From: Al Viro <viro@ZenIV.linux.org.uk>
To: H?vard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>,
Matthias Brugger <matthias.bgg@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Dave Jones <davej@redhat.com>, Will Deacon <will.deacon@arm.com>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arch: avr32: add dummy syscalls
Date: Mon, 4 Feb 2013 05:05:50 +0000 [thread overview]
Message-ID: <20130204050550.GA4503@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CACiLriQbrKvo128hhH4Cd3U+qZwgXPGFEAs4b3=SsK59=4Kkkw@mail.gmail.com>
On Sun, Feb 03, 2013 at 08:52:18PM -0800, H?vard Skinnemoen wrote:
> You're right on -- in this case, the compiler will skip r10, and do
> (r12, r11, r8:r9, stack). We pass the syscall number in r8, but we
> also unconditionally move r7 to r8 in the syscall path, so it
> shouldn't matter (libc does the opposite when necessary).
>
> I remember some talk about having the compiler reuse r10 for the next
> 32-bit argument in cases like this, but I don't think it ever
> happened.
Umm... In case of fallocate() the next argument is 64bit one, though;
sys_fallocate() will be looking for two 32bit words on stack, so no
matter how do we pass them to syscall, we'd better push two words in
the wrapper.
But yes, 32bit/32bit/64bit/32bit is another interesting case -
fanotify_mark is 32/32/64/32/32. From what ABI says it would seem to
be r12/r11/r8:r9/r10/stack, but if I understand you correctly, we'll
end up wanting *two* arguments on stack...
next prev parent reply other threads:[~2013-02-04 5:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-27 12:50 [PATCH] arch: avr32: add dummy syscalls Matthias Brugger
2013-01-27 19:57 ` Hans-Christian Egtvedt
2013-01-27 20:30 ` Al Viro
2013-01-27 20:39 ` Hans-Christian Egtvedt
2013-02-04 0:10 ` Al Viro
2013-02-04 0:30 ` Al Viro
2013-02-04 1:31 ` Al Viro
2013-02-04 3:02 ` Al Viro
2013-02-04 4:52 ` Håvard Skinnemoen
2013-02-04 5:05 ` Al Viro [this message]
2013-02-04 5:35 ` Håvard Skinnemoen
2013-02-04 15:39 ` Al Viro
2013-02-04 16:34 ` Håvard Skinnemoen
2013-02-04 22:53 ` Al Viro
2013-02-05 8:06 ` Hans-Christian Egtvedt
2013-02-04 3:21 ` H. Peter Anvin
2013-01-28 2:45 ` Håvard Skinnemoen
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