charm 0.0.1

ARM assembler & disassembler generated from the ARM exploration tools.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

//! Instructions decoder.

use super::config::*;
use super::instruction::*;
use super::operand::*;
use crate::error::Result;
use std::collections::HashSet;

pub(crate) mod decoder;

/// Main decoder object.
#[derive(Clone, Debug)]
pub struct Decoder<'a> {
    pub(crate) data: &'a [u8],
    pub(crate) config: Config,
    pub(crate) it_block: Option<ItBlock>,
    pub(crate) block_decoding: bool,
    pub(crate) pc: u32,
    pub(crate) labels: HashSet<u32>,
}

impl<'a> Decoder<'a> {
    /// Creates a new decoder.
    pub fn new(data: &'a [u8], config: Config) -> Self {
        Self {
            data,
            it_block: None,
            config,
            block_decoding: false,
            pc: 0,
            labels: HashSet::new(),
        }
    }

    /// Decodes one instruction.
    pub fn decode(&mut self) -> Result<Instruction> {
        let mut instruction = decoder::decode(self)?;
        self.check_condition(&mut instruction)?;
        instruction.pc = self.pc;
        self.pc += instruction.size as u32;
        Ok(instruction)
    }

    /// Decodes an instruction block.
    pub fn decode_block(&mut self, pc: u32) -> Result<InstructionBlock> {
        self.pc = pc;
        self.labels.clear();
        self.block_decoding = true;
        let mut block = InstructionBlock::new(pc);
        while !self.data.is_empty() {
            block.push_instruction(self.decode()?);
        }
        self.block_decoding = false;

        let instructions = block
            .instructions
            .into_iter()
            .fold(vec![], |mut v, element| match element {
                InstructionBlockElement::Label(_) => unreachable!(),
                InstructionBlockElement::Instruction(i) => {
                    if self.labels.contains(&i.pc) {
                        v.push(InstructionBlockElement::Label(i.pc as u64));
                    }
                    v.push(element);
                    v
                }
            });

        Ok(InstructionBlock::with_instructions(pc, instructions))
    }

    /// Evaluates the condition and decodes the instruction based on the current decoder's state.
    pub fn check_condition(&mut self, instruction: &mut Instruction) -> Result<()> {
        match instruction.condition() {
            ConditionalInstruction::ItBlock(cond, it_cond_1, it_cond_2, it_cond_3) => {
                if self.it_block.is_some() {
                    todo!()
                }
                let states = [ItCondition::If, it_cond_1, it_cond_2, it_cond_3];
                let count = states.iter().fold(0, |acc, c| {
                    acc + if *c == ItCondition::None { 0 } else { 1 }
                });
                self.it_block = Some(ItBlock {
                    condition: cond,
                    states,
                    index: 0,
                    count,
                });
            }
            ConditionalInstruction::Condition(index, last_only, _settable) => {
                if let Some(it_block) = &mut self.it_block {
                    match it_block.states[it_block.index] {
                        ItCondition::None => todo!(),
                        ItCondition::If => {
                            if last_only {
                                if it_block.index != it_block.states.len() - 1
                                    && !it_block.states[it_block.index + 1].is_none()
                                {
                                    todo!()
                                }
                            }
                            let op = Operand::MnemonicCondition(it_block.condition.into());
                            instruction.set_op(index, op)?;
                        }
                        ItCondition::Else => {
                            if last_only {
                                if it_block.index != it_block.states.len() - 1
                                    && !it_block.states[it_block.index + 1].is_none()
                                {
                                    todo!()
                                }
                            }
                            let op =
                                Operand::MnemonicCondition(it_block.condition.opposite().into());
                            instruction.set_op(index, op)?;
                        }
                    }
                    it_block.index += 1;
                }
            }
            ConditionalInstruction::None => {
                if let Some(it_block) = &mut self.it_block {
                    it_block.index += 1;
                } else {
                    return Ok(());
                }
            }
        }
        // Once we reached the end of the IT block conditions list, we can remove it.
        let _ = self.it_block.take_if(|b| b.index == b.count);
        Ok(())
    }
}