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Improve ARM function size inference

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This allows 2-byte padding to be trimmed in ARM functions.

Resolves #253
This commit is contained in:
Luke Street
2025-09-25 00:26:43 -06:00
parent 7a8efb4c88
commit 90e81fad7e
8 changed files with 98 additions and 19 deletions
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14
objdiff-core/src/arch/arm.rs
View File

@@ -460,12 +460,16 @@ impl Arch for ArchArm {
section: &Section,
mut next_address: u64,
) -> Result<u64> {
// Trim any trailing 4-byte zeroes from the end (padding)
while next_address >= symbol.address + 4
&& let Some(data) = section.data_range(next_address - 4, 4)
&& data == [0u8; 4]
// TODO: This should probably check the disasm mode and trim accordingly,
// but self.disasm_modes isn't populated until post_init, so it needs a refactor.
// Trim any trailing 2-byte zeroes from the end (padding)
while next_address >= symbol.address + 2
&& let Some(data) = section.data_range(next_address - 2, 2)
&& data == [0u8; 2]
&& section.relocation_at(next_address - 2, 2).is_none()
{
next_address -= 4;
next_address -= 2;
}
Ok(next_address.saturating_sub(symbol.address))
}

1
objdiff-core/src/arch/mips.rs
View File

@@ -355,6 +355,7 @@ impl Arch for ArchMips {
while new_address >= symbol.address + 4
&& let Some(data) = section.data_range(new_address - 4, 4)
&& data == [0u8; 4]
&& section.relocation_at(next_address - 4, 4).is_none()
{
new_address -= 4;
}

1
objdiff-core/src/arch/ppc/mod.rs
View File

@@ -457,6 +457,7 @@ impl Arch for ArchPpc {
while next_address >= symbol.address + 4
&& let Some(data) = section.data_range(next_address - 4, 4)
&& data == [0u8; 4]
&& section.relocation_at(next_address - 4, 4).is_none()
{
next_address -= 4;
}

29
objdiff-core/src/obj/mod.rs
View File

@@ -107,32 +107,33 @@ impl Section {
// The alignment to use when "Combine data/text sections" is enabled.
pub fn combined_alignment(&self) -> u64 {
const MIN_ALIGNMENT: u64 = 4;
self.align.map(|align| align.get().max(MIN_ALIGNMENT)).unwrap_or(MIN_ALIGNMENT)
self.align.map_or(MIN_ALIGNMENT, |align| align.get().max(MIN_ALIGNMENT))
}
pub fn relocation_at<'obj>(
&'obj self,
obj: &'obj Object,
ins_ref: InstructionRef,
) -> Option<ResolvedRelocation<'obj>> {
match self.relocations.binary_search_by_key(&ins_ref.address, |r| r.address) {
pub fn relocation_at(&self, address: u64, size: u8) -> Option<&Relocation> {
match self.relocations.binary_search_by_key(&address, |r| r.address) {
Ok(mut i) => {
// Find the first relocation at the address
while i
.checked_sub(1)
.and_then(|n| self.relocations.get(n))
.is_some_and(|r| r.address == ins_ref.address)
.is_some_and(|r| r.address == address)
{
i -= 1;
}
self.relocations.get(i)
}
Err(i) => self
.relocations
.get(i)
.filter(|r| r.address < ins_ref.address + ins_ref.size as u64),
Err(i) => self.relocations.get(i).filter(|r| r.address < address + size as u64),
}
.and_then(|relocation| {
}
pub fn resolve_relocation_at<'obj>(
&'obj self,
obj: &'obj Object,
address: u64,
size: u8,
) -> Option<ResolvedRelocation<'obj>> {
self.relocation_at(address, size).and_then(|relocation| {
let symbol = obj.symbols.get(relocation.target_symbol)?;
Some(ResolvedRelocation { relocation, symbol })
})
@@ -316,7 +317,7 @@ impl Object {
let section = self.sections.get(section_index)?;
let offset = ins_ref.address.checked_sub(section.address)?;
let code = section.data.get(offset as usize..offset as usize + ins_ref.size as usize)?;
let relocation = section.relocation_at(self, ins_ref);
let relocation = section.resolve_relocation_at(self, ins_ref.address, ins_ref.size);
Some(ResolvedInstructionRef {
ins_ref,
symbol_index,