From: "H. Peter Anvin" <hpa@zytor.com>
To: Ben Hutchings <ben@decadent.org.uk>, Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/entry/x32: Check top 32 bits of syscall number on the fast path
Date: Sun, 17 Apr 2016 21:50:35 -0700 [thread overview]
Message-ID: <5714679B.3040806@zytor.com> (raw)
In-Reply-To: <20160418004731.GB3348@decadent.org.uk>
On 04/17/16 17:47, Ben Hutchings wrote:
> We've always masked off the top 32 bits when x32 is enabled, but
> hopefully no-one relies on that. Now that the slow path is in C, we
> check all the bits there, regardless of whether x32 is enabled. Let's
> make the fast path consistent with it.
We have always masked off the top 32 bits *period*.
We have had some bugs where we haven't, because someone has tried to
"optimize" the code and they have been quite serious. The system call
number is an int, which means the upper 32 bits are undefined on call
entry: we HAVE to mask them.
-hpa
next prev parent reply other threads:[~2016-04-18 4:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 17:22 System call number masking Ben Hutchings
2016-04-14 17:48 ` Andy Lutomirski
2016-04-18 0:45 ` Ben Hutchings
2016-04-18 0:47 ` [PATCH] x86/entry/x32: Check top 32 bits of syscall number on the fast path Ben Hutchings
2016-04-18 4:50 ` H. Peter Anvin [this message]
2016-04-18 5:18 ` Andy Lutomirski
2016-04-18 5:21 ` H. Peter Anvin
2016-04-18 5:39 ` Andy Lutomirski
2016-04-18 5:45 ` H. Peter Anvin
2016-04-18 5:48 ` Andy Lutomirski
2016-04-18 6:01 ` H. Peter Anvin
2016-04-18 6:14 ` Andy Lutomirski
2016-04-18 6:19 ` H. Peter Anvin
2016-04-18 5:24 ` H. Peter Anvin
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