linux-kernel - Re: [PATCH v2 45/62] x86/extable: Define ELF section entry size for exception tables

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Message-ID: <CAMzpN2gmbgts1fFm2x=Ao=X-9g0U000+fPk_i7mMA-f0AQsQYg@mail.gmail.com>
Date: Fri, 6 Jun 2025 21:26:30 -0400
From: Brian Gerst <brgerst@...il.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>, 
	Joe Lawrence <joe.lawrence@...hat.com>, live-patching@...r.kernel.org, 
	Song Liu <song@...nel.org>, laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>, 
	Marcos Paulo de Souza <mpdesouza@...e.com>, Weinan Liu <wnliu@...gle.com>, 
	Fazla Mehrab <a.mehrab@...edance.com>, Chen Zhongjin <chenzhongjin@...wei.com>, 
	Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 45/62] x86/extable: Define ELF section entry size for
 exception tables

On Fri, Jun 6, 2025 at 3:48 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> On Thu, Jun 05, 2025 at 11:58:23PM -0400, Brian Gerst wrote:
> > On Fri, May 9, 2025 at 4:51 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> > >
> > > In preparation for the objtool klp diff subcommand, define the entry
> > > size for the __ex_table section in its ELF header.  This will allow
> > > tooling to extract individual entries.
> > >
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> > > ---
> > >  arch/x86/include/asm/asm.h | 20 ++++++++++++--------
> > >  kernel/extable.c           |  2 ++
> > >  2 files changed, 14 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
> > > index f963848024a5..62dff336f206 100644
> > > --- a/arch/x86/include/asm/asm.h
> > > +++ b/arch/x86/include/asm/asm.h
> > > @@ -138,15 +138,17 @@ static __always_inline __pure void *rip_rel_ptr(void *p)
> > >
> > >  # include <asm/extable_fixup_types.h>
> > >
> > > +#define EXTABLE_SIZE 12
> >
> > Put this in asm-offsets.c instead.
>
> But that's only for .S code right?  This is also needed for inline asm.

<asm/asm-offsets.h> can be used in C code too.  Normally it wouldn't
be needed but the inline asm case is a valid use.


Brian Gerst