[Toybox] imgtec patch: Fix static linkage of toybox binary.

[enh]

On Fri, May 6, 2016 at 10:58 PM, Rob Landley <rob at landley.net> wrote:
> On 05/07/2016 12:16 AM, Evgenii Stepanov wrote:
>> Sorry, I did not look at the problem hard enough.
>> The real issue is interaction of this code with safestack
>> (http://clang.llvm.org/docs/SafeStack.html), which splits the stack in
>> 2 disjoint memory regions. If the two variables are allocated on
>> different stacks, the comparison result is truly undefined.
>>
>> I don't really understand what this code is tying to do. Is it
>> catching unlimited stack growth? Why does the comment speak about
>> heap?
>
> It's a heuristic that enables an optimization. You could select
> CONFIG_TOYBOX_NORECURSE to disable this optimization.

i thought we were still using that, but it looks like i undid my
setting of that option here:
https://googleplex-android.git.corp.google.com/platform/external/toybox/+/a729fc8373ade0ced1cd0dd5ad43ef6a61a5cd24

https://android-review.googlesource.com/223514 (unsubmitted) turns it
back on, since that might be easier than trying to come up with a
heuristic that works well in a SafeStack world. as long as we're still
using mksh i don't think it matters much anyway.

> The help text of that option describes it a little: when one toybox
> command calls another, it can either recurse into the new command's
> main() function, or call the actual execve() to relaunch the toybox
> binary with a fresh environment. Recursing is much faster, but has the
> downside that if you do enough in a row you tend to accumulate debris
> (open filehandles and unfreed mallocs and such from being halfway
> through another program). (Plus if you do it _forever_, you'll actualy
> run out of stack.) So it checks how much stack we've used as a simple
> heuristic to see whether we should recurse or should exec.
>
> This heuristic has not been particularly tuned, that's one of my toysh
> todo items. (toysh is likely to be the heaviest user.)
>
> Rob



-- 
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
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