Allow sharing the RELRO section via a file.
Add flags and a file descriptor to android_dlopen_ext() to allow writing
the RELRO section of the loaded library to a file after relocation
processing, and to allow mapping identical pages from the file over the
top of relocated memory in another process. Explicitly comparing the
pages is required in case a page contains a reference to a symbol
defined in another library loaded at a random base address.
Bug: 13005501
Change-Id: Ibb5b2d384edfaa5acf3e97a5f8b6115c10497a1e
diff --git a/libc/include/android/dlext.h b/libc/include/android/dlext.h
index 3ae0965..90962fa 100644
--- a/libc/include/android/dlext.h
+++ b/libc/include/android/dlext.h
@@ -36,15 +36,31 @@
*/
ANDROID_DLEXT_RESERVED_ADDRESS_HINT = 0x2,
+ /* When set, write the GNU RELRO section of the mapped library to relro_fd
+ * after relocation has been performed, to allow it to be reused by another
+ * process loading the same library at the same address. This implies
+ * ANDROID_DLEXT_USE_RELRO.
+ */
+ ANDROID_DLEXT_WRITE_RELRO = 0x4,
+
+ /* When set, compare the GNU RELRO section of the mapped library to relro_fd
+ * after relocation has been performed, and replace any relocated pages that
+ * are identical with a version mapped from the file.
+ */
+ ANDROID_DLEXT_USE_RELRO = 0x8,
+
/* Mask of valid bits */
ANDROID_DLEXT_VALID_FLAG_BITS = ANDROID_DLEXT_RESERVED_ADDRESS |
- ANDROID_DLEXT_RESERVED_ADDRESS_HINT,
+ ANDROID_DLEXT_RESERVED_ADDRESS_HINT |
+ ANDROID_DLEXT_WRITE_RELRO |
+ ANDROID_DLEXT_USE_RELRO,
};
typedef struct {
int flags;
void* reserved_addr;
size_t reserved_size;
+ int relro_fd;
} android_dlextinfo;
extern void* android_dlopen_ext(const char* filename, int flag, const android_dlextinfo* extinfo);