[PATCH] arm64: idreg-override: Detect trailing "--" in __parse_cmdline()

[Thorsten Blum]

Hi Catalin,

On Tue, Oct 27, 2026 at 12:14:07PM +0000, Catalin Marinas wrote:
> On Thu, Oct 15, 2026 at 06:10:54PM +0200, Thorsten Blum wrote:
> > __parse_cmdline() detects "--" only if it is followed by whitespace.
> > However, at the end of the command line, it converts the dashes to
> > underscores and tries to match "__" as an option.
> > 
> > Detect trailing "--" directly instead of converting it to "__".
> > 
> > Fixes: dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")
> > Signed-off-by: Thorsten Blum <blum at kernel.org>
> > ---
> >  arch/arm64/kernel/pi/idreg-override.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
> > index acaf56234973..38aa28d19650 100644
> > --- a/arch/arm64/kernel/pi/idreg-override.c
> > +++ b/arch/arm64/kernel/pi/idreg-override.c
> > @@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> >  
> >  		cmdline = skip_spaces(cmdline);
> >  
> > -		/* terminate on "--" appearing on the command line by itself */
> > -		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
> > +		/* Stop at "--" appearing as a separate argument. */
> > +		if (cmdline[0] == '-' && cmdline[1] == '-' &&
> > +		    (!cmdline[2] || isspace(cmdline[2])))
> >  			return;
> 
> I guess that's more of a cleanup. Does it actually fix anything to
> deserve a Fixes tag? We skip an unnecessary lookup for "__" but there's
> no functional difference.

Yes, it's a cleanup.

Functionally, the behavior is equivalent because it also happened to
work before. However, commit dc3f5aae0638 removed the explicit detection
of a trailing "--", so I added the Fixes tag mostly for provenance.

Thanks,
Thorsten