Re: [Tinycc-devel] bounds checking with tcc

[Michael Matz]

Hello,

On Wed, 4 Dec 2019, Herman ten Brugge wrote:

> I think I have a working patch now. See attachment.
> The code runs on i386 and x86_64 on linux for large projects I have.
> 
> I found some bugs when updating the i386 code.
> The bugs are in the testcases in the patch.
> The test/boundtest.c code works for both targets.
> See below for the main changes.
> 
> I probably need some feedback now.

I'll try to look at it over the weekend.


Ciao,
Michael.

> 
> Regards,
> 
>     Herman
> 
> On 2019-12-02 22:46, Herman ten Brugge wrote:
> > Little updated patch. Still needs more work.
> >
> > Regards,
> >
> >     Herman
> >
> > On 2019-12-02 18:24, Herman ten Brugge wrote:
> >> Hello,
> >>
> >> I did some debugging with bouds-checking and came up with attached patch.
> >> I seriously doubt any one did use bounds checking in a large project
> >> before.
> >>
> >> Currently I can use this now in a large multi threaded project. It still
> >> needs some more testing so do not apply the patch yet.
> >>
> >> I disabled some errors. For example if a bounded pointer is not found I
> >> give no error. I also relaxed printing free errors.
> >> There were some off by 1 errors in lib/bcheck.c and I needed to make the
> >> code thread safe.
> >> I used the patch to not link in libtcc1.a in shared objects when bounds
> >> checking so I have only one memory pool.
> >> This has to be documented because you cannot use this with dlopen for
> >> example.
> >> I also added the pthread library when bounds checking so it is now multi
> >> threaded.
> >> I found another problem with nocode_wanted when using sizeof().
> >> Also the push/pop trick needed to push some more registers when more
> >> parameters are passed in registers.
> >>
> >> I probably forget to mention a lot a other changes. See the patch.
> >>
> >> I only tested this on linux x86_64. There are for sure problems on other
> >> targets.
> >>
> >> Regards,
> >>
> >>     Herman
> >>
> >>
> >> On 2019-11-28 17:41, Michael Matz wrote:
> >>> Hello again,
> >>>
> >>> but to maybe be a bit more constructive:
> >>>
> >>> On Thu, 28 Nov 2019, Michael Matz wrote:
> >>>
> >>>>> I fixed this with some push/pop trickery.
> >>> I see, yeah, expanding calls during calls is broken as gfunc_call in the
> >>> generators doesn't generally leave a trace in vtop[] which registers are
> >>> currently holding values.  I think you only need so push/pop si/di, as
> >>> cx/dx aren't used intentionally during reg-param setup.
> >>>
> >>> (I think i386-gen.c has a simila bug with fastcall functions).
> >>>
> >>>>> This probably could be
> >>>>> improved. I have now added a minimum patch so bounds checking works a
> >>>>> little bit. We need still to fix the shared lib reloc problems and the
> >>>>> malloc/free hooks.
> >>>> Do we?  Can we perhaps also simply declare bounds checking to work only
> >>>> with the main executable?  Or remove that whole feature altogether?
> >>> And perhaps another compromise: only conditionally enable tracking of
> >>> locals: Invent a new cmdline option (say, '-bb'), which sets
> >>> do_bounds_checking to 2.  And only if it's > 1 you would also track
> >>> locals, whereas with == 1 you would only track arrays and structs.
> >>>
> >>> Your decision, I think you can push this patch either with that change, or
> >>> without (but try to remove cx/dx from the push/pop).  It doesn't make tccs
> >>> source code larger or uglier in any meaningful way, but does fix practical
> >>> bugs.
> >>>
> >>>
> >>> Ciao,
> >>> Michael.
> >>
> >
> 
> 
>