linux-kernel - Re: [PATCH 2/7] signal: factor copy_siginfo_to_external32 from copy_siginfo_to

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Date:   Mon, 27 Apr 2020 15:40:50 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jeremy Kerr <jk@...abs.org>, Arnd Bergmann <arnd@...db.de>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 2/7] signal: factor copy_siginfo_to_external32 from
 copy_siginfo_to_user32

On Sun, 26 Apr 2020 09:40:39 +0200 Christoph Hellwig <hch@....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!