Re: TE relocations

[Andrew Fish <afish@apple.com>]

> On Oct 5, 2016, at 4:25 PM, valerij zaporogeci <vlrzprgts@gmail.com> wrote:
> 
>>> The ImageBase is the same for PE/COFF and TE.
>>> In the code ImageAddress points to the start of T or P (well P can have a DOS header
>>> prepended etc). I think a lot of the code operates on ImageAddress and thus needs the
>>> adjustment.
> 
> Well, I don't want to abuse your attention.

Well I'm doing it off the top of my head so I'm not doing a lot of research. If I get a chance at some point I'll re-read the PI spec and see if is a bug in the specification since I can file an ECR to get it fixed. 

> Just last try to explain
> the incosistency here I can not resolve.
> Suppose we have some imaginable ISA instruction somewhere in code:
> LOAD r1, [0x402f04bc]
> and 0x402f04bc is the address of some symbol, resolved by linker.
> let's parse this address. Let ImageBase be 0x402f0000, and data
> section offset be 0x400 and finally data item offset in the section be
> 0xbc. Data section is also at 0x400 from the file beginning, since
> sectionalignment==filealignment, which means the layout is the same.
> When it is loaded at 0x402f000, everything works. Data section is at
> 0x400 from there, and our variable is at 0xbc from the section start.
> Now, we make TE from it. Now, the data section in the TE file is NOT
> at 0x400 from the file beginning (it is closer). And when (and if) TE
> is loaded such that TE header is placed in memory at THE SAME
> ImageBase address as the original PE would have been, the referenced
> variable will not be at 402f04bc. And the code, referencing address
> 0x402f4bc, would get something else instead of this variable content.
> This is not the case in the reality. But why? The PI specification
> recipe, with only AddressOfEntryPoint adjustment and without
> adjustment of anything else referenced (in the code) should result in
> this incostistency.

Quick answer is sectionalignment==filealignment for XIP is from the PE/COFF image point of view. From a TE point of view the FileAlignment has to get adjusted. But please remember TE is really just a shortened version of the PE/COFF header, so other than references to those header values it is still the PE/COFF image. 

So I have to ask why are you so interested in TE?

Thanks,

Andrew Fish


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