ARMv5TE (DS) support (#68)

* Initial ARM support

* Disassemble const pool reloc

* Disasm ARM/Thumb/data based on mapping symbols

* Fallback to mapping symbol `$a`

* Support multiple DWARF sequences

* Update line info

* Rework DWARF line info parsing

- Properly handles multiple sections
  in DWARF 1
- line_info moved into ObjSection
- DWARF 2 parser no longer errors with
  no .text section
- Both parsers properly skip empty
  sections

* Simplify line_info (no Option)

* Get line info from section; output formatted ins string

* Unwrap code section in `arm.rs`

* Handle reloc `R_ARM_SBREL32`

* Update ARM disassembler

* Update README.md

* Format

* Revert "Update README.md"

This reverts commit 8bbfcc6f453c13340764bbae2946025bc41659ae.

* Update README.md

---------

Co-authored-by: Luke Street <luke.street@encounterpc.com>

Cargo.lock

@@ -3124,6 +3124,7 @@ dependencies = [
  "serde_yaml",
  "similar",
  "strum",
+ "unarm",
 ]
 
 [[package]]
@@ -4695,6 +4696,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "unarm"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c13fc9a9c95348bf7565e5c30688fc288239962958cac0ccdc7cd009141d850"
+
 [[package]]
 name = "unicase"
 version = "2.7.0"

README.md

@@ -17,6 +17,7 @@ Supports:
 - PowerPC 750CL (GameCube, Wii)
 - MIPS (N64, PS1, PS2, PSP)
 - x86 (COFF only at the moment)
+- ARM (DS)
 
 See [Usage](#usage) for more information.
 

objdiff-core/Cargo.toml

@@ -12,13 +12,14 @@ A local diffing tool for decompilation projects.
 """
 
 [features]
-all = ["config", "dwarf", "mips", "ppc", "x86"]
+all = ["config", "dwarf", "mips", "ppc", "x86", "arm"]
 any-arch = [] # Implicit, used to check if any arch is enabled
 config = ["globset", "semver", "serde_json", "serde_yaml"]
 dwarf = ["gimli"]
 mips = ["any-arch", "rabbitizer"]
 ppc = ["any-arch", "cwdemangle", "ppc750cl"]
 x86 = ["any-arch", "cpp_demangle", "iced-x86", "msvc-demangler"]
+arm = ["any-arch", "cpp_demangle", "unarm"]
 
 [dependencies]
 anyhow = "1.0.82"
@@ -53,3 +54,6 @@ rabbitizer = { version = "1.11.0", optional = true }
 cpp_demangle = { version = "0.4.3", optional = true }
 iced-x86 = { version = "1.21.0", default-features = false, features = ["std", "decoder", "intel", "gas", "masm", "nasm", "exhaustive_enums"], optional = true }
 msvc-demangler = { version = "0.10.0", optional = true }
+
+# arm
+unarm = { version = "1.0.0", optional = true }

objdiff-core/src/arch/arm.rs

@@ -0,0 +1,297 @@
+use std::{borrow::Cow, collections::HashMap};
+
+use anyhow::{anyhow, bail, Result};
+use object::{
+    elf, File, Object, ObjectSection, ObjectSymbol, Relocation, RelocationFlags, SectionIndex,
+    SectionKind, Symbol,
+};
+use unarm::{
+    args::{Argument, OffsetImm, OffsetReg, Register},
+    parse::{ArmVersion, ParseMode, Parser},
+    ParsedIns,
+};
+
+use crate::{
+    arch::{ObjArch, ProcessCodeResult},
+    diff::DiffObjConfig,
+    obj::{ObjInfo, ObjIns, ObjInsArg, ObjInsArgValue, ObjSection, SymbolRef},
+};
+
+pub struct ObjArchArm {
+    /// Maps section index, to list of disasm modes (arm, thumb or data) sorted by address
+    disasm_modes: HashMap<SectionIndex, Vec<DisasmMode>>,
+}
+
+impl ObjArchArm {
+    pub fn new(file: &File) -> Result<Self> {
+        match file {
+            File::Elf32(_) => {
+                let disasm_modes: HashMap<_, _> = file
+                    .sections()
+                    .filter(|s| s.kind() == SectionKind::Text)
+                    .map(|s| {
+                        let index = s.index();
+                        let mut mapping_symbols: Vec<_> = file
+                            .symbols()
+                            .filter(|s| s.section_index().map(|i| i == index).unwrap_or(false))
+                            .filter_map(|s| DisasmMode::from_symbol(&s))
+                            .collect();
+                        mapping_symbols.sort_unstable_by_key(|x| x.address);
+                        (s.index(), mapping_symbols)
+                    })
+                    .collect();
+                Ok(Self { disasm_modes })
+            }
+            _ => bail!("Unsupported file format {:?}", file.format()),
+        }
+    }
+}
+
+impl ObjArch for ObjArchArm {
+    fn process_code(
+        &self,
+        obj: &ObjInfo,
+        symbol_ref: SymbolRef,
+        config: &DiffObjConfig,
+    ) -> Result<ProcessCodeResult> {
+        let (section, symbol) = obj.section_symbol(symbol_ref);
+        let section = section.ok_or_else(|| anyhow!("Code symbol section not found"))?;
+        let code = &section.data
+            [symbol.section_address as usize..(symbol.section_address + symbol.size) as usize];
+
+        let start_addr = symbol.address as u32;
+        let end_addr = start_addr + symbol.size as u32;
+
+        // Mapping symbols decide what kind of data comes after it. $a for ARM code, $t for Thumb code and $d for data.
+        let fallback_mappings =
+            [DisasmMode { address: symbol.address as u32, mapping: ParseMode::Arm }];
+        let mapping_symbols = self
+            .disasm_modes
+            .get(&SectionIndex(section.orig_index))
+            .map(|x| x.as_slice())
+            .unwrap_or(&fallback_mappings);
+        let first_mapping_idx =
+            match mapping_symbols.binary_search_by_key(&(symbol.address as u32), |x| x.address) {
+                Ok(idx) => idx,
+                Err(idx) => idx - 1,
+            };
+        let first_mapping = mapping_symbols[first_mapping_idx].mapping;
+
+        let mut mappings_iter =
+            mapping_symbols.iter().skip(first_mapping_idx + 1).take_while(|x| x.address < end_addr);
+        let mut next_mapping = mappings_iter.next();
+
+        let ins_count = code.len() / first_mapping.instruction_size();
+        let mut ops = Vec::<u16>::with_capacity(ins_count);
+        let mut insts = Vec::<ObjIns>::with_capacity(ins_count);
+        let mut parser = Parser::new(ArmVersion::V5Te, first_mapping, start_addr, code);
+
+        while let Some((address, op, ins)) = parser.next() {
+            if let Some(next) = next_mapping {
+                let next_address = parser.address;
+                if next_address >= next.address {
+                    // Change mapping
+                    parser.mode = next.mapping;
+                    next_mapping = mappings_iter.next();
+                }
+            }
+
+            let line = section.line_info.range(..=address as u64).last().map(|(_, &b)| b);
+
+            let reloc =
+                section.relocations.iter().find(|r| (r.address as u32 & !1) == address).cloned();
+
+            let mut reloc_arg = None;
+            if let Some(reloc) = &reloc {
+                match reloc.flags {
+                    RelocationFlags::Elf { r_type: elf::R_ARM_THM_XPC22 }
+                    | RelocationFlags::Elf { r_type: elf::R_ARM_PC24 } => {
+                        reloc_arg =
+                            ins.args.iter().rposition(|a| matches!(a, Argument::BranchDest(_)));
+                    }
+                    _ => (),
+                }
+            };
+
+            let (args, branch_dest) = if reloc.is_some() && parser.mode == ParseMode::Data {
+                (vec![ObjInsArg::Reloc], None)
+            } else {
+                push_args(&ins, config, reloc_arg, address)?
+            };
+
+            ops.push(op.id());
+            insts.push(ObjIns {
+                address: address as u64,
+                size: (parser.address - address) as u8,
+                op: op.id(),
+                mnemonic: ins.mnemonic.to_string(),
+                args,
+                reloc,
+                branch_dest,
+                line,
+                formatted: ins.to_string(),
+                orig: None,
+            });
+        }
+
+        Ok(ProcessCodeResult { ops, insts })
+    }
+
+    fn implcit_addend(
+        &self,
+        _section: &ObjSection,
+        address: u64,
+        reloc: &Relocation,
+    ) -> anyhow::Result<i64> {
+        bail!("Unsupported ARM implicit relocation {:#x}{:?}", address, reloc.flags())
+    }
+
+    fn demangle(&self, name: &str) -> Option<String> {
+        cpp_demangle::Symbol::new(name)
+            .ok()
+            .and_then(|s| s.demangle(&cpp_demangle::DemangleOptions::default()).ok())
+    }
+
+    fn display_reloc(&self, flags: RelocationFlags) -> Cow<'static, str> {
+        Cow::Owned(format!("<{flags:?}>"))
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct DisasmMode {
+    address: u32,
+    mapping: ParseMode,
+}
+
+impl DisasmMode {
+    fn from_symbol<'a>(sym: &Symbol<'a, '_, &'a [u8]>) -> Option<Self> {
+        if let Ok(name) = sym.name() {
+            ParseMode::from_mapping_symbol(name)
+                .map(|mapping| DisasmMode { address: sym.address() as u32, mapping })
+        } else {
+            None
+        }
+    }
+}
+
+fn push_args(
+    parsed_ins: &ParsedIns,
+    config: &DiffObjConfig,
+    reloc_arg: Option<usize>,
+    cur_addr: u32,
+) -> Result<(Vec<ObjInsArg>, Option<u64>)> {
+    let mut args = vec![];
+    let mut branch_dest = None;
+    let mut writeback = false;
+    let mut deref = false;
+    for (i, arg) in parsed_ins.args_iter().enumerate() {
+        // Emit punctuation before separator
+        if deref {
+            match arg {
+                Argument::OffsetImm(OffsetImm { post_indexed: true, value: _ })
+                | Argument::OffsetReg(OffsetReg { add: _, post_indexed: true, reg: _ })
+                | Argument::CoOption(_) => {
+                    deref = false;
+                    args.push(ObjInsArg::PlainText("]".into()));
+                    if writeback {
+                        writeback = false;
+                        args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque("!".into())));
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        if i > 0 {
+            args.push(ObjInsArg::PlainText(config.separator().into()));
+        }
+
+        if reloc_arg == Some(i) {
+            args.push(ObjInsArg::Reloc);
+        } else {
+            match arg {
+                Argument::Reg(reg) => {
+                    if reg.deref {
+                        deref = true;
+                        args.push(ObjInsArg::PlainText("[".into()));
+                    }
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(reg.reg.to_string().into())));
+                    if reg.writeback {
+                        if reg.deref {
+                            writeback = true;
+                        } else {
+                            args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque("!".into())));
+                        }
+                    }
+                }
+                Argument::RegList(reg_list) => {
+                    args.push(ObjInsArg::PlainText("{".into()));
+                    let mut first = true;
+                    for i in 0..16 {
+                        if (reg_list.regs & (1 << i)) != 0 {
+                            if !first {
+                                args.push(ObjInsArg::PlainText(config.separator().into()));
+                            }
+                            args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(
+                                Register::parse(i).to_string().into(),
+                            )));
+                            first = false;
+                        }
+                    }
+                    args.push(ObjInsArg::PlainText("}".into()));
+                    if reg_list.user_mode {
+                        args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque("^".to_string().into())));
+                    }
+                }
+                Argument::UImm(value) | Argument::CoOpcode(value) => {
+                    args.push(ObjInsArg::PlainText("#".into()));
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Unsigned(*value as u64)));
+                }
+                Argument::SImm(value)
+                | Argument::OffsetImm(OffsetImm { post_indexed: _, value }) => {
+                    args.push(ObjInsArg::PlainText("#".into()));
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Signed(*value as i64)));
+                }
+                Argument::BranchDest(value) => {
+                    let dest = cur_addr.wrapping_add_signed(*value) as u64;
+                    args.push(ObjInsArg::BranchDest(dest));
+                    branch_dest = Some(dest);
+                }
+                Argument::CoOption(value) => {
+                    args.push(ObjInsArg::PlainText("{".into()));
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Unsigned(*value as u64)));
+                    args.push(ObjInsArg::PlainText("}".into()));
+                }
+                Argument::CoprocNum(value) => {
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(format!("p{}", value).into())));
+                }
+                Argument::ShiftImm(shift) => {
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(shift.op.to_string().into())));
+                    args.push(ObjInsArg::PlainText(" #".into()));
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Unsigned(shift.imm as u64)));
+                }
+                Argument::ShiftReg(shift) => {
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(shift.op.to_string().into())));
+                    args.push(ObjInsArg::PlainText(" ".into()));
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(shift.reg.to_string().into())));
+                }
+                Argument::OffsetReg(offset) => {
+                    if !offset.add {
+                        args.push(ObjInsArg::PlainText("-".into()));
+                    }
+                    args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(
+                        offset.reg.to_string().into(),
+                    )));
+                }
+                _ => args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque(arg.to_string().into()))),
+            }
+        }
+    }
+    if deref {
+        args.push(ObjInsArg::PlainText("]".into()));
+        if writeback {
+            args.push(ObjInsArg::Arg(ObjInsArgValue::Opaque("!".into())));
+        }
+    }
+    Ok((args, branch_dest))
+}

objdiff-core/src/arch/mod.rs

@@ -8,6 +8,8 @@ use crate::{
     obj::{ObjIns, ObjReloc, ObjSection},
 };
 
+#[cfg(feature = "arm")]
+mod arm;
 #[cfg(feature = "mips")]
 pub mod mips;
 #[cfg(feature = "ppc")]
@@ -46,6 +48,8 @@ pub fn new_arch(object: &object::File) -> Result<Box<dyn ObjArch>> {
         Architecture::Mips => Box::new(mips::ObjArchMips::new(object)?),
         #[cfg(feature = "x86")]
         Architecture::I386 | Architecture::X86_64 => Box::new(x86::ObjArchX86::new(object)?),
+        #[cfg(feature = "arm")]
+        Architecture::Arm => Box::new(arm::ObjArchArm::new(object)?),
         arch => bail!("Unsupported architecture: {arch:?}"),
     })
 }