From b89220dfda5ac34e12d9017ad33bbf025f4ca2f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20M=C3=B6sl?= <christian.moesl@live.at>
Date: Thu, 20 Aug 2020 14:16:16 +0200
Subject: [PATCH] feat: some stubs for (ternary) bit vectors (#9)

---
 Cargo.lock     |  3 +--
 Cargo.toml     |  2 +-
 src/bitvec.rs  | 11 +++++++++++
 src/engine.rs  | 39 +++++++++++++++++++++++++++++++++++++++
 src/main.rs    |  3 +++
 src/ternary.rs | 25 +++++++++++++++++++++++++
 6 files changed, 80 insertions(+), 3 deletions(-)
 create mode 100644 src/bitvec.rs
 create mode 100644 src/engine.rs
 create mode 100644 src/ternary.rs

diff --git a/Cargo.lock b/Cargo.lock
index 21110da3..681a7598 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -278,8 +278,7 @@ checksum = "41cc0f7e4d5d4544e8861606a285bb08d3e70712ccc7d2b84d7c0ccfaf4b05ce"
 [[package]]
 name = "riscv-decode"
 version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "920466101a1ec4ffac2ab9b72fa780eff62defa0ae9c4f77a07fa41dfd5450e6"
+source = "git+https://github.com/cksystemsgroup/riscv-decode#a0a6e21c831a6da3e078513d4a17a1f324dc7d4f"
 
 [[package]]
 name = "scopeguard"
diff --git a/Cargo.toml b/Cargo.toml
index 2170db36..b5268f7e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,7 +9,7 @@ description = "Monster is a symbolic execution engine for 64-bit RISC-V code"
 goblin = "0.2"
 byteorder = "1.3.4"
 clap = "3.0.0-beta.1"
-riscv-decode = "0.2.0"
+riscv-decode = { git = "https://github.com/cksystemsgroup/riscv-decode" }
 petgraph = "0.5.1"
 
 [dev-dependencies]
diff --git a/src/bitvec.rs b/src/bitvec.rs
new file mode 100644
index 00000000..ad419c18
--- /dev/null
+++ b/src/bitvec.rs
@@ -0,0 +1,11 @@
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct BitVector {
+    pub(crate) value: u64,
+}
+
+impl BitVector {
+    #[allow(dead_code)]
+    fn new(value: u64) -> Self {
+        BitVector { value }
+    }
+}
diff --git a/src/engine.rs b/src/engine.rs
new file mode 100644
index 00000000..7876dc1b
--- /dev/null
+++ b/src/engine.rs
@@ -0,0 +1,39 @@
+use crate::ternary::TernaryBitVector;
+
+struct Machine {
+    #[allow(dead_code)]
+    regs: [TernaryBitVector; 32],
+}
+
+impl Machine {
+    #[allow(dead_code)]
+    fn new() -> Self {
+        Machine {
+            regs: [TernaryBitVector::new(0, u64::max_value()); 32],
+        }
+    }
+}
+
+// fn has_inv_value_for_addi(raw: IType) -> bool {
+//     true
+// }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use riscv_decode::types::*;
+    use riscv_decode::Instruction;
+
+    #[test]
+    fn can_find_input_for_addi() {
+        let machine = Machine::new();
+
+        let raw = IType(0);
+        let _addi = Instruction::Addi(raw);
+
+        let _rd = raw.rd();
+        let _rs1_value = machine.regs[raw.rs1() as usize];
+
+        let _s = raw.imm();
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index e4bf6abf..a72cc938 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,11 +2,14 @@ use clap::{App, Arg};
 use std::fmt::Display;
 use std::path::Path;
 
+mod bitvec;
 mod cfg;
 mod compile;
 mod decode;
 mod disassemble;
 mod elf;
+mod engine;
+mod ternary;
 
 use compile::compile_example;
 use disassemble::disassemble_riscu;
diff --git a/src/ternary.rs b/src/ternary.rs
new file mode 100644
index 00000000..dfab42c6
--- /dev/null
+++ b/src/ternary.rs
@@ -0,0 +1,25 @@
+use crate::bitvec::BitVector;
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct TernaryBitVector {
+    xlo: u64,
+    xhi: u64,
+}
+
+impl TernaryBitVector {
+    pub fn new(xlo: u64, xhi: u64) -> Self {
+        assert!(Self::valid(xlo, xhi), "is not a valid ternary bit vector");
+        Self { xlo, xhi }
+    }
+
+    /// verifies that these two values can form a valid ternary bit vector
+    pub fn valid(xlo: u64, xhi: u64) -> bool {
+        !xlo | xhi == u64::max_value()
+    }
+
+    /// verifies that all constant bits of a ternary bit vector match a bit vector
+    #[allow(dead_code)]
+    pub fn mcb(&self, other: &BitVector) -> bool {
+        (self.xhi & other.value == other.value) && (self.xlo | other.value == other.value)
+    }
+}