Re: [LTP] [PATCH v2] mmap21.c: Test for new MAP_DROPPABLE flag for mmap

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> diff --git a/testcases/kernel/syscalls/mmap/mmap21.c b/testcases/kernel/syscalls/mmap/mmap21.c
> new file mode 100644
> index 000000000..46f3ac7c5
> --- /dev/null
> +++ b/testcases/kernel/syscalls/mmap/mmap21.c
> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2024 Wei Gao <wegao@suse.com>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Test mmap(2) with MAP_DROPPABLE flag.
> + *
> + * Test base on kernel selftests/mm/droppable.c
> + */
> +
> +#define _GNU_SOURCE
> +#include <errno.h>
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include "tst_test.h"
> +#include "lapi/mmap.h"
> +
> +#define MEM_LIMIT (256 * TST_MB)
> +#define ALLOC_SIZE (128 * TST_MB)
> +
> +static struct tst_cg_group *cg_child;
> +
> +static void test_mmap(void)
> +{
> +	size_t alloc_size = ALLOC_SIZE;
> +	size_t page_size = getpagesize();
> +	void *alloc;
> +	pid_t child;
> +
> +	cg_child = tst_cg_group_mk(tst_cg, "child");
> +	SAFE_CG_PRINTF(tst_cg, "memory.max", "%d", MEM_LIMIT);
> +	SAFE_CG_PRINTF(cg_child, "cgroup.procs", "%d", getpid());
> +
> +	alloc = SAFE_MMAP(0, alloc_size, PROT_READ | PROT_WRITE,
> +			MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> +
> +	memset(alloc, 'A', alloc_size);
> +	for (size_t i = 0; i < alloc_size; i += page_size) {
> +		if (*(char *)(alloc + i) != 'A')
> +			tst_res(TFAIL, "memset failed");
> +	}
> +
> +	int *shared_var = SAFE_MMAP(NULL, sizeof(int), PROT_READ | PROT_WRITE,
> +			MAP_SHARED | MAP_ANONYMOUS, -1, 0);
> +
> +	*shared_var = 0;
> +
> +	child = SAFE_FORK();
> +	if (!child) {
> +		for (;;) {
> +			*(char *)malloc(page_size) = 'B';
> +			if ((*shared_var) == 1)
> +				exit(0);
> +		}
> +	}
> +
> +	while (!(*shared_var)) {
> +		for (size_t i = 0; i < alloc_size; i += page_size) {
> +			if (!*(uint8_t *)(alloc + i)) {
> +				*shared_var = 1;

Why do we need the shared_var at all? Why can't we just SIGKILL the
child at this point the same way the selftest does it?

> +				break;
> +			}
> +		}
> +	}
> +
> +	TST_EXP_EQ_LI((*shared_var), 1);
> +
> +	SAFE_WAITPID(child, NULL, 0);
> +
> +	SAFE_MUNMAP(alloc, alloc_size);
> +	SAFE_MUNMAP(shared_var, sizeof(int));
> +}
> +
> +static void setup(void)
> +{
> +	void *addr = mmap(0, 1, PROT_READ | PROT_WRITE,
> +			MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> +	if (addr == MAP_FAILED && errno == EINVAL)
> +		tst_brk(TCONF, "MAP_DROPPABLE not support");
> +}
> +
> +static void cleanup(void)
> +{
> +	if (cg_child) {
> +		SAFE_CG_PRINTF(tst_cg_drain, "cgroup.procs", "%d", getpid());
> +		cg_child = tst_cg_group_rm(cg_child);
> +	}
> +}
> +
> +static struct tst_test test = {
> +	.test_all = test_mmap,
> +	.needs_tmpdir = 1,
> +	.forks_child = 1,
> +	.needs_cgroup_ctrls = (const char *const []){ "memory", NULL },
> +	.needs_root = 1,
> +	.cleanup = cleanup,
> +	.setup = setup,
> +	.min_mem_avail = 300,
> +};
> -- 
> 2.35.3
> 
> 
> -- 
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-- 
Cyril Hrubis
chrubis@suse.cz

-- 
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