linux-kernel - Re: [PATCH v4] powerpc: Use shared font data

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Message-ID: <797f0a13-350f-e26d-f1ef-876419e1c013@linux-m68k.org>
Date: Mon, 3 Nov 2025 18:26:16 +1100 (AEDT)
From: Finn Thain <fthain@...ux-m68k.org>
To: "Dr. David Alan Gilbert" <linux@...blig.org>
cc: Stan Johnson <userm57@...oo.com>, mpe@...erman.id.au, npiggin@...il.com, 
    christophe.leroy@...roup.eu, sam@...nborg.org, benh@...nel.crashing.org, 
    linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, 
    rdunlap@...radead.org, Cedar Maxwell <cedarmaxwell@....com>
Subject: Re: [PATCH v4] powerpc: Use shared font data


On Mon, 3 Nov 2025, Dr. David Alan Gilbert wrote:

> 
> > Anyway, I imagine that the problem with your patch was that it relies 
> > on font data from a different (read only) section, which is 
> > unavailable for some reason (MMU not fully configured yet?)
> > 
> > So I've asked Stan to test a patch that simply removes the relevant 
> > 'const' keywords. It's not a solution, but might narrow-down the 
> > search.
> 

Stan tested my patch to remove 'const' from the font_desc and font_data 
structs but it did not help. (There goes that theory.)

> I wonder if this is a compiler-flag-ism;  I see 
> arch/powerpc/kernel/Makefile has a pile of special flags, and for 
> btext.o it has a -fPIC (as well as turning off some other flags). I 
> wonder if bodging those in lib/fonts/Makefile for 
> lib/fonts/font_sun8x16.c fixes it? But... this is data - there's no code 
> is there - are any of those flags relevant for data only?
> 

I don't know. But I'm sure Stan would be willing to test a patch for you.

> > 
> > The BootX bootloader doesn't work on New World systems, which is 
> > probably why we don't see this regression on anything newer than a 
> > Wallstreet.
> > 
> > It's likely that other Old World systems are also affected, if they 
> > are using BootX. We don't yet know whether the regression also affects 
> > Old World systems using the iQUIK bootloader instead of BootX.
> 
> OK, remember I don't think I've ever tried PPC via MacOS booting, so not 
> familiar with it.
> 

I will try to set up a MacOS guest in QEMU, to see if the hang can be 
reproduced that way.