365 lines
12 KiB
C
365 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Tests for mremap w/ MREMAP_DONTUNMAP.
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*
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* Copyright 2020, Brian Geffon <bgeffon@google.com>
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*/
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#define _GNU_SOURCE
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#include <sys/mman.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "../kselftest.h"
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#ifndef MREMAP_DONTUNMAP
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#define MREMAP_DONTUNMAP 4
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#endif
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unsigned long page_size;
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char *page_buffer;
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static void dump_maps(void)
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{
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char cmd[32];
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snprintf(cmd, sizeof(cmd), "cat /proc/%d/maps", getpid());
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system(cmd);
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}
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#define BUG_ON(condition, description) \
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do { \
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if (condition) { \
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fprintf(stderr, "[FAIL]\t%s():%d\t%s:%s\n", __func__, \
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__LINE__, (description), strerror(errno)); \
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dump_maps(); \
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exit(1); \
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} \
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} while (0)
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// Try a simple operation for to "test" for kernel support this prevents
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// reporting tests as failed when it's run on an older kernel.
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static int kernel_support_for_mremap_dontunmap()
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{
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int ret = 0;
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unsigned long num_pages = 1;
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void *source_mapping = mmap(NULL, num_pages * page_size, PROT_NONE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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// This simple remap should only fail if MREMAP_DONTUNMAP isn't
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// supported.
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void *dest_mapping =
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mremap(source_mapping, num_pages * page_size, num_pages * page_size,
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MREMAP_DONTUNMAP | MREMAP_MAYMOVE, 0);
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if (dest_mapping == MAP_FAILED) {
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ret = errno;
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} else {
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BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
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"unable to unmap destination mapping");
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}
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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return ret;
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}
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// This helper will just validate that an entire mapping contains the expected
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// byte.
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static int check_region_contains_byte(void *addr, unsigned long size, char byte)
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{
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BUG_ON(size & (page_size - 1),
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"check_region_contains_byte expects page multiples");
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BUG_ON((unsigned long)addr & (page_size - 1),
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"check_region_contains_byte expects page alignment");
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memset(page_buffer, byte, page_size);
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unsigned long num_pages = size / page_size;
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unsigned long i;
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// Compare each page checking that it contains our expected byte.
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for (i = 0; i < num_pages; ++i) {
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int ret =
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memcmp(addr + (i * page_size), page_buffer, page_size);
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if (ret) {
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return ret;
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}
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}
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return 0;
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}
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// this test validates that MREMAP_DONTUNMAP moves the pagetables while leaving
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// the source mapping mapped.
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static void mremap_dontunmap_simple()
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{
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unsigned long num_pages = 5;
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void *source_mapping =
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mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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memset(source_mapping, 'a', num_pages * page_size);
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// Try to just move the whole mapping anywhere (not fixed).
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void *dest_mapping =
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mremap(source_mapping, num_pages * page_size, num_pages * page_size,
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MREMAP_DONTUNMAP | MREMAP_MAYMOVE, NULL);
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BUG_ON(dest_mapping == MAP_FAILED, "mremap");
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// Validate that the pages have been moved, we know they were moved if
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// the dest_mapping contains a's.
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BUG_ON(check_region_contains_byte
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(dest_mapping, num_pages * page_size, 'a') != 0,
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"pages did not migrate");
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BUG_ON(check_region_contains_byte
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(source_mapping, num_pages * page_size, 0) != 0,
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"source should have no ptes");
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BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
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"unable to unmap destination mapping");
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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}
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// This test validates that MREMAP_DONTUNMAP on a shared mapping works as expected.
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static void mremap_dontunmap_simple_shmem()
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{
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unsigned long num_pages = 5;
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int mem_fd = memfd_create("memfd", MFD_CLOEXEC);
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BUG_ON(mem_fd < 0, "memfd_create");
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BUG_ON(ftruncate(mem_fd, num_pages * page_size) < 0,
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"ftruncate");
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void *source_mapping =
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mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
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MAP_FILE | MAP_SHARED, mem_fd, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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BUG_ON(close(mem_fd) < 0, "close");
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memset(source_mapping, 'a', num_pages * page_size);
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// Try to just move the whole mapping anywhere (not fixed).
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void *dest_mapping =
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mremap(source_mapping, num_pages * page_size, num_pages * page_size,
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MREMAP_DONTUNMAP | MREMAP_MAYMOVE, NULL);
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if (dest_mapping == MAP_FAILED && errno == EINVAL) {
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// Old kernel which doesn't support MREMAP_DONTUNMAP on shmem.
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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return;
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}
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BUG_ON(dest_mapping == MAP_FAILED, "mremap");
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// Validate that the pages have been moved, we know they were moved if
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// the dest_mapping contains a's.
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BUG_ON(check_region_contains_byte
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(dest_mapping, num_pages * page_size, 'a') != 0,
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"pages did not migrate");
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// Because the region is backed by shmem, we will actually see the same
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// memory at the source location still.
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BUG_ON(check_region_contains_byte
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(source_mapping, num_pages * page_size, 'a') != 0,
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"source should have no ptes");
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BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
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"unable to unmap destination mapping");
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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}
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// This test validates MREMAP_DONTUNMAP will move page tables to a specific
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// destination using MREMAP_FIXED, also while validating that the source
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// remains intact.
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static void mremap_dontunmap_simple_fixed()
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{
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unsigned long num_pages = 5;
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// Since we want to guarantee that we can remap to a point, we will
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// create a mapping up front.
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void *dest_mapping =
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mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(dest_mapping == MAP_FAILED, "mmap");
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memset(dest_mapping, 'X', num_pages * page_size);
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void *source_mapping =
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mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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memset(source_mapping, 'a', num_pages * page_size);
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void *remapped_mapping =
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mremap(source_mapping, num_pages * page_size, num_pages * page_size,
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MREMAP_FIXED | MREMAP_DONTUNMAP | MREMAP_MAYMOVE,
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dest_mapping);
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BUG_ON(remapped_mapping == MAP_FAILED, "mremap");
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BUG_ON(remapped_mapping != dest_mapping,
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"mremap should have placed the remapped mapping at dest_mapping");
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// The dest mapping will have been unmap by mremap so we expect the Xs
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// to be gone and replaced with a's.
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BUG_ON(check_region_contains_byte
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(dest_mapping, num_pages * page_size, 'a') != 0,
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"pages did not migrate");
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// And the source mapping will have had its ptes dropped.
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BUG_ON(check_region_contains_byte
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(source_mapping, num_pages * page_size, 0) != 0,
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"source should have no ptes");
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BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
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"unable to unmap destination mapping");
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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}
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// This test validates that we can MREMAP_DONTUNMAP for a portion of an
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// existing mapping.
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static void mremap_dontunmap_partial_mapping()
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{
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/*
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* source mapping:
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* --------------
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* | aaaaaaaaaa |
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* --------------
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* to become:
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* --------------
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* | aaaaa00000 |
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* --------------
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* With the destination mapping containing 5 pages of As.
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* ---------
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* | aaaaa |
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* ---------
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*/
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unsigned long num_pages = 10;
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void *source_mapping =
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mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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memset(source_mapping, 'a', num_pages * page_size);
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// We will grab the last 5 pages of the source and move them.
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void *dest_mapping =
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mremap(source_mapping + (5 * page_size), 5 * page_size,
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5 * page_size,
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MREMAP_DONTUNMAP | MREMAP_MAYMOVE, NULL);
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BUG_ON(dest_mapping == MAP_FAILED, "mremap");
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// We expect the first 5 pages of the source to contain a's and the
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// final 5 pages to contain zeros.
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BUG_ON(check_region_contains_byte(source_mapping, 5 * page_size, 'a') !=
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0, "first 5 pages of source should have original pages");
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BUG_ON(check_region_contains_byte
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(source_mapping + (5 * page_size), 5 * page_size, 0) != 0,
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"final 5 pages of source should have no ptes");
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// Finally we expect the destination to have 5 pages worth of a's.
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BUG_ON(check_region_contains_byte(dest_mapping, 5 * page_size, 'a') !=
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0, "dest mapping should contain ptes from the source");
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BUG_ON(munmap(dest_mapping, 5 * page_size) == -1,
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"unable to unmap destination mapping");
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BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
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"unable to unmap source mapping");
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}
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// This test validates that we can remap over only a portion of a mapping.
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static void mremap_dontunmap_partial_mapping_overwrite(void)
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{
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/*
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* source mapping:
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* ---------
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* |aaaaa|
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* ---------
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* dest mapping initially:
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* -----------
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* |XXXXXXXXXX|
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* ------------
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* Source to become:
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* ---------
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* |00000|
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* ---------
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* With the destination mapping containing 5 pages of As.
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* ------------
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* |aaaaaXXXXX|
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* ------------
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*/
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void *source_mapping =
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mmap(NULL, 5 * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(source_mapping == MAP_FAILED, "mmap");
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memset(source_mapping, 'a', 5 * page_size);
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void *dest_mapping =
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mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(dest_mapping == MAP_FAILED, "mmap");
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memset(dest_mapping, 'X', 10 * page_size);
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// We will grab the last 5 pages of the source and move them.
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void *remapped_mapping =
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mremap(source_mapping, 5 * page_size,
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5 * page_size,
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MREMAP_DONTUNMAP | MREMAP_MAYMOVE | MREMAP_FIXED, dest_mapping);
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BUG_ON(dest_mapping == MAP_FAILED, "mremap");
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BUG_ON(dest_mapping != remapped_mapping, "expected to remap to dest_mapping");
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BUG_ON(check_region_contains_byte(source_mapping, 5 * page_size, 0) !=
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0, "first 5 pages of source should have no ptes");
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// Finally we expect the destination to have 5 pages worth of a's.
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BUG_ON(check_region_contains_byte(dest_mapping, 5 * page_size, 'a') != 0,
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"dest mapping should contain ptes from the source");
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// Finally the last 5 pages shouldn't have been touched.
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BUG_ON(check_region_contains_byte(dest_mapping + (5 * page_size),
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5 * page_size, 'X') != 0,
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"dest mapping should have retained the last 5 pages");
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BUG_ON(munmap(dest_mapping, 10 * page_size) == -1,
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"unable to unmap destination mapping");
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BUG_ON(munmap(source_mapping, 5 * page_size) == -1,
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"unable to unmap source mapping");
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}
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int main(void)
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{
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page_size = sysconf(_SC_PAGE_SIZE);
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// test for kernel support for MREMAP_DONTUNMAP skipping the test if
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// not.
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if (kernel_support_for_mremap_dontunmap() != 0) {
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printf("No kernel support for MREMAP_DONTUNMAP\n");
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return KSFT_SKIP;
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}
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// Keep a page sized buffer around for when we need it.
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page_buffer =
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mmap(NULL, page_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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BUG_ON(page_buffer == MAP_FAILED, "unable to mmap a page.");
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mremap_dontunmap_simple();
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mremap_dontunmap_simple_shmem();
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mremap_dontunmap_simple_fixed();
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mremap_dontunmap_partial_mapping();
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mremap_dontunmap_partial_mapping_overwrite();
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BUG_ON(munmap(page_buffer, page_size) == -1,
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"unable to unmap page buffer");
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printf("OK\n");
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return 0;
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}
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