llvm dev - Feb 2016 - Transfer information IR to binary

Hi,

I want to know if it is possible to pass information from IR to the final binary
(like a constant value)?

I have a module pass in IR who make some transformation and, once the
compilation is finished, I need to apply a post-processing.

The post-processing need information from the IR part.

Greetings,

Johan


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What kind of constant: type, value and how is it created?

You can make public symbols that you can extract in a linker script to a
special section.

Or perhaps you want some metadata that a special late state (machine instr)
pass is extracting and adding.

The "best" solution really depends on what you are trying to achieve
overall and what kind of data you are working with.

--
Mats

On 22 February 2016 at 13:04, Wehrli Johan via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> I want to know if it is possible to pass information from IR to the final
> binary (like a constant value)?
>
> I have a module pass in IR who make some transformation and, once the
> compilation is finished, I need to apply a post-processing.
>
> The post-processing need information from the IR part.
>
> Greetings,
>
> Johan
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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I will try to explain better what I do.

The main goal behind this is to verify that a part of code is not modified by
someone else (it is an integrity check).

To do this, I create in IR a function who take 2 parameters, a begin and an end
value.

This function perform an hash over the code area (from begin to end) and return
it.

At first, I don’t know the addresses and the hash value so I put random value
(it is an integer 64 bits).

The function look like uint32_t isModified(uint64_t* begin, uint64_t* end).

Once the compilation is over, I need to update the begin address, end address
and the hash value.

When I say the compilation is over, I mean the clang driver has finished all of
his action (compiling, linking, etc.).

Greetings,

Johan

> On 22 Feb 2016, at 15:04, mats petersson <mats at planetcatfish.com>
wrote:
> 
> What kind of constant: type, value and how is it created?
> 
> You can make public symbols that you can extract in a linker script to a
special section.
> 
> Or perhaps you want some metadata that a special late state (machine instr)
pass is extracting and adding.
> 
> The "best" solution really depends on what you are trying to
achieve overall and what kind of data you are working with.
> 
> --
> Mats
> 
> On 22 February 2016 at 13:04, Wehrli Johan via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> Hi,
> 
> I want to know if it is possible to pass information from IR to the final
binary (like a constant value)?
> 
> I have a module pass in IR who make some transformation and, once the
compilation is finished, I need to apply a post-processing.
> 
> The post-processing need information from the IR part.
> 
> Greetings,
> 
> Johan
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> 
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