Messages in this thread | | | Subject | Re: [RFC v4 07/18] objtool: Introduce INSN_UNKNOWN type | From | Julien <> | Date | Thu, 22 Aug 2019 21:45:00 +0100 |
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Hi Josh,
On 22/08/19 21:04, Josh Poimboeuf wrote: > On Fri, Aug 16, 2019 at 01:23:52PM +0100, Raphael Gault wrote: >> On arm64 some object files contain data stored in the .text section. >> This data is interpreted by objtool as instruction but can't be >> identified as a valid one. In order to keep analysing those files we >> introduce INSN_UNKNOWN type. The "unknown instruction" warning will thus >> only be raised if such instructions are uncountered while validating an >> execution branch. >> >> This change doesn't impact the x86 decoding logic since 0 is still used >> as a way to specify an unknown type, raising the "unknown instruction" >> warning during the decoding phase still. >> >> Signed-off-by: Raphael Gault <raphael.gault@arm.com> > > Is there a reason such data can't be moved to .rodata? That would seem > like the proper fix. >
Raphaël can confirm, if I remember correctly, that issue was encountered on assembly files implementing crypto algorithms were some words/double-words of data were in the middle of the .text. I think it is done this way to make sure the data can be loaded in a single instruction. So moving it to another section could impact the crypto performance depending on the relocations.
That was my understanding at least.
Cheers,
-- Julien Thierry
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