specifying alignment of loader files

[Warner Losh]

On Tue, Jun 12, 2018 at 11:16 AM, Mark Johnston <markj at freebsd.org> wrote:

> On Tue, Jun 12, 2018 at 11:11:25AM -0600, Warner Losh wrote:
> > On Tue, Jun 12, 2018 at 11:04 AM, Mark Johnston <markj at freebsd.org>
> wrote:
> >
> > > Hi,
> > >
> > > I'm writing some code which processes a file loaded by the loader.  I
> > > want the file's contents to be available at a certain alignment in
> > > memory, and as far as I can see, the loader provides no alignment
> > > guarantees today.  The access will happen early enough during boot that
> > > making an aligned copy of the data will be awkward, so I'd like the
> > > loader to provide the desired alignment.
> > >
> > > I'm considering adding a new "module_align" variable that would specify
> > > the alignment for a given file type, and plumb that through to
> > > command_load().  Does anyone have an alternate suggestion, or an
> > > objection to my proposal?
> > >
> >
> > I thought the loader already did that for ELF sections... Why not wrap
> your
> > file in such a segment?
>
> In this case it's a raw binary file (CPU microcode), and I want to be
> able to load it without any modifications or wrappers.
>

How do you identify the type then? I'm ok in theory with this (though a
variable is more flexible than needed), but that's my main concern. What's
the alignment required btw?

Warner