4.3BSD/usr/src/sys/sys/vm_text.c
/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
* @(#)vm_text.c 7.1 (Berkeley) 6/5/86
*/
#include "../machine/pte.h"
#include "param.h"
#include "systm.h"
#include "map.h"
#include "dir.h"
#include "user.h"
#include "proc.h"
#include "text.h"
#include "inode.h"
#include "buf.h"
#include "seg.h"
#include "vm.h"
#include "cmap.h"
#include "uio.h"
#include "exec.h"
#define X_LOCK(xp) { \
while ((xp)->x_flag & XLOCK) { \
(xp)->x_flag |= XWANT; \
sleep((caddr_t)(xp), PSWP); \
} \
(xp)->x_flag |= XLOCK; \
}
#define XUNLOCK(xp) { \
if ((xp)->x_flag & XWANT) \
wakeup((caddr_t)(xp)); \
(xp)->x_flag &= ~(XLOCK|XWANT); \
}
#define FREE_AT_HEAD(xp) { \
(xp)->x_forw = xhead; \
xhead = (xp); \
(xp)->x_back = &xhead; \
if (xtail == &xhead) \
xtail = &(xp)->x_forw; \
else \
(xp)->x_forw->x_back = &(xp)->x_forw; \
}
#define FREE_AT_TAIL(xp) { \
(xp)->x_back = xtail; \
*xtail = (xp); \
xtail = &(xp)->x_forw; \
/* x_forw is NULL */ \
}
#define ALLOC(xp) { \
*((xp)->x_back) = (xp)->x_forw; \
if ((xp)->x_forw) \
(xp)->x_forw->x_back = (xp)->x_back; \
else \
xtail = (xp)->x_back; \
(xp)->x_forw = NULL; \
(xp)->x_back = NULL; \
}
/*
* We place free text table entries on a free list.
* All text images are treated as "sticky,"
* and are placed on the free list (as an LRU cache) when unused.
* They may be reclaimed from the free list until reused.
* Files marked sticky are locked into the table, and are never freed.
* For machines with limited swap space, this may result
* in filling up swap, and thus we allow a limit
* to be placed on the number of text images to cache.
* (In that case, really should change the algorithm
* for freeing a text when the cache is full;
* should free least-recently-used text rather than current one.)
*/
struct text *xhead, **xtail; /* text table free list */
int xcache; /* number of "sticky" texts retained */
int maxtextcache = -1; /* maximum number of "sticky" texts */
struct xstats xstats; /* cache statistics */
/*
* initialize text table
*/
xinit()
{
register struct text *xp;
xtail = &xhead;
for (xp = text; xp < textNTEXT; xp++)
FREE_AT_TAIL(xp);
if (maxtextcache == -1)
maxtextcache = ntext;
}
/*
* relinquish use of the shared text segment
* of a process.
*/
xfree()
{
register struct text *xp;
if ((xp = u.u_procp->p_textp) == NULL)
return;
xstats.free++;
X_LOCK(xp);
if (--xp->x_count == 0 && (xp->x_iptr->i_mode & ISVTX) == 0) {
if (xcache >= maxtextcache || xp->x_flag & XTRC ||
xp->x_iptr->i_nlink == 0) { /* XXX */
xp->x_rssize -= vmemfree(tptopte(u.u_procp, 0),
(int)u.u_tsize);
if (xp->x_rssize != 0)
panic("xfree rssize");
while (xp->x_poip)
sleep((caddr_t)&xp->x_poip, PSWP+1);
xp->x_flag &= ~XLOCK;
xuntext(xp);
FREE_AT_HEAD(xp);
} else {
if (xp->x_flag & XWRIT) {
xstats.free_cacheswap++;
xp->x_flag |= XUNUSED;
}
xcache++;
xstats.free_cache++;
xccdec(xp, u.u_procp);
FREE_AT_TAIL(xp);
}
} else {
xccdec(xp, u.u_procp);
xstats.free_inuse++;
}
xunlink(u.u_procp);
XUNLOCK(xp);
u.u_procp->p_textp = NULL;
}
/*
* Attach to a shared text segment.
* If there is no shared text, just return.
* If there is, hook up to it:
* if it is not currently being used, it has to be read
* in from the inode (ip); the written bit is set to force it
* to be written out as appropriate.
* If it is being used, but is not currently in core,
* a swap has to be done to get it back.
*/
xalloc(ip, ep, pagi)
struct exec *ep;
register struct inode *ip;
{
register struct text *xp;
register size_t ts;
if (ep->a_text == 0)
return;
xstats.alloc++;
while ((xp = ip->i_text) != NULL) {
if (xp->x_flag&XLOCK) {
/*
* Wait for text to be unlocked,
* then start over (may have changed state).
*/
xwait(xp);
continue;
}
X_LOCK(xp);
if (xp->x_back) {
xstats.alloc_cachehit++;
ALLOC(xp);
xp->x_flag &= ~XUNUSED;
xcache--;
} else
xstats.alloc_inuse++;
xp->x_count++;
u.u_procp->p_textp = xp;
xlink(u.u_procp);
XUNLOCK(xp);
return;
}
xp = xhead;
if (xp == NULL) {
tablefull("text");
psignal(u.u_procp, SIGKILL);
return;
}
ALLOC(xp);
if (xp->x_iptr) {
xstats.alloc_cacheflush++;
if (xp->x_flag & XUNUSED)
xstats.alloc_unused++;
xuntext(xp);
xcache--;
}
xp->x_flag = XLOAD|XLOCK;
if (pagi)
xp->x_flag |= XPAGI;
ts = clrnd(btoc(ep->a_text));
xp->x_size = ts;
if (vsxalloc(xp) == NULL) {
swkill(u.u_procp, "xalloc: no swap space");
return;
}
xp->x_count = 1;
xp->x_ccount = 0;
xp->x_rssize = 0;
xp->x_iptr = ip;
ip->i_flag |= ITEXT;
ip->i_text = xp;
ip->i_count++;
u.u_procp->p_textp = xp;
xlink(u.u_procp);
if (pagi == 0) {
settprot(RW);
u.u_procp->p_flag |= SKEEP;
(void) rdwri(UIO_READ, ip,
(caddr_t)ctob(tptov(u.u_procp, 0)),
(int)ep->a_text, (off_t)sizeof (struct exec),
2, (int *)0);
u.u_procp->p_flag &= ~SKEEP;
}
settprot(RO);
xp->x_flag |= XWRIT;
xp->x_flag &= ~XLOAD;
XUNLOCK(xp);
}
/*
* Lock and unlock a text segment from swapping
*/
xlock(xp)
register struct text *xp;
{
X_LOCK(xp);
}
/*
* Wait for xp to be unlocked if it is currently locked.
*/
xwait(xp)
register struct text *xp;
{
X_LOCK(xp);
XUNLOCK(xp);
}
xunlock(xp)
register struct text *xp;
{
XUNLOCK(xp);
}
/*
* Decrement the in-core usage count of a shared text segment,
* which must be locked. When the count drops to zero,
* free the core space.
*/
xccdec(xp, p)
register struct text *xp;
register struct proc *p;
{
if (--xp->x_ccount == 0) {
if (xp->x_flag & XWRIT) {
vsswap(p, tptopte(p, 0), CTEXT, 0, (int)xp->x_size,
(struct dmap *)0);
if (xp->x_flag & XPAGI)
(void)swap(p, xp->x_ptdaddr,
(caddr_t)tptopte(p, 0),
(int)xp->x_size * sizeof (struct pte),
B_WRITE, B_PAGET, swapdev, 0);
xp->x_flag &= ~XWRIT;
} else
xp->x_rssize -= vmemfree(tptopte(p, 0),
(int)xp->x_size);
if (xp->x_rssize != 0)
panic("text rssize");
}
}
/*
* Detach a process from the in-core text.
* External interface to xccdec, used when swapping out a process.
*/
xdetach(xp, p)
register struct text *xp;
struct proc *p;
{
if (xp && xp->x_ccount != 0) {
X_LOCK(xp);
xccdec(xp, p);
xunlink(p);
XUNLOCK(xp);
}
}
/*
* Free the swap image of all unused saved-text text segments
* which are from device dev (used by umount system call).
* If dev is NODEV, do all devices (used when rebooting).
*/
xumount(dev)
register dev_t dev;
{
register struct text *xp;
for (xp = text; xp < textNTEXT; xp++)
if (xp->x_iptr != NULL &&
(dev == xp->x_iptr->i_dev || dev == NODEV))
xuntext(xp);
}
/*
* remove a shared text segment from the text table, if possible.
*/
xrele(ip)
register struct inode *ip;
{
if (ip->i_flag & ITEXT)
xuntext(ip->i_text);
}
/*
* remove text image from the text table.
* the use count must be zero.
*/
xuntext(xp)
register struct text *xp;
{
register struct inode *ip;
X_LOCK(xp);
if (xp->x_count == 0) {
ip = xp->x_iptr;
xp->x_iptr = NULL;
vsxfree(xp, (long)xp->x_size);
ip->i_flag &= ~ITEXT;
ip->i_text = NULL;
irele(ip);
}
XUNLOCK(xp);
}
/*
* Add a process to those sharing a text segment by
* getting the page tables and then linking to x_caddr.
*/
xlink(p)
register struct proc *p;
{
register struct text *xp = p->p_textp;
if (xp == 0)
return;
vinitpt(p);
p->p_xlink = xp->x_caddr;
xp->x_caddr = p;
xp->x_ccount++;
}
xunlink(p)
register struct proc *p;
{
register struct text *xp = p->p_textp;
register struct proc *q;
if (xp == 0)
return;
if (xp->x_caddr == p) {
xp->x_caddr = p->p_xlink;
p->p_xlink = 0;
return;
}
for (q = xp->x_caddr; q->p_xlink; q = q->p_xlink)
if (q->p_xlink == p) {
q->p_xlink = p->p_xlink;
p->p_xlink = 0;
return;
}
panic("lost text");
}
/*
* Replace p by q in a text incore linked list.
* Used by vfork(), internally.
*/
xrepl(p, q)
struct proc *p, *q;
{
register struct text *xp = q->p_textp;
if (xp == 0)
return;
xunlink(p);
q->p_xlink = xp->x_caddr;
xp->x_caddr = q;
}