Implemented spslr_field_fixed attribute

pinpoint/pinpoint_config.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #define SPSLR_ATTRIBUTE "spslr"
+#define SPSLR_FIELD_FIXED_ATTRIBUTE "spslr_field_fixed"
 #define SPSLR_PINPOINT_STAGE0_SEPARATOR "__spslr_offsetof"
 #define SPSLR_PINFILE_EXTENSION ".spslr"
 #define SPSLR_PINPOINT_STAGE2_PIN "__spslr_ipin_" /* suffixed with "<cuhash>_<uid>" */

pinpoint/safegcc/safe-attribs.h

@@ -0,0 +1,8 @@
+#include <safe-gcc-plugin.h>
+
+#ifndef SAFEGCC_ATTRIBS_H
+#define SAFEGCC_ATTRIBS_H
+
+#include <attribs.h>
+
+#endif

pinpoint/stage0/on_register_attributes.cpp

@@ -1,5 +1,6 @@
 #include <stage0.h>
 #include <pinpoint_config.h>
+#include <cstdio>
 
 static tree log_new_target(tree* node, tree name, tree args, int flags, bool* no_add_attrs) {
 	if (node)
@@ -8,11 +9,24 @@ static tree log_new_target(tree* node, tree name, tree args, int flags, bool* no
 	return NULL_TREE;
 }
 
+static tree check_field_fixed_attribute(tree* node, tree name, tree args, int flags, bool* no_add_attrs) {
+	if (!node || !*node || TREE_CODE(*node) != FIELD_DECL) {
+		*no_add_attrs = true;
+		fprintf(stderr, "%qs attribute only applies to struct/union fields", SPSLR_FIELD_FIXED_ATTRIBUTE);
+	}
+	return NULL_TREE;
+}
+
 static struct attribute_spec spslr_attribute = {
 	SPSLR_ATTRIBUTE, 0, 0, false, false, false, false, log_new_target, NULL
 };
 
+static struct attribute_spec spslr_fixed_field_attribute = {
+	SPSLR_FIELD_FIXED_ATTRIBUTE, 0, 0, false, false, false, false, check_field_fixed_attribute, NULL
+};
+
 void on_register_attributes(void* plugin_data, void* user_data) {
 	register_attribute(&spslr_attribute);
+	register_attribute(&spslr_fixed_field_attribute);
 }
 

pinpoint/stage0/target.cpp

@@ -2,6 +2,9 @@
 #include <functional>
 
 #include <safe-langhooks.h>
+#include <safe-attribs.h>
+
+#include <pinpoint_config.h>
 
 static UID next_uid = 0;
 static std::unordered_map<UID, TargetType> targets;
@@ -251,7 +254,10 @@ static bool foreach_record_field(tree t, std::function<bool(const TargetType::Fi
 		if (!field_info(field_decl, &field.offset, &field.size, &field.alignment, &is_bitfield))
 			return false;
 
-		field.flags = (is_bitfield ? TargetType::Field::FLAG_DANGEROUS : 0);
+		tree attrs = DECL_ATTRIBUTES(field_decl);
+		bool is_fixed = lookup_attribute(SPSLR_FIELD_FIXED_ATTRIBUTE, attrs) != NULL_TREE;
+
+		field.flags = ((is_fixed || is_bitfield) ? TargetType::Field::FLAG_DANGEROUS : 0);
 
 		if (!callback(field))
 			return false;

subject/task_struct.h

@@ -7,6 +7,7 @@
 
 # define randomized_struct_fields_start struct {
 # define randomized_struct_fields_end } __attribute__((spslr));
+# define __spslr_field_fixed __attribute__((spslr_field_fixed))
 
 // Minimal doubly linked list
 struct list_head {
@@ -66,7 +67,14 @@ struct task_struct {
 
 	randomized_struct_fields_end
 
-	struct list_head tasks; // linkage for global task list
+	/*
+	 * TODO
+	 * This field is used to statically initialize list heads.
+	 * To make the offset available at compile-time, it must be fixed.
+	 * The actual solution to this problem is dppins
+	 *     -> Any static pointer into a randomized object must be patched too
+	 */
+	struct list_head tasks __spslr_field_fixed; // linkage for global task list
 
 	randomized_struct_fields_end