about to be resumed, we
71    call redir_to_child, which redirects the standard handles to where
72    the debuggee expects them to be.  When the debuggee stops and GDB
73    regains control, we call redir_to_debugger, which redirects those 3
74    handles back to where GDB expects.
75 
76    Note that only the first 3 handles are swapped, so if the debuggee
77    redirects or closes any other handles, GDB will not notice.  In
78    particular, the exit code of a DJGPP program forcibly closes all
79    file handles beyond the first 3 ones, so when the debuggee exits,
80    GDB currently loses its stdaux and stdprn streams.  Fortunately,
81    GDB does not use those as of this writing, and will never need
82    to.  */
83 
84 #include "defs.h"
85 
86 #include <fcntl.h>
87 
88 #include "x86-nat.h"
89 #include "inferior.h"
90 #include "infrun.h"
91 #include "gdbthread.h"
92 #include "common/gdb_wait.h"
93 #include "gdbcore.h"
94 #include "command.h"
95 #include "gdbcmd.h"
96 #include "floatformat.h"
97 #include "buildsym-legacy.h"
98 #include "i387-tdep.h"
99 #include "i386-tdep.h"
100 #include "nat/x86-cpuid.h"
101 #include "value.h"
102 #include "regcache.h"
103 #include "top.h"
104 #include "cli/cli-utils.h"
105 #include "inf-child.h"
106 
107 #include <ctype.h>
108 #include <unistd.h>
109 #include <sys/utsname.h>
110 #include <io.h>
111 #include <dos.h>
112 #include <dpmi.h>
113 #include <go32.h>
114 #include <sys/farptr.h>
115 #include <debug/v2load.h>
116 #include <debug/dbgcom.h>
117 #if __DJGPP_MINOR__ > 2
118 #include <debug/redir.h>
119 #endif
120 
121 #include <langinfo.h>
122 
123 #if __DJGPP_MINOR__ < 3
124 /* This code will be provided from DJGPP 2.03 on.  Until then I code it
125    here.  */
126 typedef struct
127   {
128     unsigned short sig0;
129     unsigned short sig1;
130     unsigned short sig2;
131     unsigned short sig3;
132     unsigned short exponent:15;
133     unsigned short sign:1;
134   }
135 NPXREG;
136 
137 typedef struct
138   {
139     unsigned int control;
140     unsigned int status;
141     unsigned int tag;
142     unsigned int eip;
143     unsigned int cs;
144     unsigned int dataptr;
145     unsigned int datasel;
146     NPXREG reg[8];
147   }
148 NPX;
149 
150 static NPX npx;
151 
152 static void save_npx (void);	/* Save the FPU of the debugged program.  */
153 static void load_npx (void);	/* Restore the FPU of the debugged program.  */
154 
155 /* ------------------------------------------------------------------------- */
156 /* Store the contents of the NPX in the global variable `npx'.  */
157 /* *INDENT-OFF* */
158 
159 static void
160 save_npx (void)
161 {
162   asm ("inb    $0xa0, %%al  \n\
163        testb $0x20, %%al    \n\
164        jz 1f 	    	    \n\
165        xorb %%al, %%al	    \n\
166        outb %%al, $0xf0     \n\
167        movb $0x20, %%al	    \n\
168        outb %%al, $0xa0     \n\
169        outb %%al, $0x20     \n\
170 1:     	       	   	    \n\
171        fnsave %0	    \n\
172        fwait "
173 :     "=m" (npx)
174 :				/* No input */
175 :     "%eax");
176 }
177 
178 /* *INDENT-ON* */
179 
180 
181 /* ------------------------------------------------------------------------- */
182 /* Reload the contents of the NPX from the global variable `npx'.  */
183 
184 static void
185 load_npx (void)
186 {
187   asm ("frstor %0":"=m" (npx));
188 }
189 /* ------------------------------------------------------------------------- */
190 /* Stubs for the missing redirection functions.  */
191 typedef struct {
192   char *command;
193   int redirected;
194 } cmdline_t;
195 
196 void
197 redir_cmdline_delete (cmdline_t *ptr)
198 {
199   ptr->redirected = 0;
200 }
201 
202 int
203 redir_cmdline_parse (const char *args, cmdline_t *ptr)
204 {
205   return -1;
206 }
207 
208 int
209 redir_to_child (cmdline_t *ptr)
210 {
211   return 1;
212 }
213 
214 int
215 redir_to_debugger (cmdline_t *ptr)
216 {
217   return 1;
218 }
219 
220 int
221 redir_debug_init (cmdline_t *ptr)
222 {
223   return 0;
224 }
225 #endif /* __DJGPP_MINOR < 3 */
226 
227 typedef enum { wp_insert, wp_remove, wp_count } wp_op;
228 
229 /* This holds the current reference counts for each debug register.  */
230 static int dr_ref_count[4];
231 
232 #define SOME_PID 42
233 
234 static int prog_has_started = 0;
235 
236 #define r_ofs(x) (offsetof(TSS,x))
237 
238 static struct
239 {
240   size_t tss_ofs;
241   size_t size;
242 }
243 regno_mapping[] =
244 {
245   {r_ofs (tss_eax), 4},	/* normal registers, from a_tss */
246   {r_ofs (tss_ecx), 4},
247   {r_ofs (tss_edx), 4},
248   {r_ofs (tss_ebx), 4},
249   {r_ofs (tss_esp), 4},
250   {r_ofs (tss_ebp), 4},
251   {r_ofs (tss_esi), 4},
252   {r_ofs (tss_edi), 4},
253   {r_ofs (tss_eip), 4},
254   {r_ofs (tss_eflags), 4},
255   {r_ofs (tss_cs), 2},
256   {r_ofs (tss_ss), 2},
257   {r_ofs (tss_ds), 2},
258   {r_ofs (tss_es), 2},
259   {r_ofs (tss_fs), 2},
260   {r_ofs (tss_gs), 2},
261   {0, 10},		/* 8 FP registers, from npx.reg[] */
262   {1, 10},
263   {2, 10},
264   {3, 10},
265   {4, 10},
266   {5, 10},
267   {6, 10},
268   {7, 10},
269 	/* The order of the next 7 registers must be consistent
270 	   with their numbering in config/i386/tm-i386.h, which see.  */
271   {0, 2},		/* control word, from npx */
272   {4, 2},		/* status word, from npx */
273   {8, 2},		/* tag word, from npx */
274   {16, 2},		/* last FP exception CS from npx */
275   {12, 4},		/* last FP exception EIP from npx */
276   {24, 2},		/* last FP exception operand selector from npx */
277   {20, 4},		/* last FP exception operand offset from npx */
278   {18, 2}		/* last FP opcode from npx */
279 };
280 
281 static struct
282   {
283     int go32_sig;
284     enum gdb_signal gdb_sig;
285   }
286 sig_map[] =
287 {
288   {0, GDB_SIGNAL_FPE},
289   {1, GDB_SIGNAL_TRAP},
290   /* Exception 2 is triggered by the NMI.  DJGPP handles it as SIGILL,
291      but I think SIGBUS is better, since the NMI is usually activated
292      as a result of a memory parity check failure.  */
293   {2, GDB_SIGNAL_BUS},
294   {3, GDB_SIGNAL_TRAP},
295   {4, GDB_SIGNAL_FPE},
296   {5, GDB_SIGNAL_SEGV},
297   {6, GDB_SIGNAL_ILL},
298   {7, GDB_SIGNAL_EMT},	/* no-coprocessor exception */
299   {8, GDB_SIGNAL_SEGV},
300   {9, GDB_SIGNAL_SEGV},
301   {10, GDB_SIGNAL_BUS},
302   {11, GDB_SIGNAL_SEGV},
303   {12, GDB_SIGNAL_SEGV},
304   {13, GDB_SIGNAL_SEGV},
305   {14, GDB_SIGNAL_SEGV},
306   {16, GDB_SIGNAL_FPE},
307   {17, GDB_SIGNAL_BUS},
308   {31, GDB_SIGNAL_ILL},
309   {0x1b, GDB_SIGNAL_INT},
310   {0x75, GDB_SIGNAL_FPE},
311   {0x78, GDB_SIGNAL_ALRM},
312   {0x79, GDB_SIGNAL_INT},
313   {0x7a, GDB_SIGNAL_QUIT},
314   {-1, GDB_SIGNAL_LAST}
315 };
316 
317 static struct {
318   enum gdb_signal gdb_sig;
319   int djgpp_excepno;
320 } excepn_map[] = {
321   {GDB_SIGNAL_0, -1},
322   {GDB_SIGNAL_ILL, 6},	/* Invalid Opcode */
323   {GDB_SIGNAL_EMT, 7},	/* triggers SIGNOFP */
324   {GDB_SIGNAL_SEGV, 13},	/* GPF */
325   {GDB_SIGNAL_BUS, 17},	/* Alignment Check */
326   /* The rest are fake exceptions, see dpmiexcp.c in djlsr*.zip for
327      details.  */
328   {GDB_SIGNAL_TERM, 0x1b},	/* triggers Ctrl-Break type of SIGINT */
329   {GDB_SIGNAL_FPE, 0x75},
330   {GDB_SIGNAL_INT, 0x79},
331   {GDB_SIGNAL_QUIT, 0x7a},
332   {GDB_SIGNAL_ALRM, 0x78},	/* triggers SIGTIMR */
333   {GDB_SIGNAL_PROF, 0x78},
334   {GDB_SIGNAL_LAST, -1}
335 };
336 
337 /* The go32 target.  */
338 
339 struct go32_nat_target final : public x86_nat_target<inf_child_target>
340 {
341   void attach (const char *, int) override;
342 
343   void resume (ptid_t, int, enum gdb_signal) override;
344 
345   ptid_t wait (ptid_t, struct target_waitstatus *, int) override;
346 
347   void fetch_registers (struct regcache *, int) override;
348   void store_registers (struct regcache *, int) override;
349 
350   enum target_xfer_status xfer_partial (enum target_object object,
351 					const char *annex,
352 					gdb_byte *readbuf,
353 					const gdb_byte *writebuf,
354 					ULONGEST offset, ULONGEST len,
355 					ULONGEST *xfered_len) override;
356 
357   void files_info () override;
358 
359   void terminal_init () override;
360 
361   void terminal_inferior () override;
362 
363   void terminal_ours_for_output () override;
364 
365   void terminal_ours () override;
366 
367   void terminal_info (const char *, int) override;
368 
369   void pass_ctrlc () override;
370 
371   void kill () override;
372 
373   void create_inferior (const char *, const std::string &,
374 			char **, int) override;
375 
376   void mourn_inferior () override;
377 
378   bool thread_alive (ptid_t ptid) override;
379 
380   const char *pid_to_str (ptid_t) override;
381 };
382 
383 static go32_nat_target the_go32_nat_target;
384 
385 void
386 go32_nat_target::attach (const char *args, int from_tty)
387 {
388   error (_("\
389 You cannot attach to a running program on this platform.\n\
390 Use the `run' command to run DJGPP programs."));
391 }
392 
393 static int resume_is_step;
394 static int resume_signal = -1;
395 
396 void
397 go32_nat_target::resume (ptid_t ptid, int step, enum gdb_signal siggnal)
398 {
399   int i;
400 
401   resume_is_step = step;
402 
403   if (siggnal != GDB_SIGNAL_0 && siggnal != GDB_SIGNAL_TRAP)
404   {
405     for (i = 0, resume_signal = -1;
406 	 excepn_map[i].gdb_sig != GDB_SIGNAL_LAST; i++)
407       if (excepn_map[i].gdb_sig == siggnal)
408       {
409 	resume_signal = excepn_map[i].djgpp_excepno;
410 	break;
411       }
412     if (resume_signal == -1)
413       printf_unfiltered ("Cannot deliver signal %s on this platform.\n",
414 			 gdb_signal_to_name (siggnal));
415   }
416 }
417 
418 static char child_cwd[FILENAME_MAX];
419 
420 ptid_t
421 go32_nat_target::wait (ptid_t ptid, struct target_waitstatus *status,
422 		       int options)
423 {
424   int i;
425   unsigned char saved_opcode;
426   unsigned long INT3_addr = 0;
427   int stepping_over_INT = 0;
428 
429   a_tss.tss_eflags &= 0xfeff;	/* Reset the single-step flag (TF).  */
430   if (resume_is_step)
431     {
432       /* If the next instruction is INT xx or INTO, we need to handle
433 	 them specially.  Intel manuals say that these instructions
434 	 reset the single-step flag (a.k.a. TF).  However, it seems
435 	 that, at least in the DPMI environment, and at least when
436 	 stepping over the DPMI interrupt 31h, the problem is having
437 	 TF set at all when INT 31h is executed: the debuggee either
438 	 crashes (and takes the system with it) or is killed by a
439 	 SIGTRAP.
440 
441 	 So we need to emulate single-step mode: we put an INT3 opcode
442 	 right after the INT xx instruction, let the debuggee run
443 	 until it hits INT3 and stops, then restore the original
444 	 instruction which we overwrote with the INT3 opcode, and back
445 	 up the debuggee's EIP to that instruction.  */
446       read_child (a_tss.tss_eip, &saved_opcode, 1);
447       if (saved_opcode == 0xCD || saved_opcode == 0xCE)
448 	{
449 	  unsigned char INT3_opcode = 0xCC;
450 
451 	  INT3_addr
452 	    = saved_opcode == 0xCD ? a_tss.tss_eip + 2 : a_tss.tss_eip + 1;
453 	  stepping_over_INT = 1;
454 	  read_child (INT3_addr, &saved_opcode, 1);
455 	  write_child (INT3_addr, &INT3_opcode, 1);
456 	}
457       else
458 	a_tss.tss_eflags |= 0x0100; /* normal instruction: set TF */
459     }
460 
461   /* The special value FFFFh in tss_trap indicates to run_child that
462      tss_irqn holds a signal to be delivered to the debuggee.  */
463   if (resume_signal <= -1)
464     {
465       a_tss.tss_trap = 0;
466       a_tss.tss_irqn = 0xff;
467     }
468   else
469     {
470       a_tss.tss_trap = 0xffff;	/* run_child looks for this.  */
471       a_tss.tss_irqn = resume_signal;
472     }
473 
474   /* The child might change working directory behind our back.  The
475      GDB users won't like the side effects of that when they work with
476      relative file names, and GDB might be confused by its current
477      directory not being in sync with the truth.  So we always make a
478      point of changing back to where GDB thinks is its cwd, when we
479      return control to the debugger, but restore child's cwd before we
480      run it.  */
481   /* Initialize child_cwd, before the first call to run_child and not
482      in the initialization, so the child get also the changed directory
483      set with the gdb-command "cd ..."  */
484   if (!*child_cwd)
485     /* Initialize child's cwd with the current one.  */
486     getcwd (child_cwd, sizeof (child_cwd));
487 
488   chdir (child_cwd);
489 
490 #if __DJGPP_MINOR__ < 3
491   load_npx ();
492 #endif
493   run_child ();
494 #if __DJGPP_MINOR__ < 3
495   save_npx ();
496 #endif
497 
498   /* Did we step over an INT xx instruction?  */
499   if (stepping_over_INT && a_tss.tss_eip == INT3_addr + 1)
500     {
501       /* Restore the original opcode.  */
502       a_tss.tss_eip--;	/* EIP points *after* the INT3 instruction.  */
503       write_child (a_tss.tss_eip, &saved_opcode, 1);
504       /* Simulate a TRAP exception.  */
505       a_tss.tss_irqn = 1;
506       a_tss.tss_eflags |= 0x0100;
507     }
508 
509   getcwd (child_cwd, sizeof (child_cwd)); /* in case it has changed */
510   chdir (current_directory);
511 
512   if (a_tss.tss_irqn == 0x21)
513     {
514       status->kind = TARGET_WAITKIND_EXITED;
515       status->value.integer = a_tss.tss_eax & 0xff;
516     }
517   else
518     {
519       status->value.sig = GDB_SIGNAL_UNKNOWN;
520       status->kind = TARGET_WAITKIND_STOPPED;
521       for (i = 0; sig_map[i].go32_sig != -1; i++)
522 	{
523 	  if (a_tss.tss_irqn == sig_map[i].go32_sig)
524 	    {
525 #if __DJGPP_MINOR__ < 3
526 	      if ((status->value.sig = sig_map[i].gdb_sig) !=
527 		  GDB_SIGNAL_TRAP)
528 		status->kind = TARGET_WAITKIND_SIGNALLED;
529 #else
530 	      status->value.sig = sig_map[i].gdb_sig;
531 #endif
532 	      break;
533 	    }
534 	}
535     }
536   return ptid_t (SOME_PID);
537 }
538 
539 static void
540 fetch_register (struct regcache *regcache, int regno)
541 {
542   struct gdbarch *gdbarch = regcache->arch ();
543   if (regno < gdbarch_fp0_regnum (gdbarch))
544     regcache->raw_supply (regno,
545 			  (char *) &a_tss + regno_mapping[regno].tss_ofs);
546   else if (i386_fp_regnum_p (gdbarch, regno) || i386_fpc_regnum_p (gdbarch,
547 								   regno))
548     i387_supply_fsave (regcache, regno, &npx);
549   else
550     internal_error (__FILE__, __LINE__,
551 		    _("Invalid register no. %d in fetch_register."), regno);
552 }
553 
554 void
555 go32_nat_target::fetch_registers (struct regcache *regcache, int regno)
556 {
557   if (regno >= 0)
558     fetch_register (regcache, regno);
559   else
560     {
561       for (regno = 0;
562 	   regno < gdbarch_fp0_regnum (regcache->arch ());
563 	   regno++)
564 	fetch_register (regcache, regno);
565       i387_supply_fsave (regcache, -1, &npx);
566     }
567 }
568 
569 static void
570 store_register (const struct regcache *regcache, int regno)
571 {
572   struct gdbarch *gdbarch = regcache->arch ();
573   if (regno < gdbarch_fp0_regnum (gdbarch))
574     regcache->raw_collect (regno,
575 			   (char *) &a_tss + regno_mapping[regno].tss_ofs);
576   else if (i386_fp_regnum_p (gdbarch, regno) || i386_fpc_regnum_p (gdbarch,
577 								   regno))
578     i387_collect_fsave (regcache, regno, &npx);
579   else
580     internal_error (__FILE__, __LINE__,
581 		    _("Invalid register no. %d in store_register."), regno);
582 }
583 
584 void
585 go32_nat_target::store_registers (struct regcache *regcache, int regno)
586 {
587   unsigned r;
588 
589   if (regno >= 0)
590     store_register (regcache, regno);
591   else
592     {
593       for (r = 0; r < gdbarch_fp0_regnum (regcache->arch ()); r++)
594 	store_register (regcache, r);
595       i387_collect_fsave (regcache, -1, &npx);
596     }
597 }
598 
599 /* Const-correct version of DJGPP's write_child, which unfortunately
600    takes a non-const buffer pointer.  */
601 
602 static int
603 my_write_child (unsigned child_addr, const void *buf, unsigned len)
604 {
605   static void *buffer = NULL;
606   static unsigned buffer_len = 0;
607   int res;
608 
609   if (buffer_len < len)
610     {
611       buffer = xrealloc (buffer, len);
612       buffer_len = len;
613     }
614 
615   memcpy (buffer, buf, len);
616   res = write_child (child_addr, buffer, len);
617   return res;
618 }
619 
620 /* Helper for go32_xfer_partial that handles memory transfers.
621    Arguments are like target_xfer_partial.  */
622 
623 static enum target_xfer_status
624 go32_xfer_memory (gdb_byte *readbuf, const gdb_byte *writebuf,
625 		  ULONGEST memaddr, ULONGEST len, ULONGEST *xfered_len)
626 {
627   int res;
628 
629   if (writebuf != NULL)
630     res = my_write_child (memaddr, writebuf, len);
631   else
632     res = read_child (memaddr, readbuf, len);
633 
634   /* read_child and write_child return zero on success, non-zero on
635      failure.  */
636   if (res != 0)
637     return TARGET_XFER_E_IO;
638 
639   *xfered_len = len;
640   return TARGET_XFER_OK;
641 }
642 
643 /* Target to_xfer_partial implementation.  */
644 
645 enum target_xfer_status
646 go32_nat_target::xfer_partial (enum target_object object,
647 			       const char *annex, gdb_byte *readbuf,
648 			       const gdb_byte *writebuf, ULONGEST offset,
649 			       ULONGEST len,
650 			       ULONGEST *xfered_len)
651 {
652   switch (object)
653     {
654     case TARGET_OBJECT_MEMORY:
655       return go32_xfer_memory (readbuf, writebuf, offset, len, xfered_len);
656 
657     default:
658       return this->beneath ()->xfer_partial (object, annex,
659 					     readbuf, writebuf, offset, len,
660 					     xfered_len);
661     }
662 }
663 
664 static cmdline_t child_cmd;	/* Parsed child's command line kept here.  */
665 
666 void
667 go32_nat_target::files_info ()
668 {
669   printf_unfiltered ("You are running a DJGPP V2 program.\n");
670 }
671 
672 void
673 go32_nat_target::kill_inferior ()
674 {
675   mourn_inferior ();
676 }
677 
678 void
679 go32_nat_target::create_inferior (const char *exec_file,
680 				  const std::string &allargs,
681 				  char **env, int from_tty)
682 {
683   extern char **environ;
684   jmp_buf start_state;
685   char *cmdline;
686   char **env_save = environ;
687   size_t cmdlen;
688   struct inferior *inf;
689   int result;
690   const char *args = allargs.c_str ();
691 
692   /* If no exec file handed to us, get it from the exec-file command -- with
693      a good, common error message if none is specified.  */
694   if (exec_file == 0)
695     exec_file = get_exec_file (1);
696 
697   resume_signal = -1;
698   resume_is_step = 0;
699 
700   /* Initialize child's cwd as empty to be initialized when starting
701      the child.  */
702   *child_cwd = 0;
703 
704   /* Init command line storage.  */
705   if (redir_debug_init (&child_cmd) == -1)
706     internal_error (__FILE__, __LINE__,
707 		    _("Cannot allocate redirection storage: "
708 		      "not enough memory.\n"));
709 
710   /* Parse the command line and create redirections.  */
711   if (strpbrk (args, "<>"))
712     {
713       if (redir_cmdline_parse (args, &child_cmd) == 0)
714 	args = child_cmd.command;
715       else
716 	error (_("Syntax error in command line."));
717     }
718   else
719     child_cmd.command = xstrdup (args);
720 
721   cmdlen = strlen (args);
722   /* v2loadimage passes command lines via DOS memory, so it cannot
723      possibly handle commands longer than 1MB.  */
724   if (cmdlen > 1024*1024)
725     error (_("Command line too long."));
726 
727   cmdline = (char *) xmalloc (cmdlen + 4);
728   strcpy (cmdline + 1, args);
729   /* If the command-line length fits into DOS 126-char limits, use the
730      DOS command tail format; otherwise, tell v2loadimage to pass it
731      through a buffer in conventional memory.  */
732   if (cmdlen < 127)
733     {
734       cmdline[0] = strlen (args);
735       cmdline[cmdlen + 1] = 13;
736     }
737   else
738     cmdline[0] = 0xff;	/* Signal v2loadimage it's a long command.  */
739 
740   environ = env;
741 
742   result = v2loadimage (exec_file, cmdline, start_state);
743 
744   environ = env_save;
745   xfree (cmdline);
746 
747   if (result != 0)
748     error (_("Load failed for image %s"), exec_file);
749 
750   edi_init (start_state);
751 #if __DJGPP_MINOR__ < 3
752   save_npx ();
753 #endif
754 
755   inferior_ptid = ptid_t (SOME_PID);
756   inf = current_inferior ();
757   inferior_appeared (inf, SOME_PID);
758 
759   if (!target_is_pushed (this))
760     push_target (this);
761 
762   add_thread_silent (inferior_ptid);
763 
764   clear_proceed_status (0);
765   insert_breakpoints ();
766   prog_has_started = 1;
767 }
768 
769 void
770 go32_nat_target::mourn_inferior ()
771 {
772   ptid_t ptid;
773 
774   redir_cmdline_delete (&child_cmd);
775   resume_signal = -1;
776   resume_is_step = 0;
777 
778   cleanup_client ();
779 
780   /* We need to make sure all the breakpoint enable bits in the DR7
781      register are reset when the inferior exits.  Otherwise, if they
782      rerun the inferior, the uncleared bits may cause random SIGTRAPs,
783      failure to set more watchpoints, and other calamities.  It would
784      be nice if GDB itself would take care to remove all breakpoints
785      at all times, but it doesn't, probably under an assumption that
786      the OS cleans up when the debuggee exits.  */
787   x86_cleanup_dregs ();
788 
789   ptid = inferior_ptid;
790   inferior_ptid = null_ptid;
791   prog_has_started = 0;
792 
793   generic_mourn_inferior ();
794   maybe_unpush_target ();
795 }
796 
797 /* Hardware watchpoint support.  */
798 
799 #define D_REGS edi.dr
800 #define CONTROL D_REGS[7]
801 #define STATUS D_REGS[6]
802 
803 /* Pass the address ADDR to the inferior in the I'th debug register.
804    Here we just store the address in D_REGS, the watchpoint will be
805    actually set up when go32_wait runs the debuggee.  */
806 static void
807 go32_set_dr (int i, CORE_ADDR addr)
808 {
809   if (i < 0 || i > 3)
810     internal_error (__FILE__, __LINE__,
811 		    _("Invalid register %d in go32_set_dr.\n"), i);
812   D_REGS[i] = addr;
813 }
814 
815 /* Pass the value VAL to the inferior in the DR7 debug control
816    register.  Here we just store the address in D_REGS, the watchpoint
817    will be actually set up when go32_wait runs the debuggee.  */
818 static void
819 go32_set_dr7 (unsigned long val)
820 {
821   CONTROL = val;
822 }
823 
824 /* Get the value of the DR6 debug status register from the inferior.
825    Here we just return the value stored in D_REGS, as we've got it
826    from the last go32_wait call.  */
827 static unsigned long
828 go32_get_dr6 (void)
829 {
830   return STATUS;
831 }
832 
833 /* Get the value of the DR7 debug status register from the inferior.
834    Here we just return the value stored in D_REGS, as we've got it
835    from the last go32_wait call.  */
836 
837 static unsigned long
838 go32_get_dr7 (void)
839 {
840   return CONTROL;
841 }
842 
843 /* Get the value of the DR debug register I from the inferior.  Here
844    we just return the value stored in D_REGS, as we've got it from the
845    last go32_wait call.  */
846 
847 static CORE_ADDR
848 go32_get_dr (int i)
849 {
850   if (i < 0 || i > 3)
851     internal_error (__FILE__, __LINE__,
852 		    _("Invalid register %d in go32_get_dr.\n"), i);
853   return D_REGS[i];
854 }
855 
856 /* Put the device open on handle FD into either raw or cooked
857    mode, return 1 if it was in raw mode, zero otherwise.  */
858 
859 static int
860 device_mode (int fd, int raw_p)
861 {
862   int oldmode, newmode;
863   __dpmi_regs regs;
864 
865   regs.x.ax = 0x4400;
866   regs.x.bx = fd;
867   __dpmi_int (0x21, &regs);
868   if (regs.x.flags & 1)
869     return -1;
870   newmode = oldmode = regs.x.dx;
871 
872   if (raw_p)
873     newmode |= 0x20;
874   else
875     newmode &= ~0x20;
876 
877   if (oldmode & 0x80)	/* Only for character dev.  */
878   {
879     regs.x.ax = 0x4401;
880     regs.x.bx = fd;
881     regs.x.dx = newmode & 0xff;   /* Force upper byte zero, else it fails.  */
882     __dpmi_int (0x21, &regs);
883     if (regs.x.flags & 1)
884       return -1;
885   }
886   return (oldmode & 0x20) == 0x20;
887 }
888 
889 
890 static int inf_mode_valid = 0;
891 static int inf_terminal_mode;
892 
893 /* This semaphore is needed because, amazingly enough, GDB calls
894    target.to_terminal_ours more than once after the inferior stops.
895    But we need the information from the first call only, since the
896    second call will always see GDB's own cooked terminal.  */
897 static int terminal_is_ours = 1;
898 
899 void
900 go32_nat_target::terminal_init ()
901 {
902   inf_mode_valid = 0;	/* Reinitialize, in case they are restarting child.  */
903   terminal_is_ours = 1;
904 }
905 
906 void
907 go32_nat_target::terminal_info (const char *args, int from_tty)
908 {
909   printf_unfiltered ("Inferior's terminal is in %s mode.\n",
910 		     !inf_mode_valid
911 		     ? "default" : inf_terminal_mode ? "raw" : "cooked");
912 
913 #if __DJGPP_MINOR__ > 2
914   if (child_cmd.redirection)
915   {
916     int i;
917 
918     for (i = 0; i < DBG_HANDLES; i++)
919     {
920       if (child_cmd.redirection[i]->file_name)
921 	printf_unfiltered ("\tFile handle %d is redirected to `%s'.\n",
922 			   i, child_cmd.redirection[i]->file_name);
923       else if (_get_dev_info (child_cmd.redirection[i]->inf_handle) == -1)
924 	printf_unfiltered
925 	  ("\tFile handle %d appears to be closed by inferior.\n", i);
926       /* Mask off the raw/cooked bit when comparing device info words.  */
927       else if ((_get_dev_info (child_cmd.redirection[i]->inf_handle) & 0xdf)
928 	       != (_get_dev_info (i) & 0xdf))
929 	printf_unfiltered
930 	  ("\tFile handle %d appears to be redirected by inferior.\n", i);
931     }
932   }
933 #endif
934 }
935 
936 void
937 go32_nat_target::terminal_inferior ()
938 {
939   /* Redirect standard handles as child wants them.  */
940   errno = 0;
941   if (redir_to_child (&child_cmd) == -1)
942   {
943     redir_to_debugger (&child_cmd);
944     error (_("Cannot redirect standard handles for program: %s."),
945 	   safe_strerror (errno));
946   }
947   /* Set the console device of the inferior to whatever mode
948      (raw or cooked) we found it last time.  */
949   if (terminal_is_ours)
950   {
951     if (inf_mode_valid)
952       device_mode (0, inf_terminal_mode);
953     terminal_is_ours = 0;
954   }
955 }
956 
957 void
958 go32_nat_target::terminal_ours ()
959 {
960   /* Switch to cooked mode on the gdb terminal and save the inferior
961      terminal mode to be restored when it is resumed.  */
962   if (!terminal_is_ours)
963   {
964     inf_terminal_mode = device_mode (0, 0);
965     if (inf_terminal_mode != -1)
966       inf_mode_valid = 1;
967     else
968       /* If device_mode returned -1, we don't know what happens with
969 	 handle 0 anymore, so make the info invalid.  */
970       inf_mode_valid = 0;
971     terminal_is_ours = 1;
972 
973     /* Restore debugger's standard handles.  */
974     errno = 0;
975     if (redir_to_debugger (&child_cmd) == -1)
976     {
977       redir_to_child (&child_cmd);
978       error (_("Cannot redirect standard handles for debugger: %s."),
979 	     safe_strerror (errno));
980     }
981   }
982 }
983 
984 void
985 go32_nat_target::pass_ctrlc ()
986 {
987 }
988 
989 bool
990 go32_nat_target::thread_alive (ptid_t ptid)
991 {
992   return ptid != null_ptid;
993 }
994 
995 const char *
996 go32_nat_target::pid_to_str (ptid_t ptid)
997 {
998   return normal_pid_to_str (ptid);
999 }
1000 
1001 /* Return the current DOS codepage number.  */
1002 static int
1003 dos_codepage (void)
1004 {
1005   __dpmi_regs regs;
1006 
1007   regs.x.ax = 0x6601;
1008   __dpmi_int (0x21, &regs);
1009   if (!(regs.x.flags & 1))
1010     return regs.x.bx & 0xffff;
1011   else
1012     return 437;	/* default */
1013 }
1014 
1015 /* Limited emulation of `nl_langinfo', for charset.c.  */
1016 char *
1017 nl_langinfo (nl_item item)
1018 {
1019   char *retval;
1020 
1021   switch (item)
1022     {
1023       case CODESET:
1024 	{
1025 	  /* 8 is enough for SHORT_MAX + "CP" + null.  */
1026 	  char buf[8];
1027 	  int blen = sizeof (buf);
1028 	  int needed = snprintf (buf, blen, "CP%d", dos_codepage ());
1029 
1030 	  if (needed > blen)	/* Should never happen.  */
1031 	    buf[0] = 0;
1032 	  retval = xstrdup (buf);
1033 	}
1034 	break;
1035       default:
1036 	retval = xstrdup ("");
1037 	break;
1038     }
1039   return retval;
1040 }
1041 
1042 unsigned short windows_major, windows_minor;
1043 
1044 /* Compute the version Windows reports via Int 2Fh/AX=1600h.  */
1045 static void
1046 go32_get_windows_version(void)
1047 {
1048   __dpmi_regs r;
1049 
1050   r.x.ax = 0x1600;
1051   __dpmi_int(0x2f, &r);
1052   if (r.h.al > 2 && r.h.al != 0x80 && r.h.al != 0xff
1053       && (r.h.al > 3 || r.h.ah > 0))
1054     {
1055       windows_major = r.h.al;
1056       windows_minor = r.h.ah;
1057     }
1058   else
1059     windows_major = 0xff;	/* meaning no Windows */
1060 }
1061 
1062 /* A subroutine of go32_sysinfo to display memory info.  */
1063 static void
1064 print_mem (unsigned long datum, const char *header, int in_pages_p)
1065 {
1066   if (datum != 0xffffffffUL)
1067     {
1068       if (in_pages_p)
1069 	datum <<= 12;
1070       puts_filtered (header);
1071       if (datum > 1024)
1072 	{
1073 	  printf_filtered ("%lu KB", datum >> 10);
1074 	  if (datum > 1024 * 1024)
1075 	    printf_filtered (" (%lu MB)", datum >> 20);
1076 	}
1077       else
1078 	printf_filtered ("%lu Bytes", datum);
1079       puts_filtered ("\n");
1080     }
1081 }
1082 
1083 /* Display assorted information about the underlying OS.  */
1084 static void
1085 go32_sysinfo (const char *arg, int from_tty)
1086 {
1087   static const char test_pattern[] =
1088     "deadbeafdeadbeafdeadbeafdeadbeafdeadbeaf"
1089     "deadbeafdeadbeafdeadbeafdeadbeafdeadbeaf"
1090     "deadbeafdeadbeafdeadbeafdeadbeafdeadbeafdeadbeaf";
1091   struct utsname u;
1092   char cpuid_vendor[13];
1093   unsigned cpuid_max = 0, cpuid_eax, cpuid_ebx, cpuid_ecx, cpuid_edx;
1094   unsigned true_dos_version = _get_dos_version (1);
1095   unsigned advertized_dos_version = ((unsigned int)_osmajor << 8) | _osminor;
1096   int dpmi_flags;
1097   char dpmi_vendor_info[129];
1098   int dpmi_vendor_available;
1099   __dpmi_version_ret dpmi_version_data;
1100   long eflags;
1101   __dpmi_free_mem_info mem_info;
1102   __dpmi_regs regs;
1103 
1104   cpuid_vendor[0] = '\0';
1105   if (uname (&u))
1106     strcpy (u.machine, "Unknown x86");
1107   else if (u.machine[0] == 'i' && u.machine[1] > 4)
1108     {
1109       /* CPUID with EAX = 0 returns the Vendor ID.  */
1110 #if 0
1111       /* Ideally we would use x86_cpuid(), but it needs someone to run
1112          native tests first to make sure things actually work.  They should.
1113          http://sourceware.org/ml/gdb-patches/2013-05/msg00164.html  */
1114       unsigned int eax, ebx, ecx, edx;
1115 
1116       if (x86_cpuid (0, &eax, &ebx, &ecx, &edx))
1117 	{
1118 	  cpuid_max = eax;
1119 	  memcpy (&vendor[0], &ebx, 4);
1120 	  memcpy (&vendor[4], &ecx, 4);
1121 	  memcpy (&vendor[8], &edx, 4);
1122 	  cpuid_vendor[12] = '\0';
1123 	}
1124 #else
1125       __asm__ __volatile__ ("xorl   %%ebx, %%ebx;"
1126 			    "xorl   %%ecx, %%ecx;"
1127 			    "xorl   %%edx, %%edx;"
1128 			    "movl   $0,    %%eax;"
1129 			    "cpuid;"
1130 			    "movl   %%ebx,  %0;"
1131 			    "movl   %%edx,  %1;"
1132 			    "movl   %%ecx,  %2;"
1133 			    "movl   %%eax,  %3;"
1134 			    : "=m" (cpuid_vendor[0]),
1135 			      "=m" (cpuid_vendor[4]),
1136 			      "=m" (cpuid_vendor[8]),
1137 			      "=m" (cpuid_max)
1138 			    :
1139 			    : "%eax", "%ebx", "%ecx", "%edx");
1140       cpuid_vendor[12] = '\0';
1141 #endif
1142     }
1143 
1144   printf_filtered ("CPU Type.......................%s", u.machine);
1145   if (cpuid_vendor[0])
1146     printf_filtered (" (%s)", cpuid_vendor);
1147   puts_filtered ("\n");
1148 
1149   /* CPUID with EAX = 1 returns processor signature and features.  */
1150   if (cpuid_max >= 1)
1151     {
1152       static const char *brand_name[] = {
1153 	"",
1154 	" Celeron",
1155 	" III",
1156 	" III Xeon",
1157 	"", "", "", "",
1158 	" 4"
1159       };
1160       char cpu_string[80];
1161       char cpu_brand[20];
1162       unsigned brand_idx;
1163       int intel_p = strcmp (cpuid_vendor, "GenuineIntel") == 0;
1164       int amd_p = strcmp (cpuid_vendor, "AuthenticAMD") == 0;
1165       unsigned cpu_family, cpu_model;
1166 
1167 #if 0
1168       /* See comment above about cpuid usage.  */
1169       x86_cpuid (1, &cpuid_eax, &cpuid_ebx, NULL, &cpuid_edx);
1170 #else
1171       __asm__ __volatile__ ("movl   $1, %%eax;"
1172 			    "cpuid;"
1173 			    : "=a" (cpuid_eax),
1174 			      "=b" (cpuid_ebx),
1175 			      "=d" (cpuid_edx)
1176 			    :
1177 			    : "%ecx");
1178 #endif
1179       brand_idx = cpuid_ebx & 0xff;
1180       cpu_family = (cpuid_eax >> 8) & 0xf;
1181       cpu_model  = (cpuid_eax >> 4) & 0xf;
1182       cpu_brand[0] = '\0';
1183       if (intel_p)
1184 	{
1185 	  if (brand_idx > 0
1186 	      && brand_idx < sizeof(brand_name)/sizeof(brand_name[0])
1187 	      && *brand_name[brand_idx])
1188 	    strcpy (cpu_brand, brand_name[brand_idx]);
1189 	  else if (cpu_family == 5)
1190 	    {
1191 	      if (((cpuid_eax >> 12) & 3) == 0 && cpu_model == 4)
1192 		strcpy (cpu_brand, " MMX");
1193 	      else if (cpu_model > 1 && ((cpuid_eax >> 12) & 3) == 1)
1194 		strcpy (cpu_brand, " OverDrive");
1195 	      else if (cpu_model > 1 && ((cpuid_eax >> 12) & 3) == 2)
1196 		strcpy (cpu_brand, " Dual");
1197 	    }
1198 	  else if (cpu_family == 6 && cpu_model < 8)
1199 	    {
1200 	      switch (cpu_model)
1201 		{
1202 		  case 1:
1203 		    strcpy (cpu_brand, " Pro");
1204 		    break;
1205 		  case 3:
1206 		    strcpy (cpu_brand, " II");
1207 		    break;
1208 		  case 5:
1209 		    strcpy (cpu_brand, " II Xeon");
1210 		    break;
1211 		  case 6:
1212 		    strcpy (cpu_brand, " Celeron");
1213 		    break;
1214 		  case 7:
1215 		    strcpy (cpu_brand, " III");
1216 		    break;
1217 		}
1218 	    }
1219 	}
1220       else if (amd_p)
1221 	{
1222 	  switch (cpu_family)
1223 	    {
1224 	      case 4:
1225 		strcpy (cpu_brand, "486/5x86");
1226 		break;
1227 	      case 5:
1228 		switch (cpu_model)
1229 		  {
1230 		    case 0:
1231 		    case 1:
1232 		    case 2:
1233 		    case 3:
1234 		      strcpy (cpu_brand, "-K5");
1235 		      break;
1236 		    case 6:
1237 		    case 7:
1238 		      strcpy (cpu_brand, "-K6");
1239 		      break;
1240 		    case 8:
1241 		      strcpy (cpu_brand, "-K6-2");
1242 		      break;
1243 		    case 9:
1244 		      strcpy (cpu_brand, "-K6-III");
1245 		      break;
1246 		  }
1247 		break;
1248 	      case 6:
1249 		switch (cpu_model)
1250 		  {
1251 		    case 1:
1252 		    case 2:
1253 		    case 4:
1254 		      strcpy (cpu_brand, " Athlon");
1255 		      break;
1256 		    case 3:
1257 		      strcpy (cpu_brand, " Duron");
1258 		      break;
1259 		  }
1260 		break;
1261 	    }
1262 	}
1263       xsnprintf (cpu_string, sizeof (cpu_string), "%s%s Model %d Stepping %d",
1264 	         intel_p ? "Pentium" : (amd_p ? "AMD" : "ix86"),
1265 	         cpu_brand, cpu_model, cpuid_eax & 0xf);
1266       printfi_filtered (31, "%s\n", cpu_string);
1267       if (((cpuid_edx & (6 | (0x0d << 23))) != 0)
1268 	  || ((cpuid_edx & 1) == 0)
1269 	  || (amd_p && (cpuid_edx & (3 << 30)) != 0))
1270 	{
1271 	  puts_filtered ("CPU Features...................");
1272 	  /* We only list features which might be useful in the DPMI
1273 	     environment.  */
1274 	  if ((cpuid_edx & 1) == 0)
1275 	    puts_filtered ("No FPU "); /* It's unusual to not have an FPU.  */
1276 	  if ((cpuid_edx & (1 << 1)) != 0)
1277 	    puts_filtered ("VME ");
1278 	  if ((cpuid_edx & (1 << 2)) != 0)
1279 	    puts_filtered ("DE ");
1280 	  if ((cpuid_edx & (1 << 4)) != 0)
1281 	    puts_filtered ("TSC ");
1282 	  if ((cpuid_edx & (1 << 23)) != 0)
1283 	    puts_filtered ("MMX ");
1284 	  if ((cpuid_edx & (1 << 25)) != 0)
1285 	    puts_filtered ("SSE ");
1286 	  if ((cpuid_edx & (1 << 26)) != 0)
1287 	    puts_filtered ("SSE2 ");
1288 	  if (amd_p)
1289 	    {
1290 	      if ((cpuid_edx & (1 << 31)) != 0)
1291 		puts_filtered ("3DNow! ");
1292 	      if ((cpuid_edx & (1 << 30)) != 0)
1293 		puts_filtered ("3DNow!Ext");
1294 	    }
1295 	  puts_filtered ("\n");
1296 	}
1297     }
1298   puts_filtered ("\n");
1299   printf_filtered ("DOS Version....................%s %s.%s",
1300 		   _os_flavor, u.release, u.version);
1301   if (true_dos_version != advertized_dos_version)
1302     printf_filtered (" (disguised as v%d.%d)", _osmajor, _osminor);
1303   puts_filtered ("\n");
1304   if (!windows_major)
1305     go32_get_windows_version ();
1306   if (windows_major != 0xff)
1307     {
1308       const char *windows_flavor;
1309 
1310       printf_filtered ("Windows Version................%d.%02d (Windows ",
1311 		       windows_major, windows_minor);
1312       switch (windows_major)
1313 	{
1314 	  case 3:
1315 	    windows_flavor = "3.X";
1316 	    break;
1317 	  case 4:
1318 	    switch (windows_minor)
1319 	      {
1320 		case 0:
1321 		  windows_flavor = "95, 95A, or 95B";
1322 		  break;
1323 		case 3:
1324 		  windows_flavor = "95B OSR2.1 or 95C OSR2.5";
1325 		  break;
1326 		case 10:
1327 		  windows_flavor = "98 or 98 SE";
1328 		  break;
1329 		case 90:
1330 		  windows_flavor = "ME";
1331 		  break;
1332 		default:
1333 		  windows_flavor = "9X";
1334 		  break;
1335 	      }
1336 	    break;
1337 	  default:
1338 	    windows_flavor = "??";
1339 	    break;
1340 	}
1341       printf_filtered ("%s)\n", windows_flavor);
1342     }
1343   else if (true_dos_version == 0x532 && advertized_dos_version == 0x500)
1344     printf_filtered ("Windows Version................"
1345 		     "Windows NT family (W2K/XP/W2K3/Vista/W2K8)\n");
1346   puts_filtered ("\n");
1347   /* On some versions of Windows, __dpmi_get_capabilities returns
1348      zero, but the buffer is not filled with info, so we fill the
1349      buffer with a known pattern and test for it afterwards.  */
1350   memcpy (dpmi_vendor_info, test_pattern, sizeof(dpmi_vendor_info));
1351   dpmi_vendor_available =
1352     __dpmi_get_capabilities (&dpmi_flags, dpmi_vendor_info);
1353   if (dpmi_vendor_available == 0
1354       && memcmp (dpmi_vendor_info, test_pattern,
1355 		 sizeof(dpmi_vendor_info)) != 0)
1356     {
1357       /* The DPMI spec says the vendor string should be ASCIIZ, but
1358 	 I don't trust the vendors to follow that...  */
1359       if (!memchr (&dpmi_vendor_info[2], 0, 126))
1360 	dpmi_vendor_info[128] = '\0';
1361       printf_filtered ("DPMI Host......................"
1362 		       "%s v%d.%d (capabilities: %#x)\n",
1363 		       &dpmi_vendor_info[2],
1364 		       (unsigned)dpmi_vendor_info[0],
1365 		       (unsigned)dpmi_vendor_info[1],
1366 		       ((unsigned)dpmi_flags & 0x7f));
1367     }
1368   else
1369     printf_filtered ("DPMI Host......................(Info not available)\n");
1370   __dpmi_get_version (&dpmi_version_data);
1371   printf_filtered ("DPMI Version...................%d.%02d\n",
1372 		   dpmi_version_data.major, dpmi_version_data.minor);
1373   printf_filtered ("DPMI Info......................"
1374 		   "%s-bit DPMI, with%s Virtual Memory support\n",
1375 		   (dpmi_version_data.flags & 1) ? "32" : "16",
1376 		   (dpmi_version_data.flags & 4) ? "" : "out");
1377   printfi_filtered (31, "Interrupts reflected to %s mode\n",
1378 		   (dpmi_version_data.flags & 2) ? "V86" : "Real");
1379   printfi_filtered (31, "Processor type: i%d86\n",
1380 		   dpmi_version_data.cpu);
1381   printfi_filtered (31, "PIC base interrupt: Master: %#x  Slave: %#x\n",
1382 		   dpmi_version_data.master_pic, dpmi_version_data.slave_pic);
1383 
1384   /* a_tss is only initialized when the debuggee is first run.  */
1385   if (prog_has_started)
1386     {
1387       __asm__ __volatile__ ("pushfl ; popl %0" : "=g" (eflags));
1388       printf_filtered ("Protection....................."
1389 		       "Ring %d (in %s), with%s I/O protection\n",
1390 		       a_tss.tss_cs & 3, (a_tss.tss_cs & 4) ? "LDT" : "GDT",
1391 		       (a_tss.tss_cs & 3) > ((eflags >> 12) & 3) ? "" : "out");
1392     }
1393   puts_filtered ("\n");
1394   __dpmi_get_free_memory_information (&mem_info);
1395   print_mem (mem_info.total_number_of_physical_pages,
1396 	     "DPMI Total Physical Memory.....", 1);
1397   print_mem (mem_info.total_number_of_free_pages,
1398 	     "DPMI Free Physical Memory......", 1);
1399   print_mem (mem_info.size_of_paging_file_partition_in_pages,
1400 	     "DPMI Swap Space................", 1);
1401   print_mem (mem_info.linear_address_space_size_in_pages,
1402 	     "DPMI Total Linear Address Size.", 1);
1403   print_mem (mem_info.free_linear_address_space_in_pages,
1404 	     "DPMI Free Linear Address Size..", 1);
1405   print_mem (mem_info.largest_available_free_block_in_bytes,
1406 	     "DPMI Largest Free Memory Block.", 0);
1407 
1408   regs.h.ah = 0x48;
1409   regs.x.bx = 0xffff;
1410   __dpmi_int (0x21, &regs);
1411   print_mem (regs.x.bx << 4, "Free DOS Memory................", 0);
1412   regs.x.ax = 0x5800;
1413   __dpmi_int (0x21, &regs);
1414   if ((regs.x.flags & 1) == 0)
1415     {
1416       static const char *dos_hilo[] = {
1417 	"Low", "", "", "", "High", "", "", "", "High, then Low"
1418       };
1419       static const char *dos_fit[] = {
1420 	"First", "Best", "Last"
1421       };
1422       int hilo_idx = (regs.x.ax >> 4) & 0x0f;
1423       int fit_idx  = regs.x.ax & 0x0f;
1424 
1425       if (hilo_idx > 8)
1426 	hilo_idx = 0;
1427       if (fit_idx > 2)
1428 	fit_idx = 0;
1429       printf_filtered ("DOS Memory Allocation..........%s memory, %s fit\n",
1430 		       dos_hilo[hilo_idx], dos_fit[fit_idx]);
1431       regs.x.ax = 0x5802;
1432       __dpmi_int (0x21, &regs);
1433       if ((regs.x.flags & 1) != 0)
1434 	regs.h.al = 0;
1435       printfi_filtered (31, "UMBs %sin DOS memory chain\n",
1436 			regs.h.al == 0 ? "not " : "");
1437     }
1438 }
1439 
1440 struct seg_descr {
1441   unsigned short limit0;
1442   unsigned short base0;
1443   unsigned char  base1;
1444   unsigned       stype:5;
1445   unsigned       dpl:2;
1446   unsigned       present:1;
1447   unsigned       limit1:4;
1448   unsigned       available:1;
1449   unsigned       dummy:1;
1450   unsigned       bit32:1;
1451   unsigned       page_granular:1;
1452   unsigned char  base2;
1453 } __attribute__ ((packed));
1454 
1455 struct gate_descr {
1456   unsigned short offset0;
1457   unsigned short selector;
1458   unsigned       param_count:5;
1459   unsigned       dummy:3;
1460   unsigned       stype:5;
1461   unsigned       dpl:2;
1462   unsigned       present:1;
1463   unsigned short offset1;
1464 } __attribute__ ((packed));
1465 
1466 /* Read LEN bytes starting at logical address ADDR, and put the result
1467    into DEST.  Return 1 if success, zero if not.  */
1468 static int
1469 read_memory_region (unsigned long addr, void *dest, size_t len)
1470 {
1471   unsigned long dos_ds_limit = __dpmi_get_segment_limit (_dos_ds);
1472   int retval = 1;
1473 
1474   /* For the low memory, we can simply use _dos_ds.  */
1475   if (addr <= dos_ds_limit - len)
1476     dosmemget (addr, len, dest);
1477   else
1478     {
1479       /* For memory above 1MB we need to set up a special segment to
1480 	 be able to access that memory.  */
1481       int sel = __dpmi_allocate_ldt_descriptors (1);
1482 
1483       if (sel <= 0)
1484 	retval = 0;
1485       else
1486 	{
1487 	  int access_rights = __dpmi_get_descriptor_access_rights (sel);
1488 	  size_t segment_limit = len - 1;
1489 
1490 	  /* Make sure the crucial bits in the descriptor access
1491 	     rights are set correctly.  Some DPMI providers might barf
1492 	     if we set the segment limit to something that is not an
1493 	     integral multiple of 4KB pages if the granularity bit is
1494 	     not set to byte-granular, even though the DPMI spec says
1495 	     it's the host's responsibility to set that bit correctly.  */
1496 	  if (len > 1024 * 1024)
1497 	    {
1498 	      access_rights |= 0x8000;
1499 	      /* Page-granular segments should have the low 12 bits of
1500 		 the limit set.  */
1501 	      segment_limit |= 0xfff;
1502 	    }
1503 	  else
1504 	    access_rights &= ~0x8000;
1505 
1506 	  if (__dpmi_set_segment_base_address (sel, addr) != -1
1507 	      && __dpmi_set_descriptor_access_rights (sel, access_rights) != -1
1508 	      && __dpmi_set_segment_limit (sel, segment_limit) != -1
1509 	      /* W2K silently fails to set the segment limit, leaving
1510 		 it at zero; this test avoids the resulting crash.  */
1511 	      && __dpmi_get_segment_limit (sel) >= segment_limit)
1512 	    movedata (sel, 0, _my_ds (), (unsigned)dest, len);
1513 	  else
1514 	    retval = 0;
1515 
1516 	  __dpmi_free_ldt_descriptor (sel);
1517 	}
1518     }
1519   return retval;
1520 }
1521 
1522 /* Get a segment descriptor stored at index IDX in the descriptor
1523    table whose base address is TABLE_BASE.  Return the descriptor
1524    type, or -1 if failure.  */
1525 static int
1526 get_descriptor (unsigned long table_base, int idx, void *descr)
1527 {
1528   unsigned long addr = table_base + idx * 8; /* 8 bytes per entry */
1529 
1530   if (read_memory_region (addr, descr, 8))
1531     return (int)((struct seg_descr *)descr)->stype;
1532   return -1;
1533 }
1534 
1535 struct dtr_reg {
1536   unsigned short limit __attribute__((packed));
1537   unsigned long  base  __attribute__((packed));
1538 };
1539 
1540 /* Display a segment descriptor stored at index IDX in a descriptor
1541    table whose type is TYPE and whose base address is BASE_ADDR.  If
1542    FORCE is non-zero, display even invalid descriptors.  */
1543 static void
1544 display_descriptor (unsigned type, unsigned long base_addr, int idx, int force)
1545 {
1546   struct seg_descr descr;
1547   struct gate_descr gate;
1548 
1549   /* Get the descriptor from the table.  */
1550   if (idx == 0 && type == 0)
1551     puts_filtered ("0x000: null descriptor\n");
1552   else if (get_descriptor (base_addr, idx, &descr) != -1)
1553     {
1554       /* For each type of descriptor table, this has a bit set if the
1555 	 corresponding type of selectors is valid in that table.  */
1556       static unsigned allowed_descriptors[] = {
1557 	  0xffffdafeL,   /* GDT */
1558 	  0x0000c0e0L,   /* IDT */
1559 	  0xffffdafaL    /* LDT */
1560       };
1561 
1562       /* If the program hasn't started yet, assume the debuggee will
1563 	 have the same CPL as the debugger.  */
1564       int cpl = prog_has_started ? (a_tss.tss_cs & 3) : _my_cs () & 3;
1565       unsigned long limit = (descr.limit1 << 16) | descr.limit0;
1566 
1567       if (descr.present
1568 	  && (allowed_descriptors[type] & (1 << descr.stype)) != 0)
1569 	{
1570 	  printf_filtered ("0x%03x: ",
1571 			   type == 1
1572 			   ? idx : (idx * 8) | (type ? (cpl | 4) : 0));
1573 	  if (descr.page_granular)
1574 	    limit = (limit << 12) | 0xfff; /* big segment: low 12 bit set */
1575 	  if (descr.stype == 1 || descr.stype == 2 || descr.stype == 3
1576 	      || descr.stype == 9 || descr.stype == 11
1577 	      || (descr.stype >= 16 && descr.stype < 32))
1578 	    printf_filtered ("base=0x%02x%02x%04x limit=0x%08lx",
1579 			     descr.base2, descr.base1, descr.base0, limit);
1580 
1581 	  switch (descr.stype)
1582 	    {
1583 	      case 1:
1584 	      case 3:
1585 		printf_filtered (" 16-bit TSS  (task %sactive)",
1586 				 descr.stype == 3 ? "" : "in");
1587 		break;
1588 	      case 2:
1589 		puts_filtered (" LDT");
1590 		break;
1591 	      case 4:
1592 		memcpy (&gate, &descr, sizeof gate);
1593 		printf_filtered ("selector=0x%04x  offs=0x%04x%04x",
1594 				 gate.selector, gate.offset1, gate.offset0);
1595 		printf_filtered (" 16-bit Call Gate (params=%d)",
1596 				 gate.param_count);
1597 		break;
1598 	      case 5:
1599 		printf_filtered ("TSS selector=0x%04x", descr.base0);
1600 		printfi_filtered (16, "Task Gate");
1601 		break;
1602 	      case 6:
1603 	      case 7:
1604 		memcpy (&gate, &descr, sizeof gate);
1605 		printf_filtered ("selector=0x%04x  offs=0x%04x%04x",
1606 				 gate.selector, gate.offset1, gate.offset0);
1607 		printf_filtered (" 16-bit %s Gate",
1608 				 descr.stype == 6 ? "Interrupt" : "Trap");
1609 		break;
1610 	      case 9:
1611 	      case 11:
1612 		printf_filtered (" 32-bit TSS (task %sactive)",
1613 				 descr.stype == 3 ? "" : "in");
1614 		break;
1615 	      case 12:
1616 		memcpy (&gate, &descr, sizeof gate);
1617 		printf_filtered ("selector=0x%04x  offs=0x%04x%04x",
1618 				 gate.selector, gate.offset1, gate.offset0);
1619 		printf_filtered (" 32-bit Call Gate (params=%d)",
1620 				 gate.param_count);
1621 		break;
1622 	      case 14:
1623 	      case 15:
1624 		memcpy (&gate, &descr, sizeof gate);
1625 		printf_filtered ("selector=0x%04x  offs=0x%04x%04x",
1626 				 gate.selector, gate.offset1, gate.offset0);
1627 		printf_filtered (" 32-bit %s Gate",
1628 				 descr.stype == 14 ? "Interrupt" : "Trap");
1629 		break;
1630 	      case 16:		/* data segments */
1631 	      case 17:
1632 	      case 18:
1633 	      case 19:
1634 	      case 20:
1635 	      case 21:
1636 	      case 22:
1637 	      case 23:
1638 		printf_filtered (" %s-bit Data (%s Exp-%s%s)",
1639 				 descr.bit32 ? "32" : "16",
1640 				 descr.stype & 2
1641 				 ? "Read/Write," : "Read-Only, ",
1642 				 descr.stype & 4 ? "down" : "up",
1643 				 descr.stype & 1 ? "" : ", N.Acc");
1644 		break;
1645 	      case 24:		/* code segments */
1646 	      case 25:
1647 	      case 26:
1648 	      case 27:
1649 	      case 28:
1650 	      case 29:
1651 	      case 30:
1652 	      case 31:
1653 		printf_filtered (" %s-bit Code (%s,  %sConf%s)",
1654 				 descr.bit32 ? "32" : "16",
1655 				 descr.stype & 2 ? "Exec/Read" : "Exec-Only",
1656 				 descr.stype & 4 ? "" : "N.",
1657 				 descr.stype & 1 ? "" : ", N.Acc");
1658 		break;
1659 	      default:
1660 		printf_filtered ("Unknown type 0x%02x", descr.stype);
1661 		break;
1662 	    }
1663 	  puts_filtered ("\n");
1664 	}
1665       else if (force)
1666 	{
1667 	  printf_filtered ("0x%03x: ",
1668 			   type == 1
1669 			   ? idx : (idx * 8) | (type ? (cpl | 4) : 0));
1670 	  if (!descr.present)
1671 	    puts_filtered ("Segment not present\n");
1672 	  else
1673 	    printf_filtered ("Segment type 0x%02x is invalid in this table\n",
1674 			     descr.stype);
1675 	}
1676     }
1677   else if (force)
1678     printf_filtered ("0x%03x: Cannot read this descriptor\n", idx);
1679 }
1680 
1681 static void
1682 go32_sldt (const char *arg, int from_tty)
1683 {
1684   struct dtr_reg gdtr;
1685   unsigned short ldtr = 0;
1686   int ldt_idx;
1687   struct seg_descr ldt_descr;
1688   long ldt_entry = -1L;
1689   int cpl = (prog_has_started ? a_tss.tss_cs : _my_cs ()) & 3;
1690 
1691   if (arg && *arg)
1692     {
1693       arg = skip_spaces (arg);
1694 
1695       if (*arg)
1696 	{
1697 	  ldt_entry = parse_and_eval_long (arg);
1698 	  if (ldt_entry < 0
1699 	      || (ldt_entry & 4) == 0
1700 	      || (ldt_entry & 3) != (cpl & 3))
1701 	    error (_("Invalid LDT entry 0x%03lx."), (unsigned long)ldt_entry);
1702 	}
1703     }
1704 
1705   __asm__ __volatile__ ("sgdt   %0" : "=m" (gdtr) : /* no inputs */ );
1706   __asm__ __volatile__ ("sldt   %0" : "=m" (ldtr) : /* no inputs */ );
1707   ldt_idx = ldtr / 8;
1708   if (ldt_idx == 0)
1709     puts_filtered ("There is no LDT.\n");
1710   /* LDT's entry in the GDT must have the type LDT, which is 2.  */
1711   else if (get_descriptor (gdtr.base, ldt_idx, &ldt_descr) != 2)
1712     printf_filtered ("LDT is present (at %#x), but unreadable by GDB.\n",
1713 		     ldt_descr.base0
1714 		     | (ldt_descr.base1 << 16)
1715 		     | (ldt_descr.base2 << 24));
1716   else
1717     {
1718       unsigned base =
1719 	ldt_descr.base0
1720 	| (ldt_descr.base1 << 16)
1721 	| (ldt_descr.base2 << 24);
1722       unsigned limit = ldt_descr.limit0 | (ldt_descr.limit1 << 16);
1723       int max_entry;
1724 
1725       if (ldt_descr.page_granular)
1726 	/* Page-granular segments must have the low 12 bits of their
1727 	   limit set.  */
1728 	limit = (limit << 12) | 0xfff;
1729       /* LDT cannot have more than 8K 8-byte entries, i.e. more than
1730 	 64KB.  */
1731       if (limit > 0xffff)
1732 	limit = 0xffff;
1733 
1734       max_entry = (limit + 1) / 8;
1735 
1736       if (ldt_entry >= 0)
1737 	{
1738 	  if (ldt_entry > limit)
1739 	    error (_("Invalid LDT entry %#lx: outside valid limits [0..%#x]"),
1740 		   (unsigned long)ldt_entry, limit);
1741 
1742 	  display_descriptor (ldt_descr.stype, base, ldt_entry / 8, 1);
1743 	}
1744       else
1745 	{
1746 	  int i;
1747 
1748 	  for (i = 0; i < max_entry; i++)
1749 	    display_descriptor (ldt_descr.stype, base, i, 0);
1750 	}
1751     }
1752 }
1753 
1754 static void
1755 go32_sgdt (const char *arg, int from_tty)
1756 {
1757   struct dtr_reg gdtr;
1758   long gdt_entry = -1L;
1759   int max_entry;
1760 
1761   if (arg && *arg)
1762     {
1763       arg = skip_spaces (arg);
1764 
1765       if (*arg)
1766 	{
1767 	  gdt_entry = parse_and_eval_long (arg);
1768 	  if (gdt_entry < 0 || (gdt_entry & 7) != 0)
1769 	    error (_("Invalid GDT entry 0x%03lx: "
1770 		     "not an integral multiple of 8."),
1771 		   (unsigned long)gdt_entry);
1772 	}
1773     }
1774 
1775   __asm__ __volatile__ ("sgdt   %0" : "=m" (gdtr) : /* no inputs */ );
1776   max_entry = (gdtr.limit + 1) / 8;
1777 
1778   if (gdt_entry >= 0)
1779     {
1780       if (gdt_entry > gdtr.limit)
1781 	error (_("Invalid GDT entry %#lx: outside valid limits [0..%#x]"),
1782 	       (unsigned long)gdt_entry, gdtr.limit);
1783 
1784       display_descriptor (0, gdtr.base, gdt_entry / 8, 1);
1785     }
1786   else
1787     {
1788       int i;
1789 
1790       for (i = 0; i < max_entry; i++)
1791 	display_descriptor (0, gdtr.base, i, 0);
1792     }
1793 }
1794 
1795 static void
1796 go32_sidt (const char *arg, int from_tty)
1797 {
1798   struct dtr_reg idtr;
1799   long idt_entry = -1L;
1800   int max_entry;
1801 
1802   if (arg && *arg)
1803     {
1804       arg = skip_spaces (arg);
1805 
1806       if (*arg)
1807 	{
1808 	  idt_entry = parse_and_eval_long (arg);
1809 	  if (idt_entry < 0)
1810 	    error (_("Invalid (negative) IDT entry %ld."), idt_entry);
1811 	}
1812     }
1813 
1814   __asm__ __volatile__ ("sidt   %0" : "=m" (idtr) : /* no inputs */ );
1815   max_entry = (idtr.limit + 1) / 8;
1816   if (max_entry > 0x100)	/* No more than 256 entries.  */
1817     max_entry = 0x100;
1818 
1819   if (idt_entry >= 0)
1820     {
1821       if (idt_entry > idtr.limit)
1822 	error (_("Invalid IDT entry %#lx: outside valid limits [0..%#x]"),
1823 	       (unsigned long)idt_entry, idtr.limit);
1824 
1825       display_descriptor (1, idtr.base, idt_entry, 1);
1826     }
1827   else
1828     {
1829       int i;
1830 
1831       for (i = 0; i < max_entry; i++)
1832 	display_descriptor (1, idtr.base, i, 0);
1833     }
1834 }
1835 
1836 /* Cached linear address of the base of the page directory.  For
1837    now, available only under CWSDPMI.  Code based on ideas and
1838    suggestions from Charles Sandmann <sandmann@clio.rice.edu>.  */
1839 static unsigned long pdbr;
1840 
1841 static unsigned long
1842 get_cr3 (void)
1843 {
1844   unsigned offset;
1845   unsigned taskreg;
1846   unsigned long taskbase, cr3;
1847   struct dtr_reg gdtr;
1848 
1849   if (pdbr > 0 && pdbr <= 0xfffff)
1850     return pdbr;
1851 
1852   /* Get the linear address of GDT and the Task Register.  */
1853   __asm__ __volatile__ ("sgdt   %0" : "=m" (gdtr) : /* no inputs */ );
1854   __asm__ __volatile__ ("str    %0" : "=m" (taskreg) : /* no inputs */ );
1855 
1856   /* Task Register is a segment selector for the TSS of the current
1857      task.  Therefore, it can be used as an index into the GDT to get
1858      at the segment descriptor for the TSS.  To get the index, reset
1859      the low 3 bits of the selector (which give the CPL).  Add 2 to the
1860      offset to point to the 3 low bytes of the base address.  */
1861   offset = gdtr.base + (taskreg & 0xfff8) + 2;
1862 
1863 
1864   /* CWSDPMI's task base is always under the 1MB mark.  */
1865   if (offset > 0xfffff)
1866     return 0;
1867 
1868   _farsetsel (_dos_ds);
1869   taskbase  = _farnspeekl (offset) & 0xffffffU;
1870   taskbase += _farnspeekl (offset + 2) & 0xff000000U;
1871   if (taskbase > 0xfffff)
1872     return 0;
1873 
1874   /* CR3 (a.k.a. PDBR, the Page Directory Base Register) is stored at
1875      offset 1Ch in the TSS.  */
1876   cr3 = _farnspeekl (taskbase + 0x1c) & ~0xfff;
1877   if (cr3 > 0xfffff)
1878     {
1879 #if 0  /* Not fullly supported yet.  */
1880       /* The Page Directory is in UMBs.  In that case, CWSDPMI puts
1881 	 the first Page Table right below the Page Directory.  Thus,
1882 	 the first Page Table's entry for its own address and the Page
1883 	 Directory entry for that Page Table will hold the same
1884 	 physical address.  The loop below searches the entire UMB
1885 	 range of addresses for such an occurence.  */
1886       unsigned long addr, pte_idx;
1887 
1888       for (addr = 0xb0000, pte_idx = 0xb0;
1889 	   pte_idx < 0xff;
1890 	   addr += 0x1000, pte_idx++)
1891 	{
1892 	  if (((_farnspeekl (addr + 4 * pte_idx) & 0xfffff027) ==
1893 	       (_farnspeekl (addr + 0x1000) & 0xfffff027))
1894 	      && ((_farnspeekl (addr + 4 * pte_idx + 4) & 0xfffff000) == cr3))
1895 	    {
1896 	      cr3 = addr + 0x1000;
1897 	      break;
1898 	    }
1899 	}
1900 #endif
1901 
1902       if (cr3 > 0xfffff)
1903 	cr3 = 0;
1904     }
1905 
1906   return cr3;
1907 }
1908 
1909 /* Return the N'th Page Directory entry.  */
1910 static unsigned long
1911 get_pde (int n)
1912 {
1913   unsigned long pde = 0;
1914 
1915   if (pdbr && n >= 0 && n < 1024)
1916     {
1917       pde = _farpeekl (_dos_ds, pdbr + 4*n);
1918     }
1919   return pde;
1920 }
1921 
1922 /* Return the N'th entry of the Page Table whose Page Directory entry
1923    is PDE.  */
1924 static unsigned long
1925 get_pte (unsigned long pde, int n)
1926 {
1927   unsigned long pte = 0;
1928 
1929   /* pde & 0x80 tests the 4MB page bit.  We don't support 4MB
1930      page tables, for now.  */
1931   if ((pde & 1) && !(pde & 0x80) && n >= 0 && n < 1024)
1932     {
1933       pde &= ~0xfff;	/* Clear non-address bits.  */
1934       pte = _farpeekl (_dos_ds, pde + 4*n);
1935     }
1936   return pte;
1937 }
1938 
1939 /* Display a Page Directory or Page Table entry.  IS_DIR, if non-zero,
1940    says this is a Page Directory entry.  If FORCE is non-zero, display
1941    the entry even if its Present flag is off.  OFF is the offset of the
1942    address from the page's base address.  */
1943 static void
1944 display_ptable_entry (unsigned long entry, int is_dir, int force, unsigned off)
1945 {
1946   if ((entry & 1) != 0)
1947     {
1948       printf_filtered ("Base=0x%05lx000", entry >> 12);
1949       if ((entry & 0x100) && !is_dir)
1950 	puts_filtered (" Global");
1951       if ((entry & 0x40) && !is_dir)
1952 	puts_filtered (" Dirty");
1953       printf_filtered (" %sAcc.", (entry & 0x20) ? "" : "Not-");
1954       printf_filtered (" %sCached", (entry & 0x10) ? "" : "Not-");
1955       printf_filtered (" Write-%s", (entry & 8) ? "Thru" : "Back");
1956       printf_filtered (" %s", (entry & 4) ? "Usr" : "Sup");
1957       printf_filtered (" Read-%s", (entry & 2) ? "Write" : "Only");
1958       if (off)
1959 	printf_filtered (" +0x%x", off);
1960       puts_filtered ("\n");
1961     }
1962   else if (force)
1963     printf_filtered ("Page%s not present or not supported; value=0x%lx.\n",
1964 		     is_dir ? " Table" : "", entry >> 1);
1965 }
1966 
1967 static void
1968 go32_pde (const char *arg, int from_tty)
1969 {
1970   long pde_idx = -1, i;
1971 
1972   if (arg && *arg)
1973     {
1974       arg = skip_spaces (arg);
1975 
1976       if (*arg)
1977 	{
1978 	  pde_idx = parse_and_eval_long (arg);
1979 	  if (pde_idx < 0 || pde_idx >= 1024)
1980 	    error (_("Entry %ld is outside valid limits [0..1023]."), pde_idx);
1981 	}
1982     }
1983 
1984   pdbr = get_cr3 ();
1985   if (!pdbr)
1986     puts_filtered ("Access to Page Directories is "
1987 		   "not supported on this system.\n");
1988   else if (pde_idx >= 0)
1989     display_ptable_entry (get_pde (pde_idx), 1, 1, 0);
1990   else
1991     for (i = 0; i < 1024; i++)
1992       display_ptable_entry (get_pde (i), 1, 0, 0);
1993 }
1994 
1995 /* A helper function to display entries in a Page Table pointed to by
1996    the N'th entry in the Page Directory.  If FORCE is non-zero, say
1997    something even if the Page Table is not accessible.  */
1998 static void
1999 display_page_table (long n, int force)
2000 {
2001   unsigned long pde = get_pde (n);
2002 
2003   if ((pde & 1) != 0)
2004     {
2005       int i;
2006 
2007       printf_filtered ("Page Table pointed to by "
2008 		       "Page Directory entry 0x%lx:\n", n);
2009       for (i = 0; i < 1024; i++)
2010 	display_ptable_entry (get_pte (pde, i), 0, 0, 0);
2011       puts_filtered ("\n");
2012     }
2013   else if (force)
2014     printf_filtered ("Page Table not present; value=0x%lx.\n", pde >> 1);
2015 }
2016 
2017 static void
2018 go32_pte (const char *arg, int from_tty)
2019 {
2020   long pde_idx = -1L, i;
2021 
2022   if (arg && *arg)
2023     {
2024       arg = skip_spaces (arg);
2025 
2026       if (*arg)
2027 	{
2028 	  pde_idx = parse_and_eval_long (arg);
2029 	  if (pde_idx < 0 || pde_idx >= 1024)
2030 	    error (_("Entry %ld is outside valid limits [0..1023]."), pde_idx);
2031 	}
2032     }
2033 
2034   pdbr = get_cr3 ();
2035   if (!pdbr)
2036     puts_filtered ("Access to Page Tables is not supported on this system.\n");
2037   else if (pde_idx >= 0)
2038     display_page_table (pde_idx, 1);
2039   else
2040     for (i = 0; i < 1024; i++)
2041       display_page_table (i, 0);
2042 }
2043 
2044 static void
2045 go32_pte_for_address (const char *arg, int from_tty)
2046 {
2047   CORE_ADDR addr = 0, i;
2048 
2049   if (arg && *arg)
2050     {
2051       arg = skip_spaces (arg);
2052 
2053       if (*arg)
2054 	addr = parse_and_eval_address (arg);
2055     }
2056   if (!addr)
2057     error_no_arg (_("linear address"));
2058 
2059   pdbr = get_cr3 ();
2060   if (!pdbr)
2061     puts_filtered ("Access to Page Tables is not supported on this system.\n");
2062   else
2063     {
2064       int pde_idx = (addr >> 22) & 0x3ff;
2065       int pte_idx = (addr >> 12) & 0x3ff;
2066       unsigned offs = addr & 0xfff;
2067 
2068       printf_filtered ("Page Table entry for address %s:\n",
2069 		       hex_string(addr));
2070       display_ptable_entry (get_pte (get_pde (pde_idx), pte_idx), 0, 1, offs);
2071     }
2072 }
2073 
2074 static struct cmd_list_element *info_dos_cmdlist = NULL;
2075 
2076 static void
2077 go32_info_dos_command (const char *args, int from_tty)
2078 {
2079   help_list (info_dos_cmdlist, "info dos ", class_info, gdb_stdout);
2080 }
2081 
2082 void
2083 _initialize_go32_nat (void)
2084 {
2085   x86_dr_low.set_control = go32_set_dr7;
2086   x86_dr_low.set_addr = go32_set_dr;
2087   x86_dr_low.get_status = go32_get_dr6;
2088   x86_dr_low.get_control = go32_get_dr7;
2089   x86_dr_low.get_addr = go32_get_dr;
2090   x86_set_debug_register_length (4);
2091 
2092   add_inf_child_target (&the_go32_nat_target);
2093 
2094   /* Initialize child's cwd as empty to be initialized when starting
2095      the child.  */
2096   *child_cwd = 0;
2097 
2098   /* Initialize child's command line storage.  */
2099   if (redir_debug_init (&child_cmd) == -1)
2100     internal_error (__FILE__, __LINE__,
2101 		    _("Cannot allocate redirection storage: "
2102 		      "not enough memory.\n"));
2103 
2104   /* We are always processing GCC-compiled programs.  */
2105   processing_gcc_compilation = 2;
2106 
2107   add_prefix_cmd ("dos", class_info, go32_info_dos_command, _("\
2108 Print information specific to DJGPP (aka MS-DOS) debugging."),
2109 		  &info_dos_cmdlist, "info dos ", 0, &infolist);
2110 
2111   add_cmd ("sysinfo", class_info, go32_sysinfo, _("\
2112 Display information about the target system, including CPU, OS, DPMI, etc."),
2113 	   &info_dos_cmdlist);
2114   add_cmd ("ldt", class_info, go32_sldt, _("\
2115 Display entries in the LDT (Local Descriptor Table).\n\
2116 Entry number (an expression) as an argument means display only that entry."),
2117 	   &info_dos_cmdlist);
2118   add_cmd ("gdt", class_info, go32_sgdt, _("\
2119 Display entries in the GDT (Global Descriptor Table).\n\
2120 Entry number (an expression) as an argument means display only that entry."),
2121 	   &info_dos_cmdlist);
2122   add_cmd ("idt", class_info, go32_sidt, _("\
2123 Display entries in the IDT (Interrupt Descriptor Table).\n\
2124 Entry number (an expression) as an argument means display only that entry."),
2125 	   &info_dos_cmdlist);
2126   add_cmd ("pde", class_info, go32_pde, _("\
2127 Display entries in the Page Directory.\n\
2128 Entry number (an expression) as an argument means display only that entry."),
2129 	   &info_dos_cmdlist);
2130   add_cmd ("pte", class_info, go32_pte, _("\
2131 Display entries in Page Tables.\n\
2132 Entry number (an expression) as an argument means display only entries\n\
2133 from the Page Table pointed to by the specified Page Directory entry."),
2134 	   &info_dos_cmdlist);
2135   add_cmd ("address-pte", class_info, go32_pte_for_address, _("\
2136 Display a Page Table entry for a linear address.\n\
2137 The address argument must be a linear address, after adding to\n\
2138 it the base address of the appropriate segment.\n\
2139 The base address of variables and functions in the debuggee's data\n\
2140 or code segment is stored in the variable __djgpp_base_address,\n\
2141 so use `__djgpp_base_address + (char *)&var' as the argument.\n\
2142 For other segments, look up their base address in the output of\n\
2143 the `info dos ldt' command."),
2144 	   &info_dos_cmdlist);
2145 }
2146 
2147 pid_t
2148 tcgetpgrp (int fd)
2149 {
2150   if (isatty (fd))
2151     return SOME_PID;
2152   errno = ENOTTY;
2153   return -1;
2154 }
2155 
2156 int
2157 tcsetpgrp (int fd, pid_t pgid)
2158 {
2159   if (isatty (fd) && pgid == SOME_PID)
2160     return 0;
2161   errno = pgid == SOME_PID ? ENOTTY : ENOSYS;
2162   return -1;
2163 }
2164