Use symbol name when comparing against an externed reloc (#214)

* Use symbol name when comparing against an externed reloc

For partial matching files, often a symbol is externed even though it
should exist in the target object. We can still compare the symbol name,
instead of always returning a mismatch.

* Combine cases, and apply change reloc_eq in code.rs

objdiff-core/src/arch/x86.rs

@@ -6,7 +6,7 @@ use iced_x86::{
     Decoder, DecoderOptions, DecoratorKind, FormatterOutput, FormatterTextKind, GasFormatter,
     Instruction, IntelFormatter, MasmFormatter, NasmFormatter, NumberKind, OpKind, Register,
 };
-use object::{Endian as _, Object as _, ObjectSection as _, pe};
+use object::{Endian as _, Object as _, ObjectSection as _, elf, pe};
 
 use crate::{
     arch::Arch,
@@ -67,7 +67,11 @@ impl ArchX86 {
                     pe::IMAGE_REL_I386_DIR32 | pe::IMAGE_REL_I386_REL32 => Some(4),
                     _ => None,
                 },
-                _ => None,
+                RelocationFlags::Elf(typ) => match typ {
+                    elf::R_386_32 | elf::R_386_PC32 => Some(4),
+                    elf::R_386_16 => Some(2),
+                    _ => None,
+                },
             },
             Architecture::X86_64 => match flags {
                 RelocationFlags::Coff(typ) => match typ {
@@ -75,7 +79,11 @@ impl ArchX86 {
                     pe::IMAGE_REL_AMD64_ADDR64 => Some(8),
                     _ => None,
                 },
-                _ => None,
+                RelocationFlags::Elf(typ) => match typ {
+                    elf::R_X86_64_PC32 => Some(4),
+                    elf::R_X86_64_64 => Some(8),
+                    _ => None,
+                },
             },
         }
     }
@@ -227,7 +235,8 @@ impl Arch for ArchX86 {
     ) -> Result<i64> {
         match self.arch {
             Architecture::X86 => match flags {
-                RelocationFlags::Coff(pe::IMAGE_REL_I386_DIR32 | pe::IMAGE_REL_I386_REL32) => {
+                RelocationFlags::Coff(pe::IMAGE_REL_I386_DIR32 | pe::IMAGE_REL_I386_REL32)
+                | RelocationFlags::Elf(elf::R_386_32 | elf::R_386_PC32) => {
                     let data =
                         section.data()?[address as usize..address as usize + 4].try_into()?;
                     Ok(self.endianness.read_i32_bytes(data) as i64)
@@ -235,12 +244,14 @@ impl Arch for ArchX86 {
                 flags => bail!("Unsupported x86 implicit relocation {flags:?}"),
             },
             Architecture::X86_64 => match flags {
-                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR32NB | pe::IMAGE_REL_AMD64_REL32) => {
+                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR32NB | pe::IMAGE_REL_AMD64_REL32)
+                | RelocationFlags::Elf(elf::R_X86_64_32 | elf::R_X86_64_PC32) => {
                     let data =
                         section.data()?[address as usize..address as usize + 4].try_into()?;
                     Ok(self.endianness.read_i32_bytes(data) as i64)
                 }
-                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR64) => {
+                RelocationFlags::Coff(pe::IMAGE_REL_AMD64_ADDR64)
+                | RelocationFlags::Elf(elf::R_X86_64_64) => {
                     let data =
                         section.data()?[address as usize..address as usize + 8].try_into()?;
                     Ok(self.endianness.read_i64_bytes(data))

objdiff-core/src/diff/code.rs

@@ -325,12 +325,11 @@ fn reloc_eq(
                     || display_ins_data_literals(left_obj, left_ins)
                         == display_ins_data_literals(right_obj, right_ins))
         }
-        (Some(_), None) => false,
         (None, Some(_)) => {
             // Match if possibly stripped weak symbol
             symbol_name_addend_matches && right_reloc.symbol.flags.contains(SymbolFlag::Weak)
         }
-        (None, None) => symbol_name_addend_matches,
+        (Some(_), None) | (None, None) => symbol_name_addend_matches,
     }
 }
 

objdiff-core/src/diff/data.rs

@@ -53,12 +53,11 @@ fn reloc_eq(
             section_name_eq(left_obj, right_obj, sl, sr)
                 && (symbol_name_addend_matches || address_eq(left, right))
         }
-        (Some(_), None) => false,
         (None, Some(_)) => {
             // Match if possibly stripped weak symbol
             symbol_name_addend_matches && right.symbol.flags.contains(SymbolFlag::Weak)
         }
-        (None, None) => symbol_name_addend_matches,
+        (Some(_), None) | (None, None) => symbol_name_addend_matches,
     }
 }