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

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Date:	Mon, 5 Sep 2011 08:11:32 -0700
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Valdis.Kletnieks@...edu,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, 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 Mon, Sep 5, 2011 at 12:48 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Sunday 04 September 2011 15:13:18 H.J. Lu wrote:
>> On Sun, Sep 4, 2011 at 2:41 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> > On Sunday 04 September 2011 14:25:53 H.J. Lu wrote:
>> >> >> >> #define __NR_x32_recvfrom
>> >> >> >> #define __NR_x32_sendmsg
>> >> >> >> #define __NR_x32_recvmsg
>> >> >> >> #define __NR_x32_recvmmsg
>> >> >> >> #define __NR_x32_sendmmsg
>> >> >> >
>> >> >> > These today use the MSG_CMSG_COMPAT flag to distinguish native and compat
>> >> >> > calls. Do you plan to have another flag here to handle cmsg time values?
>> >> >>
>> >> >> I am using x86-32 calls for them.
>> >> >
>> >> > But isn't that broken? These all pass u64 or time_t values at some point.
>> >> >
>> >>
>> >> time_t isn't a problem since time_t/timeval/timespec are identical for
>> >> x32 and x86-64.  As for u64, I added NATIVE_LONG_TYPE, which is
>> >> defined as long long for x32,  and use it instead of long in types for
>> >> 64bit system calls.
>> >
>> > Sorry, I misread you as saying you use the compat syscalls for these.
>> > If you use the native 64 bit syscalls, you have the opposite problem:
>> > Some network protocols (e.g. netlink or rxrpc) use other data structures
>> > that require conversion, e.g. 'long' members that x32 will get wrong.
>>
>> For those, I use x86-32 calls.
>
> So to ask again, what do you plan to do about SCM_TIMESTAMP*?
>

I added MSG_CMSG_COMPAT64 and new compat system calls with
64bit timespec/val to support it.  See the enclosed patch.

BTW, I also added

compat_sys_preadv64(unsigned long fd, const struct compat_iovec __user *vec,
         unsigned long vlen, loff_t pos)
compat_sys_pwritev64(unsigned long fd, const struct compat_iovec __user *vec,
         unsigned long vlen, loff_t pos)

to support 32bit compat_iovec * and 64bit offset.


-- 
H.J.

View attachment "linux-cmsg-x32-1.patch" of type "text/plain" (4267 bytes)