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Mon, 12 May 2025 12:05:46 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGt6c/+hSLCeKTstnF7HByGZMvRFK2q/hvgYOFwRbJGmP6yQNG635mjwOvgAGzaG68rlTNt/w== X-Received: by 2002:a05:6000:3110:b0:3a2:2ea9:4378 with SMTP id ffacd0b85a97d-3a22ea94501mr2015069f8f.31.1747076746171; Mon, 12 May 2025 12:05:46 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 07/16] target/i386: ignore misplaced REX prefixes Date: Mon, 12 May 2025 21:05:15 +0200 Message-ID: <20250512190524.179419-8-pbonzini@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250512190524.179419-1-pbonzini@redhat.com> References: <20250512190524.179419-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.551, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1747076816185019000 Content-Type: text/plain; charset="utf-8" Signed-off-by: Paolo Bonzini --- target/i386/tcg/decode-new.c.inc | 36 ++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 9 deletions(-) diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.= c.inc index cda32ee6784..55216e0d249 100644 --- a/target/i386/tcg/decode-new.c.inc +++ b/target/i386/tcg/decode-new.c.inc @@ -2542,7 +2542,13 @@ static void disas_insn(DisasContext *s, CPUState *cp= u) s->has_modrm =3D false; s->prefix =3D 0; =20 - next_byte: + next_byte:; +#ifdef TARGET_X86_64 + /* clear any REX prefix followed by other prefixes. */ + int rex; + rex =3D -1; + next_byte_rex: +#endif b =3D x86_ldub_code(env, s); =20 /* Collect prefixes. */ @@ -2585,13 +2591,12 @@ static void disas_insn(DisasContext *s, CPUState *c= pu) #ifdef TARGET_X86_64 case 0x40 ... 0x4f: if (CODE64(s)) { - /* REX prefix */ - s->prefix |=3D PREFIX_REX; - s->vex_w =3D (b >> 3) & 1; - s->rex_r =3D (b & 0x4) << 1; - s->rex_x =3D (b & 0x2) << 2; - s->rex_b =3D (b & 0x1) << 3; - goto next_byte; + /* + * REX prefix; ignored unless it is the last prefix, so + * for now just stash it + */ + rex =3D b; + goto next_byte_rex; } break; #endif @@ -2618,10 +2623,13 @@ static void disas_insn(DisasContext *s, CPUState *c= pu) =20 /* 4.1.1-4.1.3: No preceding lock, 66, f2, f3, or rex prefixes= . */ if (s->prefix & (PREFIX_REPZ | PREFIX_REPNZ - | PREFIX_LOCK | PREFIX_DATA | PREFIX_REX)) { + | PREFIX_LOCK | PREFIX_DATA)) { goto illegal_op; } #ifdef TARGET_X86_64 + if (rex !=3D -1) { + goto illegal_op; + } s->rex_r =3D (~vex2 >> 4) & 8; #endif if (b =3D=3D 0xc5) { @@ -2661,6 +2669,16 @@ static void disas_insn(DisasContext *s, CPUState *cp= u) =20 /* Post-process prefixes. */ if (CODE64(s)) { +#ifdef TARGET_X86_64 + if (rex !=3D -1) { + s->prefix |=3D PREFIX_REX; + s->vex_w =3D (rex >> 3) & 1; + s->rex_r =3D (rex & 0x4) << 1; + s->rex_x =3D (rex & 0x2) << 2; + s->rex_b =3D (rex & 0x1) << 3; + } +#endif + /* * In 64-bit mode, the default data size is 32-bit. Select 64-bit * data with rex_w, and 16-bit data with 0x66; rex_w takes precede= nce --=20 2.49.0