priv: Implement explicit_bzero as a function if not available

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Alberto Aguirre <albaguirre@gmail.com>

ConfigureChecks.cmake

@@ -291,7 +291,7 @@ int main(void)
 {
     char buf[] = \"This is some content\";
 
-    memset(buf, '\\\\0', sizeof(buf)); __asm__ volatile(\"\" : : \"r\"(&buf) : \"memory\");
+    memset(buf, '\\\\0', sizeof(buf)); __asm__ volatile(\"\" : : \"g\"(&buf) : \"memory\");
 
     return 0;
 }" HAVE_GCC_VOLATILE_MEMORY_PROTECTION)

include/libssh/priv.h

@@ -281,21 +281,7 @@ int ssh_connector_remove_event(ssh_connector connector);
 #define ARRAY_SIZE(a) (sizeof(a)/sizeof(a[0]))
 
 #ifndef HAVE_EXPLICIT_BZERO
-/*
- * See http://llvm.org/bugs/show_bug.cgi?id=15495
- */
-#if defined(HAVE_GCC_VOLATILE_MEMORY_PROTECTION)
-#define explicit_bzero(s, n) do { \
-    if ((s) != NULL) { \
-        void *_x = (s); \
-        memset((_x), '\0', (n)); __asm__ volatile("" : : "r"(&(_x)) : "memory"); \
-    } \
-} while (0)
-#else /* HAVE_GCC_VOLATILE_MEMORY_PROTECTION */
-#define explicit_bzero(s, n) do { \
-    memset((s), '\0', (n)); \
-} while (0)
-#endif /* HAVE_GCC_VOLATILE_MEMORY_PROTECTION */
+void explicit_bzero(void *s, size_t n);
 #endif /* !HAVE_EXPLICIT_BZERO */
 
 /**

src/misc.c

@@ -1052,6 +1052,17 @@ int ssh_match_group(const char *group, const char *object)
     return 0;
 }
 
+#if !defined(HAVE_EXPLICIT_BZERO)
+void explicit_bzero(void *s, size_t n)
+{
+    memset(s, '\0', n);
+#if defined(HAVE_GCC_VOLATILE_MEMORY_PROTECTION)
+    /* See http://llvm.org/bugs/show_bug.cgi?id=15495 */
+    __asm__ volatile("" : : "g"(s) : "memory");
+#endif /* HAVE_GCC_VOLATILE_MEMORY_PROTECTION */
+}
+#endif /* !HAVE_EXPLICIT_BZERO */
+
 /** @} */
 
 /* vim: set ts=4 sw=4 et cindent: */