Re: [PATCH 2/7] signal: factor copy_siginfo_to_external32 from copy_siginfo_to_user32

From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Jeremy Kerr <jk@ozlabs.org>, Arnd Bergmann <arnd@arndb.de>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 2/7] signal: factor copy_siginfo_to_external32 from copy_siginfo_to_user32
Date: Mon, 27 Apr 2020 15:40:50 -0700	[thread overview]
Message-ID: <20200427154050.e431ad7fb228610cc6b95973@linux-foundation.org> (raw)
In-Reply-To: <20200426074039.GA31501@lst.de>

On Sun, 26 Apr 2020 09:40:39 +0200 Christoph Hellwig <hch@lst.de> wrote:

> On Sat, Apr 25, 2020 at 09:47:24PM -0700, Andrew Morton wrote:
> > I looked at fixing it but surely this sort of thing:
> > 
> > 
> > int copy_siginfo_to_user32(struct compat_siginfo __user *to,
> > 			   const struct kernel_siginfo *from)
> > #if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
> > {
> > 	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
> > }
> > int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
> > 			     const struct kernel_siginfo *from, bool x32_ABI)
> > #endif
> > {
> > 	...
> > 
> > 
> > is too ugly to live?
> 
> I fixed it up in my earlier versions, but Eric insisted to keep it,
> which is why I switched to his version given that he is the defacto
> signal.c maintainer.
> 
> Here is what I would have preferred:
> 
> https://www.spinics.net/lists/kernel/msg3473847.html
> https://www.spinics.net/lists/kernel/msg3473840.html
> https://www.spinics.net/lists/kernel/msg3473843.html

OK, but that doesn't necessitate the above monstrosity?  How about

static int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
			     const struct kernel_siginfo *from, bool x32_ABI)
{
	struct compat_siginfo new;
	copy_siginfo_to_external32(&new, from);
	...
}

int copy_siginfo_to_user32(struct compat_siginfo __user *to,
			   const struct kernel_siginfo *from)
{
#if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
#else
	return __copy_siginfo_to_user32(to, from, 0);
#endif
}

Or something like that - I didn't try very hard.  We know how to do
this stuff, and surely this thing isn't how!