Messages in this thread | | | Date | Thu, 22 Aug 2019 16:51:12 -0500 | From | Josh Poimboeuf <> | Subject | Re: [RFC v4 07/18] objtool: Introduce INSN_UNKNOWN type |
| |
On Thu, Aug 22, 2019 at 09:45:00PM +0100, Julien wrote: > 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.
Thanks. If that's the case then that would be useful information to put in the patch description. A code excerpt of an example code site would be useful too.
I'm not sure INSN_UNKNOWN is the right name though, since the decoder does actually know about it. Maybe INSN_DATA or something?
-- Josh
| |