Messages in this thread | | | Date | Fri, 24 Jul 2015 12:06:56 -0400 | From | Steven Rostedt <> | Subject | Re: Dealing with the NMI mess |
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On Fri, 24 Jul 2015 08:48:57 -0700 Andy Lutomirski <luto@amacapital.net> wrote:
> So by the time we detect that we've hit a watchpoint, the instruction > that tripped it is done and we don't need RF. Furthermore, after > reading 17.3.1.1: I *think* that regs->flags withh have RF *clear* if > we hit a watchpoint. So this might be as simple as: > > if ((dr6 && (0xf * DR_TRAP0) && (regs->flags & (X86_EFLAGS_RF | > X86_EFLAGS_IF)) == X86_EFLAGS_RF && !user_mode(regs))
Also, wouldn't !(regs->X86_EFLAGS_IF) && !user_mode(regs) be a bug? When do we allow coming from userspace with interrupts disabled?
-- Steve
> for (i = 0; i < 4; i++) > if (dr6 & (DR_TRAP0<<i)) { > /* hit a kernel breakpoint with IF clear */ > dr7 &= ~(DR_GLOBAL_ENABLE << (i * DR_ENABLE_SHIFT)); > } > > I'm not saying that your code is wrong, but I think this is simpler > and avoids poking at yet more per-cpu state from NMI context, which is > kind of nice. > > If you don't like the RF games above, it would also be straightforward > to parse dr0..dr3 for each DR_TRAP bit that's set and see if it's a > breakpoint. > > --Andy
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