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Don't follow null pointers if we somehow have a null devswitch entry

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despite having a non-null cn_tab entry.  This case now works the same
as if there is no physical console, except i/o at the kernel printf
level may still work.  This frees drivers of physical console drivers
from the responsibility of attaching the device no matter what.
This commit is contained in:
Bruce Evans 2000-01-25 09:20:08 +00:00
parent be16a3aba0
commit f4675a30ed
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=56582
1 changed files with 17 additions and 11 deletions
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18
sys/kern/tty_cons.c
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@ -165,10 +165,12 @@ cninit_finish()
* Hook the open and close functions.
*/
cdp = devsw(cn_tab->cn_dev);
if (cdp != NULL) {
cn_phys_close = cdp->d_close;
cdp->d_close = cnclose;
cn_phys_open = cdp->d_open;
cdp->d_open = cnopen;
}
cn_dev_t = cn_tab->cn_dev;
cn_udev_t = dev2udev(cn_dev_t);
}
@ -185,9 +187,11 @@ cnuninit(void)
* Unhook the open and close functions.
*/
cdp = devsw(cn_tab->cn_dev);
if (cdp != NULL) {
cdp->d_close = cn_phys_close;
cn_phys_close = NULL;
cdp->d_open = cn_phys_open;
}
cn_phys_close = NULL;
cn_phys_open = NULL;
cn_dev_t = NODEV;
cn_udev_t = NOUDEV;
@ -250,7 +254,7 @@ cnopen(dev, flag, mode, p)
dev_t cndev, physdev;
int retval = 0;
if (cn_tab == NULL)
if (cn_tab == NULL || cn_phys_open == NULL)
return (0);
cndev = cn_tab->cn_dev;
physdev = (major(dev) == major(cndev) ? dev : cndev);
@ -287,7 +291,7 @@ cnclose(dev, flag, mode, p)
dev_t cndev;
struct tty *cn_tp;
if (cn_tab == NULL)
if (cn_tab == NULL || cn_phys_open == NULL)
return (0);
cndev = cn_tab->cn_dev;
cn_tp = cndev->si_tty;
@ -327,7 +331,8 @@ cnread(dev, uio, flag)
struct uio *uio;
int flag;
{
if ((cn_tab == NULL) || cn_mute)
if (cn_tab == NULL || cn_phys_open == NULL)
return (0);
dev = cn_tab->cn_dev;
return ((*devsw(dev)->d_read)(dev, uio, flag));
@ -339,7 +344,8 @@ cnwrite(dev, uio, flag)
struct uio *uio;
int flag;
{
if ((cn_tab == NULL) || cn_mute) {
if (cn_tab == NULL || cn_phys_open == NULL) {
uio->uio_resid = 0; /* dump the data */
return (0);
}
@ -360,7 +366,7 @@ cnioctl(dev, cmd, data, flag, p)
{
int error;
if ((cn_tab == NULL) || cn_mute)
if (cn_tab == NULL || cn_phys_open == NULL)
return (0);
/*
* Superuser can always use this to wrest control of console