google3/third_party/grte/v5_src/glibc-2.27/nptl/sem_open.c - GRTEv5 - Git at Google

 /* Copyright (C) 2002-2018 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    The GNU C Library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */

 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <search.h>
 #include <semaphore.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include "semaphoreP.h"
 #include <shm-directory.h>
 #include <futex-internal.h>
 #include <libc-lock.h>

 /* Comparison function for search of existing mapping.  */
 int
 attribute_hidden
 __sem_search (const void *a, const void *b)
 {
   const struct inuse_sem *as = (const struct inuse_sem *) a;
   const struct inuse_sem *bs = (const struct inuse_sem *) b;

   if (as->ino != bs->ino)
     /* Cannot return the difference the type is larger than int.  */
     return as->ino < bs->ino ? -1 : (as->ino == bs->ino ? 0 : 1);

   if (as->dev != bs->dev)
     /* Cannot return the difference the type is larger than int.  */
     return as->dev < bs->dev ? -1 : (as->dev == bs->dev ? 0 : 1);

   return strcmp (as->name, bs->name);
 }


 /* The search tree for existing mappings.  */
 void *__sem_mappings attribute_hidden;

 /* Lock to protect the search tree.  */
 int __sem_mappings_lock attribute_hidden = LLL_LOCK_INITIALIZER;


 /* Search for existing mapping and if possible add the one provided.  */
 static sem_t *
 check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
 {
   sem_t *result = SEM_FAILED;

   /* Get the information about the file.  */
   struct stat64 st;
   if (__fxstat64 (_STAT_VER, fd, &st) == 0)
     {
       /* Get the lock.  */
       lll_lock (__sem_mappings_lock, LLL_PRIVATE);

       /* Search for an existing mapping given the information we have.  */
       struct inuse_sem *fake;
       fake = (struct inuse_sem *) alloca (sizeof (*fake) + namelen);
       memcpy (fake->name, name, namelen);
       fake->dev = st.st_dev;
       fake->ino = st.st_ino;

       struct inuse_sem **foundp = __tfind (fake, &__sem_mappings,
 					   __sem_search);
       if (foundp != NULL)
 	{
 	  /* There is already a mapping.  Use it.  */
 	  result = (*foundp)->sem;
 	  ++(*foundp)->refcnt;
 	}
       else
 	{
 	  /* We haven't found a mapping.  Install ione.  */
 	  struct inuse_sem *newp;

 	  newp = (struct inuse_sem *) malloc (sizeof (*newp) + namelen);
 	  if (newp != NULL)
 	    {
 	      /* If the caller hasn't provided any map it now.  */
 	      if (existing == SEM_FAILED)
 		existing = (sem_t *) mmap (NULL, sizeof (sem_t),
 					   PROT_READ | PROT_WRITE, MAP_SHARED,
 					   fd, 0);

 	      newp->dev = st.st_dev;
 	      newp->ino = st.st_ino;
 	      newp->refcnt = 1;
 	      newp->sem = existing;
 	      memcpy (newp->name, name, namelen);

 	      /* Insert the new value.  */
 	      if (existing != MAP_FAILED
 		  && __tsearch (newp, &__sem_mappings, __sem_search) != NULL)
 		/* Successful.  */
 		result = existing;
 	      else
 		/* Something went wrong while inserting the new
 		   value.  We fail completely.  */
 		free (newp);
 	    }
 	}

       /* Release the lock.  */
       lll_unlock (__sem_mappings_lock, LLL_PRIVATE);
     }

   if (result != existing && existing != SEM_FAILED && existing != MAP_FAILED)
     {
       /* Do not disturb errno.  */
       int save = errno;
       munmap (existing, sizeof (sem_t));
       errno = save;
     }

   return result;
 }


 sem_t *
 sem_open (const char *name, int oflag, ...)
 {
   int fd;
   sem_t *result;

   /* Check that shared futexes are supported.  */
   int err = futex_supports_pshared (PTHREAD_PROCESS_SHARED);
   if (err != 0)
     {
       __set_errno (err);
       return SEM_FAILED;
     }

   /* Create the name of the final file in local variable SHM_NAME.  */
   SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX);

   /* Disable asynchronous cancellation.  */
 #ifdef __libc_ptf_call
   int state;
   __libc_ptf_call (__pthread_setcancelstate,
                    (PTHREAD_CANCEL_DISABLE, &state), 0);
 #endif

   /* If the semaphore object has to exist simply open it.  */
   if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
     {
     try_again:
       fd = __libc_open (shm_name,
 			(oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR);

       if (fd == -1)
 	{
 	  /* If we are supposed to create the file try this next.  */
 	  if ((oflag & O_CREAT) != 0 && errno == ENOENT)
 	    goto try_create;

 	  /* Return.  errno is already set.  */
 	}
       else
 	/* Check whether we already have this semaphore mapped and
 	   create one if necessary.  */
 	result = check_add_mapping (name, namelen, fd, SEM_FAILED);
     }
   else
     {
       /* We have to open a temporary file first since it must have the
 	 correct form before we can start using it.  */
       char *tmpfname;
       mode_t mode;
       unsigned int value;
       va_list ap;

     try_create:
       va_start (ap, oflag);

       mode = va_arg (ap, mode_t);
       value = va_arg (ap, unsigned int);

       va_end (ap);

       if (value > SEM_VALUE_MAX)
 	{
 	  __set_errno (EINVAL);
 	  result = SEM_FAILED;
 	  goto out;
 	}

       /* Create the initial file content.  */
       union
       {
 	sem_t initsem;
 	struct new_sem newsem;
       } sem;

 #if __HAVE_64B_ATOMICS
       sem.newsem.data = value;
 #else
       sem.newsem.value = value << SEM_VALUE_SHIFT;
       /* pad is used as a mutex on pre-v9 sparc and ignored otherwise.  */
       sem.newsem.pad = 0;
       sem.newsem.nwaiters = 0;
 #endif
       /* This always is a shared semaphore.  */
       sem.newsem.private = FUTEX_SHARED;

       /* Initialize the remaining bytes as well.  */
       memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0',
 	      sizeof (sem_t) - sizeof (struct new_sem));

       tmpfname = __alloca (shm_dirlen + sizeof SEM_SHM_PREFIX + 6);
       char *xxxxxx = __mempcpy (tmpfname, shm_dir, shm_dirlen);

       int retries = 0;
 #define NRETRIES 50
       while (1)
 	{
 	  /* Add the suffix for mktemp.  */
 	  strcpy (xxxxxx, "XXXXXX");

 	  /* We really want to use mktemp here.  We cannot use mkstemp
 	     since the file must be opened with a specific mode.  The
 	     mode cannot later be set since then we cannot apply the
 	     file create mask.  */
 	  if (__mktemp (tmpfname) == NULL)
 	    {
 	      result = SEM_FAILED;
 	      goto out;
 	    }

 	  /* Open the file.  Make sure we do not overwrite anything.  */
 	  fd = __libc_open (tmpfname, O_RDWR | O_CREAT | O_EXCL, mode);
 	  if (fd == -1)
 	    {
 	      if (errno == EEXIST)
 		{
 		  if (++retries < NRETRIES)
 		    continue;

 		  __set_errno (EAGAIN);
 		}

 	      result = SEM_FAILED;
 	      goto out;
 	    }

 	  /* We got a file.  */
 	  break;
 	}

       if (TEMP_FAILURE_RETRY (__libc_write (fd, &sem.initsem, sizeof (sem_t)))
 	  == sizeof (sem_t)
 	  /* Map the sem_t structure from the file.  */
 	  && (result = (sem_t *) mmap (NULL, sizeof (sem_t),
 				       PROT_READ | PROT_WRITE, MAP_SHARED,
 				       fd, 0)) != MAP_FAILED)
 	{
 	  /* Create the file.  Don't overwrite an existing file.  */
 	  if (link (tmpfname, shm_name) != 0)
 	    {
 	      /* Undo the mapping.  */
 	      (void) munmap (result, sizeof (sem_t));

 	      /* Reinitialize 'result'.  */
 	      result = SEM_FAILED;

 	      /* This failed.  If O_EXCL is not set and the problem was
 		 that the file exists, try again.  */
 	      if ((oflag & O_EXCL) == 0 && errno == EEXIST)
 		{
 		  /* Remove the file.  */
 		  (void) unlink (tmpfname);

 		  /* Close the file.  */
 		  (void) __libc_close (fd);

 		  goto try_again;
 		}
 	    }
 	  else
 	    /* Insert the mapping into the search tree.  This also
 	       determines whether another thread sneaked by and already
 	       added such a mapping despite the fact that we created it.  */
 	    result = check_add_mapping (name, namelen, fd, result);
 	}

       /* Now remove the temporary name.  This should never fail.  If
 	 it fails we leak a file name.  Better fix the kernel.  */
       (void) unlink (tmpfname);
     }

   /* Map the mmap error to the error we need.  */
   if (MAP_FAILED != (void *) SEM_FAILED && result == MAP_FAILED)
     result = SEM_FAILED;

   /* We don't need the file descriptor anymore.  */
   if (fd != -1)
     {
       /* Do not disturb errno.  */
       int save = errno;
       __libc_close (fd);
       errno = save;
     }

 out:
 #ifdef __libc_ptf_call
   __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
 #endif

   return result;
 }
	/* Copyright (C) 2002-2018 Free Software Foundation, Inc.
	This file is part of the GNU C Library.
	Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

	The GNU C Library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License as published by the Free Software Foundation; either
	version 2.1 of the License, or (at your option) any later version.

	The GNU C Library is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public
	License along with the GNU C Library; if not, see
	<http://www.gnu.org/licenses/>. */

	#include <errno.h>
	#include <fcntl.h>
	#include <pthread.h>
	#include <search.h>
	#include <semaphore.h>
	#include <stdarg.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <sys/mman.h>
	#include <sys/stat.h>
	#include "semaphoreP.h"
	#include <shm-directory.h>
	#include <futex-internal.h>
	#include <libc-lock.h>

	/* Comparison function for search of existing mapping. */
	int
	attribute_hidden
	__sem_search (const void a, const void b)
	{
	const struct inuse_sem as = (const struct inuse_sem ) a;
	const struct inuse_sem bs = (const struct inuse_sem ) b;

	if (as->ino != bs->ino)
	/* Cannot return the difference the type is larger than int. */
	return as->ino < bs->ino ? -1 : (as->ino == bs->ino ? 0 : 1);

	if (as->dev != bs->dev)
	/* Cannot return the difference the type is larger than int. */
	return as->dev < bs->dev ? -1 : (as->dev == bs->dev ? 0 : 1);

	return strcmp (as->name, bs->name);
	}


	/* The search tree for existing mappings. */
	void *__sem_mappings attribute_hidden;

	/* Lock to protect the search tree. */
	int __sem_mappings_lock attribute_hidden = LLL_LOCK_INITIALIZER;


	/* Search for existing mapping and if possible add the one provided. */
	static sem_t *
	check_add_mapping (const char name, size_t namelen, int fd, sem_t existing)
	{
	sem_t *result = SEM_FAILED;

	/* Get the information about the file. */
	struct stat64 st;
	if (__fxstat64 (_STAT_VER, fd, &st) == 0)
	{
	/* Get the lock. */
	lll_lock (__sem_mappings_lock, LLL_PRIVATE);

	/* Search for an existing mapping given the information we have. */
	struct inuse_sem *fake;
	fake = (struct inuse_sem ) alloca (sizeof (fake) + namelen);
	memcpy (fake->name, name, namelen);
	fake->dev = st.st_dev;
	fake->ino = st.st_ino;

	struct inuse_sem **foundp = __tfind (fake, &__sem_mappings,
	__sem_search);
	if (foundp != NULL)
	{
	/* There is already a mapping. Use it. */
	result = (*foundp)->sem;
	++(*foundp)->refcnt;
	}
	else
	{
	/* We haven't found a mapping. Install ione. */
	struct inuse_sem *newp;

	newp = (struct inuse_sem ) malloc (sizeof (newp) + namelen);
	if (newp != NULL)
	{
	/* If the caller hasn't provided any map it now. */
	if (existing == SEM_FAILED)
	existing = (sem_t *) mmap (NULL, sizeof (sem_t),
	PROT_READ \| PROT_WRITE, MAP_SHARED,
	fd, 0);

	newp->dev = st.st_dev;
	newp->ino = st.st_ino;
	newp->refcnt = 1;
	newp->sem = existing;
	memcpy (newp->name, name, namelen);

	/* Insert the new value. */
	if (existing != MAP_FAILED
	&& __tsearch (newp, &__sem_mappings, __sem_search) != NULL)
	/* Successful. */
	result = existing;
	else
	/* Something went wrong while inserting the new
	value. We fail completely. */
	free (newp);
	}
	}

	/* Release the lock. */
	lll_unlock (__sem_mappings_lock, LLL_PRIVATE);
	}

	if (result != existing && existing != SEM_FAILED && existing != MAP_FAILED)
	{
	/* Do not disturb errno. */
	int save = errno;
	munmap (existing, sizeof (sem_t));
	errno = save;
	}

	return result;
	}


	sem_t *
	sem_open (const char *name, int oflag, ...)
	{
	int fd;
	sem_t *result;

	/* Check that shared futexes are supported. */
	int err = futex_supports_pshared (PTHREAD_PROCESS_SHARED);
	if (err != 0)
	{
	__set_errno (err);
	return SEM_FAILED;
	}

	/* Create the name of the final file in local variable SHM_NAME. */
	SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX);

	/* Disable asynchronous cancellation. */
	#ifdef __libc_ptf_call
	int state;
	__libc_ptf_call (__pthread_setcancelstate,
	(PTHREAD_CANCEL_DISABLE, &state), 0);
	#endif

	/* If the semaphore object has to exist simply open it. */
	if ((oflag & O_CREAT) == 0 \|\| (oflag & O_EXCL) == 0)
	{
	try_again:
	fd = __libc_open (shm_name,
	(oflag & ~(O_CREAT\|O_ACCMODE)) \| O_NOFOLLOW \| O_RDWR);

	if (fd == -1)
	{
	/* If we are supposed to create the file try this next. */
	if ((oflag & O_CREAT) != 0 && errno == ENOENT)
	goto try_create;

	/* Return. errno is already set. */
	}
	else
	/* Check whether we already have this semaphore mapped and
	create one if necessary. */
	result = check_add_mapping (name, namelen, fd, SEM_FAILED);
	}
	else
	{
	/* We have to open a temporary file first since it must have the
	correct form before we can start using it. */
	char *tmpfname;
	mode_t mode;
	unsigned int value;
	va_list ap;

	try_create:
	va_start (ap, oflag);

	mode = va_arg (ap, mode_t);
	value = va_arg (ap, unsigned int);

	va_end (ap);

	if (value > SEM_VALUE_MAX)
	{
	__set_errno (EINVAL);
	result = SEM_FAILED;
	goto out;
	}

	/* Create the initial file content. */
	union
	{
	sem_t initsem;
	struct new_sem newsem;
	} sem;

	#if __HAVE_64B_ATOMICS
	sem.newsem.data = value;
	#else
	sem.newsem.value = value << SEM_VALUE_SHIFT;
	/* pad is used as a mutex on pre-v9 sparc and ignored otherwise. */
	sem.newsem.pad = 0;
	sem.newsem.nwaiters = 0;
	#endif
	/* This always is a shared semaphore. */
	sem.newsem.private = FUTEX_SHARED;

	/* Initialize the remaining bytes as well. */
	memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0',
	sizeof (sem_t) - sizeof (struct new_sem));

	tmpfname = __alloca (shm_dirlen + sizeof SEM_SHM_PREFIX + 6);
	char *xxxxxx = __mempcpy (tmpfname, shm_dir, shm_dirlen);

	int retries = 0;
	#define NRETRIES 50
	while (1)
	{
	/* Add the suffix for mktemp. */
	strcpy (xxxxxx, "XXXXXX");

	/* We really want to use mktemp here. We cannot use mkstemp
	since the file must be opened with a specific mode. The
	mode cannot later be set since then we cannot apply the
	file create mask. */
	if (__mktemp (tmpfname) == NULL)
	{
	result = SEM_FAILED;
	goto out;
	}

	/* Open the file. Make sure we do not overwrite anything. */
	fd = __libc_open (tmpfname, O_RDWR \| O_CREAT \| O_EXCL, mode);
	if (fd == -1)
	{
	if (errno == EEXIST)
	{
	if (++retries < NRETRIES)
	continue;

	__set_errno (EAGAIN);
	}

	result = SEM_FAILED;
	goto out;
	}

	/* We got a file. */
	break;
	}

	if (TEMP_FAILURE_RETRY (__libc_write (fd, &sem.initsem, sizeof (sem_t)))
	== sizeof (sem_t)
	/* Map the sem_t structure from the file. */
	&& (result = (sem_t *) mmap (NULL, sizeof (sem_t),
	PROT_READ \| PROT_WRITE, MAP_SHARED,
	fd, 0)) != MAP_FAILED)
	{
	/* Create the file. Don't overwrite an existing file. */
	if (link (tmpfname, shm_name) != 0)
	{
	/* Undo the mapping. */
	(void) munmap (result, sizeof (sem_t));

	/* Reinitialize 'result'. */
	result = SEM_FAILED;

	/* This failed. If O_EXCL is not set and the problem was
	that the file exists, try again. */
	if ((oflag & O_EXCL) == 0 && errno == EEXIST)
	{
	/* Remove the file. */
	(void) unlink (tmpfname);

	/* Close the file. */
	(void) __libc_close (fd);

	goto try_again;
	}
	}
	else
	/* Insert the mapping into the search tree. This also
	determines whether another thread sneaked by and already
	added such a mapping despite the fact that we created it. */
	result = check_add_mapping (name, namelen, fd, result);
	}

	/* Now remove the temporary name. This should never fail. If
	it fails we leak a file name. Better fix the kernel. */
	(void) unlink (tmpfname);
	}

	/* Map the mmap error to the error we need. */
	if (MAP_FAILED != (void *) SEM_FAILED && result == MAP_FAILED)
	result = SEM_FAILED;

	/* We don't need the file descriptor anymore. */
	if (fd != -1)
	{
	/* Do not disturb errno. */
	int save = errno;
	__libc_close (fd);
	errno = save;
	}

	out:
	#ifdef __libc_ptf_call
	__libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
	#endif

	return result;
	}