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Re: PaX MPROTECT gdb and software breakpoints
On Sat, May 21, 2016 at 04:21:45PM -0400, Christos Zoulas wrote:
> There are three solutions I can think of (maybe you can think of a better
> 1. Leave it as it is and document that people will have to paxctl +m
> the executables that they need to mprotect before they can debug
> 2. create a uvm_io1() and a new UVM_EXTRACT that breaks MPROTECT and
> fetches with the right mappings. I don't like that, it breaks MPROTECT
> and uvm contracts. But it has the advantage of working on already
> started process we PT_ATTACH to.
> 3. when process is execed and is already traced (PT_TRACE_ME), disable
> MPROTECT. This should work with processes started from gdb, but
> not attached ones. We will still need to explain that to attach
> and insert breakpoints you need to set MPROTECT off.
Tricky. I find (3) is a bit too limited, but it is the only clean way.
Like David suggested, (1) could be extended by a gdb message explaining
(2) is evil, but may be needed. Of course we should restrict the new
path to traced processes, and maybe even limit it to root additionally?
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