Fix ASLR related invalid opline handler issues

Opcache stores `opline->handler`s in shared memory.  These pointers are
invalid, if the main PHP DLL is loaded at another base address due to
ASLR.  We therefore store the address of `execute_ex` in the mmap base
file, and check on startup whether it matches its current address.  If
not, we fall back on the file cache if enabled, and bail out otherwise.

This still does not address cases where the opline handler is located
inside of another DLL (e.g. for some profilers, debuggers), but there
seems to be no general solution for now.

ext/opcache/shared_alloc_win32.c

@@ -22,6 +22,7 @@
 #include "ZendAccelerator.h"
 #include "zend_shared_alloc.h"
 #include "zend_accelerator_util_funcs.h"
+#include "zend_execute.h"
 #include "tsrm_win32.h"
 #include "win32/winutil.h"
 #include <winbase.h>
@@ -133,6 +134,8 @@ static int zend_shared_alloc_reattach(size_t requested_size, char **error_in)
 	char *mmap_base_file = get_mmap_base_file();
 	FILE *fp = fopen(mmap_base_file, "r");
 	MEMORY_BASIC_INFORMATION info;
+	void *execute_ex_base;
+	int execute_ex_moved;
 
 	if (!fp) {
 		err = GetLastError();
@@ -148,15 +151,25 @@ static int zend_shared_alloc_reattach(size_t requested_size, char **error_in)
 		fclose(fp);
 		return ALLOC_FAILURE;
 	}
+	if (!fscanf(fp, "%p", &execute_ex_base)) {
+		err = GetLastError();
+		zend_win_error_message(ACCEL_LOG_FATAL, "Unable to read execute_ex base address", err);
+		*error_in="read execute_ex base";
+		fclose(fp);
+		return ALLOC_FAILURE;
+	}
 	fclose(fp);
 
 	if (0 > win32_utime(mmap_base_file, NULL)) {
 		err = GetLastError();
 		zend_win_error_message(ACCEL_LOG_WARNING, mmap_base_file, err);
 	}
 
-	/* Check if the requested address space is free */
-	if (VirtualQuery(wanted_mapping_base, &info, sizeof(info)) == 0 ||
+	execute_ex_moved = (void *)execute_ex != execute_ex_base;
+
+	/* Check if execute_ex is at the same address and if the requested address space is free */
+	if (execute_ex_moved ||
+	    VirtualQuery(wanted_mapping_base, &info, sizeof(info)) == 0 ||
 	    info.State != MEM_FREE ||
 	    info.RegionSize < requested_size) {
 #if ENABLE_FILE_CACHE_FALLBACK
@@ -165,8 +178,13 @@ static int zend_shared_alloc_reattach(size_t requested_size, char **error_in)
 
 			wanted_mb_save = (size_t)wanted_mapping_base;
 
-			err = ERROR_INVALID_ADDRESS;
-			zend_win_error_message(ACCEL_LOG_WARNING, "Base address marks unusable memory region (fall-back to file cache)", err);
+			if (execute_ex_moved) {
+				err = ERROR_INVALID_ADDRESS;
+				zend_win_error_message(ACCEL_LOG_WARNING, "Opcode handlers are unusable due to ASLR (fall-back to file cache)", err);
+			} else {
+				err = ERROR_INVALID_ADDRESS;
+				zend_win_error_message(ACCEL_LOG_WARNING, "Base address marks unusable memory region (fall-back to file cache)", err);
+			}
 
 			pre_size = ZEND_ALIGNED_SIZE(sizeof(zend_smm_shared_globals)) + ZEND_ALIGNED_SIZE(sizeof(zend_shared_segment)) + ZEND_ALIGNED_SIZE(sizeof(void *)) + ZEND_ALIGNED_SIZE(sizeof(int));
 			/* Map only part of SHM to have access opcache shared globals */
@@ -181,10 +199,15 @@ static int zend_shared_alloc_reattach(size_t requested_size, char **error_in)
 			return ALLOC_FALLBACK;
 		}
 #endif
-	    err = ERROR_INVALID_ADDRESS;
-		zend_win_error_message(ACCEL_LOG_FATAL, "Base address marks unusable memory region. Please setup opcache.file_cache and opcache.file_cache_fallback directives for more convenient Opcache usage", err);
+		if (execute_ex_moved) {
+			err = ERROR_INVALID_ADDRESS;
+			zend_win_error_message(ACCEL_LOG_FATAL, "Opcode handlers are unusable due to ASLR. Please setup opcache.file_cache and opcache.file_cache_fallback directives for more convenient Opcache usage", err);
+		} else {
+			err = ERROR_INVALID_ADDRESS;
+			zend_win_error_message(ACCEL_LOG_FATAL, "Base address marks unusable memory region. Please setup opcache.file_cache and opcache.file_cache_fallback directives for more convenient Opcache usage", err);
+		}
 		return ALLOC_FAILURE;
-   	}
+	}
 
 	mapping_base = MapViewOfFileEx(memfile, FILE_MAP_ALL_ACCESS, 0, 0, 0, wanted_mapping_base);
 
@@ -315,6 +338,7 @@ static int create_segments(size_t requested_size, zend_shared_segment ***shared_
 		return ALLOC_FAILURE;
 	} else {
 		char *mmap_base_file = get_mmap_base_file();
+		void *execute_ex_base = (void *)execute_ex;
 		FILE *fp = fopen(mmap_base_file, "w");
 		if (!fp) {
 			err = GetLastError();
@@ -324,6 +348,7 @@ static int create_segments(size_t requested_size, zend_shared_segment ***shared_
 			return ALLOC_FAILURE;
 		}
 		fprintf(fp, "%p\n", mapping_base);
+		fprintf(fp, "%p\n", execute_ex_base);
 		fclose(fp);
 	}