Comment 16 for bug 1921948

On Wed, 7 Apr 2021 at 19:54, Alex Bennée <email address hidden> wrote:
>
>
> Richard Henderson <email address hidden> writes:
>
> > We were incorrectly assuming that only the first byte of an MTE access
> > is checked against the tags. But per the ARM, unaligned accesses are
> > pre-decomposed into single-byte accesses. So by the time we reach the
> > actual MTE check in the ARM pseudocode, all accesses are aligned.
> >
> > Therefore, the first failure is always either the first byte of the
> > access, or the first byte of the granule.
> >
> > In addition, some of the arithmetic is off for last-first -> count.
> > This does not become directly visible until a later patch that passes
> > single bytes into this function, so ptr == ptr_last.
> >
> > Buglink: https://bugs.launchpad.net/bugs/1921948
>
> Minor note: you can Cc: Bug 1921948 <email address hidden> to
> automatically copy patches to the appropriate bugs which is useful if
> you don't have the Cc for the reporter.

I'm not sure cc'ing bugs on patches is very useful, though (and especially
not for big series). I usually prefer to just add a note to the bug with
the URL of the series in patchew afterwards.

-- PMM