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From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, qemu-stable@nongnu.org,
Michael Tokarev <mjt@tls.msk.ru>
Subject: [PATCH] target/i386: Do not re-compute new pc with CF_PCREL
Date: Tue, 2 Jan 2024 10:06:17 +1100
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With PCREL, we have a page-relative view of EIP, and an
approximation of PC =3D EIP+CSBASE that is good enough to
detect page crossings. If we try to recompute PC after
masking EIP, we will mess up that approximation and write
a corrupt value to EIP.
We already handled masking properly for PCREL, so the
fix in b5e0d5d2 was only needed for the !PCREL path.
Cc: qemu-stable@nongnu.org
Fixes: b5e0d5d22fbf ("target/i386: Fix 32-bit wrapping of pc/eip computatio=
n")
Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
target/i386/tcg/translate.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index 037bc47e7c..e68375b19d 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -2845,10 +2845,6 @@ static void gen_jmp_rel(DisasContext *s, MemOp ot, i=
nt diff, int tb_num)
}
}
new_eip &=3D mask;
- new_pc =3D new_eip + s->cs_base;
- if (!CODE64(s)) {
- new_pc =3D (uint32_t)new_pc;
- }
=20
gen_update_cc_op(s);
set_cc_op(s, CC_OP_DYNAMIC);
@@ -2864,6 +2860,8 @@ static void gen_jmp_rel(DisasContext *s, MemOp ot, in=
t diff, int tb_num)
tcg_gen_andi_tl(cpu_eip, cpu_eip, mask);
use_goto_tb =3D false;
}
+ } else if (!CODE64(s)) {
+ new_pc =3D (uint32_t)(new_eip + s->cs_base);
}
=20
if (use_goto_tb && translator_use_goto_tb(&s->base, new_pc)) {
--=20
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