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write/object: calculate relocation flags before adjusting addend
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This simplifies the code because we no longer need to avoid
modifying the addend in the relocation.

Also make the implicit addend handling clearer.
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@philipc
philipc committed Dec 5, 2023
1 parent 7e4bb81 commit fedd590
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Showing 5 changed files with 72 additions and 77 deletions.
88 changes: 45 additions & 43 deletions src/write/coff/object.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -99,57 +99,59 @@ impl<'a> Object<'a> {

pub(crate) fn coff_relocation_flags(&self, reloc: &Relocation) -> Result<RelocationFlags> {
let typ = match self.architecture {
Architecture::I386 => match (reloc.kind, reloc.size, reloc.addend) {
(RelocationKind::Absolute, 16, 0) => coff::IMAGE_REL_I386_DIR16,
(RelocationKind::Relative, 16, 0) => coff::IMAGE_REL_I386_REL16,
(RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_I386_DIR32,
(RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_I386_DIR32NB,
(RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_I386_SECTION,
(RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_I386_SECREL,
(RelocationKind::SectionOffset, 7, 0) => coff::IMAGE_REL_I386_SECREL7,
(RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_I386_REL32,
(RelocationKind::Coff(x), _, _) => x,
Architecture::I386 => match (reloc.kind, reloc.size) {
(RelocationKind::Absolute, 16) => coff::IMAGE_REL_I386_DIR16,
(RelocationKind::Relative, 16) => coff::IMAGE_REL_I386_REL16,
(RelocationKind::Absolute, 32) => coff::IMAGE_REL_I386_DIR32,
(RelocationKind::ImageOffset, 32) => coff::IMAGE_REL_I386_DIR32NB,
(RelocationKind::SectionIndex, 16) => coff::IMAGE_REL_I386_SECTION,
(RelocationKind::SectionOffset, 32) => coff::IMAGE_REL_I386_SECREL,
(RelocationKind::SectionOffset, 7) => coff::IMAGE_REL_I386_SECREL7,
(RelocationKind::Relative, 32) => coff::IMAGE_REL_I386_REL32,
(RelocationKind::Coff(x), _) => x,
_ => {
return Err(Error(format!("unimplemented relocation {:?}", reloc)));
}
},
Architecture::X86_64 => match (reloc.kind, reloc.size, reloc.addend) {
(RelocationKind::Absolute, 64, 0) => coff::IMAGE_REL_AMD64_ADDR64,
(RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_AMD64_ADDR32,
(RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_AMD64_ADDR32NB,
(RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_AMD64_REL32,
(RelocationKind::Relative, 32, -5) => coff::IMAGE_REL_AMD64_REL32_1,
(RelocationKind::Relative, 32, -6) => coff::IMAGE_REL_AMD64_REL32_2,
(RelocationKind::Relative, 32, -7) => coff::IMAGE_REL_AMD64_REL32_3,
(RelocationKind::Relative, 32, -8) => coff::IMAGE_REL_AMD64_REL32_4,
(RelocationKind::Relative, 32, -9) => coff::IMAGE_REL_AMD64_REL32_5,
(RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_AMD64_SECTION,
(RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_AMD64_SECREL,
(RelocationKind::SectionOffset, 7, 0) => coff::IMAGE_REL_AMD64_SECREL7,
(RelocationKind::Coff(x), _, _) => x,
Architecture::X86_64 => match (reloc.kind, reloc.size) {
(RelocationKind::Absolute, 64) => coff::IMAGE_REL_AMD64_ADDR64,
(RelocationKind::Absolute, 32) => coff::IMAGE_REL_AMD64_ADDR32,
(RelocationKind::ImageOffset, 32) => coff::IMAGE_REL_AMD64_ADDR32NB,
(RelocationKind::Relative, 32) => match reloc.addend {
-5 => coff::IMAGE_REL_AMD64_REL32_1,
-6 => coff::IMAGE_REL_AMD64_REL32_2,
-7 => coff::IMAGE_REL_AMD64_REL32_3,
-8 => coff::IMAGE_REL_AMD64_REL32_4,
-9 => coff::IMAGE_REL_AMD64_REL32_5,
_ => coff::IMAGE_REL_AMD64_REL32,
},
(RelocationKind::SectionIndex, 16) => coff::IMAGE_REL_AMD64_SECTION,
(RelocationKind::SectionOffset, 32) => coff::IMAGE_REL_AMD64_SECREL,
(RelocationKind::SectionOffset, 7) => coff::IMAGE_REL_AMD64_SECREL7,
(RelocationKind::Coff(x), _) => x,
_ => {
return Err(Error(format!("unimplemented relocation {:?}", reloc)));
}
},
Architecture::Arm => match (reloc.kind, reloc.size, reloc.addend) {
(RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_ARM_ADDR32,
(RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_ARM_ADDR32NB,
(RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_ARM_REL32,
(RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_ARM_SECTION,
(RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_ARM_SECREL,
(RelocationKind::Coff(x), _, _) => x,
Architecture::Arm => match (reloc.kind, reloc.size) {
(RelocationKind::Absolute, 32) => coff::IMAGE_REL_ARM_ADDR32,
(RelocationKind::ImageOffset, 32) => coff::IMAGE_REL_ARM_ADDR32NB,
(RelocationKind::Relative, 32) => coff::IMAGE_REL_ARM_REL32,
(RelocationKind::SectionIndex, 16) => coff::IMAGE_REL_ARM_SECTION,
(RelocationKind::SectionOffset, 32) => coff::IMAGE_REL_ARM_SECREL,
(RelocationKind::Coff(x), _) => x,
_ => {
return Err(Error(format!("unimplemented relocation {:?}", reloc)));
}
},
Architecture::Aarch64 => match (reloc.kind, reloc.size, reloc.addend) {
(RelocationKind::Absolute, 32, 0) => coff::IMAGE_REL_ARM64_ADDR32,
(RelocationKind::ImageOffset, 32, 0) => coff::IMAGE_REL_ARM64_ADDR32NB,
(RelocationKind::SectionIndex, 16, 0) => coff::IMAGE_REL_ARM64_SECTION,
(RelocationKind::SectionOffset, 32, 0) => coff::IMAGE_REL_ARM64_SECREL,
(RelocationKind::Absolute, 64, 0) => coff::IMAGE_REL_ARM64_ADDR64,
(RelocationKind::Relative, 32, -4) => coff::IMAGE_REL_ARM64_REL32,
(RelocationKind::Coff(x), _, _) => x,
Architecture::Aarch64 => match (reloc.kind, reloc.size) {
(RelocationKind::Absolute, 32) => coff::IMAGE_REL_ARM64_ADDR32,
(RelocationKind::ImageOffset, 32) => coff::IMAGE_REL_ARM64_ADDR32NB,
(RelocationKind::SectionIndex, 16) => coff::IMAGE_REL_ARM64_SECTION,
(RelocationKind::SectionOffset, 32) => coff::IMAGE_REL_ARM64_SECREL,
(RelocationKind::Absolute, 64) => coff::IMAGE_REL_ARM64_ADDR64,
(RelocationKind::Relative, 32) => coff::IMAGE_REL_ARM64_REL32,
(RelocationKind::Coff(x), _) => x,
_ => {
return Err(Error(format!("unimplemented relocation {:?}", reloc)));
}
Expand All @@ -164,8 +166,8 @@ impl<'a> Object<'a> {
Ok(RelocationFlags::Coff { typ })
}

pub(crate) fn coff_adjust_addend(&self, relocation: &mut Relocation) -> i64 {
let constant = match self.architecture {
pub(crate) fn coff_adjust_addend(&self, relocation: &mut Relocation) -> bool {
let addend = match self.architecture {
Architecture::I386 | Architecture::Arm | Architecture::Aarch64 => match relocation.kind
{
RelocationKind::Relative => {
Expand All @@ -187,8 +189,8 @@ impl<'a> Object<'a> {
},
_ => unimplemented!(),
};
relocation.addend -= constant;
constant
relocation.addend = addend;
true
}

pub(crate) fn coff_relocation_size(&self, reloc: &crate::write::RawRelocation) -> Result<u8> {
Expand Down
11 changes: 3 additions & 8 deletions src/write/elf/object.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -459,15 +459,10 @@ impl<'a> Object<'a> {
Ok(RelocationFlags::Elf { r_type })
}

pub(crate) fn elf_adjust_addend(&mut self, relocation: &mut Relocation) -> Result<i64> {
pub(crate) fn elf_adjust_addend(&mut self, _relocation: &mut Relocation) -> Result<bool> {
// Determine whether the addend is stored in the relocation or the data.
if self.elf_has_relocation_addend()? {
Ok(0)
} else {
let constant = relocation.addend;
relocation.addend = 0;
Ok(constant)
}
let implicit = !self.elf_has_relocation_addend()?;
Ok(implicit)
}

pub(crate) fn elf_relocation_size(&self, reloc: &crate::write::RawRelocation) -> Result<u8> {
Expand Down
10 changes: 4 additions & 6 deletions src/write/macho.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -331,7 +331,7 @@ impl<'a> Object<'a> {
})
}

pub(crate) fn macho_adjust_addend(&mut self, relocation: &mut Relocation) -> i64 {
pub(crate) fn macho_adjust_addend(&mut self, relocation: &mut Relocation) -> bool {
let relative = match relocation.kind {
RelocationKind::Relative
| RelocationKind::GotRelative
Expand Down Expand Up @@ -370,21 +370,19 @@ impl<'a> Object<'a> {
// Check for relocations that use an explicit addend.
if self.architecture == Architecture::Aarch64 {
if relocation.encoding == RelocationEncoding::AArch64Call {
return 0;
return false;
}
if let RelocationKind::MachO { value, .. } = relocation.kind {
match value {
macho::ARM64_RELOC_BRANCH26
| macho::ARM64_RELOC_PAGE21
| macho::ARM64_RELOC_PAGEOFF12 => return 0,
| macho::ARM64_RELOC_PAGEOFF12 => return false,
_ => {}
}
}
}
// Signify implicit addend.
let constant = relocation.addend;
relocation.addend = 0;
constant
true
}

pub(crate) fn macho_relocation_size(&self, reloc: &crate::write::RawRelocation) -> Result<u8> {
Expand Down
32 changes: 16 additions & 16 deletions src/write/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -530,36 +530,37 @@ impl<'a> Object<'a> {
BinaryFormat::Xcoff => self.xcoff_translate_relocation(&mut relocation),
_ => unimplemented!(),
}
let addend = match self.format {
let flags = match self.format {
#[cfg(feature = "coff")]
BinaryFormat::Coff => self.coff_adjust_addend(&mut relocation),
BinaryFormat::Coff => self.coff_relocation_flags(&relocation)?,
#[cfg(feature = "elf")]
BinaryFormat::Elf => self.elf_adjust_addend(&mut relocation)?,
BinaryFormat::Elf => self.elf_relocation_flags(&relocation)?,
#[cfg(feature = "macho")]
BinaryFormat::MachO => self.macho_adjust_addend(&mut relocation),
BinaryFormat::MachO => self.macho_relocation_flags(&relocation)?,
#[cfg(feature = "xcoff")]
BinaryFormat::Xcoff => self.xcoff_adjust_addend(&mut relocation),
BinaryFormat::Xcoff => self.xcoff_relocation_flags(&relocation)?,
_ => unimplemented!(),
};
let flags = match self.format {
let implicit = match self.format {
#[cfg(feature = "coff")]
BinaryFormat::Coff => self.coff_relocation_flags(&relocation)?,
BinaryFormat::Coff => self.coff_adjust_addend(&mut relocation),
#[cfg(feature = "elf")]
BinaryFormat::Elf => self.elf_relocation_flags(&relocation)?,
BinaryFormat::Elf => self.elf_adjust_addend(&mut relocation)?,
#[cfg(feature = "macho")]
BinaryFormat::MachO => self.macho_relocation_flags(&relocation)?,
BinaryFormat::MachO => self.macho_adjust_addend(&mut relocation),
#[cfg(feature = "xcoff")]
BinaryFormat::Xcoff => self.xcoff_relocation_flags(&relocation)?,
BinaryFormat::Xcoff => self.xcoff_adjust_addend(&mut relocation),
_ => unimplemented!(),
};
let relocation = RawRelocation {
let mut relocation = RawRelocation {
offset: relocation.offset,
symbol: relocation.symbol,
addend: relocation.addend,
flags,
};
if addend != 0 {
self.write_relocation_addend(section, &relocation, addend)?;
if implicit && relocation.addend != 0 {
self.write_relocation_addend(section, &relocation)?;
relocation.addend = 0;
}
self.sections[section.0].relocations.push(relocation);
Ok(())
Expand All @@ -569,7 +570,6 @@ impl<'a> Object<'a> {
&mut self,
section: SectionId,
relocation: &RawRelocation,
addend: i64,
) -> Result<()> {
let size = match self.format {
#[cfg(feature = "coff")]
Expand All @@ -585,8 +585,8 @@ impl<'a> Object<'a> {
let data = self.sections[section.0].data_mut();
let offset = relocation.offset as usize;
match size {
32 => data.write_at(offset, &U32::new(self.endian, addend as u32)),
64 => data.write_at(offset, &U64::new(self.endian, addend as u64)),
32 => data.write_at(offset, &U32::new(self.endian, relocation.addend as u32)),
64 => data.write_at(offset, &U64::new(self.endian, relocation.addend as u64)),
_ => {
return Err(Error(format!(
"unimplemented relocation addend {:?}",
Expand Down
8 changes: 4 additions & 4 deletions src/write/xcoff.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -82,13 +82,13 @@ impl<'a> Object<'a> {
Ok(RelocationFlags::Xcoff { r_rtype, r_rsize })
}

pub(crate) fn xcoff_adjust_addend(&mut self, relocation: &mut Relocation) -> i64 {
let constant = match relocation.kind {
pub(crate) fn xcoff_adjust_addend(&mut self, relocation: &mut Relocation) -> bool {
let addend = match relocation.kind {
RelocationKind::Relative => relocation.addend + 4,
_ => relocation.addend,
};
relocation.addend -= constant;
constant
relocation.addend = addend;
true
}

pub(crate) fn xcoff_relocation_size(&self, reloc: &crate::write::RawRelocation) -> Result<u8> {
Expand Down

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