*at syscalls: Implementation

diff -durp linux/fs/compat.c linux/fs/compat.c
@@ -68,10 +68,10 @@ asmlinkage long compat_sys_utime(char __
 		tv[0].tv_usec = 0;
 		tv[1].tv_usec = 0;
 	}
-	return do_utimes(filename, t ? tv : NULL);
+	return do_utimes(AT_FDCWD, filename, t ? tv : NULL);
 }
 
-asmlinkage long compat_sys_utimes(char __user *filename, struct compat_timeval __user *t)
+asmlinkage long compat_sys_futimesat(int dfd, char __user *filename, struct compat_timeval __user *t)
 {
 	struct timeval tv[2];
 

@@ -82,14 +82,19 @@ asmlinkage long compat_sys_utimes(char _
 		    get_user(tv[1].tv_usec, &t[1].tv_usec))
 			return -EFAULT; 
 	} 
-	return do_utimes(filename, t ? tv : NULL);
+	return do_utimes(dfd, filename, t ? tv : NULL);
+}
+
+asmlinkage long compat_sys_utimes(char __user *filename, struct compat_timeval __user *t)
+{
+	return compat_sys_futimesat(AT_FDCWD, filename, t);
 }
 
 asmlinkage long compat_sys_newstat(char __user * filename,
 		struct compat_stat __user *statbuf)
 {
 	struct kstat stat;
-	int error = vfs_stat(filename, &stat);
+	int error = vfs_stat_fd(AT_FDCWD, filename, &stat);
 
 	if (!error)
 		error = cp_compat_stat(&stat, statbuf);

@@ -100,10 +105,31 @@ asmlinkage long compat_sys_newlstat(char
 		struct compat_stat __user *statbuf)
 {
 	struct kstat stat;
-	int error = vfs_lstat(filename, &stat);
+	int error = vfs_lstat_fd(AT_FDCWD, filename, &stat);
+
+	if (!error)
+		error = cp_compat_stat(&stat, statbuf);
+	return error;
+}
+
+asmlinkage long compat_sys_newfstatat(int dfd, char __user * filename,
+		struct compat_stat __user *statbuf, int flag)
+{
+	struct kstat stat;
+	int error = -EINVAL;
+
+	if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
+		goto out;
+
+	if (flag & AT_SYMLINK_NOFOLLOW)
+		error = vfs_lstat_fd(dfd, filename, &stat);
+	else
+		error = vfs_stat_fd(dfd, filename, &stat);
 
 	if (!error)
 		error = cp_compat_stat(&stat, statbuf);
+
+out:
 	return error;
 }
 

@@ -1276,7 +1302,17 @@ out:
 asmlinkage long
 compat_sys_open(const char __user *filename, int flags, int mode)
 {
-	return do_sys_open(filename, flags, mode);
+	return do_sys_open(AT_FDCWD, filename, flags, mode);
+}
+
+/*
+ * Exactly like fs/open.c:sys_openat(), except that it doesn't set the
+ * O_LARGEFILE flag.
+ */
+asmlinkage long
+compat_sys_openat(int dfd, const char __user *filename, int flags, int mode)
+{
+	return do_sys_open(dfd, filename, flags, mode);
 }
 
 /*

diff -durp linux/fs/exec.c linux/fs/exec.c
@@ -477,7 +477,7 @@ struct file *open_exec(const char *name)
 	int err;
 	struct file *file;
 
-	err = path_lookup_open(name, LOOKUP_FOLLOW, &nd, FMODE_READ);
+	err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ);
 	file = ERR_PTR(err);
 
 	if (!err) {

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diff -durp linux/include/linux/fcntl.h linux/include/linux/fcntl.h
@@ -23,6 +23,13 @@
 #define DN_ATTRIB	0x00000020	/* File changed attibutes */
 #define DN_MULTISHOT	0x80000000	/* Don't remove notifier */
 
+#define AT_FDCWD		-100    /* Special value used to indicate
+                                           openat should use the current
+                                           working directory. */
+#define AT_SYMLINK_NOFOLLOW	0x100   /* Do not follow symbolic links.  */
+#define AT_REMOVEDIR		0x200   /* Remove directory instead of
+                                           unlinking file.  */
+
 #ifdef __KERNEL__
 
 #ifndef force_o_largefile

diff -durp linux/include/linux/fs.h linux/include/linux/fs.h
@@ -1314,7 +1314,8 @@ static inline int break_lease(struct ino
 /* fs/open.c */
 
 extern int do_truncate(struct dentry *, loff_t start, struct file *filp);
-extern long do_sys_open(const char __user *filename, int flags, int mode);
+extern long do_sys_open(int fdf, const char __user *filename, int flags,
+			int mode);
 extern struct file *filp_open(const char *, int, int);
 extern struct file * dentry_open(struct dentry *, struct vfsmount *, int);
 extern int filp_close(struct file *, fl_owner_t id);

@@ -1442,7 +1443,7 @@ static inline void allow_write_access(st
 }
 extern int do_pipe(int *);
 
-extern int open_namei(const char *, int, int, struct nameidata *);
+extern int open_namei(int dfd, const char *, int, int, struct nameidata *);
 extern int may_open(struct nameidata *, int, int);
 
 extern int kernel_read(struct file *, unsigned long, char *, unsigned long);

@@ -1640,6 +1641,8 @@ extern int vfs_readdir(struct file *, fi
 
 extern int vfs_stat(char __user *, struct kstat *);
 extern int vfs_lstat(char __user *, struct kstat *);
+extern int vfs_stat_fd(int dfd, char __user *, struct kstat *);
+extern int vfs_lstat_fd(int dfd, char __user *, struct kstat *);
 extern int vfs_fstat(unsigned int, struct kstat *);
 
 extern int vfs_ioctl(struct file *, unsigned int, unsigned int, unsigned long);

diff -durp linux/include/linux/namei.h linux/include/linux/namei.h
@@ -56,10 +56,11 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
 #define LOOKUP_ACCESS		(0x0400)
 
 extern int FASTCALL(__user_walk(const char __user *, unsigned, struct nameidata *));
+extern int FASTCALL(__user_walk_fd(int dfd, const char __user *, unsigned, struct nameidata *));
 #define user_path_walk(name,nd) \
-	__user_walk(name, LOOKUP_FOLLOW, nd)
+	__user_walk_fd(AT_FDCWD, name, LOOKUP_FOLLOW, nd)
 #define user_path_walk_link(name,nd) \
-	__user_walk(name, 0, nd)
+	__user_walk_fd(AT_FDCWD, name, 0, nd)
 extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
 extern int FASTCALL(path_walk(const char *, struct nameidata *));
 extern int FASTCALL(link_path_walk(const char *, struct nameidata *));

@@ -67,7 +68,7 @@ extern void path_release(struct nameidat
 extern void path_release_on_umount(struct nameidata *);
 
 extern int __user_path_lookup_open(const char __user *, unsigned lookup_flags, struct nameidata *nd, int open_flags);
-extern int path_lookup_open(const char *, unsigned lookup_flags, struct nameidata *, int open_flags);
+extern int path_lookup_open(int dfd, const char *name, unsigned lookup_flags, struct nameidata *, int open_flags);
 extern struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
 		int (*open)(struct inode *, struct file *));
 extern struct file *nameidata_to_filp(struct nameidata *nd, int flags);

diff -durp linux/include/linux/time.h linux/include/linux/time.h
@@ -90,7 +90,7 @@ extern int do_settimeofday(struct timesp
 extern int do_sys_settimeofday(struct timespec *tv, struct timezone *tz);
 extern void clock_was_set(void); // call when ever the clock is set
 extern int do_posix_clock_monotonic_gettime(struct timespec *tp);
-extern long do_utimes(char __user * filename, struct timeval * times);
+extern long do_utimes(int dfd, char __user * filename, struct timeval * times);
 struct itimerval;
 extern int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue);
 extern int do_getitimer(int which, struct itimerval *value);