linux-kernel - Re: RFD: x32 ABI system call numbers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4E5F88F8.2040008@redhat.com>
Date:	Thu, 01 Sep 2011 16:30:32 +0300
From:	Avi Kivity <avi@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"H.J. Lu" <hjl.tools@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Kuo <rkuo@...eaurora.org>,
	Mark Salter <msalter@...hat.com>,
	Jonas Bonn <jonas@...thpole.se>,
	Tobias Klauser <tklauser@...tanz.ch>
Subject: Re: RFD: x32 ABI system call numbers

On 08/31/2011 08:09 PM, H. Peter Anvin wrote:
> >  I really think that "x32" should try to aim *VERY* hard at using the
> >  64-bit system calls, and seeing itself as being a "32-bit application
> >  in a 64-bit world".  That's not just true for time_t (which I think
> >  should be 64-bit on anything new that expects to survive for any
> >  amount of time), but in general.
>
> We're trying for it.  The things we're trying to avoid is to muck (too
> much) with the compat layer for the mega-multiplex system calls like
> ioctl.  We can't just use the 64-bit ioctl because ioctl structures
> generally contain pointers.
>

     struct iovec
     {
         void __user *iov_base;    /* BSD uses caddr_t (1003.1g requires 
void *) */
         __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
     } __attribute__((x32_abi_64));

     typedef long time_t __attribute__((x32_abi_64));

The x32_abi_64 attribute converts pointers and longs back to 64-bit and 
adjusts the alignment accordingly.  If we tag all userspace visible 
structures with this attribute, we can use the 64-bit ABI without changes.

Issues:
&my_iovec->iov_base yields something that is not a void ** (reads of a 
64-bit pointer decay to a 32-bit pointer, writes zero extend).
   printf formats will break
   if someone embeds an iovec in a structure, it will occupy more space 
than expected


-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/