mem: add memtaint().

[ccan] / ccan / mem / mem.c

diff --git a/ccan/mem/mem.c b/ccan/mem/mem.c
index af41f9e011edbc6738667c3fc89d9d043b1dbcf6..13027a2a7b0fec1b18ae386f9704d84aed41c5f1 100644 (file)
--- a/ccan/mem/mem.c
+++ b/ccan/mem/mem.c
@@ -92,13 +92,37 @@ void memswap(void *a, void *b, size_t n)
 bool memeqzero(const void *data, size_t length)
 {
        const unsigned char *p = data;
-       static unsigned long zeroes[16];
+       size_t len;
 
-       while (length > sizeof(zeroes)) {
-               if (memcmp(zeroes, p, sizeof(zeroes)))
+       /* Check first 16 bytes manually */
+       for (len = 0; len < 16; len++) {
+               if (!length)
+                       return true;
+               if (*p)
                        return false;
-               p += sizeof(zeroes);
-               length -= sizeof(zeroes);
+               p++;
+               length--;
        }
-       return memcmp(zeroes, p, length) == 0;
+
+       /* Now we know that's zero, memcmp with self. */
+       return memcmp(data, p, length) == 0;
+}
+
+void memtaint(void *data, size_t len)
+{
+       /* Using 16 bytes is a bit quicker than 4 */
+       const unsigned tainter[]
+               = { 0xdeadbeef, 0xdeadbeef, 0xdeadbeef, 0xdeadbeef };
+       char *p = data;
+
+       while (len >= sizeof(tainter)) {
+               memcpy(p, tainter, sizeof(tainter));
+               p += sizeof(tainter);
+               len -= sizeof(tainter);
+       }
+       memcpy(p, tainter, len);
+
+#if HAVE_VALGRIND_MEMCHECK_H
+       VALGRIND_MAKE_MEM_UNDEFINED(data, len);
+#endif
 }