[lldb-dev] About lldbHost

[Zachary Turner via lldb-dev]

(Correction: I just double checked and the bug is not present in LLDB)

On Tue, Feb 21, 2017 at 2:05 PM Zachary Turner <zturner at google.com> wrote:

> I bet that's it.  The 4 failing tests are:
>
>  LLVM-Unit.Support/SupportTests.FileOutputBuffer.Test
>  LLVM-Unit.Support/SupportTests.FileSystemTest.FileMapping
>  LLVM.DebugInfo/PDB.pdbdump-readwrite.test
>  LLVM.DebugInfo/PDB.pdbdump-write.test
>
> All of which appear to be related to writing.  It looks like the bug is
> present in LLDB as well, but it just never creates a writable mapping so
> the bug is never encountered.
>
> Thanks!
>
> On Tue, Feb 21, 2017 at 2:02 PM Jim Ingham <jingham at apple.com> wrote:
>
> mman.h, which defines these flags, says:
>
>  * The MAP_RESILIENT_* flags can be used when the caller wants to map some
>  * possibly unreliable memory and be able to access it safely, possibly
>  * getting the wrong contents rather than raising any exception.
>  * For safety reasons, such mappings have to be read-only (PROT_READ access
>  * only).
>  *
>  * MAP_RESILIENT_CODESIGN:
>  *      accessing this mapping will not generate code-signing violations,
>  *      even if the contents are tainted.
>  * MAP_RESILIENT_MEDIA:
>  *      accessing this mapping will not generate an exception if the
> contents
>  *      are not available (unreachable removable or remote media, access
> beyond
>  *      end-of-file, ...).  Missing contents will be replaced with zeroes.
>  */
>
> Are you trying to use them for read-write access?  That's all I can see.
>
> Jim
>
>
> > On Feb 21, 2017, at 1:47 PM, Zachary Turner via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
> >
> >
> >
> > On Wed, Feb 15, 2017 at 11:02 AM Greg Clayton <gclayton at apple.com>
> wrote:
> >
> > The other thing is on Mac we add new flags to mmap that allow us not to
> crash if the backing store (network mount) goes away. There is also a flag
> that says "if code signature is borked, please still allow me to read the
> file without crashing. That functionality will need to be ported into the
> LLVM code somehow so we don't start crashing again. Previously we would
> crash if someone would do:
> >
> > (lldb) file /tmp/invalid_codesig_app
> >
> > And also if the network mounted share would go away on something that
> was mmap'ed and someone would touch any byte within it. Our version of mmap
> works around this and we need that to be in any version we adopt.
> >
> > Greg
> >
> > Hi Greg,
> >
> > I tried to get a change into LLVM to add these two flags.  However, I
> started getting some buildbot failures  that only occurred on OSX with the
> error message "The operation is not permitted".  Since it was only on OSX,
> and since it mentioned permissions, I suspect that MAP_RESILIENT_CODESIGN
> and MAP_RESILIENT_MEDIA are causing a problem.  Do you know what the
> requirements of using these two flags are?  And why they might fail?
> >
> > I'm guessing you can reproduce my issue locally by checking out up to
> r295769 and then running "ninja check-llvm".  How come LLDB doesn't fail
> but LLVM does when using these flags?
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
>
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