diff options
| author | Kees Cook <keescook@chromium.org> | 2024-01-26 22:09:50 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2024-02-29 13:38:01 -0800 |
| commit | 08d45ee84bb2650e237e150caca87cc4ded9b3e2 (patch) | |
| tree | 0f0474672597c717e276bcd41242f7d50535aa9c /lib | |
| parent | d70de8054c58d7bd9a4654c9f4797d29fa46d545 (diff) | |
overflow: Introduce wrapping_assign_add() and wrapping_assign_sub()
This allows replacements of the idioms "var += offset" and "var -=
offset" with the wrapping_assign_add() and wrapping_assign_sub() helpers
respectively. They will avoid wrap-around sanitizer instrumentation.
Add to the selftests to validate behavior and lack of side-effects.
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/overflow_kunit.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c index d3fdb906d3fe..65e8a72a83bf 100644 --- a/lib/overflow_kunit.c +++ b/lib/overflow_kunit.c @@ -284,6 +284,45 @@ DEFINE_TEST_ARRAY(s64) = { "Unexpected wrap " #op " macro side-effect!\n"); \ } while (0) +static int global_counter; +static void bump_counter(void) +{ + global_counter++; +} + +static int get_index(void) +{ + volatile int index = 0; + bump_counter(); + return index; +} + +#define check_self_op(fmt, op, sym, a, b) do { \ + typeof(a + 0) _a = a; \ + typeof(b + 0) _b = b; \ + typeof(a + 0) _a_sym = a; \ + typeof(a + 0) _a_orig[1] = { a }; \ + typeof(b + 0) _b_orig = b; \ + typeof(b + 0) _b_bump = b + 1; \ + typeof(a + 0) _r; \ + \ + _a_sym sym _b; \ + _r = wrapping_ ## op(_a, _b); \ + KUNIT_EXPECT_TRUE_MSG(test, _r == _a_sym, \ + "expected "fmt" "#op" "fmt" == "fmt", got "fmt"\n", \ + a, b, _a_sym, _r); \ + KUNIT_EXPECT_TRUE_MSG(test, _a == _a_sym, \ + "expected "fmt" "#op" "fmt" == "fmt", got "fmt"\n", \ + a, b, _a_sym, _a); \ + /* Check for internal macro side-effects. */ \ + global_counter = 0; \ + wrapping_ ## op(_a_orig[get_index()], _b_orig++); \ + KUNIT_EXPECT_EQ_MSG(test, global_counter, 1, \ + "Unexpected wrapping_" #op " macro side-effect on arg1!\n"); \ + KUNIT_EXPECT_EQ_MSG(test, _b_orig, _b_bump, \ + "Unexpected wrapping_" #op " macro side-effect on arg2!\n"); \ +} while (0) + #define DEFINE_TEST_FUNC_TYPED(n, t, fmt) \ static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ { \ @@ -293,6 +332,10 @@ static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ check_one_op(t, fmt, sub, "-", p->a, p->b, p->diff, p->d_of); \ check_one_op(t, fmt, mul, "*", p->a, p->b, p->prod, p->p_of); \ check_one_op(t, fmt, mul, "*", p->b, p->a, p->prod, p->p_of); \ + /* wrapping_assign_{add,sub}() */ \ + check_self_op(fmt, assign_add, +=, p->a, p->b); \ + check_self_op(fmt, assign_add, +=, p->b, p->a); \ + check_self_op(fmt, assign_sub, -=, p->a, p->b); \ } \ \ static void n ## _overflow_test(struct kunit *test) { \ |