[LTP] [PATCH v3] Migrating the libhugetlbfs/testcases/truncate_sigbus_versus_oom.c test

[Cyril Hrubis]

Hi!
> Some kernel have a bug in the positioning of the test against
> i_size.  This bug means that attempting to instantiate a page
> beyond the end of a hugepage file can result in an OOM and SIGKILL
> instead of the correct SIGBUS.
> 
> Signed-off-by: Samir Mulani <samir@linux.vnet.ibm.com>
> ---
> v3:
> --Addressed the below requested changes
>   1. Added volatile variable in signal handler to varify the SIGBUS signal in runtest method.
>   2. Fixed run test more times (-iN)
>   3. Removed number of required hugepages.
>   4. Corrected commit numberin struct tst_test.
>   5. Ran make check and fixed the issues.
> ---
>  runtest/hugetlb                               |   1 +
>  testcases/kernel/mem/.gitignore               |   1 +
>  .../kernel/mem/hugetlb/hugemmap/hugemmap37.c  | 103 ++++++++++++++++++
>  3 files changed, 105 insertions(+)
>  create mode 100644 testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c
> 
> diff --git a/runtest/hugetlb b/runtest/hugetlb
> index 299c07ac9..7b7c44b77 100644
> --- a/runtest/hugetlb
> +++ b/runtest/hugetlb
> @@ -35,6 +35,7 @@ hugemmap29 hugemmap29
>  hugemmap30 hugemmap30
>  hugemmap31 hugemmap31
>  hugemmap32 hugemmap32
> +hugemmap37 hugemmap37
>  hugemmap05_1 hugemmap05 -m
>  hugemmap05_2 hugemmap05 -s
>  hugemmap05_3 hugemmap05 -s -m
> diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
> index c96fe8bfc..a74260689 100644
> --- a/testcases/kernel/mem/.gitignore
> +++ b/testcases/kernel/mem/.gitignore
> @@ -34,6 +34,7 @@
>  /hugetlb/hugemmap/hugemmap30
>  /hugetlb/hugemmap/hugemmap31
>  /hugetlb/hugemmap/hugemmap32
> +/hugetlb/hugemmap/hugemmap37
>  /hugetlb/hugeshmat/hugeshmat01
>  /hugetlb/hugeshmat/hugeshmat02
>  /hugetlb/hugeshmat/hugeshmat03
> diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c
> new file mode 100644
> index 000000000..5c55afe54
> --- /dev/null
> +++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c
> @@ -0,0 +1,103 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Test Name: Truncate_sigbus_versus_oom

Please drop the test name here as well.

> + * Some kernel have a bug in the positioning of the test against
> + * i_size.  This bug means that attempting to instantiate a page
> + * beyond the end of a hugepage file can result in an OOM and SIGKILL
> + * instead of the correct SIGBUS.
> + */
> +
> +#include <setjmp.h>
> +#include <signal.h>
> +#include "hugetlb.h"
> +
> +#define MNTPOINT "hugetlbfs/"
> +#define PTS_PASS 0

This macro is unused now.

> +static int  fd = -1, fdx = -1;
> +
> +static unsigned long long hpage_size;
> +static unsigned long totpages;
> +struct sigaction sa;
> +static sigjmp_buf sig_escape;
> +static volatile int test_pass;
> +static int sigbus_count;
> +
> +static void sigbus_handler(int signum LTP_ATTRIBUTE_UNUSED)
> +{
> +	test_pass = 1;
> +	siglongjmp(sig_escape, 17);
> +}
> +
> +static void run_test(void)
> +{
> +	void *p, *q;
> +	unsigned long i;
> +
> +	sigbus_count = 0;
> +	test_pass = 0;
> +
> +	fd = tst_creat_unlinked(MNTPOINT, 0);
> +	p = SAFE_MMAP(NULL, hpage_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
> +	SAFE_FTRUNCATE(fd, 0);
> +
> +	fdx = tst_creat_unlinked(MNTPOINT, 0);
> +	totpages = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
> +	q = SAFE_MMAP(NULL, totpages * hpage_size, PROT_READ|PROT_WRITE, MAP_SHARED, fdx, 0);
> +	/* Touch the pages to ensure they're removed from the pool */
> +	for (i = 0; i < totpages; i++) {
> +		volatile char *x = (volatile char *)q + i*hpage_size;
> +		*x = 0;
> +	}
> +	/* SIGBUS is what *should* happen */
> +	SAFE_FTRUNCATE(fdx, 0);
> +	if (sigsetjmp(sig_escape, 1) == 0)
> +		*((volatile unsigned int *)p);
> +	else
> +		sigbus_count++;

I still think that this is actually useless, we already set a flag in
the signal handler so we can drop the whole sigbus_count logic from the
test and it could be simplified as:

	if (segsetjmp(sig_escape, 1) == 0)
		*((voilatile unsigned int *)p);

	if (test_pass)
		tst_res(TPASS, ...);
	else
		tst_res(TFAIL, ...);

I mean we are not going to get to the else branch that increments the
sigbus_count from anywhere else than the signal handler which already
set the test_pass, so the values of test_pass and sigbus_count will be
always the same.

> +	if (sigbus_count != 1)
> +		tst_res(TFAIL, "Didn't SIGBUS");
> +
> +	if (test_pass == 1)
> +		tst_res(TPASS, "Expected SIGBUS triggered");
> +}
> +
> +void setup(void)
> +{
> +	sa.sa_flags = SA_SIGINFO;
> +	sa.sa_handler = sigbus_handler;
> +	SAFE_SIGACTION(SIGBUS, &sa, NULL);
> +	totpages = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
> +	hpage_size = tst_get_hugepage_size();
> +}
> +
> +void cleanup(void)
> +{
> +	if (fd > 0)
> +		SAFE_CLOSE(fd);
> +	if (fdx > 0)
> +		SAFE_CLOSE(fdx);
> +}
> +
> +
> +static struct tst_test test = {
> +	.tags = (struct tst_tag[]) {
> +		{"linux-git", "ebed4bfc8da8"},
> +		{}
> +	},
> +	.needs_root = 1,
> +	.mntpoint = MNTPOINT,
> +	.needs_hugetlbfs = 1,
> +	.needs_tmpdir = 1,
> +	.setup = setup,
> +	.cleanup = cleanup,
> +	.test_all = run_test,
> +	.hugepages = {1, TST_NEEDS},
> +};
> -- 
> 2.43.0
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz