arch-x86: Implement the real mode versions of LDS, LES, etc.

Change-Id: I8956d9871c8819acd4669423b3b59fa615ac2a7c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55588
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/x86/isa/decoder/one_byte_opcodes.isa

@@ -362,10 +362,12 @@
             0x3: RET_NEAR();
             0x4: decode MODE_SUBMODE {
                 0x0: UD2();
+                0x4: LES_REAL(Gz,Mz);
                 default: WarnUnimpl::les_Gz_Mp();
             }
             0x5: decode MODE_SUBMODE {
                 0x0: UD2();
+                0x4: LDS_REAL(Gz,Mz);
                 default: WarnUnimpl::lds_Gz_Mp();
             }
             //0x6: group12_Eb_Ib();

src/arch/x86/isa/decoder/two_byte_opcodes.isa

@@ -744,10 +744,19 @@
             0x16: decode OPCODE_OP_BOTTOM3 {
                 0x0: CMPXCHG(Eb,Gb);
                 0x1: CMPXCHG(Ev,Gv);
-                0x2: WarnUnimpl::lss_Gz_Mp();
+                0x2: decode MODE_SUBMODE {
+                    0x4: LSS_REAL(Gz,Mz);
+                    default: WarnUnimpl::lss_Gz_Mp();
+                }
                 0x3: BTR(Ev,Gv);
-                0x4: WarnUnimpl::lfs_Gz_Mp();
-                0x5: WarnUnimpl::lgs_Gz_Mp();
+                0x4: decode MODE_SUBMODE {
+                    0x4: LFS_REAL(Gz,Mz);
+                    default: WarnUnimpl::lfs_Gz_Mp();
+                }
+                0x5: decode MODE_SUBMODE {
+                    0x4: LGS_REAL(Gz,Mz);
+                    default: WarnUnimpl::lgs_Gz_Mp();
+                }
                 //The size of the second operand in these instructions
                 //should really be "b" or "w", but it's set to v in order
                 //to have a consistent register size. This shouldn't

src/arch/x86/isa/insts/general_purpose/load_segment_registers.py

@@ -33,7 +33,121 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-microcode = ""
+microcode = '''
+
+#
+# Real mode versions of the load far pointer instructions.
+#
+
+def macroop LDS_REAL_R_M {
+    # Calculate the address of the pointer.
+    lea t1, seg, sib, disp, dataSize=asz
+
+    # Load the selector into a temporary.
+    ld t2, seg, [1, t0, t1], dsz, dataSize=2
+    # Load the offset.
+    ld reg, seg, [1, t0, t1], 0
+    # Install the selector value.
+    wrsel ds, t2
+    # Make sure there isn't any junk in the upper bits of the base.
+    mov t2, t0, t2
+    # Compute and set the base.
+    slli t2, t2, 4, dataSize=8
+    wrbase ds, t2, dataSize=8
+};
+
+def macroop LES_REAL_R_M {
+    # Calculate the address of the pointer.
+    lea t1, seg, sib, disp, dataSize=asz
+
+    # Load the selector into a temporary.
+    ld t2, seg, [1, t0, t1], dsz, dataSize=2
+    # Load the offset.
+    ld reg, seg, [1, t0, t1], 0
+    # Install the selector value.
+    wrsel es, t2
+    # Make sure there isn't any junk in the upper bits of the base.
+    mov t2, t0, t2
+    # Compute and set the base.
+    slli t2, t2, 4, dataSize=8
+    wrbase es, t2, dataSize=8
+};
+
+def macroop LFS_REAL_R_M {
+    # Calculate the address of the pointer.
+    lea t1, seg, sib, disp, dataSize=asz
+
+    # Load the selector into a temporary.
+    ld t2, seg, [1, t0, t1], dsz, dataSize=2
+    # Load the offset.
+    ld reg, seg, [1, t0, t1], 0
+    # Install the selector value.
+    wrsel fs, t2
+    # Make sure there isn't any junk in the upper bits of the base.
+    mov t2, t0, t2
+    # Compute and set the base.
+    slli t2, t2, 4, dataSize=8
+    wrbase fs, t2, dataSize=8
+};
+
+def macroop LGS_REAL_R_M {
+    # Calculate the address of the pointer.
+    lea t1, seg, sib, disp, dataSize=asz
+
+    # Load the selector into a temporary.
+    ld t2, seg, [1, t0, t1], dsz, dataSize=2
+    # Load the offset.
+    ld reg, seg, [1, t0, t1], 0
+    # Install the selector value.
+    wrsel gs, t2
+    # Make sure there isn't any junk in the upper bits of the base.
+    mov t2, t0, t2
+    # Compute and set the base.
+    slli t2, t2, 4, dataSize=8
+    wrbase gs, t2, dataSize=8
+};
+
+def macroop LSS_REAL_R_M {
+    # Calculate the address of the pointer.
+    lea t1, seg, sib, disp, dataSize=asz
+
+    # Load the selector into a temporary.
+    ld t2, seg, [1, t0, t1], dsz, dataSize=2
+    # Load the offset.
+    ld reg, seg, [1, t0, t1], 0
+    # Install the selector value.
+    wrsel ss, t2
+    # Make sure there isn't any junk in the upper bits of the base.
+    mov t2, t0, t2
+    # Compute and set the base.
+    slli t2, t2, 4, dataSize=8
+    wrbase ss, t2, dataSize=8
+};
+
+# Versions for RIP relative addressing, even though these instructions are
+# illegal in 64 bit mode, where RIP relative addressing is available.
+
+def macroop LDS_REAL_R_P {
+    panic "Real mode LDS doesn't support RIP relative addressing."
+};
+
+def macroop LES_REAL_R_P {
+    panic "Real mode LES doesn't support RIP relative addressing."
+};
+
+def macroop LFS_REAL_R_P {
+    panic "Real mode LFS doesn't support RIP relative addressing."
+};
+
+def macroop LGS_REAL_R_P {
+    panic "Real mode LGS doesn't support RIP relative addressing."
+};
+
+def macroop LSS_REAL_R_P {
+    panic "Real mode LSS doesn't support RIP relative addressing."
+};
+
+'''
 #let {{
 #    class LDS(Inst):
 #       "GenFault ${new UnimpInstFault}"