Make kvlog more safe if buffer is too small

Author: maxdev1

libc/src/stdio/kvlog.c

@@ -27,11 +27,45 @@
 /**
  *
  */
-void kvlog(const char* message, va_list l) {
-	uint32_t msglen = strlen(message);
-	uint32_t buflen = msglen * 4;
-	char* buf = (char*) malloc(buflen);
-	vsnprintf(buf, buflen, message, l);
-	g_log(buf);
+void kvlog(const char* message, va_list l)
+{
+	va_list lc;
+	va_copy(lc, l);
+
+	// First try
+	uint32_t messageLen = strlen(message);
+	uint32_t bufLen = messageLen * 4;
+
+	char* buf = malloc(bufLen);
+	if(!buf)
+	{
+		g_log("failed to allocate buffer for kernel logging");
+		return;
+	}
+
+	int printed = vsnprintf(buf, bufLen, message, l);
+	int success = printed == messageLen - 1;
+	if(success)
+		g_log(buf);
+
 	free(buf);
+
+	// Buffer too small? Second try
+	if(!success)
+	{
+		bufLen = messageLen * 8;
+		buf = (char*) malloc(bufLen);
+		if(!buf)
+		{
+			g_log("failed to allocate buffer for kernel logging on retry");
+			return;
+		}
+
+		vsnprintf(buf, bufLen, message, lc);
+		g_log(buf);
+
+		free(buf);
+	}
+
+	va_end(lc);
 }