linux-kernel - [PATCH] x86_64 : fix vtime() vsyscall

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Message-id: <460A0989.9000106@cosmosbay.com>
Date:	Wed, 28 Mar 2007 08:22:01 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <ak@...e.de>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86_64 : fix vtime() vsyscall

There is a tiny probability that the return value from vtime(time_t *t) is 
different than the value stored in *t

Using a temporary variable solves the problem and gives a faster code.

   17:   48 85 ff                test   %rdi,%rdi
   1a:   48 8b 05 00 00 00 00    mov    0(%rip),%rax        # 
__vsyscall_gtod_data.wall_time_tv.tv_sec
   21:   74 03                   je     26
   23:   48 89 07                mov    %rax,(%rdi)
   26:   c9                      leaveq
   27:   c3                      retq

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

View attachment "vtime_fix.patch" of type "text/plain" (668 bytes)