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bionic: make property area expandable

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The property area is initially one 4K region, automatically expanding as
needed up to 64 regions.

To avoid duplicating code, __system_property_area_init() now allocates
and initializes the first region (previously it was allocated in init's
init_property_area() and initialized in bionic).  For testing purposes,
__system_property_set_filename() may be used to override the file used
to map in regions.

Signed-off-by: Greg Hackmann <ghackmann@google.com>

(cherry picked from commit d32969701b)

Change-Id: I038d451fe8849b0c4863663eec6f57f6521bf4a7
This commit is contained in:
Greg Hackmann
2013-02-13 14:41:48 -08:00
committed by Colin Cross
parent 0ea1d5c0ae
commit cb215a7e9e
4 changed files with 264 additions and 74 deletions
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187
libc/bionic/system_properties.c
View File

@@ -55,7 +55,6 @@ struct prop_area {
unsigned volatile serial;
unsigned magic;
unsigned version;
unsigned reserved[4];
unsigned toc[1];
};
@@ -70,10 +69,9 @@ struct prop_info {
typedef struct prop_info prop_info;
static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
static char property_filename[PATH_MAX] = PROP_FILENAME;
static unsigned dummy_props = 0;
prop_area *__system_property_area__ = (void*) &dummy_props;
prop_area *__system_property_regions__[PA_REGION_COUNT] = { NULL, };
static int get_fd_from_env(void)
{
@@ -86,27 +84,79 @@ static int get_fd_from_env(void)
return atoi(env);
}
void __system_property_area_init(void *data)
static int map_prop_region_rw(size_t region)
{
prop_area *pa = data;
prop_area *pa;
int fd;
size_t offset = region * PA_SIZE;
if (__system_property_regions__[region]) {
return 0;
}
/* dev is a tmpfs that we can use to carve a shared workspace
* out of, so let's do that...
*/
fd = open(property_filename, O_RDWR | O_CREAT | O_NOFOLLOW, 0644);
if (fd < 0) {
if (errno == EACCES) {
/* for consistency with the case where the process has already
* mapped the page in and segfaults when trying to write to it
*/
abort();
}
return -1;
}
if (ftruncate(fd, offset + PA_SIZE) < 0)
goto out;
pa = mmap(NULL, PA_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
if(pa == MAP_FAILED)
goto out;
memset(pa, 0, PA_SIZE);
pa->magic = PROP_AREA_MAGIC;
pa->version = PROP_AREA_VERSION;
/* plug into the lib property services */
__system_property_area__ = pa;
__system_property_regions__[region] = pa;
close(fd);
return 0;
out:
close(fd);
return -1;
}
int __system_properties_init(void)
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_region_rw(0);
}
static int map_prop_region(size_t region)
{
bool fromFile = true;
bool swapped;
size_t offset = region * PA_SIZE;
int result = -1;
if(__system_property_area__ != ((void*) &dummy_props)) {
if(__system_property_regions__[region]) {
return 0;
}
int fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW);
int fd = open(property_filename, O_RDONLY | O_NOFOLLOW);
if ((fd < 0) && (errno == ENOENT)) {
/*
@@ -133,23 +183,33 @@ int __system_properties_init(void)
if ((fd_stat.st_uid != 0)
|| (fd_stat.st_gid != 0)
|| ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0)) {
|| ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0)
|| (fd_stat.st_size < offset + PA_SIZE) ) {
goto cleanup;
}
prop_area *pa = mmap(NULL, fd_stat.st_size, PROT_READ, MAP_SHARED, fd, 0);
prop_area *pa = mmap(NULL, PA_SIZE, PROT_READ, MAP_SHARED, fd, offset);
if (pa == MAP_FAILED) {
goto cleanup;
}
if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
munmap(pa, fd_stat.st_size);
munmap(pa, PA_SIZE);
goto cleanup;
}
__system_property_area__ = pa;
result = 0;
swapped = __sync_bool_compare_and_swap(&__system_property_regions__[region],
NULL, pa);
if (!swapped) {
/**
* In the event of a race either mapping is equally good, so
* the thread that lost can just throw its mapping away and proceed as
* normal.
*/
munmap(pa, PA_SIZE);
}
cleanup:
if (fromFile) {
@@ -159,17 +219,31 @@ cleanup:
return result;
}
int __system_properties_init()
{
return map_prop_region(0);
}
int __system_property_foreach(
void (*propfn)(const prop_info *pi, void *cookie),
void *cookie)
{
prop_area *pa = __system_property_area__;
unsigned i;
size_t region;
for (i = 0; i < pa->count; i++) {
unsigned entry = pa->toc[i];
prop_info *pi = TOC_TO_INFO(pa, entry);
propfn(pi, cookie);
for (region = 0; region < PA_REGION_COUNT; region++) {
prop_area *pa;
unsigned i;
int err = map_prop_region(region);
if (err < 0)
break;
pa = __system_property_regions__[region];
for (i = 0; i < pa->count; i++) {
unsigned entry = pa->toc[i];
prop_info *pi = TOC_TO_INFO(pa, entry);
propfn(pi, cookie);
}
}
return 0;
@@ -177,9 +251,15 @@ int __system_property_foreach(
const prop_info *__system_property_find_nth(unsigned n)
{
prop_area *pa = __system_property_area__;
size_t region = n / PA_COUNT_MAX;
prop_area *pa;
if(n >= pa->count) {
int err = map_prop_region(region);
if (err < 0)
return NULL;
pa = __system_property_regions__[region];
if((n % PA_COUNT_MAX) >= pa->count) {
return 0;
} else {
return TOC_TO_INFO(pa, pa->toc[n]);
@@ -188,25 +268,36 @@ const prop_info *__system_property_find_nth(unsigned 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;
size_t region;
if (len >= PROP_NAME_MAX)
return 0;
if (len < 1)
return 0;
while(count--) {
unsigned entry = *toc++;
if(TOC_NAME_LEN(entry) != len) continue;
for (region = 0; region < PA_REGION_COUNT; region++) {
prop_area *pa;
unsigned count;
unsigned *toc;
prop_info *pi;
pi = TOC_TO_INFO(pa, entry);
if(memcmp(name, pi->name, len)) continue;
int err = map_prop_region(region);
if (err < 0)
return 0;
pa = __system_property_regions__[region];
count = pa->count;
toc = pa->toc;
return 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;
@@ -333,7 +424,7 @@ int __system_property_wait(const prop_info *pi)
{
unsigned n;
if(pi == 0) {
prop_area *pa = __system_property_area__;
prop_area *pa = __system_property_regions__[0];
n = pa->serial;
do {
__futex_wait(&pa->serial, n, 0);
@@ -349,7 +440,7 @@ int __system_property_wait(const prop_info *pi)
int __system_property_update(prop_info *pi, const char *value, unsigned int len)
{
prop_area *pa = __system_property_area__;
prop_area *pa = __system_property_regions__[0];
if (len >= PROP_VALUE_MAX)
return -1;
@@ -368,12 +459,11 @@ int __system_property_update(prop_info *pi, const char *value, unsigned int len)
int __system_property_add(const char *name, unsigned int namelen,
const char *value, unsigned int valuelen)
{
prop_area *pa = __system_property_area__;
prop_info *pa_info_array = (void*) (((char*) pa) + PA_INFO_START);
prop_area *pa;
prop_info *pa_info_array;
prop_info *pi;
size_t region;
if (pa->count == PA_COUNT_MAX)
return -1;
if (namelen >= PROP_NAME_MAX)
return -1;
if (valuelen >= PROP_VALUE_MAX)
@@ -381,13 +471,28 @@ int __system_property_add(const char *name, unsigned int namelen,
if (namelen < 1)
return -1;
for (region = 0; region < PA_REGION_COUNT; region++)
{
int err = map_prop_region_rw(region);
if (err < 0)
return -1;
pa = __system_property_regions__[region];
if (pa->count < PA_COUNT_MAX)
break;
}
if (region == PA_REGION_COUNT)
return -1;
pa_info_array = (void*) (((char*) pa) + PA_INFO_START);
pi = pa_info_array + pa->count;
pi->serial = (valuelen << 24);
memcpy(pi->name, name, namelen + 1);
memcpy(pi->value, value, valuelen + 1);
pa->toc[pa->count] =
(namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
pa->toc[pa->count] = (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
pa->count++;
pa->serial++;
@@ -403,7 +508,7 @@ unsigned int __system_property_serial(const prop_info *pi)
unsigned int __system_property_wait_any(unsigned int serial)
{
prop_area *pa = __system_property_area__;
prop_area *pa = __system_property_regions__[0];
do {
__futex_wait(&pa->serial, serial, 0);