Fix appsec tests in 8.1-8.3

The use of pipe() creates an extra file descriptor which makes the
helper unable to find the correct pipe file descriptor. While this could
perhaps be improved by telling the helper explicitly the id of the
correct file descriptor, it's probably better to swap write() calls of
reading invalid addresses with mincore().

zend_abstract_interface/jit_utils/jit_blacklist.c

@@ -88,10 +88,6 @@ typedef union _zend_op_trace_info {
 
 #define ZEND_OP_TRACE_INFO(opline, offset) \
 	((zend_op_trace_info*)(((char*)opline) + offset))
-
-#ifndef _WIN32
-static int dd_probe_pipes[2];
-#endif
 #endif
 
 #define ZEND_FUNC_INFO(op_array) \
@@ -107,9 +103,6 @@ static void zai_jit_find_opcache_handle(void *ext) {
 
 // opcache startup NULLs its handle. MINIT is executed before extension startup.
 void zai_jit_minit(void) {
-#if PHP_VERSION_ID < 80400 && !defined(_WIN32)
-    pipe(dd_probe_pipes);
-#endif
     zend_llist_apply(&zend_extensions, zai_jit_find_opcache_handle);
 }
 
@@ -185,6 +178,42 @@ int zai_get_zend_func_rid(zend_op_array *op_array) {
     return zend_func_info_rid;
 }
 
+#if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__)) && PHP_VERSION_ID < 80400
+static bool is_mapped(void *addr, size_t size) {
+    uintptr_t page_size = sysconf(_SC_PAGESIZE);
+    assert(size <= page_size);
+    uintptr_t page_addr = ((uintptr_t)addr & ~(page_size - 1));
+    unsigned char vec;
+
+    uintptr_t last_page_addr = ((uintptr_t)(addr + size - 1) & ~(page_size - 1));
+
+#ifdef __x86_64__
+#define SYS_mincore 0x1B
+#else // aarch64
+#define SYS_mincore 0xE8
+#endif
+
+again:
+    if (syscall(SYS_mincore, page_addr, page_size, &vec) == 0) {
+        if (page_addr == last_page_addr) {
+            return true;
+        } else {
+            page_addr = last_page_addr;
+            goto again;
+        }
+    } else if (errno == EFAULT || errno == ENOMEM) {
+        return false;
+    } else {
+        // we don't know... asume true
+#ifdef ZEND_DEBUG
+        abort();
+#else
+        return true;
+#endif
+    }
+}
+#endif
+
 void zai_jit_blacklist_function_inlining(zend_op_array *op_array) {
 #if PHP_VERSION_ID >= 80400
     if (opcache_handle) {
@@ -210,14 +239,12 @@ void zai_jit_blacklist_function_inlining(zend_op_array *op_array) {
 
     size_t offset = jit_extension->offset;
 
-#ifndef _WIN32
+#if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__))
     // check whether the op_trace_info is actually readable or EFAULTing
     // we can't trust opcache too much here...
-    char dummy_buf[sizeof(zend_op_trace_info)];
-    if (write(dd_probe_pipes[1], ZEND_OP_TRACE_INFO(opline, offset), sizeof(zend_op_trace_info)) < 0) {
+    if (!is_mapped(ZEND_OP_TRACE_INFO(opline, offset), sizeof(zend_op_trace_info))) {
         return;
     }
-    read(dd_probe_pipes[0], dummy_buf, sizeof(zend_op_trace_info));
 #endif
 
     if (!(ZEND_OP_TRACE_INFO(opline, offset)->trace_flags & ZEND_JIT_TRACE_BLACKLISTED)) {