Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

write/elf: x86-64 branches should always use R_X86_64_PLT32 #590

Merged
merged 1 commit into from
Nov 10, 2023
Merged

write/elf: x86-64 branches should always use R_X86_64_PLT32 #590

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
47 changes: 3 additions & 44 deletions src/write/elf/object.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -153,50 +153,6 @@ impl<'a> Object<'a> {
}

pub(crate) fn elf_fixup_relocation(&mut self, relocation: &mut Relocation) -> Result<i64> {
// Return true if we should use a section symbol to avoid preemption.
fn want_section_symbol(relocation: &Relocation, symbol: &Symbol) -> bool {
if symbol.scope != SymbolScope::Dynamic {
// Only dynamic symbols can be preemptible.
return false;
}
match symbol.kind {
SymbolKind::Text | SymbolKind::Data => {}
_ => return false,
}
match relocation.kind {
// Anything using GOT or PLT is preemptible.
// We also require that `Other` relocations must already be correct.
RelocationKind::Got
| RelocationKind::GotRelative
| RelocationKind::GotBaseRelative
| RelocationKind::PltRelative
| RelocationKind::Elf(_) => return false,
// Absolute relocations are preemptible for non-local data.
// TODO: not sure if this rule is exactly correct
// This rule was added to handle global data references in debuginfo.
// Maybe this should be a new relocation kind so that the caller can decide.
RelocationKind::Absolute => {
if symbol.kind == SymbolKind::Data {
return false;
}
}
_ => {}
}
true
}

// Use section symbols for relocations where required to avoid preemption.
// Otherwise, the linker will fail with:
// relocation R_X86_64_PC32 against symbol `SomeSymbolName' can not be used when
// making a shared object; recompile with -fPIC
let symbol = &self.symbols[relocation.symbol.0];
if want_section_symbol(relocation, symbol) {
if let Some(section) = symbol.section.id() {
relocation.addend += symbol.value as i64;
relocation.symbol = self.section_symbol(section);
}
}

// Determine whether the addend is stored in the relocation or the data.
if self.elf_has_relocation_addend()? {
Ok(0)
Expand Down Expand Up @@ -581,6 +537,9 @@ impl<'a> Object<'a> {
(RelocationKind::Absolute, RelocationEncoding::Generic, 64) => {
elf::R_X86_64_64
}
(RelocationKind::Relative, RelocationEncoding::X86Branch, 32) => {
elf::R_X86_64_PLT32
}
(RelocationKind::Relative, _, 32) => elf::R_X86_64_PC32,
(RelocationKind::Got, _, 32) => elf::R_X86_64_GOT32,
(RelocationKind::PltRelative, _, 32) => elf::R_X86_64_PLT32,
Expand Down