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UNIX V6 struct user in /usr/sys/user.h .
/*
* The user structure.
* One allocated per process.
* Contains all per process data
* that doesn't need to be referenced
* while the process is swapped.
* The user block is USIZE*64 bytes
* long; resides at virtual kernel
* loc 140000; contains the system
* stack per user; is cross referenced
* with the proc structure for the
* same process.
*/
struct user
{
int u_rsav[2]; /* save r5,r6 when exchanging stacks */
int u_fsav[25]; /* save fp registers */
/* rsav and fsav must be first in structure */
char u_segflg; /* flag for IO; user or kernel space */
char u_error; /* return error code */
char u_uid; /* effective user id */
char u_gid; /* effective group id */
char u_ruid; /* real user id */
char u_rgid; /* real group id */
int u_procp; /* pointer to proc structure */
char *u_base; /* base address for IO */
char *u_count; /* bytes remaining for IO */
char *u_offset[2]; /* offset in file for IO */
int *u_cdir; /* pointer to inode of current directory */
char u_dbuf[DIRSIZ]; /* current pathname component */
char *u_dirp; /* current pointer to inode */
struct { /* current directory entry */
int u_ino;
char u_name[DIRSIZ];
} u_dent;
int *u_pdir; /* inode of parent directory of dirp */
int u_uisa[16]; /* prototype of segmentation addresses */
int u_uisd[16]; /* prototype of segmentation descriptors */
int u_ofile[NOFILE]; /* pointers to file structures of open files */
int u_arg[5]; /* arguments to current system call */
int u_tsize; /* text size (*64) */
int u_dsize; /* data size (*64) */
int u_ssize; /* stack size (*64) */
int u_sep; /* flag for I and D separation */
int u_qsav[2]; /* label variable for quits and interrupts */
int u_ssav[2]; /* label variable for swapping */
int u_signal[NSIG]; /* disposition of signals */
int u_utime; /* this process user time */
int u_stime; /* this process system time */
int u_cutime[2]; /* sum of childs' utimes */
int u_cstime[2]; /* sum of childs' stimes */
int *u_ar0; /* address of users saved R0 */
int u_prof[4]; /* profile arguments */
char u_intflg; /* catch intr from sys */
/* kernel stack per user
* extends from u + USIZE*64
* backward not to reach here
*/
} u;
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