Dynamically allocate soinfo-structs in linker
Request memory from the system when needed instead of having a fixed
array for soinfo structs. Note that malloc() et al can't be used in
linker, so use mmap() instead.
Change-Id: I4b495995931d7752b0e8c944e64d1fe41b9f7144
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 479d4b9..f7f8125 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -51,8 +51,6 @@
#include "linker_format.h"
#include "linker_phdr.h"
-#define SO_MAX 128
-
/* Assume average path length of 64 and max 8 paths */
#define LDPATH_BUFSIZE 512
#define LDPATH_MAX 8
@@ -76,16 +74,22 @@
* and NOEXEC
* - linker hardcodes PAGE_SIZE and PAGE_MASK because the kernel
* headers provide versions that are negative...
- * - allocate space for soinfo structs dynamically instead of
- * having a hard limit (SO_MAX)
*/
static bool soinfo_link_image(soinfo* si);
-static int socount = 0;
-static soinfo sopool[SO_MAX];
-static soinfo *freelist = NULL;
+// We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous
+// maps, each a single page in size. The pages are broken up into as many struct soinfo
+// objects as will fit, and they're all threaded together on a free list.
+#define SOINFO_PER_POOL ((PAGE_SIZE - sizeof(soinfo_pool_t*)) / sizeof(soinfo))
+struct soinfo_pool_t {
+ soinfo_pool_t* next;
+ soinfo info[SOINFO_PER_POOL];
+};
+static struct soinfo_pool_t* gSoInfoPools = NULL;
+static soinfo* gSoInfoFreeList = NULL;
+
static soinfo *solist = &libdl_info;
static soinfo *sonext = &libdl_info;
static soinfo *somain; /* main process, always the one after libdl_info */
@@ -263,38 +267,57 @@
rtld_db_dlactivity();
}
-static soinfo *soinfo_alloc(const char *name)
-{
- if (strlen(name) >= SOINFO_NAME_LEN) {
- DL_ERR("library name \"%s\" too long", name);
- return NULL;
- }
+static bool ensure_free_list_non_empty() {
+ if (gSoInfoFreeList != NULL) {
+ return true;
+ }
- /* The freelist is populated when we call soinfo_free(), which in turn is
- done only by dlclose(), which is not likely to be used.
- */
- if (!freelist) {
- if (socount == SO_MAX) {
- DL_ERR("too many libraries when loading \"%s\"", name);
- return NULL;
- }
- freelist = sopool + socount++;
- freelist->next = NULL;
- }
+ // Allocate a new pool.
+ soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool),
+ PROT_READ|PROT_WRITE,
+ MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
+ if (pool == MAP_FAILED) {
+ return false;
+ }
- soinfo* si = freelist;
- freelist = freelist->next;
+ // Add the pool to our list of pools.
+ pool->next = gSoInfoPools;
+ gSoInfoPools = pool;
- /* Make sure we get a clean block of soinfo */
- memset(si, 0, sizeof(soinfo));
- strlcpy((char*) si->name, name, sizeof(si->name));
- sonext->next = si;
- si->next = NULL;
- si->refcount = 0;
- sonext = si;
+ // Chain the entries in the new pool onto the free list.
+ gSoInfoFreeList = &pool->info[0];
+ soinfo* next = NULL;
+ for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) {
+ pool->info[i].next = next;
+ next = &pool->info[i];
+ }
- TRACE("%5d name %s: allocated soinfo @ %p\n", pid, name, si);
- return si;
+ return true;
+}
+
+static soinfo* soinfo_alloc(const char* name) {
+ if (strlen(name) >= SOINFO_NAME_LEN) {
+ DL_ERR("library name \"%s\" too long", name);
+ return NULL;
+ }
+
+ if (!ensure_free_list_non_empty()) {
+ DL_ERR("out of memory when loading \"%s\"", name);
+ return NULL;
+ }
+
+ // Take the head element off the free list.
+ soinfo* si = gSoInfoFreeList;
+ gSoInfoFreeList = gSoInfoFreeList->next;
+
+ // Initialize the new element.
+ memset(si, 0, sizeof(soinfo));
+ strlcpy(si->name, name, sizeof(si->name));
+ sonext->next = si;
+ sonext = si;
+
+ TRACE("%5d name %s: allocated soinfo @ %p\n", pid, name, si);
+ return si;
}
static void soinfo_free(soinfo* si)
@@ -323,8 +346,8 @@
*/
prev->next = si->next;
if (si == sonext) sonext = prev;
- si->next = freelist;
- freelist = si;
+ si->next = gSoInfoFreeList;
+ gSoInfoFreeList = si;
}
#ifdef ANDROID_ARM_LINKER
diff --git a/linker/linker.h b/linker/linker.h
index cb33602..de83a8c 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -165,7 +165,6 @@
bool has_DT_SYMBOLIC;
};
-
extern soinfo libdl_info;
