linux-kernel - Re: [PATCH v2 3/4] MIPS: uaccess: Remove get_fs/set

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Message-ID: <20210401125100.GA9556@alpha.franken.de>
Date:   Thu, 1 Apr 2021 14:51:00 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] MIPS: uaccess: Remove get_fs/set_fs call sites

On Thu, Apr 01, 2021 at 08:30:55AM +0200, Christoph Hellwig wrote:
> On Wed, Mar 31, 2021 at 01:56:00PM +0200, Thomas Bogendoerfer wrote:
> > +#define __get_user_nofault(dst, src, type, err_label)			\
> > +do {									\
> > +	int __gu_err;							\
> > +									\
> > +	__get_user_common(*((type *)(dst)), sizeof(type),		\
> > +			  (__force type *)(src));			\
> > +	if (unlikely(__gu_err))						\
> > +		goto err_label;						\
> > +} while (0)
> > +
> > +
> > +static inline int __get_addr(unsigned long *a, unsigned long *p, bool user)
> > +{
> > +	if (user)
> > +		__get_user_nofault(a, p, unsigned long, fault);
> > +	else
> > +		__get_kernel_nofault(a, p, unsigned long, fault);
> > +
> > +	return 0;
> > +
> > +fault:
> > +	return -EFAULT;
> > +}
> 
> Why can't these use plain old get_user and get_kernel_nofault?
> You "optimize" away the access_ok / get_kernel_nofaul_allowed checks
> here, but now use totally non-standard and possibly dangerous APIs.

thanks, I was too deep into the macro wormhole... using standard API
makes this even look nicer. Posting v3 in a few minutes.

Thomas.

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