vfs: fix flags conversion on open()

The vfs converts the read/write flags from 0/1/2 (read-only/write-only/rw) to
bit fields which are more easily testable.  But in doing so it corrupts the
other flags.

Fix FFLAGS and OFLAGS to preserve those other flags.  The test for a file
that is not readable or writable is dropped, since it is impossible to fail.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>

fs/vfs/vfs_syscalls.c

@@ -65,9 +65,7 @@ sys_open(char *path, int flags, mode_t mode, struct file *fp)
 	DPRINTF(VFSDB_SYSCALL, ("sys_open: path=%s flags=%x mode=%x\n",
 				path, flags, mode));
 
-	flags = FFLAGS(flags);
-	if  ((flags & (FREAD | FWRITE)) == 0)
-		return EINVAL;
+	flags = fflags(flags);
 	if (flags & O_CREAT) {
 		error = namei(path, &dp);
 		if (error == ENOENT) {

include/osv/fcntl.h

@@ -9,6 +9,7 @@
 #define OSV_FCNTL_H
 
 #include <sys/cdefs.h>
+#include <fcntl.h>
 
 __BEGIN_DECLS
 
@@ -20,8 +21,19 @@ __BEGIN_DECLS
 #define FWRITE          0x00000002
 
 /* convert from open() flags to/from fflags; convert O_RD/WR to FREAD/FWRITE */
-#define FFLAGS(oflags)  ((oflags) + 1)
-#define OFLAGS(fflags)  ((fflags) - 1)
+static inline int fflags(int oflags)
+{
+    int rw = oflags & O_ACCMODE;
+    oflags &= ~O_ACCMODE;
+    return (rw + 1) | oflags;
+}
+
+static inline int oflags(int fflags)
+{
+    int rw = fflags & (FREAD|FWRITE);
+    fflags &= ~(FREAD|FWRITE);
+    return (rw - 1) | fflags;
+}
 
 __END_DECLS