Support PPC64 ELFs (PS3); refactor relocation processing

README.md

@@ -19,7 +19,7 @@ Supports:
 - ARM (GBA, DS, 3DS)
 - ARM64 (Switch)
 - MIPS (N64, PS1, PS2, PSP)
-- PowerPC (GameCube, Wii, Xbox 360)
+- PowerPC (GameCube, Wii, PS3, Xbox 360)
 - SuperH (Saturn, Dreamcast)
 - x86, x86_64 (PC)
 

objdiff-core/Cargo.toml

@@ -128,7 +128,7 @@ itertools = { version = "0.14", default-features = false, features = ["use_alloc
 log = { version = "0.4", default-features = false, optional = true }
 memmap2 = { version = "0.9", optional = true }
 num-traits = { version = "0.2", default-features = false, optional = true }
-object = { git = "https://github.com/gimli-rs/object", rev = "16ff70aa6fbd97d6bb7b92375929f4d72414c32b", default-features = false, features = ["read_core", "elf", "pe"] }
+object = { git = "https://github.com/gimli-rs/object", rev = "16ff70aa6fbd97d6bb7b92375929f4d72414c32b", default-features = false, features = ["read_core", "elf", "coff"] }
 pbjson = { version = "0.7", default-features = false, optional = true }
 prost = { version = "0.13", default-features = false, features = ["prost-derive"], optional = true }
 regex = { version = "1.11", default-features = false, features = [], optional = true }

objdiff-core/src/arch/arm.rs

@@ -11,7 +11,7 @@ use object::{Endian as _, Object as _, ObjectSection as _, ObjectSymbol as _, el
 use unarm::{args, arm, thumb};
 
 use crate::{
-    arch::Arch,
+    arch::{Arch, RelocationOverride, RelocationOverrideTarget},
     diff::{ArmArchVersion, ArmR9Usage, DiffObjConfig, display::InstructionPart},
     obj::{
         InstructionRef, Relocation, RelocationFlags, ResolvedInstructionRef, ResolvedRelocation,
@@ -356,47 +356,57 @@ impl Arch for ArchArm {
         Ok(())
     }
 
-    fn implcit_addend(
+    fn relocation_override(
         &self,
         _file: &object::File<'_>,
         section: &object::Section,
         address: u64,
-        _relocation: &object::Relocation,
+        relocation: &object::Relocation,
-        flags: RelocationFlags,
+    ) -> Result<Option<RelocationOverride>> {
-    ) -> Result<Option<i64>> {
+        match relocation.flags() {
-        let section_data = section.data()?;
+            // Handle ELF implicit relocations
-        let address = address as usize;
+            object::RelocationFlags::Elf { r_type } => {
-        Ok(Some(match flags {
+                if relocation.has_implicit_addend() {
-            // ARM calls
+                    let section_data = section.data()?;
-            RelocationFlags::Elf(elf::R_ARM_PC24)
+                    let address = address as usize;
-            | RelocationFlags::Elf(elf::R_ARM_XPC25)
+                    let addend = match r_type {
-            | RelocationFlags::Elf(elf::R_ARM_CALL) => {
+                        // ARM calls
-                let data = section_data[address..address + 4].try_into()?;
+                        elf::R_ARM_PC24 | elf::R_ARM_XPC25 | elf::R_ARM_CALL => {
-                let addend = self.endianness.read_i32_bytes(data);
+                            let data = section_data[address..address + 4].try_into()?;
-                let imm24 = addend & 0xffffff;
+                            let addend = self.endianness.read_i32_bytes(data);
-                (imm24 << 2) << 8 >> 8
+                            let imm24 = addend & 0xffffff;
+                            (imm24 << 2) << 8 >> 8
+                        }
+
+                        // Thumb calls
+                        elf::R_ARM_THM_PC22 | elf::R_ARM_THM_XPC22 => {
+                            let data = section_data[address..address + 2].try_into()?;
+                            let high = self.endianness.read_i16_bytes(data) as i32;
+                            let data = section_data[address + 2..address + 4].try_into()?;
+                            let low = self.endianness.read_i16_bytes(data) as i32;
+
+                            let imm22 = ((high & 0x7ff) << 11) | (low & 0x7ff);
+                            (imm22 << 1) << 9 >> 9
+                        }
+
+                        // Data
+                        elf::R_ARM_ABS32 => {
+                            let data = section_data[address..address + 4].try_into()?;
+                            self.endianness.read_i32_bytes(data)
+                        }
+
+                        flags => bail!("Unsupported ARM implicit relocation {flags:?}"),
+                    };
+                    Ok(Some(RelocationOverride {
+                        target: RelocationOverrideTarget::Keep,
+                        addend: addend as i64,
+                    }))
+                } else {
+                    Ok(None)
+                }
             }
-
+            _ => Ok(None),
-            // Thumb calls
+        }
-            RelocationFlags::Elf(elf::R_ARM_THM_PC22)
-            | RelocationFlags::Elf(elf::R_ARM_THM_XPC22) => {
-                let data = section_data[address..address + 2].try_into()?;
-                let high = self.endianness.read_i16_bytes(data) as i32;
-                let data = section_data[address + 2..address + 4].try_into()?;
-                let low = self.endianness.read_i16_bytes(data) as i32;
-
-                let imm22 = ((high & 0x7ff) << 11) | (low & 0x7ff);
-                (imm22 << 1) << 9 >> 9
-            }
-
-            // Data
-            RelocationFlags::Elf(elf::R_ARM_ABS32) => {
-                let data = section_data[address..address + 4].try_into()?;
-                self.endianness.read_i32_bytes(data)
-            }
-
-            flags => bail!("Unsupported ARM implicit relocation {flags:?}"),
-        } as i64))
     }
 
     fn demangle(&self, name: &str) -> Option<String> {

objdiff-core/src/arch/arm64.rs

@@ -5,7 +5,7 @@ use alloc::{
 };
 use core::cmp::Ordering;
 
-use anyhow::{Result, bail};
+use anyhow::Result;
 use object::elf;
 use yaxpeax_arch::{Arch as YaxpeaxArch, Decoder, Reader, U8Reader};
 use yaxpeax_arm::armv8::a64::{
@@ -108,17 +108,6 @@ impl Arch for ArchArm64 {
         Ok(())
     }
 
-    fn implcit_addend(
-        &self,
-        _file: &object::File<'_>,
-        _section: &object::Section,
-        address: u64,
-        _relocation: &object::Relocation,
-        flags: RelocationFlags,
-    ) -> Result<Option<i64>> {
-        bail!("Unsupported ARM64 implicit relocation {:#x}:{:?}", address, flags)
-    }
-
     fn demangle(&self, name: &str) -> Option<String> {
         cpp_demangle::Symbol::new(name)
             .ok()

objdiff-core/src/arch/mips.rs

@@ -14,7 +14,7 @@ use rabbitizer::{
 };
 
 use crate::{
-    arch::Arch,
+    arch::{Arch, RelocationOverride, RelocationOverrideTarget},
     diff::{DiffObjConfig, MipsAbi, MipsInstrCategory, display::InstructionPart},
     obj::{
         InstructionArg, InstructionArgValue, InstructionRef, Relocation, RelocationFlags,
@@ -225,53 +225,67 @@ impl Arch for ArchMips {
         Ok(())
     }
 
-    fn implcit_addend(
+    fn relocation_override(
         &self,
         file: &object::File<'_>,
         section: &object::Section,
         address: u64,
-        reloc: &object::Relocation,
+        relocation: &object::Relocation,
-        flags: RelocationFlags,
+    ) -> Result<Option<RelocationOverride>> {
-    ) -> Result<Option<i64>> {
+        match relocation.flags() {
-        // Check for paired R_MIPS_HI16 and R_MIPS_LO16 relocations.
+            // Handle ELF implicit relocations
-        if let RelocationFlags::Elf(elf::R_MIPS_HI16 | elf::R_MIPS_LO16) = flags {
+            object::RelocationFlags::Elf { r_type } => {
-            if let Some(addend) = self
+                if relocation.has_implicit_addend() {
-                .paired_relocations
+                    // Check for paired R_MIPS_HI16 and R_MIPS_LO16 relocations.
-                .get(section.index().0)
+                    if let elf::R_MIPS_HI16 | elf::R_MIPS_LO16 = r_type {
-                .and_then(|m| m.get(&address).copied())
+                        if let Some(addend) = self
-            {
+                            .paired_relocations
-                return Ok(Some(addend));
+                            .get(section.index().0)
-            }
+                            .and_then(|m| m.get(&address).copied())
-        }
+                        {
+                            return Ok(Some(RelocationOverride {
+                                target: RelocationOverrideTarget::Keep,
+                                addend,
+                            }));
+                        }
+                    }
 
-        let data = section.data()?;
+                    let data = section.data()?;
-        let code = data[address as usize..address as usize + 4].try_into()?;
+                    let code = self
-        let addend = self.endianness.read_u32_bytes(code);
+                        .endianness
-        Ok(Some(match flags {
+                        .read_u32_bytes(data[address as usize..address as usize + 4].try_into()?);
-            RelocationFlags::Elf(elf::R_MIPS_32) => addend as i64,
+                    let addend = match r_type {
-            RelocationFlags::Elf(elf::R_MIPS_26) => ((addend & 0x03FFFFFF) << 2) as i64,
+                        elf::R_MIPS_32 => code as i64,
-            RelocationFlags::Elf(elf::R_MIPS_HI16) => ((addend & 0x0000FFFF) << 16) as i32 as i64,
+                        elf::R_MIPS_26 => ((code & 0x03FFFFFF) << 2) as i64,
-            RelocationFlags::Elf(elf::R_MIPS_LO16 | elf::R_MIPS_GOT16 | elf::R_MIPS_CALL16) => {
+                        elf::R_MIPS_HI16 => ((code & 0x0000FFFF) << 16) as i32 as i64,
-                (addend & 0x0000FFFF) as i16 as i64
+                        elf::R_MIPS_LO16 | elf::R_MIPS_GOT16 | elf::R_MIPS_CALL16 => {
-            }
+                            (code & 0x0000FFFF) as i16 as i64
-            RelocationFlags::Elf(elf::R_MIPS_GPREL16 | elf::R_MIPS_LITERAL) => {
+                        }
-                let object::RelocationTarget::Symbol(idx) = reloc.target() else {
+                        elf::R_MIPS_GPREL16 | elf::R_MIPS_LITERAL => {
-                    bail!("Unsupported R_MIPS_GPREL16 relocation against a non-symbol");
+                            let object::RelocationTarget::Symbol(idx) = relocation.target() else {
-                };
+                                bail!("Unsupported R_MIPS_GPREL16 relocation against a non-symbol");
-                let sym = file.symbol_by_index(idx)?;
+                            };
+                            let sym = file.symbol_by_index(idx)?;
 
-                // if the symbol we are relocating against is in a local section we need to add
+                            // if the symbol we are relocating against is in a local section we need to add
-                // the ri_gp_value from .reginfo to the addend.
+                            // the ri_gp_value from .reginfo to the addend.
-                if sym.section().index().is_some() {
+                            if sym.section().index().is_some() {
-                    ((addend & 0x0000FFFF) as i16 as i64) + self.ri_gp_value as i64
+                                ((code & 0x0000FFFF) as i16 as i64) + self.ri_gp_value as i64
+                            } else {
+                                (code & 0x0000FFFF) as i16 as i64
+                            }
+                        }
+                        elf::R_MIPS_PC16 => 0, // PC-relative relocation
+                        R_MIPS15_S3 => ((code & 0x001FFFC0) >> 3) as i64,
+                        flags => bail!("Unsupported MIPS implicit relocation {flags:?}"),
+                    };
+                    Ok(Some(RelocationOverride { target: RelocationOverrideTarget::Keep, addend }))
                 } else {
-                    (addend & 0x0000FFFF) as i16 as i64
+                    Ok(None)
                 }
             }
-            RelocationFlags::Elf(elf::R_MIPS_PC16) => 0, // PC-relative relocation
+            _ => Ok(None),
-            RelocationFlags::Elf(R_MIPS15_S3) => ((addend & 0x001FFFC0) >> 3) as i64,
+        }
-            flags => bail!("Unsupported MIPS implicit relocation {flags:?}"),
-        }))
     }
 
     fn demangle(&self, name: &str) -> Option<String> {

objdiff-core/src/arch/mod.rs

@@ -357,14 +357,15 @@ pub trait Arch: Send + Sync + Debug {
         None
     }
 
-    fn implcit_addend(
+    fn relocation_override(
         &self,
-        file: &object::File<'_>,
+        _file: &object::File<'_>,
-        section: &object::Section,
+        _section: &object::Section,
-        address: u64,
+        _address: u64,
-        relocation: &object::Relocation,
+        _relocation: &object::Relocation,
-        flags: RelocationFlags,
+    ) -> Result<Option<RelocationOverride>> {
-    ) -> Result<Option<i64>>;
+        Ok(None)
+    }
 
     fn demangle(&self, _name: &str) -> Option<String> { None }
 
@@ -411,7 +412,9 @@ pub fn new_arch(object: &object::File) -> Result<Box<dyn Arch>> {
     use object::Object as _;
     Ok(match object.architecture() {
         #[cfg(feature = "ppc")]
-        object::Architecture::PowerPc => Box::new(ppc::ArchPpc::new(object)?),
+        object::Architecture::PowerPc | object::Architecture::PowerPc64 => {
+            Box::new(ppc::ArchPpc::new(object)?)
+        }
         #[cfg(feature = "mips")]
         object::Architecture::Mips => Box::new(mips::ArchMips::new(object)?),
         #[cfg(feature = "x86")]
@@ -456,16 +459,17 @@ impl Arch for ArchDummy {
         Ok(())
     }
 
-    fn implcit_addend(
-        &self,
-        _file: &object::File<'_>,
-        _section: &object::Section,
-        _address: u64,
-        _relocation: &object::Relocation,
-        _flags: RelocationFlags,
-    ) -> Result<Option<i64>> {
-        Ok(Some(0))
-    }
-
     fn data_reloc_size(&self, _flags: RelocationFlags) -> usize { 0 }
 }
+
+pub enum RelocationOverrideTarget {
+    Keep,
+    Skip,
+    Symbol(object::SymbolIndex),
+    Section(object::SectionIndex),
+}
+
+pub struct RelocationOverride {
+    pub target: RelocationOverrideTarget,
+    pub addend: i64,
+}

objdiff-core/src/arch/ppc/mod.rs

@@ -12,7 +12,7 @@ use flagset::Flags;
 use object::{Object as _, ObjectSection as _, ObjectSymbol as _, elf, pe};
 
 use crate::{
-    arch::{Arch, DataType},
+    arch::{Arch, DataType, RelocationOverride, RelocationOverrideTarget},
     diff::{
         DiffObjConfig,
         data::resolve_relocation,
@@ -100,6 +100,7 @@ impl ArchPpc {
             | RelocationFlags::Coff(pe::IMAGE_REL_PPC_REFHI | pe::IMAGE_REL_PPC_REFLO) => {
                 ins.args.iter().rposition(is_rel_abs_arg)
             }
+            RelocationFlags::Elf(elf::R_PPC64_TOC16) => ins.args.iter().rposition(is_offset_arg),
             _ => None,
         }
     }
@@ -208,18 +209,18 @@ impl Arch for ArchPpc {
         Some(flow_analysis::ppc_data_flow_analysis(obj, symbol, code, relocations, self.extensions))
     }
 
-    fn implcit_addend(
+    fn relocation_override(
         &self,
-        _file: &object::File<'_>,
+        file: &object::File<'_>,
         section: &object::Section,
         address: u64,
-        _relocation: &object::Relocation,
+        relocation: &object::Relocation,
-        flags: RelocationFlags,
+    ) -> Result<Option<RelocationOverride>> {
-    ) -> Result<Option<i64>> {
+        match relocation.flags() {
-        match flags {
             // IMAGE_REL_PPC_PAIR contains the REF{HI,LO} displacement instead of a symbol index
-            RelocationFlags::Coff(pe::IMAGE_REL_PPC_REFHI)
+            object::RelocationFlags::Coff {
-            | RelocationFlags::Coff(pe::IMAGE_REL_PPC_REFLO) => section
+                typ: pe::IMAGE_REL_PPC_REFHI | pe::IMAGE_REL_PPC_REFLO,
+            } => section
                 .relocations()
                 .skip_while(|&(a, _)| a < address)
                 .take_while(|&(a, _)| a == address)
@@ -228,23 +229,81 @@ impl Arch for ArchPpc {
                         typ: pe::IMAGE_REL_PPC_PAIR
                     })
                 })
-                .map_or(Ok(Some(0)), |(_, reloc)| match reloc.target() {
+                .map_or(Ok(None), |(_, reloc)| match reloc.target() {
-                    object::RelocationTarget::Symbol(index) => {
+                    object::RelocationTarget::Symbol(index) => Ok(Some(RelocationOverride {
-                        Ok(Some(index.0 as u16 as i16 as i64))
+                        target: RelocationOverrideTarget::Keep,
-                    }
+                        addend: index.0 as u16 as i16 as i64,
+                    })),
                     target => Err(anyhow!("Unsupported IMAGE_REL_PPC_PAIR target {target:?}")),
                 }),
             // Skip PAIR relocations as they are handled by the previous case
-            RelocationFlags::Coff(pe::IMAGE_REL_PPC_PAIR) => Ok(None),
+            object::RelocationFlags::Coff { typ: pe::IMAGE_REL_PPC_PAIR } => {
-            RelocationFlags::Coff(_) => Ok(Some(0)),
+                Ok(Some(RelocationOverride { target: RelocationOverrideTarget::Skip, addend: 0 }))
-            flags => Err(anyhow!("Unsupported PPC implicit relocation {flags:?}")),
+            }
+            // Any other COFF relocation has an addend of 0
+            object::RelocationFlags::Coff { .. } => {
+                Ok(Some(RelocationOverride { target: RelocationOverrideTarget::Keep, addend: 0 }))
+            }
+            // Handle ELF implicit relocations
+            flags @ object::RelocationFlags::Elf { r_type } => {
+                ensure!(
+                    !relocation.has_implicit_addend(),
+                    "Unsupported implicit relocation {:?}",
+                    flags
+                );
+                match r_type {
+                    elf::R_PPC64_TOC16 => {
+                        let offset = u64::try_from(relocation.addend())
+                            .map_err(|_| anyhow!("Negative addend for R_PPC64_TOC16 relocation"))?;
+                        let Some(toc_section) = file.section_by_name(".toc") else {
+                            bail!("Missing .toc section for R_PPC64_TOC16 relocation");
+                        };
+                        // If TOC target is a relocation, replace it with the target symbol
+                        let Some((_, toc_relocation)) =
+                            toc_section.relocations().find(|&(a, _)| a == offset)
+                        else {
+                            return Ok(None);
+                        };
+                        if toc_relocation.has_implicit_addend() {
+                            log::warn!(
+                                "Unsupported implicit addend for R_PPC64_TOC16 relocation: {toc_relocation:?}"
+                            );
+                            return Ok(None);
+                        }
+                        let addend = toc_relocation.addend();
+                        match toc_relocation.target() {
+                            object::RelocationTarget::Symbol(symbol_index) => {
+                                Ok(Some(RelocationOverride {
+                                    target: RelocationOverrideTarget::Symbol(symbol_index),
+                                    addend,
+                                }))
+                            }
+                            object::RelocationTarget::Section(section_index) => {
+                                Ok(Some(RelocationOverride {
+                                    target: RelocationOverrideTarget::Section(section_index),
+                                    addend,
+                                }))
+                            }
+                            target => {
+                                log::warn!(
+                                    "Unsupported R_PPC64_TOC16 relocation target {target:?}"
+                                );
+                                Ok(None)
+                            }
+                        }
+                    }
+                    _ => Ok(None),
+                }
+            }
+            _ => Ok(None),
         }
     }
 
-    fn demangle(&self, name: &str) -> Option<String> {
+    fn demangle(&self, mut name: &str) -> Option<String> {
         if name.starts_with('?') {
             msvc_demangler::demangle(name, msvc_demangler::DemangleFlags::llvm()).ok()
         } else {
+            name = name.trim_start_matches('.');
             cpp_demangle::Symbol::new(name)
                 .ok()
                 .and_then(|s| s.demangle(&cpp_demangle::DemangleOptions::default()).ok())
@@ -264,6 +323,7 @@ impl Arch for ArchPpc {
                 elf::R_PPC_UADDR32 => Some("R_PPC_UADDR32"),
                 elf::R_PPC_REL24 => Some("R_PPC_REL24"),
                 elf::R_PPC_REL14 => Some("R_PPC_REL14"),
+                elf::R_PPC64_TOC16 => Some("R_PPC64_TOC16"),
                 _ => None,
             },
             RelocationFlags::Coff(r_type) => match r_type {

objdiff-core/src/arch/superh/mod.rs

@@ -1,6 +1,6 @@
 use alloc::{collections::BTreeMap, format, string::String, vec, vec::Vec};
 
-use anyhow::{Result, bail};
+use anyhow::Result;
 use object::elf;
 
 use crate::{
@@ -132,17 +132,6 @@ impl Arch for ArchSuperH {
         Ok(())
     }
 
-    fn implcit_addend(
-        &self,
-        _file: &object::File<'_>,
-        _section: &object::Section,
-        address: u64,
-        _relocation: &object::Relocation,
-        flags: RelocationFlags,
-    ) -> Result<Option<i64>> {
-        bail!("Unsupported SuperH implicit relocation {:#x}:{:?}", address, flags)
-    }
-
     fn demangle(&self, name: &str) -> Option<String> {
         cpp_demangle::Symbol::new(name)
             .ok()

objdiff-core/src/arch/x86.rs

@@ -9,7 +9,7 @@ use iced_x86::{
 use object::{Endian as _, Object as _, ObjectSection as _, elf, pe};
 
 use crate::{
-    arch::Arch,
+    arch::{Arch, RelocationOverride, RelocationOverrideTarget},
     diff::{DiffObjConfig, X86Formatter, display::InstructionPart},
     obj::{InstructionRef, Relocation, RelocationFlags, ResolvedInstructionRef},
 };
@@ -225,40 +225,47 @@ impl Arch for ArchX86 {
         Ok(())
     }
 
-    fn implcit_addend(
+    fn relocation_override(
         &self,
         _file: &object::File<'_>,
         section: &object::Section,
         address: u64,
-        _relocation: &object::Relocation,
+        relocation: &object::Relocation,
-        flags: RelocationFlags,
+    ) -> Result<Option<RelocationOverride>> {
-    ) -> Result<Option<i64>> {
+        if !relocation.has_implicit_addend() {
-        match self.arch {
+            return Ok(None);
-            Architecture::X86 => match flags {
+        }
-                RelocationFlags::Coff(pe::IMAGE_REL_I386_DIR32 | pe::IMAGE_REL_I386_REL32)
+        let addend = match self.arch {
-                | RelocationFlags::Elf(elf::R_386_32 | elf::R_386_PC32) => {
+            Architecture::X86 => match relocation.flags() {
+                object::RelocationFlags::Coff {
+                    typ: pe::IMAGE_REL_I386_DIR32 | pe::IMAGE_REL_I386_REL32,
+                }
+                | object::RelocationFlags::Elf { r_type: elf::R_386_32 | elf::R_386_PC32 } => {
                     let data =
                         section.data()?[address as usize..address as usize + 4].try_into()?;
-                    Ok(Some(self.endianness.read_i32_bytes(data) as i64))
+                    self.endianness.read_i32_bytes(data) as i64
                 }
                 flags => bail!("Unsupported x86 implicit relocation {flags:?}"),
             },
-            Architecture::X86_64 => match flags {
+            Architecture::X86_64 => match relocation.flags() {
-                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR32NB | pe::IMAGE_REL_AMD64_REL32)
+                object::RelocationFlags::Coff {
-                | RelocationFlags::Elf(elf::R_X86_64_32 | elf::R_X86_64_PC32) => {
+                    typ: pe::IMAGE_REL_AMD64_ADDR32NB | pe::IMAGE_REL_AMD64_REL32,
+                }
+                | object::RelocationFlags::Elf { r_type: elf::R_X86_64_32 | elf::R_X86_64_PC32 } => {
                     let data =
                         section.data()?[address as usize..address as usize + 4].try_into()?;
-                    Ok(Some(self.endianness.read_i32_bytes(data) as i64))
+                    self.endianness.read_i32_bytes(data) as i64
                 }
-                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR64)
+                object::RelocationFlags::Coff { typ: pe::IMAGE_REL_AMD64_ADDR64 }
-                | RelocationFlags::Elf(elf::R_X86_64_64) => {
+                | object::RelocationFlags::Elf { r_type: elf::R_X86_64_64 } => {
                     let data =
                         section.data()?[address as usize..address as usize + 8].try_into()?;
-                    Ok(Some(self.endianness.read_i64_bytes(data)))
+                    self.endianness.read_i64_bytes(data)
                 }
                 flags => bail!("Unsupported x86-64 implicit relocation {flags:?}"),
             },
-        }
+        };
+        Ok(Some(RelocationOverride { target: RelocationOverrideTarget::Keep, addend }))
     }
 
     fn demangle(&self, name: &str) -> Option<String> {

objdiff-core/src/obj/read.rs

@@ -11,7 +11,7 @@ use anyhow::{Context, Result, anyhow, bail, ensure};
 use object::{Object as _, ObjectSection as _, ObjectSymbol as _};
 
 use crate::{
-    arch::{Arch, new_arch},
+    arch::{Arch, RelocationOverride, RelocationOverrideTarget, new_arch},
     diff::DiffObjConfig,
     obj::{
         FlowAnalysisResult, Object, Relocation, RelocationFlags, Section, SectionData, SectionFlag,
@@ -24,8 +24,13 @@ use crate::{
 fn map_section_kind(section: &object::Section) -> SectionKind {
     match section.kind() {
         object::SectionKind::Text => SectionKind::Code,
-        object::SectionKind::Data | object::SectionKind::ReadOnlyData => SectionKind::Data,
+        object::SectionKind::Data
-        object::SectionKind::UninitializedData => SectionKind::Bss,
+        | object::SectionKind::ReadOnlyData
+        | object::SectionKind::ReadOnlyString
+        | object::SectionKind::Tls => SectionKind::Data,
+        object::SectionKind::UninitializedData
+        | object::SectionKind::UninitializedTls
+        | object::SectionKind::Common => SectionKind::Bss,
         _ => SectionKind::Unknown,
     }
 }
@@ -329,63 +334,125 @@ fn map_section_relocations(
 ) -> Result<Vec<Relocation>> {
     let mut relocations = Vec::<Relocation>::with_capacity(obj_section.relocations().count());
     for (address, reloc) in obj_section.relocations() {
-        let flags = match reloc.flags() {
+        let mut target_reloc = RelocationOverride {
-            object::RelocationFlags::Elf { r_type } => RelocationFlags::Elf(r_type),
+            target: match reloc.target() {
-            object::RelocationFlags::Coff { typ } => RelocationFlags::Coff(typ),
+                object::RelocationTarget::Symbol(symbol) => {
-            flags => {
+                    RelocationOverrideTarget::Symbol(symbol)
-                bail!("Unhandled relocation flags: {:?}", flags);
+                }
-            }
+                object::RelocationTarget::Section(section) => {
+                    RelocationOverrideTarget::Section(section)
+                }
+                _ => RelocationOverrideTarget::Skip,
+            },
+            addend: reloc.addend(),
         };
-        // TODO validate reloc here?
+
-        let mut addend = if reloc.has_implicit_addend() {
+        // Allow the architecture to override the relocation target and addend
-            match arch.implcit_addend(obj_file, obj_section, address, &reloc, flags)? {
+        match arch.relocation_override(obj_file, obj_section, address, &reloc)? {
-                Some(addend) => addend,
+            Some(reloc_override) => {
-                None => continue, // Skip relocation (e.g. COFF PAIR relocations)
+                match reloc_override.target {
+                    RelocationOverrideTarget::Keep => {}
+                    target => {
+                        target_reloc.target = target;
+                    }
+                }
+                target_reloc.addend = reloc_override.addend;
             }
-        } else {
+            None => {
-            reloc.addend()
+                ensure!(
-        };
+                    !reloc.has_implicit_addend(),
-        let target_symbol = match reloc.target() {
+                    "Unsupported implicit relocation {:?}",
-            object::RelocationTarget::Symbol(idx) => {
+                    reloc.flags()
-                if idx.0 == u32::MAX as usize {
+                );
-                    // ???
+            }
+        }
+
+        // Resolve the relocation target symbol
+        let (symbol_index, addend) = match target_reloc.target {
+            RelocationOverrideTarget::Keep => unreachable!(),
+            RelocationOverrideTarget::Skip => continue,
+            RelocationOverrideTarget::Symbol(symbol_index) => {
+                // Sometimes used to indicate "absolute"
+                if symbol_index.0 == u32::MAX as usize {
                     continue;
                 }
+
                 // If the target is a section symbol, try to resolve a better symbol as the target
-                let idx = if let Some(section_symbol) = obj_file
+                if let Some(section_symbol) = obj_file
-                    .symbol_by_index(idx)
+                    .symbol_by_index(symbol_index)
                     .ok()
                     .filter(|s| s.kind() == object::SymbolKind::Section)
                 {
                     let section_index =
                         section_symbol.section_index().context("Section symbol without section")?;
-                    let target_address = section_symbol.address().wrapping_add_signed(addend);
+                    let target_address =
+                        section_symbol.address().wrapping_add_signed(target_reloc.addend);
                     if let Some((new_idx, addr)) = ordered_symbols
                         .get(section_index.0)
                         .and_then(|symbols| best_symbol(symbols, target_address))
                     {
-                        addend = target_address.wrapping_sub(addr) as i64;
+                        (new_idx, target_address.wrapping_sub(addr) as i64)
-                        new_idx
                     } else {
-                        idx
+                        (symbol_index, target_reloc.addend)
                     }
                 } else {
-                    idx
+                    (symbol_index, target_reloc.addend)
-                };
-                match symbol_indices.get(idx.0).copied() {
-                    Some(i) => i,
-                    None => {
-                        log::warn!("Invalid symbol index {}", idx.0);
-                        continue;
-                    }
                 }
             }
-            object::RelocationTarget::Absolute => {
+            RelocationOverrideTarget::Section(section_index) => {
-                let section_name = obj_section.name()?;
+                let section = match obj_file.section_by_index(section_index) {
-                log::warn!("Ignoring absolute relocation @ {section_name}:{address:#x}");
+                    Ok(section) => section,
+                    Err(e) => {
+                        log::warn!("Invalid relocation section: {e}");
+                        continue;
+                    }
+                };
+                let Ok(target_address) = u64::try_from(target_reloc.addend) else {
+                    log::warn!(
+                        "Negative section relocation addend: {}{}",
+                        section.name()?,
+                        target_reloc.addend
+                    );
+                    continue;
+                };
+                let Some(symbols) = ordered_symbols.get(section_index.0) else {
+                    log::warn!(
+                        "Couldn't resolve relocation target symbol for section {} (no symbols)",
+                        section.name()?
+                    );
+                    continue;
+                };
+                // Attempt to resolve a target symbol for the relocation
+                if let Some((new_idx, addr)) = best_symbol(symbols, target_address) {
+                    (new_idx, target_address.wrapping_sub(addr) as i64)
+                } else if let Some(section_symbol) =
+                    symbols.iter().find(|s| s.kind() == object::SymbolKind::Section)
+                {
+                    (
+                        section_symbol.index(),
+                        target_address.wrapping_sub(section_symbol.address()) as i64,
+                    )
+                } else {
+                    log::warn!(
+                        "Couldn't resolve relocation target symbol for section {}",
+                        section.name()?
+                    );
+                    continue;
+                }
+            }
+        };
+
+        let flags = match reloc.flags() {
+            object::RelocationFlags::Elf { r_type } => RelocationFlags::Elf(r_type),
+            object::RelocationFlags::Coff { typ } => RelocationFlags::Coff(typ),
+            flags => bail!("Unhandled relocation flags: {:?}", flags),
+        };
+        let target_symbol = match symbol_indices.get(symbol_index.0).copied() {
+            Some(i) => i,
+            None => {
+                log::warn!("Invalid symbol index {}", symbol_index.0);
                 continue;
             }
-            _ => bail!("Unhandled relocation target: {:?}", reloc.target()),
         };
         relocations.push(Relocation { address, flags, target_symbol, addend });
     }