Kernel, libc: Add O_EXCL

kernel/src/sys/stdio.cpp

@@ -21,6 +21,7 @@
 #define OPEN_TRUNCATED 32
 #define OPEN_CREATE 64
 #define OPEN_APPEND 128
+#define OPEN_EXCL 256
 
 #define SEEK_SET 0
 #define SEEK_CUR 1
@@ -164,6 +165,17 @@ void sys_open(Context* context, const char* filename, int flags, mode_t) // FIXM
         context->rax = -ENOENT;
         return;
     }
+    else
+    {
+        bool excl = (flags & OPEN_EXCL) > 0;
+
+        if (excl)
+        {
+            kfree(kfilename);
+            context->rax = -EEXIST;
+            return;
+        }
+    }
 
     bool can_read = (flags & OPEN_READ) > 0;
     bool can_write = (flags & OPEN_WRITE) > 0;

libs/libc/include/fcntl.h

@@ -19,6 +19,8 @@
 #define O_CREAT 64
 /* Open the file for appending. */
 #define O_APPEND 128
+/* Fail to open the file if it already exists. */
+#define O_EXCL 256
 
 /* Duplicate a file descriptor. */
 #define F_DUPFD 0