3e786987b5
This isn't declared in any header file. Bug: 14970171 Change-Id: Ib9fce61343dfb6b6ccd7e1430e1a6e34e4e869df
741 lines
20 KiB
C++
741 lines
20 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 <new>
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#include <stdio.h>
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#include <stdint.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 <string.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/system_properties.h>
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#include <sys/atomics.h>
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#include "private/bionic_atomic_inline.h"
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#include "private/bionic_macros.h"
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#define ALIGN(x, a) (((x) + (a - 1)) & ~(a - 1))
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static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
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/*
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* Properties are stored in a hybrid trie/binary tree structure.
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* Each property's name is delimited at '.' characters, and the tokens are put
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* into a trie structure. Siblings at each level of the trie are stored in a
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* binary tree. For instance, "ro.secure"="1" could be stored as follows:
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*
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* +-----+ children +----+ children +--------+
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* | |-------------->| ro |-------------->| secure |
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* +-----+ +----+ +--------+
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* / \ / |
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* left / \ right left / | prop +===========+
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* v v v +-------->| ro.secure |
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* +-----+ +-----+ +-----+ +-----------+
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* | net | | sys | | com | | 1 |
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* +-----+ +-----+ +-----+ +===========+
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*/
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// Represents a node in the trie.
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struct prop_bt {
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uint8_t namelen;
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uint8_t reserved[3];
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volatile uint32_t prop;
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volatile uint32_t left;
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volatile uint32_t right;
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volatile uint32_t children;
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char name[0];
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prop_bt(const char *name, const uint8_t name_length) {
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this->namelen = name_length;
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memcpy(this->name, name, name_length);
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this->name[name_length] = '\0';
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ANDROID_MEMBAR_FULL();
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}
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private:
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DISALLOW_COPY_AND_ASSIGN(prop_bt);
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};
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struct prop_area {
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uint32_t bytes_used;
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volatile uint32_t serial;
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uint32_t magic;
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uint32_t version;
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uint32_t reserved[28];
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char data[0];
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prop_area(const uint32_t magic, const uint32_t version) :
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serial(0), magic(magic), version(version) {
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memset(reserved, 0, sizeof(reserved));
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// Allocate enough space for the root node.
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bytes_used = sizeof(prop_bt);
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}
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private:
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DISALLOW_COPY_AND_ASSIGN(prop_area);
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};
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struct prop_info {
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volatile uint32_t serial;
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char value[PROP_VALUE_MAX];
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char name[0];
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prop_info(const char *name, const uint8_t namelen, const char *value,
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const uint8_t valuelen) {
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memcpy(this->name, name, namelen);
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this->name[namelen] = '\0';
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this->serial = (valuelen << 24);
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memcpy(this->value, value, valuelen);
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this->value[valuelen] = '\0';
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ANDROID_MEMBAR_FULL();
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}
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private:
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DISALLOW_COPY_AND_ASSIGN(prop_info);
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};
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struct find_nth_cookie {
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uint32_t count;
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const uint32_t n;
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const prop_info *pi;
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find_nth_cookie(uint32_t n) : count(0), n(n), pi(NULL) {
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}
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};
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static char property_filename[PATH_MAX] = PROP_FILENAME;
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static bool compat_mode = false;
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static size_t pa_data_size;
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static size_t pa_size;
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// NOTE: This isn't static because system_properties_compat.c
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// requires it.
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prop_area *__system_property_area__ = NULL;
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static int get_fd_from_env(void)
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{
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// This environment variable consistes of two decimal integer
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// values separated by a ",". The first value is a file descriptor
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// and the second is the size of the system properties area. The
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// size is currently unused.
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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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static int map_prop_area_rw()
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{
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/* dev is a tmpfs that we can use to carve a shared workspace
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* out of, so let's do that...
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*/
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const int fd = open(property_filename,
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O_RDWR | O_CREAT | O_NOFOLLOW | O_CLOEXEC | O_EXCL, 0444);
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if (fd < 0) {
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if (errno == EACCES) {
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/* for consistency with the case where the process has already
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* mapped the page in and segfaults when trying to write to it
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*/
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abort();
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}
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return -1;
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}
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// TODO: Is this really required ? Does android run on any kernels that
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// don't support O_CLOEXEC ?
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const int ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
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if (ret < 0) {
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close(fd);
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return -1;
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}
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if (ftruncate(fd, PA_SIZE) < 0) {
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close(fd);
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return -1;
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}
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pa_size = PA_SIZE;
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pa_data_size = pa_size - sizeof(prop_area);
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compat_mode = false;
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void *const memory_area = mmap(NULL, pa_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (memory_area == MAP_FAILED) {
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close(fd);
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return -1;
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}
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prop_area *pa = new(memory_area) prop_area(PROP_AREA_MAGIC, PROP_AREA_VERSION);
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/* plug into the lib property services */
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__system_property_area__ = pa;
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close(fd);
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return 0;
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}
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static int map_fd_ro(const int fd) {
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struct stat fd_stat;
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if (fstat(fd, &fd_stat) < 0) {
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return -1;
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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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|| (fd_stat.st_size < static_cast<off_t>(sizeof(prop_area))) ) {
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return -1;
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}
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pa_size = fd_stat.st_size;
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pa_data_size = pa_size - sizeof(prop_area);
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void* const map_result = mmap(NULL, pa_size, PROT_READ, MAP_SHARED, fd, 0);
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if (map_result == MAP_FAILED) {
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return -1;
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}
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prop_area* pa = reinterpret_cast<prop_area*>(map_result);
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if ((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION &&
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pa->version != PROP_AREA_VERSION_COMPAT)) {
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munmap(pa, pa_size);
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return -1;
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}
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if (pa->version == PROP_AREA_VERSION_COMPAT) {
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compat_mode = true;
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}
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__system_property_area__ = pa;
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return 0;
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}
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static int map_prop_area()
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{
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int fd(open(property_filename, O_RDONLY | O_NOFOLLOW | O_CLOEXEC));
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if (fd >= 0) {
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/* For old kernels that don't support O_CLOEXEC */
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const int ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
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if (ret < 0) {
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close(fd);
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return -1;
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}
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}
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bool close_fd = true;
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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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close_fd = 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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const int map_result = map_fd_ro(fd);
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if (close_fd) {
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close(fd);
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}
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return map_result;
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}
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static void *allocate_obj(const size_t size, uint32_t *const off)
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{
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prop_area *pa = __system_property_area__;
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const size_t aligned = ALIGN(size, sizeof(uint32_t));
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if (pa->bytes_used + aligned > pa_data_size) {
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return NULL;
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}
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*off = pa->bytes_used;
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pa->bytes_used += aligned;
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return pa->data + *off;
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}
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static prop_bt *new_prop_bt(const char *name, uint8_t namelen, uint32_t *const off)
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{
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uint32_t new_offset;
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void *const offset = allocate_obj(sizeof(prop_bt) + namelen + 1, &new_offset);
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if (offset) {
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prop_bt* bt = new(offset) prop_bt(name, namelen);
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*off = new_offset;
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return bt;
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}
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return NULL;
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}
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static prop_info *new_prop_info(const char *name, uint8_t namelen,
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const char *value, uint8_t valuelen, uint32_t *const off)
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{
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uint32_t off_tmp;
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void* const offset = allocate_obj(sizeof(prop_info) + namelen + 1, &off_tmp);
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if (offset) {
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prop_info* info = new(offset) prop_info(name, namelen, value, valuelen);
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*off = off_tmp;
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return info;
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}
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return NULL;
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}
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static void *to_prop_obj(const uint32_t off)
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{
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if (off > pa_data_size)
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return NULL;
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if (!__system_property_area__)
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return NULL;
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return (__system_property_area__->data + off);
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}
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static prop_bt *root_node()
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{
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return reinterpret_cast<prop_bt*>(to_prop_obj(0));
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}
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static int cmp_prop_name(const char *one, uint8_t one_len, const char *two,
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uint8_t two_len)
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{
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if (one_len < two_len)
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return -1;
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else if (one_len > two_len)
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return 1;
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else
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return strncmp(one, two, one_len);
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}
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static prop_bt *find_prop_bt(prop_bt *const bt, const char *name,
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uint8_t namelen, bool alloc_if_needed)
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{
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prop_bt* current = bt;
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while (true) {
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if (!current) {
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return NULL;
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}
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const int ret = cmp_prop_name(name, namelen, current->name, current->namelen);
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if (ret == 0) {
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return current;
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}
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if (ret < 0) {
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if (current->left) {
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current = reinterpret_cast<prop_bt*>(to_prop_obj(current->left));
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} else {
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if (!alloc_if_needed) {
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return NULL;
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}
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// Note that there isn't a race condition here. "clients" never
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// reach this code-path since It's only the (single threaded) server
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// that allocates new nodes. Though "bt->left" is volatile, it can't
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// have changed since the last value was last read.
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uint32_t new_offset = 0;
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prop_bt* new_bt = new_prop_bt(name, namelen, &new_offset);
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if (new_bt) {
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current->left = new_offset;
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}
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return new_bt;
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}
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} else {
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if (current->right) {
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current = reinterpret_cast<prop_bt*>(to_prop_obj(current->right));
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} else {
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if (!alloc_if_needed) {
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return NULL;
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}
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uint32_t new_offset;
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prop_bt* new_bt = new_prop_bt(name, namelen, &new_offset);
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if (new_bt) {
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current->right = new_offset;
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}
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return new_bt;
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}
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}
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}
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}
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static const prop_info *find_property(prop_bt *const trie, const char *name,
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uint8_t namelen, const char *value, uint8_t valuelen,
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bool alloc_if_needed)
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{
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if (!trie) return NULL;
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const char *remaining_name = name;
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prop_bt* current = trie;
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while (true) {
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const char *sep = strchr(remaining_name, '.');
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const bool want_subtree = (sep != NULL);
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const uint8_t substr_size = (want_subtree) ?
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sep - remaining_name : strlen(remaining_name);
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if (!substr_size) {
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return NULL;
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}
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prop_bt* root = NULL;
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if (current->children) {
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root = reinterpret_cast<prop_bt*>(to_prop_obj(current->children));
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} else if (alloc_if_needed) {
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uint32_t new_bt_offset;
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root = new_prop_bt(remaining_name, substr_size, &new_bt_offset);
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if (root) {
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current->children = new_bt_offset;
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}
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}
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if (!root) {
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return NULL;
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}
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current = find_prop_bt(root, remaining_name, substr_size, alloc_if_needed);
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if (!current) {
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return NULL;
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}
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if (!want_subtree)
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break;
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remaining_name = sep + 1;
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}
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if (current->prop) {
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return reinterpret_cast<prop_info*>(to_prop_obj(current->prop));
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} else if (alloc_if_needed) {
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uint32_t new_info_offset;
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prop_info* new_info = new_prop_info(name, namelen, value, valuelen, &new_info_offset);
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if (new_info) {
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current->prop = new_info_offset;
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}
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return new_info;
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} else {
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return NULL;
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}
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}
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static int send_prop_msg(const prop_msg *msg)
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{
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const int fd = socket(AF_LOCAL, SOCK_STREAM, 0);
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if (fd < 0) {
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return -1;
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}
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const size_t namelen = strlen(property_service_socket);
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sockaddr_un addr;
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memset(&addr, 0, sizeof(addr));
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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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socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
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if (TEMP_FAILURE_RETRY(connect(fd, reinterpret_cast<sockaddr*>(&addr), alen)) < 0) {
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close(fd);
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return -1;
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}
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const int num_bytes = TEMP_FAILURE_RETRY(send(fd, msg, sizeof(prop_msg), 0));
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int result = -1;
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if (num_bytes == 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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pollfd pollfds[1];
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pollfds[0].fd = fd;
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pollfds[0].events = 0;
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const int poll_result = TEMP_FAILURE_RETRY(poll(pollfds, 1, 250 /* ms */));
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if (poll_result == 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
|
|
// ms so callers who do read-after-write can reliably see
|
|
// what they've written. Most of the time.
|
|
// TODO: fix the system properties design.
|
|
result = 0;
|
|
}
|
|
}
|
|
|
|
close(fd);
|
|
return result;
|
|
}
|
|
|
|
static void find_nth_fn(const prop_info *pi, void *ptr)
|
|
{
|
|
find_nth_cookie *cookie = reinterpret_cast<find_nth_cookie*>(ptr);
|
|
|
|
if (cookie->n == cookie->count)
|
|
cookie->pi = pi;
|
|
|
|
cookie->count++;
|
|
}
|
|
|
|
static int foreach_property(const uint32_t off,
|
|
void (*propfn)(const prop_info *pi, void *cookie), void *cookie)
|
|
{
|
|
prop_bt *trie = reinterpret_cast<prop_bt*>(to_prop_obj(off));
|
|
if (!trie)
|
|
return -1;
|
|
|
|
if (trie->left) {
|
|
const int err = foreach_property(trie->left, propfn, cookie);
|
|
if (err < 0)
|
|
return -1;
|
|
}
|
|
if (trie->prop) {
|
|
prop_info *info = reinterpret_cast<prop_info*>(to_prop_obj(trie->prop));
|
|
if (!info)
|
|
return -1;
|
|
propfn(info, cookie);
|
|
}
|
|
if (trie->children) {
|
|
const int err = foreach_property(trie->children, propfn, cookie);
|
|
if (err < 0)
|
|
return -1;
|
|
}
|
|
if (trie->right) {
|
|
const int err = foreach_property(trie->right, propfn, cookie);
|
|
if (err < 0)
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __system_properties_init()
|
|
{
|
|
return map_prop_area();
|
|
}
|
|
|
|
int __system_property_set_filename(const char *filename)
|
|
{
|
|
size_t len = strlen(filename);
|
|
if (len >= sizeof(property_filename))
|
|
return -1;
|
|
|
|
strcpy(property_filename, filename);
|
|
return 0;
|
|
}
|
|
|
|
int __system_property_area_init()
|
|
{
|
|
return map_prop_area_rw();
|
|
}
|
|
|
|
const prop_info *__system_property_find(const char *name)
|
|
{
|
|
if (__predict_false(compat_mode)) {
|
|
return __system_property_find_compat(name);
|
|
}
|
|
return find_property(root_node(), name, strlen(name), NULL, 0, false);
|
|
}
|
|
|
|
int __system_property_read(const prop_info *pi, char *name, char *value)
|
|
{
|
|
if (__predict_false(compat_mode)) {
|
|
return __system_property_read_compat(pi, name, value);
|
|
}
|
|
|
|
while (true) {
|
|
uint32_t serial = __system_property_serial(pi);
|
|
size_t len = SERIAL_VALUE_LEN(serial);
|
|
memcpy(value, pi->value, len + 1);
|
|
ANDROID_MEMBAR_FULL();
|
|
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;
|
|
}
|
|
}
|
|
|
|
int __system_property_set(const char *key, const char *value)
|
|
{
|
|
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;
|
|
|
|
prop_msg msg;
|
|
memset(&msg, 0, sizeof msg);
|
|
msg.cmd = PROP_MSG_SETPROP;
|
|
strlcpy(msg.name, key, sizeof msg.name);
|
|
strlcpy(msg.value, value, sizeof msg.value);
|
|
|
|
const int err = send_prop_msg(&msg);
|
|
if (err < 0) {
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __system_property_update(prop_info *pi, const char *value, unsigned int len)
|
|
{
|
|
prop_area *pa = __system_property_area__;
|
|
|
|
if (len >= PROP_VALUE_MAX)
|
|
return -1;
|
|
|
|
pi->serial = pi->serial | 1;
|
|
ANDROID_MEMBAR_FULL();
|
|
memcpy(pi->value, value, len + 1);
|
|
ANDROID_MEMBAR_FULL();
|
|
pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
|
|
__futex_wake(&pi->serial, INT32_MAX);
|
|
|
|
pa->serial++;
|
|
__futex_wake(&pa->serial, INT32_MAX);
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __system_property_add(const char *name, unsigned int namelen,
|
|
const char *value, unsigned int valuelen)
|
|
{
|
|
prop_area *pa = __system_property_area__;
|
|
const prop_info *pi;
|
|
|
|
if (namelen >= PROP_NAME_MAX)
|
|
return -1;
|
|
if (valuelen >= PROP_VALUE_MAX)
|
|
return -1;
|
|
if (namelen < 1)
|
|
return -1;
|
|
|
|
pi = find_property(root_node(), name, namelen, value, valuelen, true);
|
|
if (!pi)
|
|
return -1;
|
|
|
|
pa->serial++;
|
|
__futex_wake(&pa->serial, INT32_MAX);
|
|
return 0;
|
|
}
|
|
|
|
unsigned int __system_property_serial(const prop_info *pi)
|
|
{
|
|
uint32_t serial = pi->serial;
|
|
while (SERIAL_DIRTY(serial)) {
|
|
__futex_wait(const_cast<volatile uint32_t*>(&pi->serial), serial, NULL);
|
|
serial = pi->serial;
|
|
}
|
|
return serial;
|
|
}
|
|
|
|
unsigned int __system_property_wait_any(unsigned int serial)
|
|
{
|
|
prop_area *pa = __system_property_area__;
|
|
|
|
do {
|
|
__futex_wait(&pa->serial, serial, NULL);
|
|
} while (pa->serial == serial);
|
|
|
|
return pa->serial;
|
|
}
|
|
|
|
const prop_info *__system_property_find_nth(unsigned n)
|
|
{
|
|
find_nth_cookie cookie(n);
|
|
|
|
const int err = __system_property_foreach(find_nth_fn, &cookie);
|
|
if (err < 0) {
|
|
return NULL;
|
|
}
|
|
|
|
return cookie.pi;
|
|
}
|
|
|
|
int __system_property_foreach(void (*propfn)(const prop_info *pi, void *cookie),
|
|
void *cookie)
|
|
{
|
|
if (__predict_false(compat_mode)) {
|
|
return __system_property_foreach_compat(propfn, cookie);
|
|
}
|
|
|
|
return foreach_property(0, propfn, cookie);
|
|
}
|