Check invalid register encodings for LdFrm/StFrm ARM instructions and flag them as

invalid instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129286 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 102 insertions, 0 deletions

diff --git a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
index d5675d26fc..26d0e03787 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
@@ -1175,6 +1175,71 @@ static bool DisassembleDPSoRegFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
   return true;
 }
 
+static bool BadRegsLdStFrm(unsigned Opcode, uint32_t insn, bool Store, bool WBack,
+                           bool Imm) {
+  const StringRef Name = ARMInsts[Opcode].Name;
+  unsigned Rt = decodeRd(insn);
+  unsigned Rn = decodeRn(insn);
+  unsigned Rm = decodeRm(insn);
+  unsigned P  = getPBit(insn);
+  unsigned W  = getWBit(insn);
+
+  if (Store) {
+    // Only STR (immediate, register) allows PC as the source.
+    if (Name.startswith("STRB") && Rt == 15) {
+      DEBUG(errs() << "if t == 15 then UNPREDICTABLE\n");
+      return true;
+    }
+    if (WBack && (Rn == 15 || Rn == Rt)) {
+      DEBUG(errs() << "if wback && (n == 15 || n == t) then UNPREDICTABLE\n");
+      return true;
+    }
+    if (!Imm && Rm == 15) {
+      DEBUG(errs() << "if m == 15 then UNPREDICTABLE\n");
+      return true;
+    }
+  } else {
+    // Only LDR (immediate, register) allows PC as the destination.
+    if (Name.startswith("LDRB") && Rt == 15) {
+      DEBUG(errs() << "if t == 15 then UNPREDICTABLE\n");
+      return true;
+    }
+    if (Imm) {
+      // Immediate
+      if (Rn == 15) {
+        // The literal form must be in offset mode; it's an encoding error
+        // otherwise.
+        if (!(P == 1 && W == 0)) {
+          DEBUG(errs() << "Ld literal form with !(P == 1 && W == 0)\n");
+          return true;
+        }
+        // LDRB (literal) does not allow PC as the destination.
+        if (Opcode != ARM::LDRi12 && Rt == 15) {
+          DEBUG(errs() << "if t == 15 then UNPREDICTABLE\n");
+          return true;
+        }
+      } else {
+        // Write back while Rn == Rt does not make sense.
+        if (WBack && (Rn == Rt)) {
+          DEBUG(errs() << "if wback && n == t then UNPREDICTABLE\n");
+          return true;
+        }
+      }
+    } else {
+      // Register
+      if (Rm == 15) {
+        DEBUG(errs() << "if m == 15 then UNPREDICTABLE\n");
+        return true;
+      }
+      if (WBack && (Rn == 15 || Rn == Rt)) {
+        DEBUG(errs() << "if wback && (n == 15 || n == t) then UNPREDICTABLE\n");
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 static bool DisassembleLdStFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
     unsigned short NumOps, unsigned &NumOpsAdded, bool isStore, BO B) {
 
@@ -1237,6 +1302,9 @@ static bool DisassembleLdStFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
   if (OpIdx + 1 >= NumOps)
     return false;
 
+  if (BadRegsLdStFrm(Opcode, insn, isStore, isPrePost, getIBit(insn)==0))
+    return false;
+
   ARM_AM::AddrOpc AddrOpcode = getUBit(insn) ? ARM_AM::add : ARM_AM::sub;
   unsigned IndexMode =
                (TID.TSFlags & ARMII::IndexModeMask) >> ARMII::IndexModeShift;
diff --git a/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt b/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt
new file mode 100644
index 0000000000..7a35c2d6ce
--- /dev/null
+++ b/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt
@@ -0,0 +1,10 @@
+# RUN: llvm-mc --disassemble %s -triple=arm-apple-darwin9 |& grep {invalid instruction encoding}
+
+# Opcode=140 Name=LDRB_POST Format=ARM_FORMAT_LDFRM(6)
+#  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0 
+# -------------------------------------------------------------------------------------------------
+# | 1: 1: 1: 0| 0: 1: 1: 0| 1: 1: 0: 1| 0: 1: 1: 1| 0: 1: 1: 1| 0: 0: 0: 0| 0: 0: 0: 0| 0: 1: 0: 1|
+# -------------------------------------------------------------------------------------------------
+# 
+# if wback && (n == 15 || n == t) then UNPREDICTABLE
+0x05 0x70 0xd7 0xe6
diff --git a/test/MC/Disassembler/ARM/invalid-LDR_POST-arm.txt b/test/MC/Disassembler/ARM/invalid-LDR_POST-arm.txt
new file mode 100644
index 0000000000..ad79986b25
--- /dev/null
+++ b/test/MC/Disassembler/ARM/invalid-LDR_POST-arm.txt
@@ -0,0 +1,4 @@
+# RUN: llvm-mc --disassemble %s -triple=arm-apple-darwin9 |& grep {invalid instruction encoding}
+
+# LDR_PRE/POST has encoding Inst{4} = 0.
+0xde 0x69 0x18 0x46
diff --git a/test/MC/Disassembler/ARM/invalid-LDR_PRE-arm.txt b/test/MC/Disassembler/ARM/invalid-LDR_PRE-arm.txt
new file mode 100644
index 0000000000..36c1124bce
--- /dev/null
+++ b/test/MC/Disassembler/ARM/invalid-LDR_PRE-arm.txt
@@ -0,0 +1,10 @@
+# RUN: llvm-mc --disassemble %s -triple=arm-apple-darwin9 |& grep {invalid instruction encoding}
+
+# Opcode=165 Name=LDR_PRE Format=ARM_FORMAT_LDFRM(6)
+#  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0 
+# -------------------------------------------------------------------------------------------------
+# | 1: 1: 1: 0| 0: 1: 1: 1| 1: 0: 1: 1| 0: 1: 1: 1| 0: 1: 1: 0| 0: 0: 0: 0| 1: 0: 0: 0| 1: 1: 1: 1|
+# -------------------------------------------------------------------------------------------------
+# 
+# if m == 15 then UNPREDICTABLE
+0x8f 0x60 0xb7 0xe7
diff --git a/test/MC/Disassembler/ARM/invalid-STRBrs-arm.txt b/test/MC/Disassembler/ARM/invalid-STRBrs-arm.txt
new file mode 100644
index 0000000000..5209323fa8
--- /dev/null
+++ b/test/MC/Disassembler/ARM/invalid-STRBrs-arm.txt
@@ -0,0 +1,10 @@
+# RUN: llvm-mc --disassemble %s -triple=arm-apple-darwin9 |& grep {invalid instruction encoding}
+
+# Opcode=355 Name=STRBrs Format=ARM_FORMAT_STFRM(7)
+#  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0 
+# -------------------------------------------------------------------------------------------------
+# | 1: 1: 1: 0| 0: 1: 1: 1| 1: 1: 0: 0| 1: 1: 1: 1| 1: 1: 1: 1| 0: 0: 0: 0| 0: 0: 0: 0| 0: 0: 0: 0|
+# -------------------------------------------------------------------------------------------------
+# 
+# if t == 15 then UNPREDICTABLE
+0x00 0xf0 0xcf 0xe7