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

[Petr Vorel]

Hi Andrea,

[ I dared to Cc Lorenzo, the author of the kernel implementation ]

> 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.

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",
> +};