[llvm-dev] Custom Binary Format Challenges

[Kenneth Adam Miller via llvm-dev]

Program counter - EIP, RIP for x86/64. I need to obtain it and pass it as
an argument to the function that calculates an ordinal from it.

I think that there must be some way to use the bitcode language to place
byte values at a designated offset. Or use the command line to specify the
section and offset for the data.

On Sun, Apr 1, 2018 at 6:00 PM, Brenda So <sogun3 at gmail.com> wrote:

> Hi Kenneth,
>
> Can you elaborate what you mean by instruction pointer value? Like the
> actual instruction with opcode and operands? With the sample code that I
> showed you, the instrucrtion pointer in the innermost for loop will have
> access to the following functions:
>
> http://llvm.org/doxygen/classllvm_1_1Instruction.html
>
> Alternatively, you can use the dump() operation to dump the instructions
> out.
>
> Unfortunately I don't know how to address your second question. That's
> stretching my knowledge in LLVM.
>
> Brenda
>
>
> On Sun, Apr 1, 2018 at 11:32 AM, Kenneth Adam Miller <
> kennethadammiller at gmail.com> wrote:
>
>> Thank you so much!
>>
>> What about discovering the instruction pointer value?
>> Also, does anybody know how to embed an artifact as a resource in a
>> binary? I'd like to have two text sections, and have one copied in from
>> another binary.
>>
>> On Sun, Apr 1, 2018 at 2:15 PM, Brenda So <sogun3 at gmail.com> wrote:
>>
>>> Hi,
>>>
>>> You can write it as if you are writing an optimization pass:
>>> http://llvm.org/docs/ProgrammersManual.html
>>>
>>> It sounds like your highest level is a module, hence you should write a
>>> module pass. There is example code on LLVM Programmer's Manual on how to do
>>> a function pass:
>>>
>>> Function* targetFunc = ...;
>>> class OurFunctionPass : public FunctionPass {
>>>   public:
>>>     OurFunctionPass(): callCounter(0) { }
>>>
>>>     virtual runOnFunction(Function& F) {
>>>       for (BasicBlock &B : F) {
>>>         for (Instruction &I: B) {
>>>           if (auto *CallInst = dyn_cast<CallInst>(&I)) {
>>>             // We know we've encountered a call instruction, so we
>>>             // need to determine if it's a call to the
>>>             // function pointed to by m_func or not.
>>>             if (CallInst->getCalledFunction() == targetFunc)
>>>               ++callCounter;
>>>           }
>>>         }
>>>       }
>>>     }
>>>
>>>   private:
>>>     unsigned callCounter;};
>>>
>>> Making the FunctionPass a Module pass should be pretty easy with the
>>> linked guide. (instead of inheriting from Function Pass you can inherit
>>> frmo module pass) Afterwards, you can build your new pass against your LLVM
>>> source code and run it using the opt functionality.
>>>
>>> Hope I didn't misunderstood your question -- if you have anymore let me
>>> know!
>>>
>>> Brenda
>>>
>>>
>>>
>>>
>>>
>>> On Sun, Apr 1, 2018 at 1:48 PM, Kenneth Adam Miller via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Hello,
>>>>
>>>>
>>>> I hope you are all doing well and thanks in advance. I need to program
>>>> a transformation of a set of llvm bitcode to have some various techniques
>>>> woven in. In particular, I need to resolve a given computed target address
>>>> to one of several in the same way that the function of a dynamic library is
>>>> resolved, but I need this resolution to happen in the binary target of my
>>>> choice where I tell it to. It's basically exactly the same facility as when
>>>> you compile a group of files as a shared library target. The only
>>>> difference is, I need this to happen under my control, according to
>>>> function targets that I can choose and for an argument value that I can
>>>> also choose as an ordinal to look them up.
>>>>
>>>> I think that I may need to write a compiler pass where this occurs but
>>>> part of the problem is 1) I don't know how to make such a thing occur at
>>>> the bitcode level, 2) and the oridinal is calculated from the instruction
>>>> pointer.
>>>>
>>>> Can anybody help? Is there a library or function call for calculating
>>>> lookup tables from a given set of targets given an ordinal? Is there a way
>>>> to obtain the instruction pointer in llvm bitcode?
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>>
>>>
>>
>
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