libc/bionic/system_properties.c - platform/bionic - Git at Google

 /*
  * Copyright (C) 2008 The Android Open Source Project
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <stddef.h>
 #include <errno.h>

 #include <sys/mman.h>

 #include <sys/socket.h>
 #include <sys/un.h>
 #include <sys/select.h>
 #include <sys/types.h>
 #include <netinet/in.h>
 #include <unistd.h>

 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
 #include <sys/_system_properties.h>

 #include <sys/atomics.h>

 static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;

 static unsigned dummy_props = 0;

 prop_area *__system_property_area__ = (void*) &dummy_props;

 int __system_properties_init(void)
 {
     prop_area *pa;
     int s, fd;
     unsigned sz;
     char *env;

     if(__system_property_area__ != ((void*) &dummy_props)) {
         return 0;
     }

     env = getenv("ANDROID_PROPERTY_WORKSPACE");
     if (!env) {
         return -1;
     }
     fd = atoi(env);
     env = strchr(env, ',');
     if (!env) {
         return -1;
     }
     sz = atoi(env + 1);

     pa = mmap(0, sz, PROT_READ, MAP_SHARED, fd, 0);

     if(pa == MAP_FAILED) {
         return -1;
     }

     if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
         munmap(pa, sz);
         return -1;
     }

     __system_property_area__ = pa;
     return 0;
 }

 const prop_info *__system_property_find_nth(unsigned n)
 {
     prop_area *pa = __system_property_area__;

     if(n >= pa->count) {
         return 0;
     } else {
         return TOC_TO_INFO(pa, pa->toc[n]);
     }
 }

 const prop_info *__system_property_find(const char *name)
 {
     prop_area *pa = __system_property_area__;
     unsigned count = pa->count;
     unsigned *toc = pa->toc;
     unsigned len = strlen(name);
     prop_info *pi;

     while(count--) {
         unsigned entry = *toc++;
         if(TOC_NAME_LEN(entry) != len) continue;

         pi = TOC_TO_INFO(pa, entry);
         if(memcmp(name, pi->name, len)) continue;

         return pi;
     }

     return 0;
 }

 int __system_property_read(const prop_info *pi, char *name, char *value)
 {
     unsigned serial, len;

     for(;;) {
         serial = pi->serial;
         while(SERIAL_DIRTY(serial)) {
             __futex_wait((volatile void *)&pi->serial, serial, 0);
             serial = pi->serial;
         }
         len = SERIAL_VALUE_LEN(serial);
         memcpy(value, pi->value, len + 1);
         if(serial == pi->serial) {
             if(name != 0) {
                 strcpy(name, pi->name);
             }
             return len;
         }
     }
 }

 int __system_property_get(const char *name, char *value)
 {
     const prop_info *pi = __system_property_find(name);

     if(pi != 0) {
         return __system_property_read(pi, 0, value);
     } else {
         value[0] = 0;
         return 0;
     }
 }


 static int send_prop_msg(prop_msg *msg)
 {
     struct sockaddr_un addr;
     socklen_t alen;
     size_t namelen;
     int s;
     int r;

     s = socket(AF_LOCAL, SOCK_STREAM, 0);
     if(s < 0) {
         return -1;
     }

     memset(&addr, 0, sizeof(addr));
     namelen = strlen(property_service_socket);
     strlcpy(addr.sun_path, property_service_socket, sizeof addr.sun_path);
     addr.sun_family = AF_LOCAL;
     alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;

     if(TEMP_FAILURE_RETRY(connect(s, (struct sockaddr *) &addr, alen) < 0)) {
         close(s);
         return -1;
     }

     r = TEMP_FAILURE_RETRY(send(s, msg, sizeof(prop_msg), 0));

     if(r == sizeof(prop_msg)) {
         r = 0;
     } else {
         r = -1;
     }

     close(s);
     return r;
 }

 int __system_property_set(const char *key, const char *value)
 {
     unsigned old_serial;
     volatile unsigned *serial;
     prop_msg msg;
     int err;
     prop_area *pa = __system_property_area__;
     int tries = 0;
     int update_seen = 0;

     if(key == 0) return -1;
     if(value == 0) value = "";
     if(strlen(key) >= PROP_NAME_MAX) return -1;
     if(strlen(value) >= PROP_VALUE_MAX) return -1;

     memset(&msg, 0, sizeof msg);
     msg.cmd = PROP_MSG_SETPROP;
     strlcpy(msg.name, key, sizeof msg.name);
     strlcpy(msg.value, value, sizeof msg.value);

     /* Note the system properties serial number before we do our update. */
     const prop_info *pi = __system_property_find(key);
     if(pi != NULL) {
         serial = &pi->serial;
     } else {
         serial = &pa->serial;
     }
     old_serial = *serial;

     err = send_prop_msg(&msg);
     if(err < 0) {
         return err;
     }

     /**
      * Wait for the shared memory page to be written back and be
      * visible in our address space before returning to the caller
      * who might reasonably expect subsequent reads to match what was
      * just written.
      *
      * Sleep 5 ms after failed checks and only wait up to a 500 ms
      * total, just in case the system property server fails to update
      * for whatever reason.
      */
     do {
         struct timespec timeout;
         timeout.tv_sec = 0;
         timeout.tv_nsec = 2500000;  // 2.5 ms

         if(tries++ > 0) {
             usleep(2500); // 2.5 ms
         }
         __futex_wait(serial, old_serial, &timeout);
         if(pi != NULL) {
             unsigned new_serial = *serial;
             /* Waiting on a specific prop_info to be updated. */
             if (old_serial != new_serial && !SERIAL_DIRTY(new_serial)) {
                 update_seen = 1;
             }
         } else {
             /* Waiting for a prop_info to be created. */
             const prop_info *new_pi = __system_property_find(key);
             if(new_pi != NULL && !SERIAL_DIRTY(new_pi->serial)) {
                 update_seen = 1;
             }
         }
     } while (!update_seen && tries < 100);

     return 0;
 }

 int __system_property_wait(const prop_info *pi)
 {
     unsigned n;
     if(pi == 0) {
         prop_area *pa = __system_property_area__;
         n = pa->serial;
         do {
             __futex_wait(&pa->serial, n, 0);
         } while(n == pa->serial);
     } else {
         n = pi->serial;
         do {
             __futex_wait((volatile void *)&pi->serial, n, 0);
         } while(n == pi->serial);
     }
     return 0;
 }
	/*
	* Copyright (C) 2008 The Android Open Source Project
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
	* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
	* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
	* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
	* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
	* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <stddef.h>
	#include <errno.h>

	#include <sys/mman.h>

	#include <sys/socket.h>
	#include <sys/un.h>
	#include <sys/select.h>
	#include <sys/types.h>
	#include <netinet/in.h>
	#include <unistd.h>

	#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
	#include <sys/_system_properties.h>

	#include <sys/atomics.h>

	static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;

	static unsigned dummy_props = 0;

	prop_area __system_property_area__ = (void) &dummy_props;

	int __system_properties_init(void)
	{
	prop_area *pa;
	int s, fd;
	unsigned sz;
	char *env;

	if(__system_property_area__ != ((void*) &dummy_props)) {
	return 0;
	}

	env = getenv("ANDROID_PROPERTY_WORKSPACE");
	if (!env) {
	return -1;
	}
	fd = atoi(env);
	env = strchr(env, ',');
	if (!env) {
	return -1;
	}
	sz = atoi(env + 1);

	pa = mmap(0, sz, PROT_READ, MAP_SHARED, fd, 0);

	if(pa == MAP_FAILED) {
	return -1;
	}

	if((pa->magic != PROP_AREA_MAGIC) \|\| (pa->version != PROP_AREA_VERSION)) {
	munmap(pa, sz);
	return -1;
	}

	__system_property_area__ = pa;
	return 0;
	}

	const prop_info *__system_property_find_nth(unsigned n)
	{
	prop_area *pa = __system_property_area__;

	if(n >= pa->count) {
	return 0;
	} else {
	return TOC_TO_INFO(pa, pa->toc[n]);
	}
	}

	const prop_info __system_property_find(const char name)
	{
	prop_area *pa = __system_property_area__;
	unsigned count = pa->count;
	unsigned *toc = pa->toc;
	unsigned len = strlen(name);
	prop_info *pi;

	while(count--) {
	unsigned entry = *toc++;
	if(TOC_NAME_LEN(entry) != len) continue;

	pi = TOC_TO_INFO(pa, entry);
	if(memcmp(name, pi->name, len)) continue;

	return pi;
	}

	return 0;
	}

	int __system_property_read(const prop_info pi, char name, char *value)
	{
	unsigned serial, len;

	for(;;) {
	serial = pi->serial;
	while(SERIAL_DIRTY(serial)) {
	__futex_wait((volatile void *)&pi->serial, serial, 0);
	serial = pi->serial;
	}
	len = SERIAL_VALUE_LEN(serial);
	memcpy(value, pi->value, len + 1);
	if(serial == pi->serial) {
	if(name != 0) {
	strcpy(name, pi->name);
	}
	return len;
	}
	}
	}

	int __system_property_get(const char name, char value)
	{
	const prop_info *pi = __system_property_find(name);

	if(pi != 0) {
	return __system_property_read(pi, 0, value);
	} else {
	value[0] = 0;
	return 0;
	}
	}


	static int send_prop_msg(prop_msg *msg)
	{
	struct sockaddr_un addr;
	socklen_t alen;
	size_t namelen;
	int s;
	int r;

	s = socket(AF_LOCAL, SOCK_STREAM, 0);
	if(s < 0) {
	return -1;
	}

	memset(&addr, 0, sizeof(addr));
	namelen = strlen(property_service_socket);
	strlcpy(addr.sun_path, property_service_socket, sizeof addr.sun_path);
	addr.sun_family = AF_LOCAL;
	alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;

	if(TEMP_FAILURE_RETRY(connect(s, (struct sockaddr *) &addr, alen) < 0)) {
	close(s);
	return -1;
	}

	r = TEMP_FAILURE_RETRY(send(s, msg, sizeof(prop_msg), 0));

	if(r == sizeof(prop_msg)) {
	r = 0;
	} else {
	r = -1;
	}

	close(s);
	return r;
	}

	int __system_property_set(const char key, const char value)
	{
	unsigned old_serial;
	volatile unsigned *serial;
	prop_msg msg;
	int err;
	prop_area *pa = __system_property_area__;
	int tries = 0;
	int update_seen = 0;

	if(key == 0) return -1;
	if(value == 0) value = "";
	if(strlen(key) >= PROP_NAME_MAX) return -1;
	if(strlen(value) >= PROP_VALUE_MAX) return -1;

	memset(&msg, 0, sizeof msg);
	msg.cmd = PROP_MSG_SETPROP;
	strlcpy(msg.name, key, sizeof msg.name);
	strlcpy(msg.value, value, sizeof msg.value);

	/* Note the system properties serial number before we do our update. */
	const prop_info *pi = __system_property_find(key);
	if(pi != NULL) {
	serial = &pi->serial;
	} else {
	serial = &pa->serial;
	}
	old_serial = *serial;

	err = send_prop_msg(&msg);
	if(err < 0) {
	return err;
	}

	/**
	* Wait for the shared memory page to be written back and be
	* visible in our address space before returning to the caller
	* who might reasonably expect subsequent reads to match what was
	* just written.
	*
	* Sleep 5 ms after failed checks and only wait up to a 500 ms
	* total, just in case the system property server fails to update
	* for whatever reason.
	*/
	do {
	struct timespec timeout;
	timeout.tv_sec = 0;
	timeout.tv_nsec = 2500000; // 2.5 ms

	if(tries++ > 0) {
	usleep(2500); // 2.5 ms
	}
	__futex_wait(serial, old_serial, &timeout);
	if(pi != NULL) {
	unsigned new_serial = *serial;
	/* Waiting on a specific prop_info to be updated. */
	if (old_serial != new_serial && !SERIAL_DIRTY(new_serial)) {
	update_seen = 1;
	}
	} else {
	/* Waiting for a prop_info to be created. */
	const prop_info *new_pi = __system_property_find(key);
	if(new_pi != NULL && !SERIAL_DIRTY(new_pi->serial)) {
	update_seen = 1;
	}
	}
	} while (!update_seen && tries < 100);

	return 0;
	}

	int __system_property_wait(const prop_info *pi)
	{
	unsigned n;
	if(pi == 0) {
	prop_area *pa = __system_property_area__;
	n = pa->serial;
	do {
	__futex_wait(&pa->serial, n, 0);
	} while(n == pa->serial);
	} else {
	n = pi->serial;
	do {
	__futex_wait((volatile void *)&pi->serial, n, 0);
	} while(n == pi->serial);
	}
	return 0;
	}