Date: Wed, 30 Oct 1996 14:13:01 -0500 From: Luoqi Chen <luoqi@watermarkgroup.com> To: hackers@freebsd.org Subject: wine crash mystery Message-ID: <3277A807.7FE8@watermarkgroup.com>
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Hi, I have been playing with wine recently. I noticed that wine would mysteriously crash my machine whenever I tried to run wine with a non-existing exe file (it was a typo initially). It seemed that wine had somehow triggered the shutdown condition on the cpu, because there was no panic when the system crashed. According to the 80x86 manual, this shutdown condition is caused by a triple fault -- fault while trying to execute double fault exception vector. Now I have a few questions I hope more experienced hackers out there can help me on. 1. For the double fault to occur, an LDT entry has to be corrupted. After looking at the kernel sources, I could see one reason this might happen. In sys_machdep.c, syscall i386_set_ldt does NOT load new ldt immediately, instead it relies on swtch to do the trick. Chances are one of the new selectors is referenced before rescheduling has taken place. There is a commented out need_reschedule() call in the code, could anyone tell me why it is commented out? 2. Another reason could be the user LDT is not incore. Is this possible? I see user ldt are allocated from kernel map, does it mean user ldt should always be resident? How is it handled in FreeBSD when the 2nd fault is a page fault? 3. For the shutdown condition to occur, the IDT vector for double fault should also be corrupted. How could this happen? I am running wine961023 on FreeBSD 2.1.5R. Do you fellow wine users have the same crashes? I'm really interested in solving this problem. Any advice is greatly appreciated. Thanks -lq
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