There may or may not be a readable ZEND_TRACE_OP_INFO()

Maybe I don't understand the code well enough, but I don't think it should happen. We had crashes there though, so that should probably should mitigate them.

Signed-off-by: Bob Weinand <bob.weinand@datadoghq.com>

zend_abstract_interface/jit_utils/jit_blacklist.c

@@ -88,6 +88,8 @@ typedef union _zend_op_trace_info {
 
 #define ZEND_OP_TRACE_INFO(opline, offset) \
 	((zend_op_trace_info*)(((char*)opline) + offset))
+
+static int dd_probe_pipes[2];
 #endif
 
 #define ZEND_FUNC_INFO(op_array) \
@@ -103,6 +105,9 @@ 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
+    pipe(dd_probe_pipes);
+#endif
     zend_llist_apply(&zend_extensions, zai_jit_find_opcache_handle);
 }
 
@@ -188,7 +193,7 @@ void zai_jit_blacklist_function_inlining(zend_op_array *op_array) {
     if (zai_get_zend_func_rid(op_array) < 0) {
         return;
     }
-    // now in PHP < 8.1, zend_func_info_rid is set
+    // now in PHP < 8.1, zend_func_info_rid is set (on newer versions it's in zend_func_info.h)
 
     zend_jit_op_array_trace_extension *jit_extension = (zend_jit_op_array_trace_extension *)ZEND_FUNC_INFO(op_array);
     if (!jit_extension) {
@@ -203,6 +208,14 @@ void zai_jit_blacklist_function_inlining(zend_op_array *op_array) {
 
     size_t offset = jit_extension->offset;
 
+    // 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) {
+        return;
+    }
+    read(dd_probe_pipes[0], dummy_buf, sizeof(zend_op_trace_info));
+
     if (!(ZEND_OP_TRACE_INFO(opline, offset)->trace_flags & ZEND_JIT_TRACE_BLACKLISTED)) {
         bool is_protected_memory = false;
         zend_string *protect_memory = zend_string_init(ZEND_STRL("opcache.protect_memory"), 0);