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Speed up sigreturn() checking.

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This commit is contained in:
mycroft 1994-02-25 21:11:50 +00:00
parent f0cf5168c0
commit 49da93f965
1 changed files with 22 additions and 17 deletions
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39
sys/arch/i386/i386/machdep.c
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@ -36,7 +36,7 @@
* SUCH DAMAGE.
*
* from: @(#)machdep.c 7.4 (Berkeley) 6/3/91
* $Id: machdep.c,v 1.87 1994/02/24 05:03:03 mycroft Exp $
* $Id: machdep.c,v 1.88 1994/02/25 21:11:50 mycroft Exp $
*/
#include <stddef.h>
@ -468,6 +468,15 @@ sendsig(catcher, sig, mask, code)
tf->tf_ss = _udatasel;
}
static __inline int
verr(u_short sel)
{
int eflags;
__asm __volatile("verr %1\n\tlahf" : "=a" (eflags) : "g" (sel));
return (eflags & (PSL_Z << 8));
}
/*
* System call to cleanup state after a signal
* has been taken. Reset signal mask and
@ -516,31 +525,27 @@ sigreturn(p, uap, retval)
return(EINVAL);
/*
* Sanity check the user's selectors and error if they
* are suspect.
* Sanity check the user's selectors and error if they are suspect.
* We assume that swtch() has loaded the correct LDT descriptor, so
* we can just use the `verr' instruction. We further assume that
* none of the segments we wish to protect are conforming. (If they
* were, this check wouldn't help much anyway.)
*/
#define max_ldt_sel(pcb) \
((pcb)->pcb_ldt ? (pcb)->pcb_ldt_len : (sizeof(ldt) / sizeof(ldt[0])))
#define valid_ldt_sel(sel) \
(ISLDT(sel) && ISPL(sel) == SEL_UPL && \
IDXSEL(sel) < max_ldt_sel(&p->p_addr->u_pcb))
#define valid_sel(sel) \
(ISPL(sel) == SEL_UPL && verr(sel))
#define null_sel(sel) \
(!ISLDT(sel) && IDXSEL(sel) == 0)
if ((context.sc_cs&0xffff != _ucodesel && !valid_ldt_sel(context.sc_cs)) ||
(context.sc_ss&0xffff != _udatasel && !valid_ldt_sel(context.sc_ss)) ||
(context.sc_ds&0xffff != _udatasel && !valid_ldt_sel(context.sc_ds) &&
!null_sel(context.sc_ds)) ||
(context.sc_es&0xffff != _udatasel && !valid_ldt_sel(context.sc_es) &&
!null_sel(context.sc_es))) {
if (!valid_sel(context.sc_cs) ||
!valid_sel(context.sc_ss) ||
(!valid_sel(context.sc_ds) && !null_sel(context.sc_ds)) ||
(!valid_sel(context.sc_es) && !null_sel(context.sc_es))) {
trapsignal(p, SIGBUS, T_PROTFLT);
return(EINVAL);
}
#undef max_ldt_sel
#undef valid_ldt_sel
#undef valid_ldt
#undef null_sel
p->p_sigacts->ps_onstack = context.sc_onstack & 01;