Re: NVidia glx stuff dies in sysarch(I386_SET_LDT, ...)

On Fri, 1 Aug 2003, Daniel Eischen wrote:

> On Fri, 1 Aug 2003, Marcel Moolenaar wrote:
> 
> OpenGL is the example that I was thinking about.
> 
> > Having a way to disallow using the static allocation should be easy
> > if we use compiler magic to test that the LDT entry is constant and
> > 0. If it is, all is ok (assuming that I'm not mistaken that we use a
> > 0 entry to indicate dynamic allocation -- I haven't actually paid
> > that close attention to it). If the LDT entry is non-constant, it
> > can still be 0 of course but I expect that to be a weird border case.
> 
> This is all good :-)

Here's my first patch..
I'd suggest this (along with man page change) to go in first
for a while before we break people's code.

cvs server: Diffing .
Index: sys_machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/sys_machdep.c,v
retrieving revision 1.86
diff -u -r1.86 sys_machdep.c
--- sys_machdep.c       31 Jul 2003 08:20:24 -0000      1.86
+++ sys_machdep.c       1 Aug 2003 23:58:29 -0000
_at__at_ -410,6 +410,9 _at__at_
        return(error);
 }
 
+static int ldt_warnings;
+#define NUM_LDT_WARNINGS 10
+
 static int
 i386_set_ldt(td, args)
        struct thread *td;
_at__at_ -441,7 +444,7 _at__at_
                        uap->start = NLDT;
                        uap->num = MAX_LD - NLDT;
                }
-               if (uap->start < NLDT || uap->num <= 0)
+               if (uap->start <= LUDATA_SEL || uap->num <= 0)
                        return (EINVAL);
                mtx_lock_spin(&sched_lock);
                pldt = mdp->md_ldt;
_at__at_ -460,10 +463,16 _at__at_
        }
 
        if (!(uap->start == 0 && uap->num == 1)) {
+               /* complain a for a while if using old methods */
+               if (ldt_warnings++ < NUM_LDT_WARNINGS) {
+                       printf("Warning: pid %d used static ldt
allocation.\n",
+                           td->td_proc->p_pid);
+                       printf("See the i386_set_ldt man page for more
info\n");
+               }
                /* verify range of descriptors to modify */
                largest_ld = uap->start + uap->num;
-               if (uap->start < NLDT || uap->start >= MAX_LD ||
uap->num < 0 ||
-                   largest_ld > MAX_LD) {
+               if (uap->start <= LUDATA_SEL || uap->start >= MAX_LD ||
+                   uap->num < 0 || largest_ld > MAX_LD) {
                        return (EINVAL);
                }
        }
_at__at_ -562,7 +571,7 _at__at_
 again:
                mtx_lock_spin(&sched_lock);
                dp = &((union descriptor *)(pldt->ldt_base))[NLDT];
-               for (i = NLDT; i < pldt->ldt_len; ++i) {
+               for (i = LUDATA_SEL + 1; i < pldt->ldt_len; ++i) {
                        if (dp->sd.sd_type == SDT_SYSNULL)
                                break;
                        dp++;



(beware white space munging.. (copy&paste))

I'd follow this with actual breakage oafer say 3 months.