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From: | Alexander Graf |
Subject: | Re: [Qemu-devel] [PATCH] Bug in AMD64 emulation Was: [AMD64] Possible problem with the DF flag during the SYSCALL instruction |
Date: | Tue, 25 Mar 2008 21:26:12 +0100 |
Hi, On Mar 25, 2008, at 8:45 PM, Jakub Jermar wrote:
as no one has picked my previous report up yet, I am resending my patch again. The patch fixes a bug in the way QEMU emulates AMD64 instruction called SYSCALL. The problem appears to be stale DF variable.
Sorry I didn't have a look at it before. Good catch though!
Jakub --- helper.c 2008-01-06 20:38:45.000000000 +0100 +++ helper.c.new 2008-03-20 22:39:17.000000000 +0100 @@ -1008,6 +1008,7 @@ DESC_S_MASK | DESC_W_MASK | DESC_A_MASK); env->eflags &= ~env->fmask; + DF = 1 - (2 * ((env->eflags >> 10) & 1));
I believe you're searching for load_eflags(), which automatically updates the DF flag. Take a look at the SVM code for that issue as well (helper.c:helper_vmrun).
if (code64) env->eip = env->lstar; else
Alex
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