[PATCH] aarch64: MTE compatible strchrnul

Szabolcs Nagy Szabolcs.Nagy@arm.com
Fri Jun 5 16:25:55 GMT 2020


The 06/05/2020 09:45, Wilco Dijkstra wrote:
> Hi,
> 
> >> Should we add a marker to indicate that an object file is
> >> mte compatible?
> >
> > i think we will need a marking for 'compatible with tagged
> > pointers' (on aarch64 pointer that's a new opt-in kernel abi
> > and user code may use the top byte of pointers) and another
> > one for 'compatible with 16byte granules'.
> >
> > e.g. the old string asm would have the first marking but not
> > the second one.
> 
> I don't see how adding different markings would help. String functions
> which are not MTE compatible simply cannot be used if MTE is enabled,
> and if they are not fixed or ifunced then all of GLIBC is not compatible
> with MTE.
> 
> Compatibility is a dynamic property, ie. an incompatible string function is
> perfectly fine if it is ifunced. So having various different markings is not useful.
> Either way all of this is unrelated to these patches.

this is for user objects so we can print reasonable
error when an incompatible lib is loaded or disable
tag checking at startup time based on the marking.

not for string functions


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