[lldb-dev] ASLR disabled by default - thoughts?

[Zachary Turner]

Correct, AFAIK the only way to disable ASLR in Windows is:

a) Editing a registry setting which will require a reboot and be system-wide
b) Compiling your executable with a specific flag which has been set to
enable ASLR by default since VS 2012.
c) Using the EMET utility <http://support.microsoft.com/kb/2458544>
(untested, but I guess should work).  Regardless, it's a manual step and
would require elevation (aka sudo)

Maybe it's just because I'm used to an environment where ASLR is per-boot,
but what are the issues with debugging when ASLR is enabled?  Source/line
breakpoints can just be resolved every time you debug.  Same with symbol
breakpoints.  Even absolute address breakpoints can be translated to
Module+offset and persist across ASLR.  The only things I can think of off
the top of my head are hardware data breakpoints, and printing addresses to
log files.  Is there other stuff that is complicated by ASLR?


On Fri, Aug 15, 2014 at 9:49 AM, Todd Fiala <tfiala at google.com> wrote:

> > Is ASLR per-launch / per-process on other platforms?
>
> Linux allows you to set it per process, and based on previous comments,
> MacOSX does as well (there's a posix_spawn flag for it on that platform).
>  You can disable it on Linux at the kernel level, but that's not how we
> want to use it in this scenario.
>
> You don't have a way to disable it just for a process on Windows?
>
> -Todd
>
>
> On Fri, Aug 15, 2014 at 9:33 AM, Greg Clayton <gclayton at apple.com> wrote:
>
>> Yes it should be disabled by default for all systems. It is this was on
>> MacOSX by default. The linux plug-in will need to be fixed.
>>
>> > On Aug 14, 2014, at 9:41 AM, Todd Fiala <todd.fiala at gmail.com> wrote:
>> >
>> > [I'm not seeing this show up in the archives two hours after I posted
>> it from my google account, so I'm sending it from my gmail account.  Pardon
>> if this shows up again in the next 24 hours from my @google.com
>> account...]
>> >
>> > ---------- Forwarded message ----------
>> > From: Todd Fiala <tfiala at google.com>
>> > Date: Thu, Aug 14, 2014 at 7:29 AM
>> > Subject: ASLR disabled by default - thoughts?
>> > To: "lldb-dev at cs.uiuc.edu" <lldb-dev at cs.uiuc.edu>
>> >
>> >
>> > Hey all,
>> >
>> > Regarding this bug:
>> > http://llvm.org/bugs/show_bug.cgi?id=20658
>> >
>> > We've been discussing the idea of having ASLR disabled by default when
>> launching processes within lldb.  Currently it looks like the default
>> behavior is to have it enabled, and require explicitly disabling to get
>> that behavior for the process.
>> >
>> > It seems like it might make more sense to have it disabled by default -
>> that way code references would likely be static across debugger runs, which
>> seems to be more what we want when tracking down issues across code runs.
>> >
>> > Any thoughts on this?
>> >
>> > The counterargument I could make for changing it would be (aside from
>> legacy compatibility issues perhaps on the MacOSX/iOS side) - taking the
>> exe out of its native state on the OS.  If a bug is ASLR sensitive, the
>> user might miss it.  And so behavior in the debugger could differ from the
>> exe in its native state.  Not sure how relevant that is for the majority of
>> usages, though.
>> >
>> > I'll be fixing the fact that Linux is ignoring this altogether.  But
>> while I'm in there, I could flip the default if we wanted to do it.  If not
>> globally, we'd probably pursue defaulting it on Linux (and Ed seems to like
>> it for FreeBSD as well, so maybe for not Apple in that case?)
>> > --
>> > Todd Fiala |   Software Engineer |     tfiala at google.com |
>> 650-943-3180
>> > --
>> > -Todd
>> > _______________________________________________
>> > lldb-dev mailing list
>> > lldb-dev at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>>
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>
>
>
> --
> Todd Fiala | Software Engineer |  tfiala at google.com |  650-943-3180
>
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