Add hack to detect strings via the addi opcode

Because we no longer have access to the actual symbol name via sections, guess_data_type can no longer detect the String data type for pooled references.

objdiff-core/src/arch/arm.rs

@@ -113,7 +113,6 @@ impl ObjArch for ObjArchArm {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        _sections: &[ObjSection],
     ) -> Result<ProcessCodeResult> {
         let start_addr = address as u32;
         let end_addr = start_addr + code.len() as u32;

objdiff-core/src/arch/arm64.rs

@@ -29,7 +29,6 @@ impl ObjArch for ObjArchArm64 {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        _sections: &[ObjSection],
     ) -> Result<ProcessCodeResult> {
         let start_address = address;
         let end_address = address + code.len() as u64;

objdiff-core/src/arch/mips.rs

@@ -87,7 +87,6 @@ impl ObjArch for ObjArchMips {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        _sections: &[ObjSection],
     ) -> Result<ProcessCodeResult> {
         let _guard = RABBITIZER_MUTEX.lock().map_err(|e| anyhow!("Failed to lock mutex: {e}"))?;
         configure_rabbitizer(match config.mips_abi {

objdiff-core/src/arch/mod.rs

@@ -126,7 +126,6 @@ impl DataType {
 }
 
 pub trait ObjArch: Send + Sync {
-    #[expect(clippy::too_many_arguments)]
     fn process_code(
         &self,
         address: u64,
@@ -135,7 +134,6 @@ pub trait ObjArch: Send + Sync {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        sections: &[ObjSection],
     ) -> Result<ProcessCodeResult>;
 
     fn implcit_addend(

objdiff-core/src/arch/ppc.rs

@@ -48,13 +48,12 @@ impl ObjArch for ObjArchPpc {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        sections: &[ObjSection],
     ) -> Result<ProcessCodeResult> {
         let ins_count = code.len() / 4;
         let mut ops = Vec::<u16>::with_capacity(ins_count);
         let mut insts = Vec::<ObjIns>::with_capacity(ins_count);
         let fake_pool_reloc_for_addr =
-            generate_fake_pool_reloc_for_addr_mapping(address, code, relocations, sections);
+            generate_fake_pool_reloc_for_addr_mapping(address, code, relocations);
         for (cur_addr, mut ins) in InsIter::new(code, address as u32) {
             let reloc = relocations.iter().find(|r| (r.address as u32 & !3) == cur_addr);
             if let Some(reloc) = reloc {
@@ -205,7 +204,21 @@ impl ObjArch for ObjArchPpc {
             return Some(DataType::String);
         }
 
-        guess_data_type_from_load_store_inst_op(Opcode::from(instruction.op as u8))
+        let op = Opcode::from(instruction.op as u8);
+        if let Some(ty) = guess_data_type_from_load_store_inst_op(op) {
+            Some(ty)
+        } else if op == Opcode::Addi {
+            // Assume that any addi instruction that references a local symbol is loading a string.
+            // This hack is not ideal and results in tons of false positives where it will show
+            // garbage strings (e.g. misinterpreting arrays, float literals, etc).
+            // But there isn't much other choice as not all strings are in the @stringBase pool.
+            // And even those that are would be missed by the target.name.starts_with("@stringBase")
+            // hack above for fake pooled relocations, as they have an empty string placeholder for
+            // the target symbol name.
+            Some(DataType::String)
+        } else {
+            None
+        }
     }
 
     fn display_data_type(&self, ty: DataType, bytes: &[u8]) -> Option<String> {
@@ -423,7 +436,7 @@ fn get_offset_and_addr_gpr_for_possible_pool_reference(
         }
     } else {
         // If it's not a load/store instruction, there's two more possibilities we need to handle.
-        // 1. It could be a reference to @stringBase.
+        // 1. It could be loading a pointer to a string.
         // 2. It could be moving the relocation address plus an offset into a different register to
         //    load from later.
         // If either of these match, we also want to return the destination register that the
@@ -453,26 +466,38 @@ fn get_offset_and_addr_gpr_for_possible_pool_reference(
 // there isn't really a relocation here, as copying the pool relocation's type wouldn't make sense.
 // Also, if this instruction is accessing the middle of a symbol instead of the start, we add an
 // addend to indicate that.
-fn make_fake_pool_reloc(
-    offset: i16,
-    cur_addr: u32,
-    pool_reloc: &ObjReloc,
-    sections: &[ObjSection],
-) -> Option<ObjReloc> {
+fn make_fake_pool_reloc(offset: i16, cur_addr: u32, pool_reloc: &ObjReloc) -> Option<ObjReloc> {
     let offset_from_pool = pool_reloc.addend + offset as i64;
     let target_address = pool_reloc.target.address.checked_add_signed(offset_from_pool)?;
     let orig_section_index = pool_reloc.target.orig_section_index?;
-    let section = sections.iter().find(|s| s.orig_index == orig_section_index)?;
-    let target_symbol = section
-        .symbols
-        .iter()
-        .find(|s| s.size > 0 && (s.address..s.address + s.size).contains(&target_address))?;
-    let addend = (target_address - target_symbol.address) as i64;
+    // We also need to create a fake target symbol to go inside our fake relocation.
+    // This is because we don't have access to list of all symbols in this section, so we can't find
+    // the real symbol yet. Instead we make a placeholder that has the correct `orig_section_index`
+    // and `address` fields, and then later on when this information is displayed to the user, we
+    // can find the real symbol by searching through the object's section's symbols for one that
+    // contains this address.
+    let fake_target_symbol = ObjSymbol {
+        name: "".to_string(),
+        demangled_name: None,
+        address: target_address,
+        section_address: 0,
+        size: 0,
+        size_known: false,
+        kind: Default::default(),
+        flags: Default::default(),
+        orig_section_index: Some(orig_section_index),
+        virtual_address: None,
+        original_index: None,
+        bytes: vec![],
+    };
+    // The addend is also fake because we don't know yet if the `target_address` here is the exact
+    // start of the symbol or if it's in the middle of it.
+    let fake_addend = 0;
     Some(ObjReloc {
         flags: RelocationFlags::Elf { r_type: elf::R_PPC_NONE },
         address: cur_addr as u64,
-        target: target_symbol.clone(),
-        addend,
+        target: fake_target_symbol,
+        addend: fake_addend,
     })
 }
 
@@ -491,7 +516,6 @@ fn generate_fake_pool_reloc_for_addr_mapping(
     address: u64,
     code: &[u8],
     relocations: &[ObjReloc],
-    sections: &[ObjSection],
 ) -> HashMap<u32, ObjReloc> {
     let mut active_pool_relocs = HashMap::new();
     let mut pool_reloc_for_addr = HashMap::new();
@@ -520,6 +544,16 @@ fn generate_fake_pool_reloc_for_addr_mapping(
                 ) => {
                     active_pool_relocs.insert(addr_dst_gpr.0, reloc.clone()); // `lis` + `ori`
                 }
+                (Opcode::B, _, _, _) => {
+                    if simplified.mnemonic == "bl" {
+                        // When encountering a function call, clear any active pool relocations from
+                        // the volatile registers (r0, r3-r12), but not the nonvolatile registers.
+                        active_pool_relocs.remove(&0);
+                        for gpr in 3..12 {
+                            active_pool_relocs.remove(&gpr);
+                        }
+                    }
+                }
                 _ => {}
             }
         } else if let Some((offset, addr_src_gpr, addr_dst_gpr)) =
@@ -528,9 +562,7 @@ fn generate_fake_pool_reloc_for_addr_mapping(
             // This instruction doesn't have a real relocation, so it may be a reference to one of
             // the already-loaded pools.
             if let Some(pool_reloc) = active_pool_relocs.get(&addr_src_gpr.0) {
-                if let Some(fake_pool_reloc) =
-                    make_fake_pool_reloc(offset, cur_addr, pool_reloc, sections)
-                {
+                if let Some(fake_pool_reloc) = make_fake_pool_reloc(offset, cur_addr, pool_reloc) {
                     pool_reloc_for_addr.insert(cur_addr, fake_pool_reloc);
                 }
                 if let Some(addr_dst_gpr) = addr_dst_gpr {

objdiff-core/src/arch/x86.rs

@@ -34,7 +34,6 @@ impl ObjArch for ObjArchX86 {
         relocations: &[ObjReloc],
         line_info: &BTreeMap<u64, u32>,
         config: &DiffObjConfig,
-        _sections: &[ObjSection],
     ) -> Result<ProcessCodeResult> {
         let mut result = ProcessCodeResult { ops: Vec::new(), insts: Vec::new() };
         let mut decoder = Decoder::with_ip(self.bits, code, address, DecoderOptions::NONE);

objdiff-core/src/diff/code.rs

@@ -28,7 +28,6 @@ pub fn process_code_symbol(
         &section.relocations,
         &section.line_info,
         config,
-        &obj.sections,
     )
 }
 

objdiff-gui/src/views/function_diff.rs

@@ -74,6 +74,19 @@ impl FunctionViewState {
     }
 }
 
+fn find_symbol_matching_fake_symbol_in_sections(
+    fake_symbol: &ObjSymbol,
+    sections: &[ObjSection],
+) -> Option<ObjSymbol> {
+    let orig_section_index = fake_symbol.orig_section_index?;
+    let section = sections.iter().find(|s| s.orig_index == orig_section_index)?;
+    let real_symbol = section
+        .symbols
+        .iter()
+        .find(|s| s.size > 0 && (s.address..s.address + s.size).contains(&fake_symbol.address))?;
+    Some(real_symbol.clone())
+}
+
 fn ins_hover_ui(
     ui: &mut egui::Ui,
     obj: &ObjInfo,
@@ -119,17 +132,29 @@ fn ins_hover_ui(
         }
 
         if let Some(reloc) = ins.reloc.as_ref().or(ins.fake_pool_reloc.as_ref()) {
+            let mut target = reloc.target.clone();
+            let mut addend = reloc.addend;
+            if target.size == 0 && target.name.is_empty() {
+                // Fake target symbol we added as a placeholder. We need to find the real one.
+                if let Some(real_target) =
+                    find_symbol_matching_fake_symbol_in_sections(&target, &obj.sections)
+                {
+                    target = real_target;
+                    addend = (reloc.target.address - target.address) as i64;
+                }
+            }
+
             ui.label(format!("Relocation type: {}", obj.arch.display_reloc(reloc.flags)));
-            let addend_str = match reloc.addend.cmp(&0i64) {
-                Ordering::Greater => format!("+{:x}", reloc.addend),
-                Ordering::Less => format!("-{:x}", -reloc.addend),
+            let addend_str = match addend.cmp(&0i64) {
+                Ordering::Greater => format!("+{:x}", addend),
+                Ordering::Less => format!("-{:x}", -addend),
                 _ => "".to_string(),
             };
             ui.colored_label(
                 appearance.highlight_color,
-                format!("Name: {}{}", reloc.target.name, addend_str),
+                format!("Name: {}{}", target.name, addend_str),
             );
-            if let Some(orig_section_index) = reloc.target.orig_section_index {
+            if let Some(orig_section_index) = target.orig_section_index {
                 if let Some(section) =
                     obj.sections.iter().find(|s| s.orig_index == orig_section_index)
                 {
@@ -140,15 +165,12 @@ fn ins_hover_ui(
                 }
                 ui.colored_label(
                     appearance.highlight_color,
-                    format!("Address: {:x}{}", reloc.target.address, addend_str),
+                    format!("Address: {:x}{}", target.address, addend_str),
                 );
-                ui.colored_label(
-                    appearance.highlight_color,
-                    format!("Size: {:x}", reloc.target.size),
-                );
-                if reloc.addend >= 0 && reloc.target.bytes.len() > reloc.addend as usize {
+                ui.colored_label(appearance.highlight_color, format!("Size: {:x}", target.size));
+                if addend >= 0 && target.bytes.len() > addend as usize {
                     if let Some(s) = obj.arch.guess_data_type(ins).and_then(|ty| {
-                        obj.arch.display_data_type(ty, &reloc.target.bytes[reloc.addend as usize..])
+                        obj.arch.display_data_type(ty, &target.bytes[addend as usize..])
                     }) {
                         ui.colored_label(appearance.highlight_color, s);
                     }