Re: issue with dom0_pvh on Xen 4.20

[Manuel Bouyer <bouyer@antioche.eu.org>]

On Tue, Sep 02, 2025 at 04:23:28PM +0200, Jan Beulich wrote:
> >>> kernel symbol table. That seems to be no longer true with Xen 4.20 and a
> >>> PVH dom0 (but probably still true in all other cases).
> >>>
> >>> I can deal with that, but with the new layout how do I get the end of the
> >>> symbol table ?
> >>
> >> You'll need to handle that internally, I expect, perhaps from properties of
> >> your (ELF) binary.
> > 
> > But I don't have access to the ELF headers from the kernel binary (nor do I
> > know which kernel was booted).
> > 
> > Hum, maybe a I can hardcode this info in some const of the binary with a
> > ld trick ?
> 
> For the symbol table to be loaded, it needs to live in some loadable section.
> You should be able to mark that section's end (or the end of the symbol
> table in the section, in case there's more stuff there) with a symbol in the
> linker script (which I assume you use). If you used the GNU toolchain, you
> could also consider using the assembler's .startof. / .sizeof. operators
> (producing symbols that the linker then recognizes and resolves accordingly).
> 
> Or wait - are you perhaps using the thing we call "bsd_symtab" in our libelf?

yes, that's it. I'm looking at how it's loaded right now

> Then, as per the scheme in elf_load_bsdsyms(), can't you find the start of
> the ELF header from the end of your kernel? At least that's how I understand
> it's supposed to work.

I can, but at this point I can't easily call C code, and doing it in
assembly doesn't look easy :(

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--