linux-kernel - Re: [PATCH v3] MIPS: Fix MAX_REG

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Message-ID: <aA4oag9MAXT3y0t8@alpha.franken.de>
Date: Sun, 27 Apr 2025 14:51:54 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	Oleg Nesterov <oleg@...hat.com>,
	"Maciej W. Rozycki" <macro@...am.me.uk>, linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] MIPS: Fix MAX_REG_OFFSET

On Sun, Apr 27, 2025 at 08:32:05PM +0800, Huacai Chen wrote:
> Hi, Thorsten,
> 
> On Sun, Apr 27, 2025 at 7:35 PM Thorsten Blum <thorsten.blum@...ux.dev> wrote:
> >
> > Fix MAX_REG_OFFSET to point to the last register in 'pt_regs' and not to
> > the marker itself, which could allow regs_get_register() to return an
> > invalid offset.
> >
> > Fixes: 40e084a506eb ("MIPS: Add uprobes support.")
> > Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> > ---
> > Compile-tested only.
> >
> > Changes in v2:
> > - Fix MAX_REG_OFFSET as suggested by Maciej (thanks!)
> > - Link to v1: https://lore.kernel.org/lkml/20250411090032.7844-1-thorsten.blum@linux.dev/
> >
> > Changes in v3:
> > - Keep the marker and avoid using #ifdef by adjusting MAX_REG_OFFSET as
> >   suggested by Thomas and Maciej
> > - Link to v2: https://lore.kernel.org/lkml/20250417174712.69292-2-thorsten.blum@linux.dev/
> > ---
> >  arch/mips/include/asm/ptrace.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
> > index 85fa9962266a..ef72c46b5568 100644
> > --- a/arch/mips/include/asm/ptrace.h
> > +++ b/arch/mips/include/asm/ptrace.h
> > @@ -65,7 +65,8 @@ static inline void instruction_pointer_set(struct pt_regs *regs,
> >
> >  /* Query offset/name of register from its name/offset */
> >  extern int regs_query_register_offset(const char *name);
> > -#define MAX_REG_OFFSET (offsetof(struct pt_regs, __last))
> > +#define MAX_REG_OFFSET \
> > +       (offsetof(struct pt_regs, __last) - sizeof(unsigned long))
> There is no 80 columns limit now, so no new line needed here.

but not forbidden to care about it. I still prefer this limit.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]