Implement a robust overflows_type() macro to test if a variable or
constant value would overflow another variable or type. This can be
used as a constant expression for static_assert() (which requires a
constant expression[1][2]) when used on constant values. This must be
constructed manually, since __builtin_add_overflow() does not produce
a constant expression[3].
Additionally adds castable_to_type(), similar to __same_type(), but for
checking if a constant value would overflow if cast to a given type.
Add unit tests for overflows_type(), __same_type(), and castable_to_type()
to the existing KUnit "overflow" test:
[16:03:33] ================== overflow (21 subtests) ==================
...
[16:03:33] [PASSED] overflows_type_test
[16:03:33] [PASSED] same_type_test
[16:03:33] [PASSED] castable_to_type_test
[16:03:33] ==================== [PASSED] overflow =====================
[16:03:33] ============================================================
[16:03:33] Testing complete. Ran 21 tests: passed: 21
[16:03:33] Elapsed time: 24.022s total, 0.002s configuring, 22.598s building, 0.767s running
[1] https://en.cppreference.com/w/c/language/_Static_assert
[2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions
[3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html
6.56 Built-in Functions to Perform Arithmetic with Overflow Checking
Built-in Function: bool __builtin_add_overflow (type1 a, type2 b,
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: Vitor Massaru Iha <vitor@massaru.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-hardening@vger.kernel.org
Cc: llvm@lists.linux.dev
Co-developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221024201125.1416422-1-gwan-gyeong.mun@intel.com
Convert test exclusion into test skipping. This brings the logic for
why a test is being skipped into the test itself, instead of having to
spread ifdefs around the code. This will make cleanup easier as minimum
tests get raised. Drop __maybe_unused so missed tests will be noticed
again and clean up whitespace.
For example, clang-11 on i386:
[15:52:32] ================== overflow (18 subtests) ==================
[15:52:32] [PASSED] u8_u8__u8_overflow_test
[15:52:32] [PASSED] s8_s8__s8_overflow_test
[15:52:32] [PASSED] u16_u16__u16_overflow_test
[15:52:32] [PASSED] s16_s16__s16_overflow_test
[15:52:32] [PASSED] u32_u32__u32_overflow_test
[15:52:32] [PASSED] s32_s32__s32_overflow_test
[15:52:32] [SKIPPED] u64_u64__u64_overflow_test
[15:52:32] [SKIPPED] s64_s64__s64_overflow_test
[15:52:32] [SKIPPED] u32_u32__int_overflow_test
[15:52:32] [PASSED] u32_u32__u8_overflow_test
[15:52:32] [PASSED] u8_u8__int_overflow_test
[15:52:32] [PASSED] int_int__u8_overflow_test
[15:52:32] [PASSED] shift_sane_test
[15:52:32] [PASSED] shift_overflow_test
[15:52:32] [PASSED] shift_truncate_test
[15:52:32] [PASSED] shift_nonsense_test
[15:52:32] [PASSED] overflow_allocation_test
[15:52:32] [PASSED] overflow_size_helpers_test
[15:52:32] ==================== [PASSED] overflow =====================
[15:52:32] ============================================================
[15:52:32] Testing complete. Ran 18 tests: passed: 15, skipped: 3
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Tom Rix <trix@redhat.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20221006230017.1833458-1-keescook@chromium.org
Building the overflow kunit tests with clang-11 fails with:
$ ./tools/testing/kunit/kunit.py run --arch=arm --make_options LLVM=1 \
overflow
...
ld.lld: error: undefined symbol: __mulodi4
...
Clang 11 and earlier generate unwanted libcalls for signed output,
unsigned input.
Disable these tests for now, but should these become used in the kernel
we might consider that as justification for dropping clang-11 support.
Keep the clang-11 build alive a little bit longer.
Avoid -Wunused-function warnings via __maybe_unused. To test W=1:
$ make LLVM=1 -j128 defconfig
$ ./scripts/config -e KUNIT -e KUNIT_ALL
$ make LLVM=1 -j128 olddefconfig lib/overflow_kunit.o W=1
Link: https://github.com/ClangBuiltLinux/linux/issues/1711
Link: 3203143f13
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221006171751.3444575-1-ndesaulniers@google.com
Pull KUnit updates from Shuah Khan:
"Several documentation fixes, UML related cleanups, and a feature to
enable/disable KUnit tests
This includes the change to rename all_test_uml.config, and use it for
'--alltests'. Note: if anyone was using all_tests_uml.config, this
change breaks them.
This change simplifies the usage and eliminates the need to type:
--kunitconfig=tools/testing/kunit/configs/all_tests_uml.config
A simple workaround to create a symlink to the new name can solve the
problem for anyone using all_tests_uml.config.
all_tests_uml.config should work across ~all architectures"
* tag 'linux-kselftest-kunit-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
Documentation: Kunit: Use full path to .kunitconfig
kunit: tool: rename all_test_uml.config, use it for --alltests
kunit: tool: remove UML specific options from all_tests_uml.config
lib: stackinit: update reference to kunit-tool
lib: overflow: update reference to kunit-tool
Documentation: KUnit: update links in the index page
Documentation: KUnit: add intro to the getting-started page
Documentation: KUnit: Reword start guide for selecting tests
Documentation: KUnit: add note about mrproper in start.rst
Documentation: KUnit: avoid repeating "kunit.py run" in start.rst
Documentation: KUnit: remove duplicated docs for kunit_tool
Documentation: Kunit: Add ref for other kinds of tests
Documentation: KUnit: Fix non-uml anchor
Documentation: Kunit: Fix inconsistent titles
Documentation: kunit: fix trivial typo
kunit: no longer call module_info(test, "Y") for kunit modules
kunit: add kunit.enable to enable/disable KUnit test
kunit: tool: make --raw_output=kunit (aka --raw_output) preserve leading spaces
The 64-bit overflow tests will trigger 64-bit division on 32-bit hosts,
which is not currently used anywhere in the kernel, and tickles bugs
in at least Clang 13 and earlier:
https://github.com/ClangBuiltLinux/linux/issues/1636
In reality, there shouldn't be a reason to not build the 64-bit test
cases on 32-bit systems, so these #ifdefs can be removed once the minimum
Clang version reaches 13.
In the meantime, silence W=1 warnings given by the current code:
../lib/overflow_kunit.c:191:19: warning: 's64_tests' defined but not used [-Wunused-const-variable=]
191 | DEFINE_TEST_ARRAY(s64) = {
| ^~~
../lib/overflow_kunit.c:24:11: note: in definition of macro 'DEFINE_TEST_ARRAY'
24 | } t ## _tests[]
| ^
../lib/overflow_kunit.c:94:19: warning: 'u64_tests' defined but not used [-Wunused-const-variable=]
94 | DEFINE_TEST_ARRAY(u64) = {
| ^~~
../lib/overflow_kunit.c:24:11: note: in definition of macro 'DEFINE_TEST_ARRAY'
24 | } t ## _tests[]
| ^
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/202205110324.7GrtxG8u-lkp@intel.com
Fixes: 455a35a6cd ("lib: add runtime test of check_*_overflow functions")
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Vitor Massaru Iha <vitor@massaru.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Tested-by: Daniel Latypov <dlatypov@google.com>
Link: https://lore.kernel.org/lkml/CAGS_qxokQAjQRip2vPi80toW7hmBnXf=KMTNT51B1wuDqSZuVQ@mail.gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
