mmap map_at_zero test: handle W^X

Use kern.elfXX.allow_wx to decide whether to map W+X or W-only memory.

Future work could expand this test to add an "allow_wx" axis to the
test matrix, but I would argue that a separate test should be written,
since that's orthogonal to map_at_zero.

MFC after:	1 week
Sponsored by:	Dell EMC Isilon

(cherry picked from commit 766c2466ff465b3c7c1a46be729b42a6da47de03)

diff --git a/tests/sys/vm/mmap_test.c b/tests/sys/vm/mmap_test.c
index 61ede96fc49bfdd9dd2314f3c19c4240650a9527..dc01a23fff2114c0637c51874e43b027bdc0aa66 100644 (file)
--- a/tests/sys/vm/mmap_test.c
+++ b/tests/sys/vm/mmap_test.c
@@ -34,6 +34,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -54,6 +55,12 @@ static const struct {
 
 #define        MAP_AT_ZERO     "security.bsd.map_at_zero"
 
+#ifdef __LP64__
+#define ALLOW_WX "kern.elf64.allow_wx"
+#else
+#define ALLOW_WX "kern.elf32.allow_wx"
+#endif
+
 ATF_TC_WITHOUT_HEAD(mmap__map_at_zero);
 ATF_TC_BODY(mmap__map_at_zero, tc)
 {
@@ -61,6 +68,8 @@ ATF_TC_BODY(mmap__map_at_zero, tc)
        size_t len;
        unsigned int i;
        int map_at_zero;
+       bool allow_wx;
+       int prot_flags;
 
        len = sizeof(map_at_zero);
        if (sysctlbyname(MAP_AT_ZERO, &map_at_zero, &len, NULL, 0) == -1) {
@@ -69,13 +78,27 @@ ATF_TC_BODY(mmap__map_at_zero, tc)
                return;
        }
 
+       len = sizeof(allow_wx);
+       if (sysctlbyname(ALLOW_WX, &allow_wx, &len, NULL, 0) == -1) {
+               if (errno == ENOENT) {
+                       /* Allow W+X if sysctl isn't present */
+                       allow_wx = true;
+               } else {
+                       atf_tc_skip("sysctl for %s failed: %s\n", ALLOW_WX,
+                           strerror(errno));
+                       return;
+               }
+       }
+
        /* Normalize to 0 or 1 for array access. */
        map_at_zero = !!map_at_zero;
 
        for (i = 0; i < nitems(map_at_zero_tests); i++) {
+               prot_flags = PROT_READ | PROT_WRITE;
+               if (allow_wx)
+                       prot_flags |= PROT_EXEC;
                p = mmap((void *)map_at_zero_tests[i].addr, PAGE_SIZE,
-                   PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANON | MAP_FIXED,
-                   -1, 0);
+                   prot_flags, MAP_ANON | MAP_FIXED, -1, 0);
                if (p == MAP_FAILED) {
                        ATF_CHECK_MSG(map_at_zero_tests[i].ok[map_at_zero] == 0,
                            "mmap(%p, ...) failed", map_at_zero_tests[i].addr);