GitLab

Our CheriABI integration test cases for small dynamic stack allocations using alloc() show a minimum bounds of 16 bytes, rather than being byte granularity:

TEST: test_bounds_stack_dynamic_uint8: Check bounds on 8-bit dynamic stack allocation
FAIL: test_bounds_stack_dynamic_uint8: length (16) not expected 1: 0x0000fffffff3cf90 [rwRW,0x0000fffffff3cf90-0x0000fffffff3cfa0]
TEST: test_bounds_stack_dynamic_uint16: Check bounds on 16-bit dynamic stack allocation
FAIL: test_bounds_stack_dynamic_uint16: length (16) not expected 2: 0x0000fffffff3cf90 [rwRW,0x0000fffffff3cf90-0x0000fffffff3cfa0]
TEST: test_bounds_stack_dynamic_uint32: Check bounds 32-bit dynamic stack allocation
FAIL: test_bounds_stack_dynamic_uint32: length (16) not expected 4: 0x0000fffffff3cf90 [rwRW,0x0000fffffff3cf90-0x0000fffffff3cfa0]
TEST: test_bounds_stack_dynamic_uint64: Check bounds on 64-bit dynamic stack allocation
FAIL: test_bounds_stack_dynamic_uint64: length (16) not expected 8: 0x0000fffffff3cf90 [rwRW,0x0000fffffff3cf90-0x0000fffffff3cfa0]

The test cases are as follows:

static void
test_bounds_stack_alloca(size_t len)
{       
        void * __capability c = (__cheri_tocap void * __capability)alloca(len);
        
        test_bounds_precise(c, len);
}

void
test_bounds_stack_dynamic_uint8(const struct cheri_test *ctp __unused)
{
        
        test_bounds_stack_alloca(sizeof(uint8_t));
}

void
test_bounds_stack_dynamic_uint16(const struct cheri_test *ctp __unused)
{
        
        test_bounds_stack_alloca(sizeof(uint16_t));
}

void
test_bounds_stack_dynamic_uint32(const struct cheri_test *ctp __unused)
{

        test_bounds_stack_alloca(sizeof(uint32_t));
}

void
test_bounds_stack_dynamic_uint64(const struct cheri_test *ctp __unused)
{

        test_bounds_stack_alloca(sizeof(uint64_t));
}

Full test suite here: https://github.com/CTSRD-CHERI/cheribsd/tree/master/bin/cheritest

Tagging @jrtc27 @brett.gutstein @arichardson as FYIs.