From a58506b748b8988a95f4fa1a2420ac5c17038b30 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 2 Jan 2024 10:06:17 +1100 Subject: [PATCH] target/i386: Do not re-compute new pc with CF_PCREL With PCREL, we have a page-relative view of EIP, and an approximation of PC = 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 computation") Reported-by: Michael Tokarev Signed-off-by: Richard Henderson Message-ID: <20240101230617.129349-1-richard.henderson@linaro.org> Signed-off-by: Paolo Bonzini --- 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 e1eb82a5c6..d4d7e904ad 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -2866,10 +2866,6 @@ static void gen_jmp_rel(DisasContext *s, MemOp ot, int diff, int tb_num) } } new_eip &= mask; - new_pc = new_eip + s->cs_base; - if (!CODE64(s)) { - new_pc = (uint32_t)new_pc; - } gen_update_cc_op(s); set_cc_op(s, CC_OP_DYNAMIC); @@ -2885,6 +2881,8 @@ static void gen_jmp_rel(DisasContext *s, MemOp ot, int diff, int tb_num) tcg_gen_andi_tl(cpu_eip, cpu_eip, mask); use_goto_tb = false; } + } else if (!CODE64(s)) { + new_pc = (uint32_t)(new_eip + s->cs_base); } if (use_goto_tb && translator_use_goto_tb(&s->base, new_pc)) {