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9 .TH CORE 4 "Jun 6, 2016"
10 .SH NAME
11 core \- process core file
12 .SH DESCRIPTION
13 .LP
14 The operating system writes out a core file for a process when the process is
15 terminated due to receiving certain signals. A core file is a disk copy of the
16 contents of the process address space at the time the process received the
17 signal, along with additional information about the state of the process. This
18 information can be consumed by a debugger. Core files can also be generated by
19 applying the \fBgcore\fR(1) utility to a running process.
20 .sp
21 .LP
22 Typically, core files are produced following abnormal termination of a process
23 resulting from a bug in the corresponding application. Whatever the cause, the
24 core file itself provides invaluable information to the programmer or support
25 engineer to aid in diagnosing the problem. The core file can be inspected using
26 a debugger such as \fBdbx\fR(1) or \fBmdb\fR(1) or by applying one of the
27 \fBproc\fR(1) tools.
28 .sp
29 .LP
30 The operating system attempts to create up to two core files for each
31 abnormally terminating process, using a global core file name pattern and a
32 per-process core file name pattern. These patterns are expanded to determine
33 the pathname of the resulting core files, and can be configured by
34 \fBcoreadm\fR(8). By default, the global core file pattern is disabled and not
35 used, and the per-process core file pattern is set to \fBcore\fR. Therefore, by
36 default, the operating system attempts to create a core file named \fBcore\fR
37 in the process's current working directory.
38 .sp
39 .LP
40 A process terminates and produces a core file whenever it receives one of the
41 signals whose default disposition is to cause a core dump. The list of signals
42 that result in generating a core file is shown in \fBsignal.h\fR(3HEAD).
43 Therefore, a process might not produce a core file if it has blocked or
44 modified the behavior of the corresponding signal. Additionally, no core dump
45 can be created under the following conditions:
46 .RS +4
47 .TP
48 .ie t \(bu
49 .el o
50 If normal file and directory access permissions prevent the creation or
51 modification of the per-process core file pathname by the current process user
52 and group ID. This test does not apply to the global core file pathname
53 because, regardless of the UID of the process dumping core, the attempt to
54 write the global core file is made as the superuser.
55 .RE
56 .RS +4
57 .TP
58 .ie t \(bu
59 .el o
60 Core files owned by the user \fBnobody\fR will not be produced. For example,
61 core files generated for the superuser on an NFS directory are owned by
62 \fBnobody\fR and are, therefore, not written.
63 .RE
64 .RS +4
65 .TP
66 .ie t \(bu
67 .el o
68 If the core file pattern expands to a pathname that contains intermediate
69 directory components that do not exist. For example, if the global pattern is
70 set to \fB/var/core/%n/core.%p\fR, and no directory \fB/var/core/`uname -n`\fR
71 has been created, no global core files are produced.
72 .RE
73 .RS +4
74 .TP
75 .ie t \(bu
76 .el o
77 If the destination directory is part of a filesystem that is mounted read-only.
78 .RE
79 .RS +4
80 .TP
81 .ie t \(bu
82 .el o
83 If the resource limit \fBRLIMIT_CORE\fR has been set to \fB0\fR for the
84 process, no per-process core file is produced. Refer to \fBsetrlimit\fR(2) and
85 \fBulimit\fR(1) for more information on resource limits.
86 .RE
87 .RS +4
88 .TP
89 .ie t \(bu
90 .el o
91 If the core file name already exists in the destination directory and is not a
92 regular file (that is, is a symlink, block or character special-file, and so
93 forth).
94 .RE
95 .RS +4
96 .TP
97 .ie t \(bu
98 .el o
99 If the kernel cannot open the destination file \fBO_EXCL\fR, which can occur if
100 same file is being created by another process simultaneously.
101 .RE
102 .RS +4
103 .TP
104 .ie t \(bu
105 .el o
106 If the process's effective user ID is different from its real user ID or if its
107 effective group ID is different from its real group ID. Similarly, set-user-ID
108 and set-group-ID programs do not produce core files as this could potentially
109 compromise system security. These processes can be explicitly granted
110 permission to produce core files using \fBcoreadm\fR(8), at the risk of
111 exposing secure information.
112 .RE
113 .sp
114 .LP
115 The core file contains all the process information pertinent to debugging:
116 contents of hardware registers, process status, and process data. The format of
117 a core file is object file specific.
118 .sp
119 .LP
120 For ELF executable programs (see \fBa.out\fR(4)), the core file generated is
121 also an ELF file, containing ELF program and file headers. The \fBe_type\fR
122 field in the file header has type \fBET_CORE\fR. The program header contains an
123 entry for every segment that was part of the process address space, including
124 shared library segments. The contents of the mappings specified by
125 \fBcoreadm\fR(8) are also part of the core image. Each program header has its
126 \fBp_memsz\fR field set to the size of the mapping. The program headers that
127 represent mappings whose data is included in the core file have their
128 \fBp_filesz\fR field set the same as \fBp_memsz\fR, otherwise \fBp_filesz\fR is
129 \fBzero\fR.
130 .sp
131 .LP
132 A mapping's data can be excluded due to the core file content settings (see
133 \fBcoreadm\fR(8)), due to a failure, or due to a signal received after
134 core dump initiation but before its completion. If the data is excluded
135 because of a failure, the program header entry will have the
136 \fBPF_SUNW_FAILURE\fR flag
137 set in its \fBp_flags\fR field; if the data is excluded because of a signal,
138 the segment's \fBp_flags\fR field will have the \fBPF_SUNW_KILLED\fR
139 flag set.
140 .sp
141 .LP
142 The program headers of an \fBELF\fR core file also contain entries for two
143 \fBNOTE\fR segments, each containing several note entries as described below.
144 The note entry header and core file note type (\fBn_type\fR) definitions are
145 contained in <\fBsys/elf.h\fR>. The first \fBNOTE\fR segment exists for binary
146 compatibility with old programs that deal with core files. It contains
147 structures defined in <\fBsys/old_procfs.h\fR>. New programs should recognize
148 and skip this \fBNOTE\fR segment, advancing instead to the new \fBNOTE\fR
149 segment. The old \fBNOTE\fR segment is deleted from core files in a future
150 release.
151 .sp
152 .LP
153 The old \fBNOTE\fR segment contains the following entries. Each has entry name
154 \fB"CORE"\fR and presents the contents of a system structure:
155 .sp
156 .ne 2
157 .na
158 \fB\fBprpsinfo_t\fR\fR
159 .ad
160 .RS 16n
161 \fBn_type\fR: \fBNT_PRPSINFO\fR. This entry contains information of interest to
162 the \fBps\fR(1) command, such as process status, \fBCPU\fR usage, \fBnice\fR
163 value, controlling terminal, user-ID, process-ID, the name of the executable,
164 and so forth. The \fBprpsinfo_t\fR structure is defined in
165 <\fBsys/old_procfs.h\fR>.
166 .RE
168 .sp
169 .ne 2
170 .na
171 \fB\fBchar\fR array\fR
172 .ad
173 .RS 16n
174 \fBn_type\fR: \fBNT_PLATFORM\fR. This entry contains a string describing the
175 specific model of the hardware platform on which this core file was created.
176 This information is the same as provided by \fBsysinfo\fR(2) when invoked with
177 the command \fBSI_PLATFORM\fR.
178 .RE
180 .sp
181 .ne 2
182 .na
183 \fB\fBauxv_t\fR array\fR
184 .ad
185 .RS 16n
186 \fBn_type\fR: \fBNT_AUXV\fR. This entry contains the array of \fBauxv_t\fR
187 structures that was passed by the operating system as startup information to
188 the dynamic linker. Auxiliary vector information is defined in
189 <\fBsys/auxv.h\fR>.
190 .RE
192 .sp
193 .LP
194 Following these entries, for each active (non-zombie) light-weight process
195 (LWP) in the process, the old \fBNOTE\fR segment contains an entry with a
196 \fBprstatus_t\fR structure, plus other optionally-present entries describing
197 the LWP, as follows:
198 .sp
199 .ne 2
200 .na
201 \fB\fBprstatus_t\fR\fR
202 .ad
203 .RS 16n
204 \fBn_type\fR: \fBNT_PRSTATUS\fR. This structure contains things of interest to
205 a debugger from the operating system, such as the general registers, signal
206 dispositions, state, reason for stopping, process-ID, and so forth. The
207 \fBprstatus_t\fR structure is defined in <\fBsys/old_procfs.h\fR>.
208 .RE
210 .sp
211 .ne 2
212 .na
213 \fB\fBprfpregset_t\fR\fR
214 .ad
215 .RS 16n
216 \fBn_type\fR: \fBNT_PRFPREG\fR. This entry is present only if the \fBLWP\fR
217 used the floating-point hardware. It contains the floating-point registers. The
218 \fBprfpregset_t\fR structure is defined in <\fBsys/procfs_isa.h\fR>.
219 .RE
221 .sp
222 .ne 2
223 .na
224 \fB\fBgwindows_t\fR\fR
225 .ad
226 .RS 16n
227 \fBn_type\fR: \fBNT_GWINDOWS\fR. This entry is present only on a SPARC machine
228 and only if the system was unable to flush all of the register windows to the
229 stack. It contains all of the unspilled register windows. The \fBgwindows_t\fR
230 structure is defined in <\fBsys/regset.h\fR>.
231 .RE
233 .sp
234 .ne 2
235 .na
236 \fB\fBprxregset_t\fR\fR
237 .ad
238 .RS 16n
239 \fBn_type\fR: \fBNT_PRXREG\fR. This entry is present only if the machine has
240 extra register state associated with it. It contains the extra register state.
241 The \fBprxregset_t\fR structure is defined in <\fBsys/procfs_isa.h\fR>.
242 .RE
244 .sp
245 .LP
246 The new \fBNOTE\fR segment contains the following entries. Each has entry name
247 "\fBCORE\fR" and presents the contents of a system structure:
248 .sp
249 .ne 2
250 .na
251 \fB\fBpsinfo_t\fR\fR
252 .ad
253 .RS 20n
254 \fBn_type\fR: \fBNT_PSINFO\fR. This structure contains information of interest
255 to the \fBps\fR(1) command, such as process status, \fBCPU\fR usage, \fBnice\fR
256 value, controlling terminal, user-ID, process-ID, the name of the executable,
257 and so forth. The \fBpsinfo_t\fR structure is defined in <\fBsys/procfs.h\fR>.
258 .RE
260 .sp
261 .ne 2
262 .na
263 \fB\fBpstatus_t\fR\fR
264 .ad
265 .RS 20n
266 \fBn_type\fR: \fBNT_PSTATUS\fR. This structure contains things of interest to a
267 debugger from the operating system, such as pending signals, state, process-ID,
268 and so forth. The \fBpstatus_t\fR structure is defined in <\fBsys/procfs.h\fR>.
269 .RE
271 .sp
272 .ne 2
273 .na
274 \fB\fBchar\fR array\fR
275 .ad
276 .RS 20n
277 \fBn_type\fR: \fBNT_PLATFORM\fR. This entry contains a string describing the
278 specific model of the hardware platform on which this core file was created.
279 This information is the same as provided by \fBsysinfo\fR(2) when invoked with
280 the command \fBSI_PLATFORM\fR.
281 .RE
283 .sp
284 .ne 2
285 .na
286 \fB\fBauxv_t\fR array\fR
287 .ad
288 .RS 20n
289 \fBn_type\fR: \fBNT_AUXV\fR. This entry contains the array of \fBauxv_t\fR
290 structures that was passed by the operating system as startup information to
291 the dynamic linker. Auxiliary vector information is defined in
292 <\fBsys/auxv.h\fR>.
293 .RE
295 .sp
296 .ne 2
297 .na
298 \fB\fBstruct utsname\fR\fR
299 .ad
300 .RS 20n
301 \fBn_type\fR: \fBNT_UTSNAME\fR. This structure contains the system information
302 that would have been returned to the process if it had performed a
303 \fBuname\fR(2) system call prior to dumping core. The \fButsname\fR structure
304 is defined in <\fBsys/utsname.h\fR>.
305 .RE
307 .sp
308 .ne 2
309 .na
310 \fB\fBprcred_t\fR\fR
311 .ad
312 .RS 20n
313 \fBn_type\fR: \fBNT_PRCRED\fR. This structure contains the process credentials,
314 including the real, saved, and effective user and group IDs. The \fBprcred_t\fR
315 structure is defined in <\fBsys/procfs.h\fR>. Following the structure is an
316 optional array of supplementary group IDs. The total number of supplementary
317 group IDs is given by the \fBpr_ngroups\fR member of the \fBprcred_t\fR
318 structure, and the structure includes space for one supplementary group. If
319 \fBpr_ngroups\fR is greater than 1, there is \fBpr_ngroups - 1\fR \fBgid_t\fR
320 items following the structure; otherwise, there is no additional data.
321 .RE
323 .sp
324 .ne 2
325 .na
326 \fB\fBchar array\fR\fR
327 .ad
328 .RS 20n
329 \fBn_type\fR: \fBNT_ZONENAME\fR. This entry contains a string which describes
330 the name of the zone in which the process was running. See \fBzones\fR(5). The
331 information is the same as provided by \fBgetzonenamebyid\fR(3C) when invoked
332 with the numerical ID returned by \fBgetzoneid\fR(3C).
333 .RE
335 .sp
336 .ne 2
337 .na
338 \fB\fBprfdinfo_t\fR\fR
339 .ad
340 .RS 20n
341 \fBn_type\fR: \fBNT_FDINFO\fR. This structure contains information about
342 any open file descriptors, including the path, flags, and
343 \fBstat\fR(2) information. The \fBprfdinfo_t\fR structure is defined in
344 <\fBsys/procfs.h\fR>.
345 .RE
347 .sp
348 .ne 2
349 .na
350 \fB\fBstruct ssd\fR array\fR
351 .ad
352 .RS 20n
353 \fBn_type\fR: \fBNT_LDT\fR. This entry is present only on an 32-bit x86 machine
354 and only if the process has set up a Local Descriptor Table (LDT). It contains
355 an array of structures of type \fBstruct ssd\fR, each of which was typically
356 used to set up the \fB%gs\fR segment register to be used to fetch the address
357 of the current thread information structure in a multithreaded process. The
358 \fBssd\fR structure is defined in <\fBsys/sysi86.h\fR>.
359 .RE
361 .sp
362 .ne 2
363 .na
364 \fB\fBcore_content_t\fR\fR
365 .ad
366 .RS 20n
367 \fBn_type\fR: \fBNT_CONTENT\fR. This optional entry indicates which parts of
368 the process image are specified to be included in the core file. See
369 \fBcoreadm\fR(8).
370 .RE
372 .sp
373 .LP
374 Following these entries, for each active and zombie \fBLWP\fR in the process,
375 the new \fBNOTE\fR segment contains an entry with an \fBlwpsinfo_t\fR structure
376 plus, for a non-zombie LWP, an entry with an \fBlwpstatus_t\fR structure, plus
377 other optionally-present entries describing the LWP, as follows. A zombie LWP
378 is a non-detached LWP that has terminated but has not yet been reaped by
379 another LWP in the same process.
380 .sp
381 .ne 2
382 .na
383 \fB\fBlwpsinfo_t\fR\fR
384 .ad
385 .RS 15n
386 \fBn_type\fR: \fBNT_LWPSINFO\fR. This structure contains information of
387 interest to the \fBps\fR(1) command, such as \fBLWP\fR status, \fBCPU\fR usage,
388 \fBnice\fR value, \fBLWP-ID\fR, and so forth. The \fBlwpsinfo_t\fR structure is
389 defined in <\fBsys/procfs.h\fR>. This is the only entry present for a zombie
390 LWP.
391 .RE
393 .sp
394 .ne 2
395 .na
396 \fB\fBlwpstatus_t\fR\fR
397 .ad
398 .RS 15n
399 \fBn_type\fR: \fBNT_LWPSTATUS\fR. This structure contains things of interest to
400 a debugger from the operating system, such as the general registers, the
401 floating point registers, state, reason for stopping, \fBLWP-ID\fR, and so
402 forth. The \fBlwpstatus_t\fR structure is defined in <\fBsys/procfs.h>\fR>.
403 .RE
405 .sp
406 .ne 2
407 .na
408 \fB\fBgwindows_t\fR\fR
409 .ad
410 .RS 15n
411 \fBn_type\fR: \fBNT_GWINDOWS\fR. This entry is present only on a SPARC machine
412 and only if the system was unable to flush all of the register windows to the
413 stack. It contains all of the unspilled register windows. The \fBgwindows_t\fR
414 structure is defined in \fB<sys/regset.h>\fR\&.
415 .RE
417 .sp
418 .ne 2
419 .na
420 \fB\fBprxregset_t\fR\fR
421 .ad
422 .RS 15n
423 \fBn_type\fR: \fBNT_PRXREG\fR. This entry is present only if the machine has
424 extra register state associated with it. It contains the extra register state.
425 The \fBprxregset_t\fR structure is defined in \fB<sys/procfs_isa.h>\fR\&.
426 .RE
428 .sp
429 .ne 2
430 .na
431 \fB\fBasrset_t\fR\fR
432 .ad
433 .RS 15n
434 \fBn_type\fR: \fBNT_ASRS\fR. This entry is present only on a SPARC V9 machine
435 and only if the process is a 64-bit process. It contains the ancillary state
436 registers for the \fBLWP.\fR The \fBasrset_t\fR structure is defined in
437 \fB<sys/regset.h>\fR\&.
438 .RE
440 .sp
441 .ne 2
442 .na
443 \fB\fBpsinfo_t\fR\fR
444 .ad
445 .RS 15n
446 \fBn_type\fR: \fBNT_SPYMASTER\fR. This entry is present only for an agent
447 LWP and contains the \fBpsinfo_t\fR of the process that created the agent
448 LWP. See the \fBproc\fR(4) description of the \fBspymaster\fR entry for
449 more details.
450 .RE
452 .sp
453 .ne 2
454 .na
455 \fB\fBprsecflags_t\fR\fR
456 .ad
457 .RS 15n
458 \fBn_type\fR: \fbNT_SECFLAGS\fR. This entry contains the process
459 security-flags, see \fBsecurity-flags\fR(5), \fBproc\fR(4), and
460 \fBpsecflags\fR(1) for more information.
461 .RE
463 .sp
464 .LP
465 Depending on the \fBcoreadm\fR(8) settings, the section header of an ELF core
466 file can contain entries for CTF, symbol table, and string table sections. The
467 \fBsh_addr\fR fields are set to the base address of the first mapping of the
468 load object that they came from to. This can be used to match those sections
469 with the corresponding load object.
470 .sp
471 .LP
472 The size of the core file created by a process can be controlled by the user
473 (see \fBgetrlimit\fR(2)).
474 .SH SEE ALSO
475 .LP
476 \fBelfdump\fR(1), \fBgcore\fR(1), \fBmdb\fR(1), \fBproc\fR(1), \fBps\fR(1),
477 \fBcoreadm\fR(8), \fBgetrlimit\fR(2), \fBsetrlimit\fR(2), \fBsetuid\fR(2),
478 \fBsysinfo\fR(2), \fBuname\fR(2), \fBgetzonenamebyid\fR(3C),
479 \fBgetzoneid\fR(3C), \fBelf\fR(3ELF), \fBsignal.h\fR(3HEAD), \fBa.out\fR(4),
480 \fBproc\fR(4), \fBzones\fR(5), \fBsecurity-flags\fR(5)
481 .sp
482 .LP
483 \fIANSI C Programmer's Guide\fR