Messages in this thread | | | Date | Thu, 20 Aug 2020 10:35:39 +0200 | From | peterz@infradea ... | Subject | Re: [REGRESSION 5.8] x86/entry: DR0 break-on-write not working |
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On Wed, Aug 19, 2020 at 10:46:36PM -0500, Josh Poimboeuf wrote: > On Wed, Aug 19, 2020 at 05:14:18PM -0700, Andy Lutomirski wrote:
> > I'm pretty sure you have the buggy sequence of events right, but for > > the wrong reason. There's nothing wrong with scheduling when > > delivering SIGTRAP, but it's definitely wrong to blindly save and > > restore DR7 around scheduling and around ptrace invocations. Remember > > this is an entry from user mode, so it runs on the user stack.
*groan*, yeah that's broken :/
> Wow, I had no idea user #DB's run on the task stack. The scheduling > from #DB blew my mind :-) What's the purpose of that?
At the very least that vm86 junk needs to I think. Also -RT needs it to send signals.
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