Re: [Qemu-devel] [PATCH 11/13] tests/vm: netbsd autoinstall, using serial console

[Kamil Rytarowski]

On 09.05.2019 18:39, Richard Henderson wrote:
> On 5/8/19 11:47 PM, Gerd Hoffmann wrote:
>> So, from looking at the patch it seems you need two mappings of the same
>> page, one writable and one executable.
>>
>> Or, maybe it is also possible with one mapping which is writable first
>> when you fill it with code, then gets flipped over to executable when
>> you are done with the initialization and want use it.
>>
>> Is that correct?
> 
> That's certainly the way I read that patch.
> 
>> I suspect supporting that in tcg isn't exactly trivial.
> 
> It shouldn't be too hard, if required.  All of the writing to the buffer is
> isolated to a couple of inline functions.
> 
> I do wonder if using paxctl -m as a part of the build process for affected 
> *BSD
> isn't just as easy?
> 

paxctl(8) is available only for NetBSD.

paxctl(8) is the last resort solution and shall be avoided due to a
security risk.

Only few exceptions shall be allowed to switch mapping protection or
request RWX mappings (mainly JIT and a process running under a debugger).

> 
> r~
>

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