linux-kernel - Re: [PATCH v2 21/31] arm64: 32-bit (compat) applications support

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Date:	Fri, 24 Aug 2012 11:43:39 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>
Subject: Re: [PATCH v2 21/31] arm64: 32-bit (compat) applications support

On Wed, Aug 15, 2012 at 03:34:04PM +0100, Arnd Bergmann wrote:
> On Tuesday 14 August 2012, Catalin Marinas wrote:
> 
> > +#ifdef CONFIG_AARCH32_EMULATION
> > +#include <linux/compat.h>
> > +
> > +#define AARCH32_KERN_SIGRET_CODE_OFFSET	0x500
> > +
> > +extern const compat_ulong_t aarch32_sigret_code[6];
> > +
> > +int compat_setup_frame(int usig, struct k_sigaction *ka, sigset_t *set,
> > +		       struct pt_regs *regs);
> > +int compat_setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
> > +			  sigset_t *set, struct pt_regs *regs);
> > +
> > +void compat_setup_restart_syscall(struct pt_regs *regs);
> > +#else
> > +
> > +static inline int compat_setup_frame(int usid, struct k_sigaction *ka,
> > +				     sigset_t *set, struct pt_regs *regs)
> > +{
> > +	BUG();
> > +}
> 
> What good is the run-time BUG() here? Nothing should be calling these
> when CONFIG_COMPAT is disabled, so I think you should just remove
> the #ifdef around the declarations, and the entire #else case.

They are called from handle_signal(), so that's to avoid #ifdef inside
functions. I can drop the BUG() (but keep the empty function) and
change the checks to is_compat_task() so that the compiler optimises the
condition out when !COMPAT.

-- 
Catalin
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