Re: [PATCH] selftests/vm: Add a test for MAP_FIXED_NOREPLACE
From: Khalid Aziz
Date: Mon Oct 15 2018 - 03:40:34 EST
On 10/13/2018 07:39 AM, Michael Ellerman wrote:
Add a test for MAP_FIXED_NOREPLACE, based on some code originally by
Jann Horn. This would have caught the overlap bug reported by Daniel Micay.
I originally suggested to Michal that we create MAP_FIXED_NOREPLACE, but
instead of writing a selftest I spent my time bike-shedding whether it
should be called MAP_FIXED_SAFE/NOCLOBBER/WEAK/NEW .. mea culpa.
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---
Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
--
Khalid
tools/testing/selftests/vm/.gitignore | 1 +
tools/testing/selftests/vm/Makefile | 1 +
.../selftests/vm/map_fixed_noreplace.c | 206 ++++++++++++++++++
3 files changed, 208 insertions(+)
create mode 100644 tools/testing/selftests/vm/map_fixed_noreplace.c
diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index af5ff83f6d7f..31b3c98b6d34 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -13,3 +13,4 @@ mlock-random-test
virtual_address_range
gup_benchmark
va_128TBswitch
+map_fixed_noreplace
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index e94b7b14bcb2..6e67e726e5a5 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -12,6 +12,7 @@ TEST_GEN_FILES += gup_benchmark
TEST_GEN_FILES += hugepage-mmap
TEST_GEN_FILES += hugepage-shm
TEST_GEN_FILES += map_hugetlb
+TEST_GEN_FILES += map_fixed_noreplace
TEST_GEN_FILES += map_populate
TEST_GEN_FILES += mlock-random-test
TEST_GEN_FILES += mlock2-tests
diff --git a/tools/testing/selftests/vm/map_fixed_noreplace.c b/tools/testing/selftests/vm/map_fixed_noreplace.c
new file mode 100644
index 000000000000..d91bde511268
--- /dev/null
+++ b/tools/testing/selftests/vm/map_fixed_noreplace.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Test that MAP_FIXED_NOREPLACE works.
+ *
+ * Copyright 2018, Jann Horn <jannh@xxxxxxxxxx>
+ * Copyright 2018, Michael Ellerman, IBM Corporation.
+ */
+
+#include <sys/mman.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#ifndef MAP_FIXED_NOREPLACE
+#define MAP_FIXED_NOREPLACE 0x100000
+#endif
+
+#define BASE_ADDRESS (256ul * 1024 * 1024)
+
+
+static void dump_maps(void)
+{
+ char cmd[32];
+
+ snprintf(cmd, sizeof(cmd), "cat /proc/%d/maps", getpid());
+ system(cmd);
+}
+
+int main(void)
+{
+ unsigned long flags, addr, size, page_size;
+ char *p;
+
+ page_size = sysconf(_SC_PAGE_SIZE);
+
+ flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE;
+
+ // Check we can map all the areas we need below
+ errno = 0;
+ addr = BASE_ADDRESS;
+ size = 5 * page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p == MAP_FAILED) {
+ dump_maps();
+ printf("Error: couldn't map the space we need for the test\n");
+ return 1;
+ }
+
+ errno = 0;
+ if (munmap((void *)addr, 5 * page_size) != 0) {
+ dump_maps();
+ printf("Error: munmap failed!?\n");
+ return 1;
+ }
+ printf("unmap() successful\n");
+
+ errno = 0;
+ addr = BASE_ADDRESS + page_size;
+ size = 3 * page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p == MAP_FAILED) {
+ dump_maps();
+ printf("Error: first mmap() failed unexpectedly\n");
+ return 1;
+ }
+
+ /*
+ * Exact same mapping again:
+ * base | free | new
+ * +1 | mapped | new
+ * +2 | mapped | new
+ * +3 | mapped | new
+ * +4 | free | new
+ */
+ errno = 0;
+ addr = BASE_ADDRESS;
+ size = 5 * page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p != MAP_FAILED) {
+ dump_maps();
+ printf("Error:1: mmap() succeeded when it shouldn't have\n");
+ return 1;
+ }
+
+ /*
+ * Second mapping contained within first:
+ *
+ * base | free |
+ * +1 | mapped |
+ * +2 | mapped | new
+ * +3 | mapped |
+ * +4 | free |
+ */
+ errno = 0;
+ addr = BASE_ADDRESS + (2 * page_size);
+ size = page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p != MAP_FAILED) {
+ dump_maps();
+ printf("Error:2: mmap() succeeded when it shouldn't have\n");
+ return 1;
+ }
+
+ /*
+ * Overlap end of existing mapping:
+ * base | free |
+ * +1 | mapped |
+ * +2 | mapped |
+ * +3 | mapped | new
+ * +4 | free | new
+ */
+ errno = 0;
+ addr = BASE_ADDRESS + (3 * page_size);
+ size = 2 * page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p != MAP_FAILED) {
+ dump_maps();
+ printf("Error:3: mmap() succeeded when it shouldn't have\n");
+ return 1;
+ }
+
+ /*
+ * Overlap start of existing mapping:
+ * base | free | new
+ * +1 | mapped | new
+ * +2 | mapped |
+ * +3 | mapped |
+ * +4 | free |
+ */
+ errno = 0;
+ addr = BASE_ADDRESS;
+ size = 2 * page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p != MAP_FAILED) {
+ dump_maps();
+ printf("Error:4: mmap() succeeded when it shouldn't have\n");
+ return 1;
+ }
+
+ /*
+ * Adjacent to start of existing mapping:
+ * base | free | new
+ * +1 | mapped |
+ * +2 | mapped |
+ * +3 | mapped |
+ * +4 | free |
+ */
+ errno = 0;
+ addr = BASE_ADDRESS;
+ size = page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p == MAP_FAILED) {
+ dump_maps();
+ printf("Error:5: mmap() failed when it shouldn't have\n");
+ return 1;
+ }
+
+ /*
+ * Adjacent to end of existing mapping:
+ * base | free |
+ * +1 | mapped |
+ * +2 | mapped |
+ * +3 | mapped |
+ * +4 | free | new
+ */
+ errno = 0;
+ addr = BASE_ADDRESS + (4 * page_size);
+ size = page_size;
+ p = mmap((void *)addr, size, PROT_NONE, flags, -1, 0);
+ printf("mmap() @ 0x%lx-0x%lx p=%p result=%m\n", addr, addr + size, p);
+
+ if (p == MAP_FAILED) {
+ dump_maps();
+ printf("Error:6: mmap() failed when it shouldn't have\n");
+ return 1;
+ }
+
+ addr = BASE_ADDRESS;
+ size = 5 * page_size;
+ if (munmap((void *)addr, size) != 0) {
+ dump_maps();
+ printf("Error: munmap failed!?\n");
+ return 1;
+ }
+ printf("unmap() successful\n");
+
+ printf("OK\n");
+ return 0;
+}