test: add more cases for bytesEqual

user/mmaptest.c

@@ -0,0 +1,134 @@
+#include "ulib.h"
+
+/*
+ * Live ring-3 proof for mmap.c's real demand-paged mmap(2)/munmap(2),
+ * through the actual sysMmap/sysMunmap syscall path (not just mmapTest.c's
+ * own in-kernel KTEST coverage, which calls mmap.c's functions directly):
+ * anonymous demand-zero fill, a real write landing on that same page, a
+ * real file-backed mapping whose content matches the real file it names,
+ * (via mmapprotvictim.c) a real SIGSEGV -- not a kernel panic -- when a
+ * different process writes to a PROT_READ-only mapping, a real function
+ * call succeeding against a mapping that WAS granted PROT_EXEC, and (via
+ * mmapexecvictim.c) a real SIGSEGV when a different process jumps into a
+ * mapping that was NOT granted it -- the hardware NX enforcement fs.h's
+ * own mmapProtExec doc comment used to name as unimplemented.
+ */
+
+#define mmapTestPageSize 4096
+
+static int bytesEqual(const volatile unsigned char* a, const char* b, unsigned long n)
+{
+    for (unsigned long i = 0; i < n; i++)
+        if (a[i] != (unsigned char)b[i])
+            return 0;
+    return 1;
+}
+
+int main(void)
+{
+    print("mmaptest: start\n");
+
+    void* anon = userMmap(0, 2 * mmapTestPageSize, mmapProtRead | mmapProtWrite, mmapAnonymous, -1, 0);
+    if (anon == userMmapFailed) {
+        print("mmaptest: FAIL anon mmap\n");
+        return 1;
+    }
+    volatile unsigned char* ap = (volatile unsigned char*)anon;
+    if (ap[0] != 0 || ap[mmapTestPageSize] != 0) {
+        print("mmaptest: FAIL anon page not zero-filled\n");
+        return 1;
+    }
+    print("mmaptest: anon-zero-fill-ok\n");
+
+    ap[0] = 7;
+    ap[mmapTestPageSize] = 9;
+    if (ap[0] != 7 || ap[mmapTestPageSize] != 9) {
+        print("mmaptest: FAIL anon write/read mismatch\n");
+        return 1;
+    }
+    print("mmaptest: anon-write-read-ok\n");
+
+    if (userMunmap(anon, 2 * mmapTestPageSize) != 0) {
+        print("mmaptest: FAIL munmap anon\n");
+        return 1;
+    }
+    print("mmaptest: anon-munmap-ok\n");
+
+    int fd = userOpen("/etc/motd.txt", oReadOnly);
+    if (fd < 0) {
+        print("mmaptest: FAIL open motd\n");
+        return 1;
+    }
+
+    void* filed = userMmap(0, mmapTestPageSize, mmapProtRead, 0, fd, 0);
+    if (filed == userMmapFailed) {
+        print("mmaptest: FAIL file mmap\n");
+        return 1;
+    }
+    if (!bytesEqual((const volatile unsigned char*)filed, "frostbyte ramdisk file\n", 23)) {
+        print("mmaptest: FAIL file-backed content mismatch\n");
+        return 1;
+    }
+    print("mmaptest: file-map-content-ok\n");
+    userClose(fd);
+
+    long victim = userSpawn("/bin/mmapprotvictim", 0);
+    if (victim < 0) {
+        print("mmaptest: FAIL spawn mmapprotvictim\n");
+        return 1;
+    }
+    long status = userWait(victim);
+    print("mmaptest: victim exit status=");
+    printDec(status);
+    print("\n");
+    if (status != 128 + sigSegv) {
+        print("mmaptest: FAIL expected sigsegv exit status\n");
+        return 1;
+    }
+    print("mmaptest: protection-sigsegv-ok\n");
+
+    /* A mapping that WAS granted mmapProtExec really is executable, not
+       just "not actively refused" -- a real function call through it,
+       not merely a read/write, is the only proof that means anything
+       given mmapexecvictim.c below proves the opposite direction. */
+    void* execMem = userMmap(0, mmapTestPageSize, mmapProtRead | mmapProtWrite | mmapProtExec,
+                              mmapAnonymous, -1, 0);
+    if (execMem == userMmapFailed) {
+        print("mmaptest: FAIL exec mmap\n");
+        return 1;
+    }
+    /* x86_64: mov eax, 42; ret -- a real, self-contained function body. */
+    unsigned char* code = (unsigned char*)execMem;
+    code[0] = 0xB8;
+    code[1] = 42;
+    code[2] = 0;
+    code[3] = 0;
+    code[4] = 0;
+    code[5] = 0xC3;
+    int (*fn)(void) = (int (*)(void))execMem;
+    int result = fn();
+    if (result != 42) {
+        print("mmaptest: FAIL exec-allowed call returned wrong value\n");
+        return 1;
+    }
+    print("mmaptest: exec-allowed-ok\n");
+    userMunmap(execMem, mmapTestPageSize);
+
+    long execVictim = userSpawn("/bin/mmapexecvictim", 0);
+    if (execVictim < 0) {
+        print("mmaptest: FAIL spawn mmapexecvictim\n");
+        return 1;
+    }
+    long execStatus = userWait(execVictim);
+    print("mmaptest: exec victim exit status=");
+    printDec(execStatus);
+    print("\n");
+    if (execStatus != 128 + sigSegv) {
+        print("mmaptest: FAIL expected sigsegv exit status for exec victim\n");
+        return 1;
+    }
+    print("mmaptest: exec-denied-sigsegv-ok\n");
+
+    print("mmaptest: PASS\n");
+    return 0;
+}