linux-kernel - Re: Linux 6.2-rc2

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Date:   Mon, 2 Jan 2023 21:26:02 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: Linux 6.2-rc2

On Mon, Jan 02, 2023 at 07:57:04PM -0800, Guenter Roeck wrote:
> On Mon, Jan 02, 2023 at 06:13:09PM -0800, Linus Torvalds wrote:
> > On Mon, Jan 2, 2023 at 5:45 PM Guenter Roeck <linux@...ck-us.net> wrote:
> > >
> > > ... and reverting commit 99cb0d917ff indeed fixes the problem.
> > 
> > Hmm. My gut feel is that this just exposes some bug in binutils.
> > 
> May well be, but it would be an architecture specific bug. The problem
> is not seen when building an x86 image with binutils 2.32. Of course it
> might affect other architectures.

It is likely a generic binutils bug, as I have seen it with PowerPC and
s390. I assume it comes down to how architectures have written their
linker scripts. I did some initial investigation yesterday and reported
my findings on Masahiro's patch thread:

https://lore.kernel.org/Y7Jal56f6UBh1abE@dev-arch.thelio-3990X/

I have seen at least three separate threads now with this issue, perhaps
it is just worth reverting the patch now and submitting a fixed version?
2.35.2 is Debian stable's binutils version so this will likely impact a
lot of CIs.

Cheers,
Nathan

> > That said, maybe that commit should not have added its own /DISCARDS/
> > thing, and instead just added that "*(.note.GNU-stack)" to the general
> > /DISCARDS/ thing that is defined by the
> > 
> >   #define DISCARDS  ..
> > 
> > a little bit later, so that we only end up with one single DISCARD
> > list. Something like this (broken patch on purpose):
> > 
> >   --- a/include/asm-generic/vmlinux.lds.h
> >   +++ b/include/asm-generic/vmlinux.lds.h
> >   @@ -897,5 +897,4 @@
> >     */
> >    #define NOTES                                        \
> >   -     /DISCARD/ : { *(.note.GNU-stack) }              \
> >         .notes : AT(ADDR(.notes) - LOAD_OFFSET) {       \
> >                 BOUNDED_SECTION_BY(.note.*, _notes)     \
> >   @@ -1016,4 +1015,5 @@
> >    #define DISCARDS                                     \
> >         /DISCARD/ : {                                   \
> >   +     *(.note.GNU-stack)                              \
> >         EXIT_DISCARDS                                   \
> >         EXIT_CALL                                       \
> > 
> 
> I don't know if and how it affects arm64 and riscv, but the above fixes
> the problem for sh.
> 
> > But maybe that DISCARDS macrop ends up being used too late?
> > 
> 
> DISCARDS is the very first entry in SECTIONS. NOTES is part of RO_DATA
> and comes much later.
> 
> > It really shouldn't matter, but here we are, with a build problem with
> > some random old binutils on an odd platform..
> 
> The one we know of. I could try to compile all architectures with
> binutils 2.32, but I don't really want to do that if I can avoid it.
> 
> Guenter