linux-kernel - Re: [PATCH 4/8] binfmt_elf: open code copy_siginfo_to

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Date:   Tue, 14 Apr 2020 15:15:09 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jeremy Kerr <jk@...abs.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] binfmt_elf: open code copy_siginfo_to_user to
 kernelspace buffer

On Tue, Apr 14, 2020 at 9:02 AM Christoph Hellwig <hch@....de> wrote:
>
> Instead of messing with the address limit just open code the trivial
> memcpy + memset logic for the native version, and a call to
> to_compat_siginfo for the compat version.
>
> Signed-off-by: Christoph Hellwig <hch@....de>

Nice!

>   */
>  #define user_long_t            compat_long_t
>  #define user_siginfo_t         compat_siginfo_t
> -#define copy_siginfo_to_user   copy_siginfo_to_user32
> +#define fill_siginfo_note(note, csigdata, siginfo)             \
> +do {                                                                   \
> +       to_compat_siginfo(csigdata, siginfo, compat_siginfo_flags());   \
> +       fill_note(note, "CORE", NT_SIGINFO, sizeof(*csigdata), csigdata); \
> +} while (0)

I don't think you are changing the behavior here, but I still wonder if it
is in fact correct for x32: is in_x32_syscall() true here when dumping an
x32 compat elf process, or should this rather be set according to which
binfmt_elf copy is being used?

     Arnd