xref: /dragonfly/contrib/gdb-7/gdb/gcore.c (revision ef5ccd6c)
1 /* Generate a core file for the inferior process.
2 
3    Copyright (C) 2001-2013 Free Software Foundation, Inc.
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 #include "defs.h"
21 #include "elf-bfd.h"
22 #include "infcall.h"
23 #include "inferior.h"
24 #include "gdbcore.h"
25 #include "objfiles.h"
26 #include "solib.h"
27 #include "symfile.h"
28 #include "arch-utils.h"
29 #include "completer.h"
30 #include "gcore.h"
31 #include "cli/cli-decode.h"
32 #include "gdb_assert.h"
33 #include <fcntl.h>
34 #include "regcache.h"
35 #include "regset.h"
36 #include "gdb_bfd.h"
37 
38 /* The largest amount of memory to read from the target at once.  We
39    must throttle it to limit the amount of memory used by GDB during
40    generate-core-file for programs with large resident data.  */
41 #define MAX_COPY_BYTES (1024 * 1024)
42 
43 static const char *default_gcore_target (void);
44 static enum bfd_architecture default_gcore_arch (void);
45 static unsigned long default_gcore_mach (void);
46 static int gcore_memory_sections (bfd *);
47 
48 /* create_gcore_bfd -- helper for gcore_command (exported).
49    Open a new bfd core file for output, and return the handle.  */
50 
51 bfd *
create_gcore_bfd(char * filename)52 create_gcore_bfd (char *filename)
53 {
54   bfd *obfd = gdb_bfd_openw (filename, default_gcore_target ());
55 
56   if (!obfd)
57     error (_("Failed to open '%s' for output."), filename);
58   bfd_set_format (obfd, bfd_core);
59   bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());
60   return obfd;
61 }
62 
63 /* write_gcore_file -- helper for gcore_command (exported).
64    Compose and write the corefile data to the core file.  */
65 
66 
67 void
write_gcore_file(bfd * obfd)68 write_gcore_file (bfd *obfd)
69 {
70   void *note_data = NULL;
71   int note_size = 0;
72   asection *note_sec = NULL;
73 
74   /* An external target method must build the notes section.  */
75   /* FIXME: uweigand/2011-10-06: All architectures that support core file
76      generation should be converted to gdbarch_make_corefile_notes; at that
77      point, the target vector method can be removed.  */
78   if (!gdbarch_make_corefile_notes_p (target_gdbarch ()))
79     note_data = target_make_corefile_notes (obfd, &note_size);
80   else
81     note_data = gdbarch_make_corefile_notes (target_gdbarch (), obfd, &note_size);
82 
83   if (note_data == NULL || note_size == 0)
84     error (_("Target does not support core file generation."));
85 
86   /* Create the note section.  */
87   note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
88 						 SEC_HAS_CONTENTS
89 						 | SEC_READONLY
90 						 | SEC_ALLOC);
91   if (note_sec == NULL)
92     error (_("Failed to create 'note' section for corefile: %s"),
93 	   bfd_errmsg (bfd_get_error ()));
94 
95   bfd_set_section_vma (obfd, note_sec, 0);
96   bfd_set_section_alignment (obfd, note_sec, 0);
97   bfd_set_section_size (obfd, note_sec, note_size);
98 
99   /* Now create the memory/load sections.  */
100   if (gcore_memory_sections (obfd) == 0)
101     error (_("gcore: failed to get corefile memory sections from target."));
102 
103   /* Write out the contents of the note section.  */
104   if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
105     warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));
106 }
107 
108 static void
do_bfd_delete_cleanup(void * arg)109 do_bfd_delete_cleanup (void *arg)
110 {
111   bfd *obfd = arg;
112   const char *filename = obfd->filename;
113 
114   gdb_bfd_unref (arg);
115   unlink (filename);
116 }
117 
118 /* gcore_command -- implements the 'gcore' command.
119    Generate a core file from the inferior process.  */
120 
121 static void
gcore_command(char * args,int from_tty)122 gcore_command (char *args, int from_tty)
123 {
124   struct cleanup *old_chain;
125   char *corefilename, corefilename_buffer[40];
126   bfd *obfd;
127 
128   /* No use generating a corefile without a target process.  */
129   if (!target_has_execution)
130     noprocess ();
131 
132   if (args && *args)
133     corefilename = args;
134   else
135     {
136       /* Default corefile name is "core.PID".  */
137       xsnprintf (corefilename_buffer, sizeof (corefilename_buffer),
138 		 "core.%d", PIDGET (inferior_ptid));
139       corefilename = corefilename_buffer;
140     }
141 
142   if (info_verbose)
143     fprintf_filtered (gdb_stdout,
144 		      "Opening corefile '%s' for output.\n", corefilename);
145 
146   /* Open the output file.  */
147   obfd = create_gcore_bfd (corefilename);
148 
149   /* Need a cleanup that will close and delete the file.  */
150   old_chain = make_cleanup (do_bfd_delete_cleanup, obfd);
151 
152   /* Call worker function.  */
153   write_gcore_file (obfd);
154 
155   /* Succeeded.  */
156   fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
157 
158   discard_cleanups (old_chain);
159   gdb_bfd_unref (obfd);
160 }
161 
162 static unsigned long
default_gcore_mach(void)163 default_gcore_mach (void)
164 {
165 #if 1	/* See if this even matters...  */
166   return 0;
167 #else
168 
169   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ());
170 
171   if (bfdarch != NULL)
172     return bfdarch->mach;
173   if (exec_bfd == NULL)
174     error (_("Can't find default bfd machine type (need execfile)."));
175 
176   return bfd_get_mach (exec_bfd);
177 #endif /* 1 */
178 }
179 
180 static enum bfd_architecture
default_gcore_arch(void)181 default_gcore_arch (void)
182 {
183   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ());
184 
185   if (bfdarch != NULL)
186     return bfdarch->arch;
187   if (exec_bfd == NULL)
188     error (_("Can't find bfd architecture for corefile (need execfile)."));
189 
190   return bfd_get_arch (exec_bfd);
191 }
192 
193 static const char *
default_gcore_target(void)194 default_gcore_target (void)
195 {
196   /* The gdbarch may define a target to use for core files.  */
197   if (gdbarch_gcore_bfd_target_p (target_gdbarch ()))
198     return gdbarch_gcore_bfd_target (target_gdbarch ());
199 
200   /* Otherwise, try to fall back to the exec_bfd target.  This will probably
201      not work for non-ELF targets.  */
202   if (exec_bfd == NULL)
203     return NULL;
204   else
205     return bfd_get_target (exec_bfd);
206 }
207 
208 /* Derive a reasonable stack segment by unwinding the target stack,
209    and store its limits in *BOTTOM and *TOP.  Return non-zero if
210    successful.  */
211 
212 static int
derive_stack_segment(bfd_vma * bottom,bfd_vma * top)213 derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
214 {
215   struct frame_info *fi, *tmp_fi;
216 
217   gdb_assert (bottom);
218   gdb_assert (top);
219 
220   /* Can't succeed without stack and registers.  */
221   if (!target_has_stack || !target_has_registers)
222     return 0;
223 
224   /* Can't succeed without current frame.  */
225   fi = get_current_frame ();
226   if (fi == NULL)
227     return 0;
228 
229   /* Save frame pointer of TOS frame.  */
230   *top = get_frame_base (fi);
231   /* If current stack pointer is more "inner", use that instead.  */
232   if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top))
233     *top = get_frame_sp (fi);
234 
235   /* Find prev-most frame.  */
236   while ((tmp_fi = get_prev_frame (fi)) != NULL)
237     fi = tmp_fi;
238 
239   /* Save frame pointer of prev-most frame.  */
240   *bottom = get_frame_base (fi);
241 
242   /* Now canonicalize their order, so that BOTTOM is a lower address
243      (as opposed to a lower stack frame).  */
244   if (*bottom > *top)
245     {
246       bfd_vma tmp_vma;
247 
248       tmp_vma = *top;
249       *top = *bottom;
250       *bottom = tmp_vma;
251     }
252 
253   return 1;
254 }
255 
256 /* call_target_sbrk --
257    helper function for derive_heap_segment.  */
258 
259 static bfd_vma
call_target_sbrk(int sbrk_arg)260 call_target_sbrk (int sbrk_arg)
261 {
262   struct objfile *sbrk_objf;
263   struct gdbarch *gdbarch;
264   bfd_vma top_of_heap;
265   struct value *target_sbrk_arg;
266   struct value *sbrk_fn, *ret;
267   bfd_vma tmp;
268 
269   if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
270     {
271       sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf);
272       if (sbrk_fn == NULL)
273 	return (bfd_vma) 0;
274     }
275   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
276     {
277       sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf);
278       if (sbrk_fn == NULL)
279 	return (bfd_vma) 0;
280     }
281   else
282     return (bfd_vma) 0;
283 
284   gdbarch = get_objfile_arch (sbrk_objf);
285   target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int,
286 					sbrk_arg);
287   gdb_assert (target_sbrk_arg);
288   ret = call_function_by_hand (sbrk_fn, 1, &target_sbrk_arg);
289   if (ret == NULL)
290     return (bfd_vma) 0;
291 
292   tmp = value_as_long (ret);
293   if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff)
294     return (bfd_vma) 0;
295 
296   top_of_heap = tmp;
297   return top_of_heap;
298 }
299 
300 /* Derive a reasonable heap segment for ABFD by looking at sbrk and
301    the static data sections.  Store its limits in *BOTTOM and *TOP.
302    Return non-zero if successful.  */
303 
304 static int
derive_heap_segment(bfd * abfd,bfd_vma * bottom,bfd_vma * top)305 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
306 {
307   bfd_vma top_of_data_memory = 0;
308   bfd_vma top_of_heap = 0;
309   bfd_size_type sec_size;
310   bfd_vma sec_vaddr;
311   asection *sec;
312 
313   gdb_assert (bottom);
314   gdb_assert (top);
315 
316   /* This function depends on being able to call a function in the
317      inferior.  */
318   if (!target_has_execution)
319     return 0;
320 
321   /* The following code assumes that the link map is arranged as
322      follows (low to high addresses):
323 
324      ---------------------------------
325      | text sections                 |
326      ---------------------------------
327      | data sections (including bss) |
328      ---------------------------------
329      | heap                          |
330      --------------------------------- */
331 
332   for (sec = abfd->sections; sec; sec = sec->next)
333     {
334       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
335 	  || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
336 	{
337 	  sec_vaddr = bfd_get_section_vma (abfd, sec);
338 	  sec_size = bfd_get_section_size (sec);
339 	  if (sec_vaddr + sec_size > top_of_data_memory)
340 	    top_of_data_memory = sec_vaddr + sec_size;
341 	}
342     }
343 
344   top_of_heap = call_target_sbrk (0);
345   if (top_of_heap == (bfd_vma) 0)
346     return 0;
347 
348   /* Return results.  */
349   if (top_of_heap > top_of_data_memory)
350     {
351       *bottom = top_of_data_memory;
352       *top = top_of_heap;
353       return 1;
354     }
355 
356   /* No additional heap space needs to be saved.  */
357   return 0;
358 }
359 
360 static void
make_output_phdrs(bfd * obfd,asection * osec,void * ignored)361 make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
362 {
363   int p_flags = 0;
364   int p_type = 0;
365 
366   /* FIXME: these constants may only be applicable for ELF.  */
367   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
368     p_type = PT_LOAD;
369   else if (strncmp (bfd_section_name (obfd, osec), "note", 4) == 0)
370     p_type = PT_NOTE;
371   else
372     p_type = PT_NULL;
373 
374   p_flags |= PF_R;	/* Segment is readable.  */
375   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
376     p_flags |= PF_W;	/* Segment is writable.  */
377   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
378     p_flags |= PF_X;	/* Segment is executable.  */
379 
380   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
381 }
382 
383 /* find_memory_region_ftype implementation.  DATA is 'bfd *' for the core file
384    GDB is creating.  */
385 
386 static int
gcore_create_callback(CORE_ADDR vaddr,unsigned long size,int read,int write,int exec,int modified,void * data)387 gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
388 		       int write, int exec, int modified, void *data)
389 {
390   bfd *obfd = data;
391   asection *osec;
392   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;
393 
394   /* If the memory segment has no permissions set, ignore it, otherwise
395      when we later try to access it for read/write, we'll get an error
396      or jam the kernel.  */
397   if (read == 0 && write == 0 && exec == 0 && modified == 0)
398     {
399       if (info_verbose)
400         {
401           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n",
402                             plongest (size), paddress (target_gdbarch (), vaddr));
403         }
404 
405       return 0;
406     }
407 
408   if (write == 0 && modified == 0 && !solib_keep_data_in_core (vaddr, size))
409     {
410       /* See if this region of memory lies inside a known file on disk.
411 	 If so, we can avoid copying its contents by clearing SEC_LOAD.  */
412       struct objfile *objfile;
413       struct obj_section *objsec;
414 
415       ALL_OBJSECTIONS (objfile, objsec)
416 	{
417 	  bfd *abfd = objfile->obfd;
418 	  asection *asec = objsec->the_bfd_section;
419 	  bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
420 								    asec);
421 	  bfd_vma start = obj_section_addr (objsec) & -align;
422 	  bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align;
423 
424 	  /* Match if either the entire memory region lies inside the
425 	     section (i.e. a mapping covering some pages of a large
426 	     segment) or the entire section lies inside the memory region
427 	     (i.e. a mapping covering multiple small sections).
428 
429 	     This BFD was synthesized from reading target memory,
430 	     we don't want to omit that.  */
431 	  if (((vaddr >= start && vaddr + size <= end)
432 	       || (start >= vaddr && end <= vaddr + size))
433 	      && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
434 	    {
435 	      flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS);
436 	      goto keep;	/* Break out of two nested for loops.  */
437 	    }
438 	}
439 
440     keep:;
441     }
442 
443   if (write == 0)
444     flags |= SEC_READONLY;
445 
446   if (exec)
447     flags |= SEC_CODE;
448   else
449     flags |= SEC_DATA;
450 
451   osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
452   if (osec == NULL)
453     {
454       warning (_("Couldn't make gcore segment: %s"),
455 	       bfd_errmsg (bfd_get_error ()));
456       return 1;
457     }
458 
459   if (info_verbose)
460     {
461       fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n",
462 			plongest (size), paddress (target_gdbarch (), vaddr));
463     }
464 
465   bfd_set_section_size (obfd, osec, size);
466   bfd_set_section_vma (obfd, osec, vaddr);
467   bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
468   return 0;
469 }
470 
471 static int
objfile_find_memory_regions(find_memory_region_ftype func,void * obfd)472 objfile_find_memory_regions (find_memory_region_ftype func, void *obfd)
473 {
474   /* Use objfile data to create memory sections.  */
475   struct objfile *objfile;
476   struct obj_section *objsec;
477   bfd_vma temp_bottom, temp_top;
478 
479   /* Call callback function for each objfile section.  */
480   ALL_OBJSECTIONS (objfile, objsec)
481     {
482       bfd *ibfd = objfile->obfd;
483       asection *isec = objsec->the_bfd_section;
484       flagword flags = bfd_get_section_flags (ibfd, isec);
485 
486       /* Separate debug info files are irrelevant for gcore.  */
487       if (objfile->separate_debug_objfile_backlink != NULL)
488 	continue;
489 
490       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
491 	{
492 	  int size = bfd_section_size (ibfd, isec);
493 	  int ret;
494 
495 	  ret = (*func) (obj_section_addr (objsec), size,
496 			 1, /* All sections will be readable.  */
497 			 (flags & SEC_READONLY) == 0, /* Writable.  */
498 			 (flags & SEC_CODE) != 0, /* Executable.  */
499 			 1, /* MODIFIED is unknown, pass it as true.  */
500 			 obfd);
501 	  if (ret != 0)
502 	    return ret;
503 	}
504     }
505 
506   /* Make a stack segment.  */
507   if (derive_stack_segment (&temp_bottom, &temp_top))
508     (*func) (temp_bottom, temp_top - temp_bottom,
509 	     1, /* Stack section will be readable.  */
510 	     1, /* Stack section will be writable.  */
511 	     0, /* Stack section will not be executable.  */
512 	     1, /* Stack section will be modified.  */
513 	     obfd);
514 
515   /* Make a heap segment.  */
516   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
517     (*func) (temp_bottom, temp_top - temp_bottom,
518 	     1, /* Heap section will be readable.  */
519 	     1, /* Heap section will be writable.  */
520 	     0, /* Heap section will not be executable.  */
521 	     1, /* Heap section will be modified.  */
522 	     obfd);
523 
524   return 0;
525 }
526 
527 static void
gcore_copy_callback(bfd * obfd,asection * osec,void * ignored)528 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
529 {
530   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
531   file_ptr offset = 0;
532   struct cleanup *old_chain = NULL;
533   void *memhunk;
534 
535   /* Read-only sections are marked; we don't have to copy their contents.  */
536   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
537     return;
538 
539   /* Only interested in "load" sections.  */
540   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
541     return;
542 
543   size = min (total_size, MAX_COPY_BYTES);
544   memhunk = xmalloc (size);
545   old_chain = make_cleanup (xfree, memhunk);
546 
547   while (total_size > 0)
548     {
549       if (size > total_size)
550 	size = total_size;
551 
552       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
553 			      memhunk, size) != 0)
554 	{
555 	  warning (_("Memory read failed for corefile "
556 		     "section, %s bytes at %s."),
557 		   plongest (size),
558 		   paddress (target_gdbarch (), bfd_section_vma (obfd, osec)));
559 	  break;
560 	}
561       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
562 	{
563 	  warning (_("Failed to write corefile contents (%s)."),
564 		   bfd_errmsg (bfd_get_error ()));
565 	  break;
566 	}
567 
568       total_size -= size;
569       offset += size;
570     }
571 
572   do_cleanups (old_chain);	/* Frees MEMHUNK.  */
573 }
574 
575 static int
gcore_memory_sections(bfd * obfd)576 gcore_memory_sections (bfd *obfd)
577 {
578   /* Try gdbarch method first, then fall back to target method.  */
579   if (!gdbarch_find_memory_regions_p (target_gdbarch ())
580       || gdbarch_find_memory_regions (target_gdbarch (),
581 				      gcore_create_callback, obfd) != 0)
582     {
583       if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
584 	return 0;			/* FIXME: error return/msg?  */
585     }
586 
587   /* Record phdrs for section-to-segment mapping.  */
588   bfd_map_over_sections (obfd, make_output_phdrs, NULL);
589 
590   /* Copy memory region contents.  */
591   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);
592 
593   return 1;
594 }
595 
596 /* Provide a prototype to silence -Wmissing-prototypes.  */
597 extern initialize_file_ftype _initialize_gcore;
598 
599 void
_initialize_gcore(void)600 _initialize_gcore (void)
601 {
602   add_com ("generate-core-file", class_files, gcore_command, _("\
603 Save a core file with the current state of the debugged process.\n\
604 Argument is optional filename.  Default filename is 'core.<process_id>'."));
605 
606   add_com_alias ("gcore", "generate-core-file", class_files, 1);
607   exec_set_find_memory_regions (objfile_find_memory_regions);
608 }
609