Re: [PATCH 1/2] exec: Add KUnit test for bprm_stack_limits()

[Guenter Roeck <linux@roeck-us.net>]

On 3/18/26 11:33, Kees Cook wrote:
> On Mon, Mar 16, 2026 at 12:16:58PM -0700, Guenter Roeck wrote:
>> Hi,
>>
>> On Sun, May 19, 2024 at 07:16:11PM -0700, Kees Cook wrote:
>>> Since bprm_stack_limits() operates with very limited side-effects, add
>>> it as the first exec.c KUnit test. Add to Kconfig and adjust MAINTAINERS
>>> file to include it.
>>>
>>> Tested on 64-bit UML:
>>> $ tools/testing/kunit/kunit.py run exec
>>>
>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>> ---
>>> Cc: Eric Biederman <ebiederm@xmission.com>
>>> Cc: Justin Stitt <justinstitt@google.com>
>>> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
>>> Cc: Christian Brauner <brauner@kernel.org>
>>> Cc: Jan Kara <jack@suse.cz>
>>> Cc: linux-fsdevel@vger.kernel.org
>>> Cc: linux-mm@kvack.org
>>> ---
>> ...
>>> +++ b/fs/exec.c
>> ...
>>> +	  .expected_argmin = ULONG_MAX - (_STK_LIM / 4 * 3) + sizeof(void *) },
>>> +	{ { .p = ULONG_MAX, .rlim_stack.rlim_cur = 4 * (_STK_LIM / 4 *  + sizeof(void *)),
>>                                                                     ^^^^^^
>>
>> Google's experimental AI review agent tagged the above change as syntactically wrong.
>> How does this even compile ?
> 
> Wow. I have no idea how this ever built either. I will get it fixed.
> 
I ended up writing a test program.

#define TESTVAL 10
...
long int x = TESTVAL / 4 * + sizeof(void *);

does build, as does

long int x = TESTVAL / 4 * - sizeof(void *);

or even

long int x = TESTVAL / 4 * 3 - - sizeof(void *);

long int x = TESTVAL / 4 * - - sizeof(void *);

It doesn't even have problems with

long int x = TESTVAL / 4 * - - + - + - sizeof(void *);

Weird. Looks like the compiler takes the "+" or "-" as sign value,
not as operator, and once can have as many of those as one desires.

Guenter