c16961b8c3
Check that the permissions on the properties file are exactly as we expect them to be. Make sure we close the fd if fstat fails. Refactor the code slightly. Change-Id: I5503fd58c3b8093ce7e6d05920748ed70eaf8e2c
296 lines
8 KiB
C
296 lines
8 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <stddef.h>
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#include <errno.h>
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#include <poll.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <sys/mman.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <sys/select.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <unistd.h>
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#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
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#include <sys/_system_properties.h>
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#include <sys/atomics.h>
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static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
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static unsigned dummy_props = 0;
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prop_area *__system_property_area__ = (void*) &dummy_props;
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static int get_fd_from_env(void)
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{
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char *env = getenv("ANDROID_PROPERTY_WORKSPACE");
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if (!env) {
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return -1;
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}
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return atoi(env);
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}
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int __system_properties_init(void)
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{
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bool fromFile = true;
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int result = -1;
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if(__system_property_area__ != ((void*) &dummy_props)) {
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return 0;
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}
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int fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW);
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if ((fd < 0) && (errno == ENOENT)) {
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/*
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* For backwards compatibility, if the file doesn't
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* exist, we use the environment to get the file descriptor.
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* For security reasons, we only use this backup if the kernel
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* returns ENOENT. We don't want to use the backup if the kernel
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* returns other errors such as ENOMEM or ENFILE, since it
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* might be possible for an external program to trigger this
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* condition.
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*/
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fd = get_fd_from_env();
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fromFile = false;
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}
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if (fd < 0) {
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return -1;
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}
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struct stat fd_stat;
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if (fstat(fd, &fd_stat) < 0) {
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goto cleanup;
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}
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if ((fd_stat.st_uid != 0)
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|| (fd_stat.st_gid != 0)
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|| ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0)) {
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goto cleanup;
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}
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prop_area *pa = mmap(0, fd_stat.st_size, PROT_READ, MAP_SHARED, fd, 0);
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if (pa == MAP_FAILED) {
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goto cleanup;
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}
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if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
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munmap(pa, fd_stat.st_size);
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goto cleanup;
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}
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__system_property_area__ = pa;
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result = 0;
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cleanup:
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if (fromFile) {
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close(fd);
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}
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return result;
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}
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const prop_info *__system_property_find_nth(unsigned n)
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{
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prop_area *pa = __system_property_area__;
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if(n >= pa->count) {
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return 0;
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} else {
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return TOC_TO_INFO(pa, pa->toc[n]);
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}
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}
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const prop_info *__system_property_find(const char *name)
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{
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prop_area *pa = __system_property_area__;
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unsigned count = pa->count;
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unsigned *toc = pa->toc;
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unsigned len = strlen(name);
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prop_info *pi;
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while(count--) {
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unsigned entry = *toc++;
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if(TOC_NAME_LEN(entry) != len) continue;
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pi = TOC_TO_INFO(pa, entry);
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if(memcmp(name, pi->name, len)) continue;
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return pi;
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}
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return 0;
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}
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int __system_property_read(const prop_info *pi, char *name, char *value)
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{
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unsigned serial, len;
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for(;;) {
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serial = pi->serial;
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while(SERIAL_DIRTY(serial)) {
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__futex_wait((volatile void *)&pi->serial, serial, 0);
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serial = pi->serial;
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}
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len = SERIAL_VALUE_LEN(serial);
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memcpy(value, pi->value, len + 1);
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if(serial == pi->serial) {
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if(name != 0) {
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strcpy(name, pi->name);
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}
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return len;
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}
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}
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}
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int __system_property_get(const char *name, char *value)
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{
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const prop_info *pi = __system_property_find(name);
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if(pi != 0) {
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return __system_property_read(pi, 0, value);
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} else {
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value[0] = 0;
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return 0;
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}
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}
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static int send_prop_msg(prop_msg *msg)
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{
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struct pollfd pollfds[1];
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struct sockaddr_un addr;
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socklen_t alen;
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size_t namelen;
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int s;
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int r;
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int result = -1;
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s = socket(AF_LOCAL, SOCK_STREAM, 0);
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if(s < 0) {
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return result;
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}
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memset(&addr, 0, sizeof(addr));
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namelen = strlen(property_service_socket);
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strlcpy(addr.sun_path, property_service_socket, sizeof addr.sun_path);
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addr.sun_family = AF_LOCAL;
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alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;
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if(TEMP_FAILURE_RETRY(connect(s, (struct sockaddr *) &addr, alen)) < 0) {
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close(s);
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return result;
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}
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r = TEMP_FAILURE_RETRY(send(s, msg, sizeof(prop_msg), 0));
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if(r == sizeof(prop_msg)) {
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// We successfully wrote to the property server but now we
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// wait for the property server to finish its work. It
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// acknowledges its completion by closing the socket so we
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// poll here (on nothing), waiting for the socket to close.
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// If you 'adb shell setprop foo bar' you'll see the POLLHUP
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// once the socket closes. Out of paranoia we cap our poll
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// at 250 ms.
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pollfds[0].fd = s;
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pollfds[0].events = 0;
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r = TEMP_FAILURE_RETRY(poll(pollfds, 1, 250 /* ms */));
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if (r == 1 && (pollfds[0].revents & POLLHUP) != 0) {
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result = 0;
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} else {
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// Ignore the timeout and treat it like a success anyway.
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// The init process is single-threaded and its property
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// service is sometimes slow to respond (perhaps it's off
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// starting a child process or something) and thus this
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// times out and the caller thinks it failed, even though
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// it's still getting around to it. So we fake it here,
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// mostly for ctl.* properties, but we do try and wait 250
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// ms so callers who do read-after-write can reliably see
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// what they've written. Most of the time.
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// TODO: fix the system properties design.
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result = 0;
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}
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}
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close(s);
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return result;
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}
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int __system_property_set(const char *key, const char *value)
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{
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int err;
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prop_msg msg;
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if(key == 0) return -1;
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if(value == 0) value = "";
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if(strlen(key) >= PROP_NAME_MAX) return -1;
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if(strlen(value) >= PROP_VALUE_MAX) return -1;
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memset(&msg, 0, sizeof msg);
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msg.cmd = PROP_MSG_SETPROP;
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strlcpy(msg.name, key, sizeof msg.name);
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strlcpy(msg.value, value, sizeof msg.value);
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err = send_prop_msg(&msg);
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if(err < 0) {
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return err;
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}
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return 0;
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}
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int __system_property_wait(const prop_info *pi)
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{
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unsigned n;
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if(pi == 0) {
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prop_area *pa = __system_property_area__;
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n = pa->serial;
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do {
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__futex_wait(&pa->serial, n, 0);
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} while(n == pa->serial);
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} else {
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n = pi->serial;
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do {
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__futex_wait((volatile void *)&pi->serial, n, 0);
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} while(n == pi->serial);
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}
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return 0;
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}
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