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[Qemu-devel] X86_64 ucomisd memory access
From: |
Alexander Bluhm |
Subject: |
[Qemu-devel] X86_64 ucomisd memory access |
Date: |
Sun, 12 Jan 2014 15:52:21 +0100 |
User-agent: |
Mutt/1.4.2.3i |
I am running a software emulated OpenBSD/amd64 on an OpenBSD/amd64
host with qemu-system-x86_64 version 1.7.0.
A perl process within the emulated machine gets a segmentation fault
at this instruction:
0x00000cbf3e13f53c <S_sv_2iuv_common+108>: ucomisd 0x28(%rax),%xmm0
The accessed address at 0x28(%rax) is 0xcbf38d13ff8, that is 8 bytes
before a page boundary. The next page is not mapped. The instruction
ucomisd should access a 64 bit memory location, so the perl programm
and the address layout are legal. qemu generates a wrong page fault
as it assumes a 16 byte operation.
This patch fixes the problem, it is against qemu 1.7.0.
Signed-off-by: Alexander Bluhm <address@hidden>
--- target-i386/translate.c.orig Wed Nov 27 23:15:55 2013
+++ target-i386/translate.c Sun Jan 12 14:44:17 2014
@@ -4579,7 +4579,11 @@ static void gen_sse(CPUX86State *env, DisasContext *s,
gen_ldq_env_A0(s->mem_index,
offsetof(CPUX86State,xmm_t0.XMM_D(0)));
}
} else {
- gen_ldo_env_A0(s->mem_index, op2_offset);
+ if (b == 0x2e || b == 0x2f) {
+ gen_ldq_env_A0(s->mem_index, op2_offset);
+ } else {
+ gen_ldo_env_A0(s->mem_index, op2_offset);
+ }
}
} else {
rm = (modrm & 7) | REX_B(s);
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