regehr

I want to speed up integer overflow checking for hardening purposes by keeping a sticky overflow flag and only trapping when necessary. I want the implementation to be simple but hopefully amenable to optimizations. In the codegen part of clang:
- each function gets an i1 for storing overflow information, initialized to 0
- each integer overflow check ORs its result into the overflow flag
- before each function call, return instruction, or other side-effecting operation, execude ud2 if overflow is set

Reasonable?

regehr

I want to speed up integer overflow checking for hardening purposes by keeping a sticky overflow flag and only trapping when necessary. I want to keep it super simple while hopefully giving the optimizers room to do their thing.

In the codegen part of clang:

• each function gets an i1 for storing overflow information, initialized to 0
• each integer overflow check ORs its result into the overflow flag
• before each function call, return instruction, or other side-effecting operation, execude ud2 if overflow is set

Reasonable?

regehr

int a1[10];
int *a2;

int foo1(int i) {
  return a1[i];
}

int foo2(int *a, int i) {
  return a[i];
}

regehr

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

volatile int x, y, tmp1, tmp2;

void *t0(void *arg) {
  x = 1;
  tmp1 = y;
  return 0;

regehr

#!/usr/bin/python3

import random

# dimensions should be odd and >= 5
W = 25
H = 25

q = []
m = []

regehr

#!/usr/bin/python3

import random

# dimensions should be odd and >= 5
W = 25
H = 25

q = []
m = []

regehr

#include <cassert>
#include <iostream>
#include <vector>
#include <random>

namespace {

template <typename Key, typename Value> class RBTree {
private:
  class RBTreeNode {

regehr

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>

enum dir { N, S, W, E };

static enum dir getcmd(void) {
  int in;
  do {
    in = getchar();

regehr

; RHS inferred successfully
%0:i32 = var
%1:i32 = add 8:i32, %0
%2:i1 = eq 0:i32, %1
pc %2 1:i1
%3:i32 = add 4:i32, %0
cand %3 4294967292:i32

; RHS inferred successfully
%0:i32 = var

regehr

-----------------------------------------------------------
; RHS inferred successfully
result 7:i32

Input was:

; start LHS
%0 = block 2
%1 = phi %0, 7:i32, 7:i32
infer %1