[cfe-dev] [llvm-dev] [RFC] Embedding Bitcode in Object Files

[Hal Finkel via cfe-dev]

----- Original Message -----

> From: "Kevin B via llvm-dev Smith" <llvm-dev at lists.llvm.org>
> To: "James Y Knight" <jyknight at google.com>, "Steven Wu"
> <stevenwu at apple.com>
> Cc: llvm-dev at lists.llvm.org, "Clang Dev" <cfe-dev at lists.llvm.org>
> Sent: Saturday, February 6, 2016 4:30:20 PM
> Subject: Re: [llvm-dev] [RFC] Embedding Bitcode in Object Files

> I don't know whether this is an issue in the current implementation,
> but I wanted to bring up a potential privacy issue.

> In embedding the information, care should be taken to avoid embedding
> any information that contains personally identifiable information.
> This can certainly occur
> if paths need to be embedded, as user names, or other
> private/confidential information may be present in the naming of
> directories and paths.
Is this any more of a problem than the information that gets included in the DWARF sections? 

-Hal 

> Generally, I suspect
> that it would be desirable to have an opt-in strategy for designating
> in the compiler which pieces of information/options need to be
> saved, and for all options marked
> as needed, determine whether there is the possibility/likelihood that
> they may contain personally identifiable information.

> Kevin B. Smith

> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
> James Y Knight via llvm-dev
> Sent: Friday, February 05, 2016 3:13 PM
> To: Steven Wu <stevenwu at apple.com>
> Cc: LLVM Developers Mailing List <llvm-dev at lists.llvm.org>; Clang Dev
> <cfe-dev at lists.llvm.org>
> Subject: Re: [llvm-dev] [RFC] Embedding Bitcode in Object Files

> On Fri, Feb 5, 2016 at 6:06 PM, Steven Wu < stevenwu at apple.com >
> wrote:
> > I don't think we need any path in the command line section. We only
> > record the command-line options that will affect CodeGen. See my
> > example in one of the preview reply:
> 

> > > $ clang -fembed-bitcode -O0 test.c -c -###
> > 
> 
> > > "clang" "-cc1" (...lots of options...) "-o" "test.bc" "-x" "c"
> > > "test.c" <--- First stage
> > 
> 
> > > "clang" "-cc1" "-triple" "x86_64-apple-macosx10.11.0" "-emit-obj"
> > > "-fembed-bitcode" "-O0" "-disable-llvm-optzns" "-o" "test.o" "-x"
> > > "ir" "test.bc" <--- Second stage
> > 
> 
> > I can't think of any source path that can affect CodeGen. There
> > should not be any paths other than the bitcode input path and
> > binary
> > output path exists in the second stage and they are excluded from
> > the command line section as well. -fdebug-prefix-map is consumed by
> > the front-end and prefixed paths are a part of the debug info in
> > the
> > metadata. You don't need to encode -fdebug-prefix-map in the
> > bitcode
> > section to reproduce the object file with the same debug info. Did
> > that answer your concern?
> 
> Great -- it wasn't clear from the first message if you were just
> embedding the whole command-line as is. If the plan instead to embed
> only a few relevant options, I agree there should be no issue as far
> as paths go.
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-- 

Hal Finkel 
Assistant Computational Scientist 
Leadership Computing Facility 
Argonne National Laboratory 
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