linux-kernel - Re: [PATCH] remove binfmts.h from header exports

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Date:	Wed, 8 Aug 2007 11:12:22 +0400
From:	"Alexey Dobriyan" <adobriyan@...il.com>
To:	"Olaf Hering" <olaf@...fle.de>
Cc:	linux-kernel@...r.kernel.org,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] remove binfmts.h from header exports

On 8/8/07, Olaf Hering <olaf@...fle.de> wrote:
> On Wed, Aug 08, Alexey Dobriyan wrote:
>
> > On Tue, Aug 07, 2007 at 10:16:03PM +0200, Olaf Hering wrote:
> > > remove linux/binfmts.h from make headers_install
> > >
> > > A recent patch added PAGE_SIZE to the part outside of __KERNEL__.
> > > qemu and ia32el have their own define of MAX_ARG_PAGES.
> >
> > Should they use kernel header instead?
>
> No, because the header will disappear. And from my understanding, the
> args limit is now gone.

OK.

> > > No package uses linux/binfmts.h, so it is safe to not provide it.
> >
> > And? Does it contain stuff which is userspace visible?
> > binfmts.h has at least CORENAME_MAX_SIZE and SUID_DUMP_*
>
> Yes, its inside __KERNEL__.

Can't you accept for a second that some stuff under __KERNEL__
was put there by mistake?

> We are talking about the part below.

No, we are talking about whole header since you're going
to unexport whole header.

> What part is useable for an application?

>From part you quoted nothing. Otherwise:

fd = open("/proc/sys/fs/suid_dumpable", 1);
snprintf(buf, sizeof(buf), "%d", SUID_DUMP_ROOT);
write(fd, buf, strlen(buf));

> #include <linux/capability.h>
>
> struct pt_regs;
>
> /*
>  * These are the maximum length and maximum number of strings passed to the
>  * execve() system call.  MAX_ARG_STRLEN is essentially random but serves to
>  * prevent the kernel from being unduly impacted by misaddressed pointers.
>  * MAX_ARG_STRINGS is chosen to fit in a signed 32-bit integer.
>  */
> #define MAX_ARG_STRLEN (PAGE_SIZE * 32)
> #define MAX_ARG_STRINGS 0x7FFFFFFF
>
> /* sizeof(linux_binprm->buf) */
> #define BINPRM_BUF_SIZE 128
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