Commit 4a1ff347 authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

tools/testing/selftests: add VMA merge tests for KSM merge 

Add test to assert that we have now allowed merging of VMAs when KSM
merging-by-default has been set by prctl(PR_SET_MEMORY_MERGE, ...).

We simply perform a trivial mapping of adjacent VMAs expecting a merge,
however prior to recent changes implementing this mode earlier than
before, these merges would not have succeeded.

Assert that we have fixed this!

Link: https://lkml.kernel.org/r/6dec7aabf062c6b121cfac992c9c716cefdda00c.1748537921.git.lorenzo.stoakes@oracle.com


Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Tested-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: Xu Xin <xu.xin16@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent cf7e7a35

tools/testing/selftests/mm/merge.c

+78 −0
Original line number Diff line number Diff line
@@ -2,11 +2,13 @@ 


#define _GNU_SOURCE

#include "../kselftest_harness.h"

#include <linux/prctl.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/mman.h>

#include <sys/prctl.h>

#include <sys/syscall.h>

#include <sys/wait.h>

#include <linux/perf_event.h>
@@ -34,6 +36,11 @@ FIXTURE_TEARDOWN(merge) 
{

	ASSERT_EQ(munmap(self->carveout, 12 * self->page_size), 0);

	ASSERT_EQ(close_procmap(&self->procmap), 0);

	/*

	 * Clear unconditionally, as some tests set this. It is no issue if this

	 * fails (KSM may be disabled for instance).

	 */

	prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0);

}



TEST_F(merge, mprotect_unfaulted_left)
@@ -498,4 +505,75 @@ TEST_F(merge, handle_uprobe_upon_merged_vma) 
	remove(probe_file);

}



TEST_F(merge, ksm_merge)

{

	unsigned int page_size = self->page_size;

	char *carveout = self->carveout;

	struct procmap_fd *procmap = &self->procmap;

	char *ptr, *ptr2;

	int err;



	/*

	 * Map two R/W immediately adjacent to one another, they should

	 * trivially merge:

	 *

	 * |-----------|-----------|

	 * |    R/W    |    R/W    |

	 * |-----------|-----------|

	 *      ptr         ptr2

	 */



	ptr = mmap(&carveout[page_size], page_size, PROT_READ | PROT_WRITE,

		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);

	ASSERT_NE(ptr, MAP_FAILED);

	ptr2 = mmap(&carveout[2 * page_size], page_size,

		    PROT_READ | PROT_WRITE,

		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);

	ASSERT_NE(ptr2, MAP_FAILED);

	ASSERT_TRUE(find_vma_procmap(procmap, ptr));

	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);

	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 2 * page_size);



	/* Unmap the second half of this merged VMA. */

	ASSERT_EQ(munmap(ptr2, page_size), 0);



	/* OK, now enable global KSM merge. We clear this on test teardown. */

	err = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);

	if (err == -1) {

		int errnum = errno;



		/* Only non-failure case... */

		ASSERT_EQ(errnum, EINVAL);

		/* ...but indicates we should skip. */

		SKIP(return, "KSM memory merging not supported, skipping.");

	}



	/*

	 * Now map a VMA adjacent to the existing that was just made

	 * VM_MERGEABLE, this should merge as well.

	 */

	ptr2 = mmap(&carveout[2 * page_size], page_size,

		    PROT_READ | PROT_WRITE,

		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);

	ASSERT_NE(ptr2, MAP_FAILED);

	ASSERT_TRUE(find_vma_procmap(procmap, ptr));

	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);

	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 2 * page_size);



	/* Now this VMA altogether. */

	ASSERT_EQ(munmap(ptr, 2 * page_size), 0);



	/* Try the same operation as before, asserting this also merges fine. */

	ptr = mmap(&carveout[page_size], page_size, PROT_READ | PROT_WRITE,

		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);

	ASSERT_NE(ptr, MAP_FAILED);

	ptr2 = mmap(&carveout[2 * page_size], page_size,

		    PROT_READ | PROT_WRITE,

		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);

	ASSERT_NE(ptr2, MAP_FAILED);

	ASSERT_TRUE(find_vma_procmap(procmap, ptr));

	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);

	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 2 * page_size);

}



TEST_HARNESS_MAIN