From: malc <av1474@comtv.ru>
To: qemu-devel@nongnu.org
Cc: Richard Henderson <rth@twiddle.net>
Subject: [Qemu-devel] TCG sar UB
Date: Mon, 22 Aug 2011 14:47:09 +0400 (MSD) [thread overview]
Message-ID: <alpine.LNX.2.00.1108221441400.4946@linmac> (raw)
While booting linux-test 0.2 following sequence of instructions is seen:
IN:
0xc03227aa: mov %esi,%edx
0xc03227ac: xor %ecx,%ecx
0xc03227ae: movzwl 0x12(%esp),%ebp
0xc03227b3: mov %edi,%eax
0xc03227b5: sar %cl,%eax
0xc03227b7: and $0x1,%eax
0xc03227ba: je 0xc0322802
OP after liveness analysis:
mov_i32 tmp0,esi
mov_i32 edx,tmp0
nopn $0x2,$0x2
movi_i32 ecx,$0x0
discard cc_src
movi_i32 cc_dst,$0x0
mov_i32 tmp2,esp
movi_i32 tmp13,$0x12
add_i32 tmp2,tmp2,tmp13
qemu_ld16u tmp0,tmp2,$0x0
mov_i32 ebp,tmp0
mov_i32 tmp0,edi
mov_i32 eax,tmp0
nopn $0x2,$0x2
mov_i32 tmp0,eax
nopn $0x2,$0x2
movi_i32 tmp1,$0x0
nopn $0x2,$0x2
movi_i32 tmp10,$0xffffffff
sar_i32 tmp3,tmp0,tmp10
Doesn't make much sense to me, guest clearly asked for 0 and not -1,
besides -1 violates TCG's sar constraints and PPC obliges by emiting
illegal instruction in this case.
--
mailto:av1474@comtv.ru
reply other threads:[~2011-08-22 10:47 UTC|newest]
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