Re: [9fans] Race condition in /sys/src/9/pc/trap.c?

[erik quanstrom <quanstro@quanstro.net>]

> I think you may be right, Elly.  Multithreaded programs indeed have their
> stack running outside the stack segment, so this could happen there.
> splhi won't even do on a multiprocessor.  One should probably lock down
> the segment.
> We've never seen this happen, of course — or rather, we haven't noticed
> this as the cause of a crash.

just to beat a dead horse, i disabled the check in question
and ran the following program with an invalid address.
the program faulted and the kernel did not care.

; cat evil.c
#include <u.h>
#include <libc.h>

extern void evil(void);

void
main(void)
{
	evil();
	exits("");
}
; cat evil.s
TEXT evil(SB), $0
	PUSHL	SP
	MOVL	$0xa0000000, SP
	MOVL	$1, AX
	INT	$64
	POPL	SP
	RET
% 8.out
8.out 78: suicide: invalid address 0xa0000000/24 in sys call pc=0x1046

- erik