process-creation-posix.cpp@ 44549

Last change on this file since 44549 was 44549, checked in by vboxsync, 12 years ago
Runtime/posix/RTProcCreateEx: unblock all signals for the new child process
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1	/* $Id: process-creation-posix.cpp 44549 2013-02-05 16:10:29Z vboxsync $ */
2	/** @file
3	* IPRT - Process Creation, POSIX.
4	*/
5
6	/*
7	* Copyright (C) 2006-2013 Oracle Corporation
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.215389.xyz. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*
17	* The contents of this file may alternatively be used under the terms
18	* of the Common Development and Distribution License Version 1.0
19	* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
20	* VirtualBox OSE distribution, in which case the provisions of the
21	* CDDL are applicable instead of those of the GPL.
22	*
23	* You may elect to license modified versions of this file under the
24	* terms and conditions of either the GPL or the CDDL or both.
25	*/
26
27
28	/*******************************************************************************
29	* Header Files *
30	*******************************************************************************/
31	#define LOG_GROUP RTLOGGROUP_PROCESS
32	#include <unistd.h>
33	#include <stdlib.h>
34	#include <errno.h>
35	#include <sys/types.h>
36	#include <sys/stat.h>
37	#include <sys/wait.h>
38	#include <fcntl.h>
39	#include <signal.h>
40	#if defined(RT_OS_LINUX) \|\| defined(RT_OS_SOLARIS)
41	# include <crypt.h>
42	# include <pwd.h>
43	# include <shadow.h>
44	#endif
45	#if defined(RT_OS_LINUX) \|\| defined(RT_OS_OS2)
46	/* While Solaris has posix_spawn() of course we don't want to use it as
47	* we need to have the child in a different process contract, no matter
48	* whether it is started detached or not. */
49	# define HAVE_POSIX_SPAWN 1
50	#endif
51	#ifdef HAVE_POSIX_SPAWN
52	# include <spawn.h>
53	#endif
54	#ifdef RT_OS_DARWIN
55	# include <mach-o/dyld.h>
56	#endif
57	#ifdef RT_OS_SOLARIS
58	# include <limits.h>
59	# include <sys/ctfs.h>
60	# include <sys/contract/process.h>
61	# include <libcontract.h>
62	#endif
63
64	#include <iprt/process.h>
65	#include "internal/iprt.h"
66
67	#include <iprt/assert.h>
68	#include <iprt/env.h>
69	#include <iprt/err.h>
70	#include <iprt/file.h>
71	#include <iprt/path.h>
72	#include <iprt/pipe.h>
73	#include <iprt/socket.h>
74	#include <iprt/string.h>
75	#include <iprt/mem.h>
76	#include "internal/process.h"
77
78
79	/**
80	* Check the credentials and return the gid/uid of user.
81	*
82	* @param pszUser username
83	* @param pszPasswd password
84	* @param gid where to store the GID of the user
85	* @param uid where to store the UID of the user
86	* @returns IPRT status code
87	*/
88	static int rtCheckCredentials(const char pszUser, const char pszPasswd, gid_t pGid, uid_t pUid)
89	{
90	#if defined(RT_OS_LINUX)
91	struct passwd *pw;
92
93	pw = getpwnam(pszUser);
94	if (!pw)
95	return VERR_PERMISSION_DENIED;
96
97	if (!pszPasswd)
98	pszPasswd = "";
99
100	struct spwd *spwd;
101	/* works only if /etc/shadow is accessible */
102	spwd = getspnam(pszUser);
103	if (spwd)
104	pw->pw_passwd = spwd->sp_pwdp;
105
106	/* be reentrant */
107	struct crypt_data data = (struct crypt_data)RTMemTmpAllocZ(sizeof(*data));
108	char *pszEncPasswd = crypt_r(pszPasswd, pw->pw_passwd, data);
109	int fCorrect = !strcmp(pszEncPasswd, pw->pw_passwd);
110	RTMemTmpFree(data);
111	if (!fCorrect)
112	return VERR_PERMISSION_DENIED;
113
114	*pGid = pw->pw_gid;
115	*pUid = pw->pw_uid;
116	return VINF_SUCCESS;
117
118	#elif defined(RT_OS_SOLARIS)
119	struct passwd *ppw, pw;
120	char szBuf[1024];
121
122	if (getpwnam_r(pszUser, &pw, szBuf, sizeof(szBuf), &ppw) != 0 \|\| ppw == NULL)
123	return VERR_PERMISSION_DENIED;
124
125	if (!pszPasswd)
126	pszPasswd = "";
127
128	struct spwd spwd;
129	char szPwdBuf[1024];
130	/* works only if /etc/shadow is accessible */
131	if (getspnam_r(pszUser, &spwd, szPwdBuf, sizeof(szPwdBuf)) != NULL)
132	ppw->pw_passwd = spwd.sp_pwdp;
133
134	char *pszEncPasswd = crypt(pszPasswd, ppw->pw_passwd);
135	if (strcmp(pszEncPasswd, ppw->pw_passwd))
136	return VERR_PERMISSION_DENIED;
137
138	*pGid = ppw->pw_gid;
139	*pUid = ppw->pw_uid;
140	return VINF_SUCCESS;
141
142	#else
143	NOREF(pszUser); NOREF(pszPasswd); NOREF(pGid); NOREF(pUid);
144	return VERR_PERMISSION_DENIED;
145	#endif
146	}
147
148
149	#ifdef RT_OS_SOLARIS
150	/** @todo the error reporting of the Solaris process contract code could be
151	* a lot better, but essentially it is not meant to run into errors after
152	* the debugging phase. */
153	static int rtSolarisContractPreFork(void)
154	{
155	int templateFd = open64(CTFS_ROOT "/process/template", O_RDWR);
156	if (templateFd < 0)
157	return -1;
158
159	/* Set template parameters and event sets. */
160	if (ct_pr_tmpl_set_param(templateFd, CT_PR_PGRPONLY))
161	{
162	close(templateFd);
163	return -1;
164	}
165	if (ct_pr_tmpl_set_fatal(templateFd, CT_PR_EV_HWERR))
166	{
167	close(templateFd);
168	return -1;
169	}
170	if (ct_tmpl_set_critical(templateFd, 0))
171	{
172	close(templateFd);
173	return -1;
174	}
175	if (ct_tmpl_set_informative(templateFd, CT_PR_EV_HWERR))
176	{
177	close(templateFd);
178	return -1;
179	}
180
181	/* Make this the active template for the process. */
182	if (ct_tmpl_activate(templateFd))
183	{
184	close(templateFd);
185	return -1;
186	}
187
188	return templateFd;
189	}
190
191	static void rtSolarisContractPostForkChild(int templateFd)
192	{
193	if (templateFd == -1)
194	return;
195
196	/* Clear the active template. */
197	ct_tmpl_clear(templateFd);
198	close(templateFd);
199	}
200
201	static void rtSolarisContractPostForkParent(int templateFd, pid_t pid)
202	{
203	if (templateFd == -1)
204	return;
205
206	/* Clear the active template. */
207	int cleared = ct_tmpl_clear(templateFd);
208	close(templateFd);
209
210	/* If the clearing failed or the fork failed there's nothing more to do. */
211	if (cleared \|\| pid <= 0)
212	return;
213
214	/* Look up the contract which was created by this thread. */
215	int statFd = open64(CTFS_ROOT "/process/latest", O_RDONLY);
216	if (statFd == -1)
217	return;
218	ct_stathdl_t statHdl;
219	if (ct_status_read(statFd, CTD_COMMON, &statHdl))
220	{
221	close(statFd);
222	return;
223	}
224	ctid_t ctId = ct_status_get_id(statHdl);
225	ct_status_free(statHdl);
226	close(statFd);
227	if (ctId < 0)
228	return;
229
230	/* Abandon this contract we just created. */
231	char ctlPath[PATH_MAX];
232	size_t len = snprintf(ctlPath, sizeof(ctlPath),
233	CTFS_ROOT "/process/%d/ctl", ctId);
234	if (len >= sizeof(ctlPath))
235	return;
236	int ctlFd = open64(ctlPath, O_WRONLY);
237	if (statFd == -1)
238	return;
239	if (ct_ctl_abandon(ctlFd) < 0)
240	{
241	close(ctlFd);
242	return;
243	}
244	close(ctlFd);
245	}
246
247	#endif /* RT_OS_SOLARIS */
248
249
250	RTR3DECL(int) RTProcCreate(const char pszExec, const char const *papszArgs, RTENV Env, unsigned fFlags, PRTPROCESS pProcess)
251	{
252	return RTProcCreateEx(pszExec, papszArgs, Env, fFlags,
253	NULL, NULL, NULL, /* standard handles */
254	NULL /pszAsUser/, NULL /* pszPassword*/,
255	pProcess);
256	}
257
258
259	/**
260	* RTPathTraverseList callback used by RTProcCreateEx to locate the executable.
261	*/
262	static DECLCALLBACK(int) rtPathFindExec(char const pchPath, size_t cchPath, void pvUser1, void *pvUser2)
263	{
264	const char pszExec = (const char )pvUser1;
265	char pszRealExec = (char )pvUser2;
266	int rc = RTPathJoinEx(pszRealExec, RTPATH_MAX, pchPath, cchPath, pszExec, RTSTR_MAX);
267	if (RT_FAILURE(rc))
268	return rc;
269	if (!access(pszRealExec, X_OK))
270	return VINF_SUCCESS;
271	if ( errno == EACCES
272	\|\| errno == EPERM)
273	return RTErrConvertFromErrno(errno);
274	return VERR_TRY_AGAIN;
275	}
276
277
278	RTR3DECL(int) RTProcCreateEx(const char pszExec, const char const *papszArgs, RTENV hEnv, uint32_t fFlags,
279	PCRTHANDLE phStdIn, PCRTHANDLE phStdOut, PCRTHANDLE phStdErr, const char *pszAsUser,
280	const char *pszPassword, PRTPROCESS phProcess)
281	{
282	int rc;
283
284	/*
285	* Input validation
286	*/
287	AssertPtrReturn(pszExec, VERR_INVALID_POINTER);
288	AssertReturn(*pszExec, VERR_INVALID_PARAMETER);
289	AssertReturn(!(fFlags & ~(RTPROC_FLAGS_DETACHED \| RTPROC_FLAGS_HIDDEN \| RTPROC_FLAGS_SERVICE \| RTPROC_FLAGS_SAME_CONTRACT \| RTPROC_FLAGS_NO_PROFILE \| RTPROC_FLAGS_SEARCH_PATH)), VERR_INVALID_PARAMETER);
290	AssertReturn(!(fFlags & RTPROC_FLAGS_DETACHED) \|\| !phProcess, VERR_INVALID_PARAMETER);
291	AssertReturn(hEnv != NIL_RTENV, VERR_INVALID_PARAMETER);
292	const char * const *papszEnv = RTEnvGetExecEnvP(hEnv);
293	AssertPtrReturn(papszEnv, VERR_INVALID_HANDLE);
294	AssertPtrReturn(papszArgs, VERR_INVALID_PARAMETER);
295	/** @todo search the PATH (add flag for this). */
296	AssertPtrNullReturn(pszAsUser, VERR_INVALID_POINTER);
297	AssertReturn(!pszAsUser \|\| *pszAsUser, VERR_INVALID_PARAMETER);
298	AssertReturn(!pszPassword \|\| pszAsUser, VERR_INVALID_PARAMETER);
299	AssertPtrNullReturn(pszPassword, VERR_INVALID_POINTER);
300	#if defined(RT_OS_OS2)
301	if (fFlags & RTPROC_FLAGS_DETACHED)
302	return VERR_PROC_DETACH_NOT_SUPPORTED;
303	#endif
304
305	/*
306	* Get the file descriptors for the handles we've been passed.
307	*/
308	PCRTHANDLE paHandles[3] = { phStdIn, phStdOut, phStdErr };
309	int aStdFds[3] = { -1, -1, -1 };
310	for (int i = 0; i < 3; i++)
311	{
312	if (paHandles[i])
313	{
314	AssertPtrReturn(paHandles[i], VERR_INVALID_POINTER);
315	switch (paHandles[i]->enmType)
316	{
317	case RTHANDLETYPE_FILE:
318	aStdFds[i] = paHandles[i]->u.hFile != NIL_RTFILE
319	? (int)RTFileToNative(paHandles[i]->u.hFile)
320	: -2 /* close it */;
321	break;
322
323	case RTHANDLETYPE_PIPE:
324	aStdFds[i] = paHandles[i]->u.hPipe != NIL_RTPIPE
325	? (int)RTPipeToNative(paHandles[i]->u.hPipe)
326	: -2 /* close it */;
327	break;
328
329	case RTHANDLETYPE_SOCKET:
330	aStdFds[i] = paHandles[i]->u.hSocket != NIL_RTSOCKET
331	? (int)RTSocketToNative(paHandles[i]->u.hSocket)
332	: -2 /* close it */;
333	break;
334
335	default:
336	AssertMsgFailedReturn(("%d: %d\n", i, paHandles[i]->enmType), VERR_INVALID_PARAMETER);
337	}
338	/** @todo check the close-on-execness of these handles? */
339	}
340	}
341
342	for (int i = 0; i < 3; i++)
343	if (aStdFds[i] == i)
344	aStdFds[i] = -1;
345
346	for (int i = 0; i < 3; i++)
347	AssertMsgReturn(aStdFds[i] < 0 \|\| aStdFds[i] > i,
348	("%i := %i not possible because we're lazy\n", i, aStdFds[i]),
349	VERR_NOT_SUPPORTED);
350
351	/*
352	* Resolve the user id if specified.
353	*/
354	uid_t uid = ~(uid_t)0;
355	gid_t gid = ~(gid_t)0;
356	if (pszAsUser)
357	{
358	rc = rtCheckCredentials(pszAsUser, pszPassword, &gid, &uid);
359	if (RT_FAILURE(rc))
360	return rc;
361	}
362
363	/*
364	* Check for execute access to the file.
365	*/
366	char szRealExec[RTPATH_MAX];
367	if (access(pszExec, X_OK))
368	{
369	if ( !(fFlags & RTPROC_FLAGS_SEARCH_PATH)
370	\|\| errno != ENOENT
371	\|\| RTPathHavePath(pszExec) )
372	return RTErrConvertFromErrno(errno);
373
374	/* search */
375	char *pszPath = RTEnvDupEx(hEnv, "PATH");
376	rc = RTPathTraverseList(pszPath, ':', rtPathFindExec, (void *)pszExec, &szRealExec[0]);
377	RTStrFree(pszPath);
378	if (RT_FAILURE(rc))
379	return rc == VERR_END_OF_STRING ? VERR_FILE_NOT_FOUND : rc;
380	pszExec = szRealExec;
381	}
382
383	pid_t pid = -1;
384
385	/*
386	* Take care of detaching the process.
387	*
388	* HACK ALERT! Put the process into a new process group with pgid = pid
389	* to make sure it differs from that of the parent process to ensure that
390	* the IPRT waitpid call doesn't race anyone (read XPCOM) doing group wide
391	* waits. setsid() includes the setpgid() functionality.
392	* 2010-10-11 XPCOM no longer waits for anything, but it cannot hurt.
393	*/
394	#ifndef RT_OS_OS2
395	if (fFlags & RTPROC_FLAGS_DETACHED)
396	{
397	# ifdef RT_OS_SOLARIS
398	int templateFd = -1;
399	if (!(fFlags & RTPROC_FLAGS_SAME_CONTRACT))
400	{
401	templateFd = rtSolarisContractPreFork();
402	if (templateFd == -1)
403	return VERR_OPEN_FAILED;
404	}
405	# endif /* RT_OS_SOLARIS */
406	pid = fork();
407	if (!pid)
408	{
409	# ifdef RT_OS_SOLARIS
410	if (!(fFlags & RTPROC_FLAGS_SAME_CONTRACT))
411	rtSolarisContractPostForkChild(templateFd);
412	# endif /* RT_OS_SOLARIS */
413	setsid(); /* see comment above */
414
415	pid = -1;
416	/* Child falls through to the actual spawn code below. */
417	}
418	else
419	{
420	#ifdef RT_OS_SOLARIS
421	if (!(fFlags & RTPROC_FLAGS_SAME_CONTRACT))
422	rtSolarisContractPostForkParent(templateFd, pid);
423	#endif /* RT_OS_SOLARIS */
424	if (pid > 0)
425	{
426	/* Must wait for the temporary process to avoid a zombie. */
427	int status = 0;
428	pid_t pidChild = 0;
429
430	/* Restart if we get interrupted. */
431	do
432	{
433	pidChild = waitpid(pid, &status, 0);
434	} while ( pidChild == -1
435	&& errno == EINTR);
436
437	/* Assume that something wasn't found. No detailed info. */
438	if (status)
439	return VERR_PROCESS_NOT_FOUND;
440	if (phProcess)
441	*phProcess = 0;
442	return VINF_SUCCESS;
443	}
444	return RTErrConvertFromErrno(errno);
445	}
446	}
447	#endif
448
449	/*
450	* Spawn the child.
451	*
452	* Any spawn code MUST not execute any atexit functions if it is for a
453	* detached process. It would lead to running the atexit functions which
454	* make only sense for the parent. libORBit e.g. gets confused by multiple
455	* execution. Remember, there was only a fork() so far, and until exec()
456	* is successfully run there is nothing which would prevent doing anything
457	* silly with the (duplicated) file descriptors.
458	*/
459	#ifdef HAVE_POSIX_SPAWN
460	/** @todo OS/2: implement DETACHED (BACKGROUND stuff), see VbglR3Daemonize. */
461	if ( uid == ~(uid_t)0
462	&& gid == ~(gid_t)0)
463	{
464	/* Spawn attributes. */
465	posix_spawnattr_t Attr;
466	rc = posix_spawnattr_init(&Attr);
467	if (!rc)
468	{
469	# ifndef RT_OS_OS2 /* We don't need this on OS/2 and I don't recall if it's actually implemented. */
470	rc = posix_spawnattr_setflags(&Attr, POSIX_SPAWN_SETPGROUP);
471	Assert(rc == 0);
472	if (!rc)
473	{
474	rc = posix_spawnattr_setpgroup(&Attr, 0 /* pg == child pid */);
475	Assert(rc == 0);
476	}
477	# endif
478	sigset_t sigmask;
479	sigemptyset(&sigmask);
480	rc = posix_spawnattr_setsigmask(&Attr, &sigmask);
481	Assert(rc == 0);
482
483	/* File changes. */
484	posix_spawn_file_actions_t FileActions;
485	posix_spawn_file_actions_t *pFileActions = NULL;
486	if (aStdFds[0] != -1 \|\| aStdFds[1] != -1 \|\| aStdFds[2] != -1)
487	{
488	rc = posix_spawn_file_actions_init(&FileActions);
489	if (!rc)
490	{
491	pFileActions = &FileActions;
492	for (int i = 0; i < 3; i++)
493	{
494	int fd = aStdFds[i];
495	if (fd == -2)
496	rc = posix_spawn_file_actions_addclose(&FileActions, i);
497	else if (fd >= 0 && fd != i)
498	{
499	rc = posix_spawn_file_actions_adddup2(&FileActions, fd, i);
500	if (!rc)
501	{
502	for (int j = i + 1; j < 3; j++)
503	if (aStdFds[j] == fd)
504	{
505	fd = -1;
506	break;
507	}
508	if (fd >= 0)
509	rc = posix_spawn_file_actions_addclose(&FileActions, fd);
510	}
511	}
512	if (rc)
513	break;
514	}
515	}
516	}
517
518	if (!rc)
519	rc = posix_spawn(&pid, pszExec, pFileActions, &Attr, (char * const *)papszArgs,
520	(char * const *)papszEnv);
521
522	/* cleanup */
523	int rc2 = posix_spawnattr_destroy(&Attr); Assert(rc2 == 0); NOREF(rc2);
524	if (pFileActions)
525	{
526	rc2 = posix_spawn_file_actions_destroy(pFileActions);
527	Assert(rc2 == 0);
528	}
529
530	/* return on success.*/
531	if (!rc)
532	{
533	/* For a detached process this happens in the temp process, so
534	* it's not worth doing anything as this process must exit. */
535	if (fFlags & RTPROC_FLAGS_DETACHED)
536	_Exit(0);
537	if (phProcess)
538	*phProcess = pid;
539	return VINF_SUCCESS;
540	}
541	}
542	/* For a detached process this happens in the temp process, so
543	* it's not worth doing anything as this process must exit. */
544	if (fFlags & RTPROC_FLAGS_DETACHED)
545	_Exit(124);
546	}
547	else
548	#endif
549	{
550	#ifdef RT_OS_SOLARIS
551	int templateFd = rtSolarisContractPreFork();
552	if (templateFd == -1)
553	return VERR_OPEN_FAILED;
554	#endif /* RT_OS_SOLARIS */
555	pid = fork();
556	if (!pid)
557	{
558	#ifdef RT_OS_SOLARIS
559	rtSolarisContractPostForkChild(templateFd);
560	#endif /* RT_OS_SOLARIS */
561	if (!(fFlags & RTPROC_FLAGS_DETACHED))
562	setpgid(0, 0); /* see comment above */
563
564	/*
565	* Change group and user if requested.
566	*/
567	#if 1 /** @todo This needs more work, see suplib/hardening. */
568	if (gid != ~(gid_t)0)
569	{
570	if (setgid(gid))
571	{
572	if (fFlags & RTPROC_FLAGS_DETACHED)
573	_Exit(126);
574	else
575	exit(126);
576	}
577	}
578
579	if (uid != ~(uid_t)0)
580	{
581	if (setuid(uid))
582	{
583	if (fFlags & RTPROC_FLAGS_DETACHED)
584	_Exit(126);
585	else
586	exit(126);
587	}
588	}
589	#endif
590
591	/*
592	* Unset the signal mask.
593	*/
594	sigset_t sigmask;
595	sigemptyset(&sigmask);
596	sigprocmask(SIG_SETMASK, &sigmask, NULL);
597
598	/*
599	* Apply changes to the standard file descriptor and stuff.
600	*/
601	for (int i = 0; i < 3; i++)
602	{
603	int fd = aStdFds[i];
604	if (fd == -2)
605	close(i);
606	else if (fd >= 0)
607	{
608	int rc2 = dup2(fd, i);
609	if (rc2 != i)
610	{
611	if (fFlags & RTPROC_FLAGS_DETACHED)
612	_Exit(125);
613	else
614	exit(125);
615	}
616	for (int j = i + 1; j < 3; j++)
617	if (aStdFds[j] == fd)
618	{
619	fd = -1;
620	break;
621	}
622	if (fd >= 0)
623	close(fd);
624	}
625	}
626
627	/*
628	* Finally, execute the requested program.
629	*/
630	rc = execve(pszExec, (char * const )papszArgs, (char const *)papszEnv);
631	if (errno == ENOEXEC)
632	{
633	/* This can happen when trying to start a shell script without the magic #!/bin/sh */
634	RTAssertMsg2Weak("Cannot execute this binary format!\n");
635	}
636	else
637	RTAssertMsg2Weak("execve returns %d errno=%d\n", rc, errno);
638	RTAssertReleasePanic();
639	if (fFlags & RTPROC_FLAGS_DETACHED)
640	_Exit(127);
641	else
642	exit(127);
643	}
644	#ifdef RT_OS_SOLARIS
645	rtSolarisContractPostForkParent(templateFd, pid);
646	#endif /* RT_OS_SOLARIS */
647	if (pid > 0)
648	{
649	/* For a detached process this happens in the temp process, so
650	* it's not worth doing anything as this process must exit. */
651	if (fFlags & RTPROC_FLAGS_DETACHED)
652	_Exit(0);
653	if (phProcess)
654	*phProcess = pid;
655	return VINF_SUCCESS;
656	}
657	/* For a detached process this happens in the temp process, so
658	* it's not worth doing anything as this process must exit. */
659	if (fFlags & RTPROC_FLAGS_DETACHED)
660	_Exit(124);
661	return RTErrConvertFromErrno(errno);
662	}
663
664	return VERR_NOT_IMPLEMENTED;
665	}
666
667
668	RTR3DECL(int) RTProcDaemonizeUsingFork(bool fNoChDir, bool fNoClose, const char *pszPidfile)
669	{
670	/*
671	* Fork the child process in a new session and quit the parent.
672	*
673	* - fork once and create a new session (setsid). This will detach us
674	* from the controlling tty meaning that we won't receive the SIGHUP
675	* (or any other signal) sent to that session.
676	* - The SIGHUP signal is ignored because the session/parent may throw
677	* us one before we get to the setsid.
678	* - When the parent exit(0) we will become an orphan and re-parented to
679	* the init process.
680	* - Because of the sometimes unexpected semantics of assigning the
681	* controlling tty automagically when a session leader first opens a tty,
682	* we will fork() once more to get rid of the session leadership role.
683	*/
684
685	/* We start off by opening the pidfile, so that we can fail straight away
686	* if it already exists. */
687	int fdPidfile = -1;
688	if (pszPidfile != NULL)
689	{
690	/* @note the exclusive create is not guaranteed on all file
691	* systems (e.g. NFSv2) */
692	if ((fdPidfile = open(pszPidfile, O_RDWR \| O_CREAT \| O_EXCL, 0644)) == -1)
693	return RTErrConvertFromErrno(errno);
694	}
695
696	/* Ignore SIGHUP straight away. */
697	struct sigaction OldSigAct;
698	struct sigaction SigAct;
699	memset(&SigAct, 0, sizeof(SigAct));
700	SigAct.sa_handler = SIG_IGN;
701	int rcSigAct = sigaction(SIGHUP, &SigAct, &OldSigAct);
702
703	/* First fork, to become independent process. */
704	pid_t pid = fork();
705	if (pid == -1)
706	{
707	if (fdPidfile != -1)
708	close(fdPidfile);
709	return RTErrConvertFromErrno(errno);
710	}
711	if (pid != 0)
712	{
713	/* Parent exits, no longer necessary. The child gets reparented
714	* to the init process. */
715	exit(0);
716	}
717
718	/* Create new session, fix up the standard file descriptors and the
719	* current working directory. */
720	/** @todo r=klaus the webservice uses this function and assumes that the
721	* contract id of the daemon is the same as that of the original process.
722	* Whenever this code is changed this must still remain possible. */
723	pid_t newpgid = setsid();
724	int SavedErrno = errno;
725	if (rcSigAct != -1)
726	sigaction(SIGHUP, &OldSigAct, NULL);
727	if (newpgid == -1)
728	{
729	if (fdPidfile != -1)
730	close(fdPidfile);
731	return RTErrConvertFromErrno(SavedErrno);
732	}
733
734	if (!fNoClose)
735	{
736	/* Open stdin(0), stdout(1) and stderr(2) as /dev/null. */
737	int fd = open("/dev/null", O_RDWR);
738	if (fd == -1) /* paranoia */
739	{
740	close(STDIN_FILENO);
741	close(STDOUT_FILENO);
742	close(STDERR_FILENO);
743	fd = open("/dev/null", O_RDWR);
744	}
745	if (fd != -1)
746	{
747	dup2(fd, STDIN_FILENO);
748	dup2(fd, STDOUT_FILENO);
749	dup2(fd, STDERR_FILENO);
750	if (fd > 2)
751	close(fd);
752	}
753	}
754
755	if (!fNoChDir)
756	{
757	int rcIgnored = chdir("/");
758	NOREF(rcIgnored);
759	}
760
761	/* Second fork to lose session leader status. */
762	pid = fork();
763	if (pid == -1)
764	{
765	if (fdPidfile != -1)
766	close(fdPidfile);
767	return RTErrConvertFromErrno(errno);
768	}
769
770	if (pid != 0)
771	{
772	/* Write the pid file, this is done in the parent, before exiting. */
773	if (fdPidfile != -1)
774	{
775	char szBuf[256];
776	size_t cbPid = RTStrPrintf(szBuf, sizeof(szBuf), "%d\n", pid);
777	ssize_t cbIgnored = write(fdPidfile, szBuf, cbPid); NOREF(cbIgnored);
778	close(fdPidfile);
779	}
780	exit(0);
781	}
782
783	if (fdPidfile != -1)
784	close(fdPidfile);
785
786	return VINF_SUCCESS;
787	}
788

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source: vbox/trunk/src/VBox/Runtime/r3/posix/process-creation-posix.cpp@ 44549

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