[LTP] [PATCH 2/2] Add madvise12 test

[Andrea Cervesato]

Thanks for the review. Pushed with suggested changes.

Andrea

On 12/11/24 10:29, Lorenzo Stoakes via ltp wrote:
> On Wed, Dec 11, 2024 at 01:30:48AM +0100, Petr Vorel wrote:
>> Hi Andrea,
>>
>> [ I dared to Cc Lorenzo, the author of the kernel implementation ]
> I'm not that scary am I? :)))
>
> Feel free to cc- me on anything relating to this even if obviously in the
> LTP project happy to be included! :)
>
>>> Verify that MADV_GUARD_INSTALL is causing SIGSEGV when someone is
>>> trying to access memory advised with it.
>> Test LGTM, thanks for covering a new kernel feature.
> All good, looks fine to me, though might be worth expanding over time, we
> have some self tests in the kernel for this, see
> tools/testing/selftests/mm/guard-pages.c.
>
> But it's nice to have a basic LTP regression test to assert the fundamental
> thing is working as it should, and also nice that you implement it from
> your perspective rather than mine, where I am obviously rather influenced
> by implementation details.
>
> Also note I submitted man pages for the change, you can pull it from [0]
> and view it via:
>
> $ man --manpath=. 2 madvise
>
> [0]:git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
>
> Hopefully these will get distributed around soon!
>
> Thanks for doing this for my feature, much appreciated overall!
>
> Cheers, Lorenzo
>
>> Closes: https://github.com/linux-test-project/ltp/issues/1210
>>
>>> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
>>> ---
>>>   runtest/syscalls                              |   1 +
>>>   testcases/kernel/syscalls/madvise/.gitignore  |   1 +
>>>   testcases/kernel/syscalls/madvise/madvise12.c | 102 ++++++++++++++++++++++++++
>>>   3 files changed, 104 insertions(+)
>>> diff --git a/runtest/syscalls b/runtest/syscalls
>>> index 5fd62617df1a116b1d94c57ff30f74693320a2ab..ded035ee82d0e97c67cc1e7c487b010634b2d1a0 100644
>>> --- a/runtest/syscalls
>>> +++ b/runtest/syscalls
>>> @@ -1000,6 +1000,7 @@ madvise08 madvise08
>>>   madvise09 madvise09
>>>   madvise10 madvise10
>>>   madvise11 madvise11
>>> +madvise12 madvise12
>>>   newuname01 newuname01
>>> diff --git a/testcases/kernel/syscalls/madvise/.gitignore b/testcases/kernel/syscalls/madvise/.gitignore
>>> index 722ac3c34306bac414313f1ce36ca98d715cd04c..758e601a9c4e7682a925f16184d14f2357009bc2 100644
>>> --- a/testcases/kernel/syscalls/madvise/.gitignore
>>> +++ b/testcases/kernel/syscalls/madvise/.gitignore
>>> @@ -8,3 +8,4 @@
>>>   /madvise09
>>>   /madvise10
>>>   /madvise11
>>> +/madvise12
>>> diff --git a/testcases/kernel/syscalls/madvise/madvise12.c b/testcases/kernel/syscalls/madvise/madvise12.c
>>> new file mode 100644
>>> index 0000000000000000000000000000000000000000..2bdf843f016a7c9d175a31b76ae805d63c4cbc80
>>> --- /dev/null
>>> +++ b/testcases/kernel/syscalls/madvise/madvise12.c
>>> @@ -0,0 +1,102 @@
>>> +// SPDX-License-Identifier: GPL-2.0-or-later
>>> +/*
>>> + * Copyright (c) 2024 Andrea Cervesato <andrea.cervesato@suse.com>
>>> + */
>>> +
>>> +/*\
>>> + * [Description]
>>> + *
>>> + * Verify that MADV_GUARD_INSTALL is causing SIGSEGV when someone is accessing
>>> + * memory advised with it.
>> Maybe add:
>> 	* This is a test for feature implemented in
>> 	* 662df3e5c376 ("mm: madvise: implement lightweight guard page mechanism")
>>
>> The rest LGTM.
>>
>> Reviewed-by: Petr Vorel <pvorel@suse.cz>
>>
>> Kind regards,
>> Petr
>>
>>> + *
>>> + * [Algorithm]
>>> + *
>>> + * - allocate a certain amount of memory
>>> + * - advise memory with MADV_GUARD_INSTALL
>>> + * - access to memory from within a child and verify it gets killed by SIGSEGV
>>> + * - release memory with MADV_GUARD_REMOVE
>>> + * - verify that memory has not been modified before child got killed
>>> + * - modify memory within a new child
>>> + * - verify that memory is accessable and child was not killed by SIGSEGV
>>> + */
>>> +
>>> +#include "tst_test.h"
>>> +#include "lapi/mmap.h"
>>> +
>>> +#define MAP_SIZE (8 * TST_KB)
>>> +
>>> +static char *addr;
>>> +
>>> +static void run(void)
>>> +{
>>> +	pid_t pid;
>>> +	int status;
>>> +
>>> +	memset(addr, 0, MAP_SIZE);
>>> +
>>> +	TST_EXP_PASS(madvise(addr, MAP_SIZE, MADV_GUARD_INSTALL));
>>> +
>>> +	pid = SAFE_FORK();
>>> +	if (!pid) {
>>> +		tst_res(TINFO, "Modifying memory content");
>>> +
>>> +		memset(addr, 'a', MAP_SIZE);
>>> +		exit(0);
>>> +	}
>>> +
>>> +	SAFE_WAITPID(pid, &status, 0);
>>> +
>>> +	if (WIFSIGNALED(status) && WTERMSIG(status) == SIGSEGV)
>>> +		tst_res(TPASS, "Child ended by SIGSEGV as expected");
>>> +	else
>>> +		tst_res(TFAIL, "Child: %s", tst_strstatus(status));
>>> +
>>> +	TST_EXP_PASS(madvise(addr, MAP_SIZE, MADV_GUARD_REMOVE));
>>> +
>>> +	for (int i = 0; i < MAP_SIZE; i++) {
>>> +		if (addr[i] == 'a') {
>>> +			tst_res(TFAIL, "Memory content has been modified");
>>> +			return;
>>> +		}
>>> +	}
>>> +
>>> +	tst_res(TPASS, "Memory content didn't change");
>>> +
>>> +	pid = SAFE_FORK();
>>> +	if (!pid) {
>>> +		tst_res(TINFO, "Modifying memory content");
>>> +
>>> +		memset(addr, 'b', MAP_SIZE);
>>> +		exit(0);
>>> +	}
>>> +
>>> +	SAFE_WAITPID(pid, &status, 0);
>>> +
>>> +	if (!WIFSIGNALED(status))
>>> +		tst_res(TPASS, "Child ended without being signaled");
>>> +	else
>>> +		tst_res(TFAIL, "Child ended with %s", tst_strstatus(status));
>>> +}
>>> +
>>> +static void setup(void)
>>> +{
>>> +	addr = SAFE_MMAP(NULL, MAP_SIZE,
>>> +			PROT_READ | PROT_WRITE,
>>> +			MAP_PRIVATE | MAP_ANONYMOUS,
>>> +			-1, 0);
>>> +}
>>> +
>>> +static void cleanup(void)
>>> +{
>>> +	if (addr)
>>> +		SAFE_MUNMAP(addr, MAP_SIZE);
>>> +}
>>> +
>>> +static struct tst_test test = {
>>> +	.test_all = run,
>>> +	.setup = setup,
>>> +	.cleanup = cleanup,
>>> +	.needs_root = 1,
>>> +	.forks_child = 1,
>>> +	.min_kver = "6.13",
>>> +};
>> --
>> Mailing list info: https://lists.linux.it/listinfo/ltp