Progress

docs/writeup.txt

@@ -13,3 +13,8 @@ precise per-instruction labels are required at RTL level
 	-> attach notes to any RTL instruction that accesses relevant structs
 	-> notes are propagated throughout RTL optimizations
 	-> at the very end of RTL handling, discover notes and add assembly labels
+
+Constant foldable expressions, e.g. "size_t myOffset = ((size_t)&((struct task_struct*)0)->tasks);", are invisible
+	-> gcc folds those expressions before PLUGIN_FINISH_PARSE_FUNCTION
+	-> any recoverability of COMPONENT_REF is impossible
+	-> requires gcc patch (fairly small one though)

plugin/CMakeLists.txt

@@ -1,4 +1,4 @@
-add_library(selfpatch-slr SHARED main.cpp attrib.cpp access_discover.cpp)
+add_library(selfpatch-slr SHARED main.cpp attrib.cpp access_discover.cpp pattern.cpp)
 
 set_target_properties(selfpatch-slr PROPERTIES PREFIX "")
 target_compile_definitions(selfpatch-slr PRIVATE _GNU_SOURCE)

plugin/access_discover.cpp

@@ -1,4 +1,5 @@
 #include "access_discover.h"
+#include "pattern.h"
 
 #include <iostream>
 
@@ -35,45 +36,11 @@ static void print_gimple_statement(gimple* stmt) {
 }
 
 static int scan_gimple_statement(const char* funcname, gimple_stmt_iterator* gsi) {
-	/*
-	gimple *stmt = gsi_stmt(gsi);
-	scan_stmt_for_offsetof(funcname, &gsi);
-	for (unsigned i = 0; i < gimple_num_ops(stmt); ++i) {
-		tree op = gimple_op(stmt, i);
-		scan_tree_for_components(op, funcname, &gsi);
-	}
-
-	Build map: location->LocationPattern
-	Build GimpleStatementPattern tree from individual gimple statement
-	Add GimpleStatementPattern to LocationPattern (attached at matching variable names (potentially unnamed ssa))
-	Patterns include markers for member offsets (type, member, value)
-	Later load a set of RTLInstructionPattern to match the patterns
-	*/
-
 	print_gimple_statement(gsi_stmt(*gsi));
-
-	gimple* stmt = gsi_stmt(*gsi);
-	enum gimple_code stmt_code = gimple_code(stmt);
-
-	switch (stmt_code) {
-		case GIMPLE_CALL:
-			// check for offsetof, then fall through to operand scanning
-		case GIMPLE_ASSIGN:
-		case GIMPLE_COND:
-		case GIMPLE_LABEL:
-		case GIMPLE_RETURN:
-			return 0;
-		default:
-			return 1;
-	}
-
+	//return register_gimple_statement_pattern(gsi);
 	return 0;
 }
 
-static void clean_unnecessary_locations() {
-	// Remove all LocationPatterns that do no do any relevant struct accesses
-}
-
 static const pass_data access_discover_pass_data = {
 	GIMPLE_PASS,
 	"access_discover",
@@ -100,6 +67,6 @@ unsigned int access_discover_pass::execute(function* fun) {
 		}
 	}
 
-	clean_unnecessary_locations();
+	clean_unnecessary_patterns();
 	return 0;
 }

plugin/gcc_includes.h

@@ -7,6 +7,8 @@
 #include <gimple.h>
 #include <gimplify.h>
 #include <gimple-iterator.h>
+#include <rtl.h>
+#include <rtl-iter.h>
 #include <basic-block.h>
 #include <gimple-ssa.h>
 #include <tree-pass.h>

plugin/pattern.cpp

@@ -0,0 +1,70 @@
+#include "pattern.h"
+
+#include <unordered_map>
+
+class LocationPattern {
+
+public:
+	LocationPattern() {}
+	~LocationPattern() {}
+};
+
+static std::unordered_map<location_t, LocationPattern> locations;
+
+int register_gimple_statement_pattern(gimple_stmt_iterator* gsi) {
+	gimple* stmt = gsi_stmt(*gsi);
+	enum gimple_code stmt_code = gimple_code(stmt);
+	location_t stmt_location = gimple_location(stmt);
+
+	auto lp_it = locations.find(stmt_location);
+	if (lp_it == locations.end()) {
+		auto [new_it, success] = locations.emplace(stmt_location, LocationPattern{});
+		if (!success)
+			return 1;
+
+		lp_it = new_it;
+	}
+
+	LocationPattern& pattern = lp_it->second;
+
+	/*
+    scan_stmt_for_offsetof(funcname, &gsi);
+    for (unsigned i = 0; i < gimple_num_ops(stmt); ++i) {
+        tree op = gimple_op(stmt, i);
+        scan_tree_for_components(op, funcname, &gsi);
+    }
+
+    Build GimpleStatementPattern tree from individual gimple statement
+    Add GimpleStatementPattern to LocationPattern (attached at matching variable names (potentially unnamed ssa))
+    Patterns include markers for member offsets (type, member, value)
+    Later load a set of RTLInstructionPattern to match the patterns
+    */
+
+    switch (stmt_code) {
+        case GIMPLE_CALL:
+            // check for offsetof, then fall through to operand scanning
+        case GIMPLE_ASSIGN:
+        case GIMPLE_COND:
+        case GIMPLE_LABEL:
+        case GIMPLE_RETURN:
+            return 0;
+        default:
+            return 1;
+    }
+
+    return 0;
+}
+
+void clean_unnecessary_patterns() {
+	// TODO
+}
+
+int register_rtl_instruction_pattern(rtx_insn* i) {
+	// TODO
+	return 0;
+}
+
+int annotate_rtl() {
+	// TODO
+	return 0;
+}

plugin/pattern.h

@@ -0,0 +1,7 @@
+#pragma once
+#include "gcc_includes.h"
+
+int register_gimple_statement_pattern(gimple_stmt_iterator* gsi); // 1
+void clean_unnecessary_patterns(); // 2
+int register_rtl_instruction_pattern(rtx_insn* i); // 3
+int annotate_rtl(); // 4

subject/main.c

@@ -75,6 +75,8 @@ int main(void)
         printf("  pid=%d, comm=%s\n", task->pid, task->comm);
     }
 
+	size_t myOffset = ((size_t)&((struct task_struct*)0)->tasks); // BROKEN, relevancy for kernel unknown
+
     return 0;
 }