swapon: decode swap flags

* file.c: Include <sys/swap.h>.
(swap_flags): New xlat structure.
(sys_swapon): New function.
* linux/dummy.h (sys_swapon): Remove.
* linux/syscall.h (sys_swapon): New declaration.

file.c

@@ -33,6 +33,7 @@
 #include "defs.h"
 
 #include <dirent.h>
+#include <sys/swap.h>
 
 struct kernel_dirent {
 	unsigned long   d_ino;
@@ -2694,3 +2695,24 @@ sys_fallocate(struct tcb *tcp)
 	}
 	return 0;
 }
+
+static const struct xlat swap_flags[] = {
+	{ SWAP_FLAG_PREFER,	"SWAP_FLAG_PREFER"	},
+	{ SWAP_FLAG_DISCARD,	"SWAP_FLAG_DISCARD"	},
+	{ 0,			NULL			}
+};
+
+int
+sys_swapon(struct tcb *tcp)
+{
+	if (entering(tcp)) {
+		int flags = tcp->u_arg[1];
+		printpath(tcp, tcp->u_arg[0]);
+		tprints(", ");
+		printflags(swap_flags, flags & ~SWAP_FLAG_PRIO_MASK,
+			"SWAP_FLAG_???");
+		if (flags & SWAP_FLAG_PREFER)
+			tprintf("|%d", flags & SWAP_FLAG_PRIO_MASK);
+	}
+	return 0;
+}

linux/dummy.h

@@ -91,7 +91,6 @@
 #define	sys_rmdir		sys_chdir
 #define	sys_sched_get_priority_max	sys_sched_get_priority_min
 #define	sys_swapoff		sys_chdir
-#define	sys_swapon		sys_chdir
 #define	sys_symlink		sys_link
 #define	sys_syncfs		sys_close
 #define	sys_umount		sys_chdir

linux/syscall.h

@@ -259,6 +259,7 @@ int sys_stat64();
 int sys_statfs();
 int sys_statfs64();
 int sys_stime();
+int sys_swapon();
 int sys_symlinkat();
 int sys_sysctl();
 int sys_sysinfo();