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Add pie as another relocation-model value
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hlopko committed Sep 28, 2021
1 parent 497ee32 commit dea3ee1
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Showing 11 changed files with 146 additions and 8 deletions.
3 changes: 2 additions & 1 deletion compiler/rustc_codegen_llvm/src/back/write.rs
Original file line number Diff line number Diff line change
Expand Up @@ -129,7 +129,8 @@ fn to_pass_builder_opt_level(cfg: config::OptLevel) -> llvm::PassBuilderOptLevel
fn to_llvm_relocation_model(relocation_model: RelocModel) -> llvm::RelocModel {
match relocation_model {
RelocModel::Static => llvm::RelocModel::Static,
RelocModel::Pic => llvm::RelocModel::PIC,
// LLVM doesn't have a PIE relocation model, it represents PIE as PIC with an extra attribute.
RelocModel::Pic | RelocModel::Pie => llvm::RelocModel::PIC,
RelocModel::DynamicNoPic => llvm::RelocModel::DynamicNoPic,
RelocModel::Ropi => llvm::RelocModel::ROPI,
RelocModel::Rwpi => llvm::RelocModel::RWPI,
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7 changes: 5 additions & 2 deletions compiler/rustc_codegen_llvm/src/context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -190,11 +190,14 @@ pub unsafe fn create_module(
let llvm_target = SmallCStr::new(&sess.target.llvm_target);
llvm::LLVMRustSetNormalizedTarget(llmod, llvm_target.as_ptr());

if sess.relocation_model() == RelocModel::Pic {
let reloc_model = sess.relocation_model();
if matches!(reloc_model, RelocModel::Pic | RelocModel::Pie) {
llvm::LLVMRustSetModulePICLevel(llmod);
// PIE is potentially more effective than PIC, but can only be used in executables.
// If all our outputs are executables, then we can relax PIC to PIE.
if sess.crate_types().iter().all(|ty| *ty == CrateType::Executable) {
if reloc_model == RelocModel::Pie
|| sess.crate_types().iter().all(|ty| *ty == CrateType::Executable)
{
llvm::LLVMRustSetModulePIELevel(llmod);
}
}
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13 changes: 10 additions & 3 deletions compiler/rustc_codegen_llvm/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -211,9 +211,16 @@ impl CodegenBackend for LlvmCodegenBackend {
match req {
PrintRequest::RelocationModels => {
println!("Available relocation models:");
for name in
&["static", "pic", "dynamic-no-pic", "ropi", "rwpi", "ropi-rwpi", "default"]
{
for name in &[
"static",
"pic",
"pie",
"dynamic-no-pic",
"ropi",
"rwpi",
"ropi-rwpi",
"default",
] {
println!(" {}", name);
}
println!();
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6 changes: 6 additions & 0 deletions compiler/rustc_codegen_llvm/src/mono_item.rs
Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,12 @@ impl CodegenCx<'ll, 'tcx> {
return true;
}

// With pie relocation model calls of functions defined in the translation
// unit can use copy relocations.
if self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration {
return true;
}

return false;
}
}
8 changes: 6 additions & 2 deletions compiler/rustc_codegen_ssa/src/back/link.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1490,9 +1490,13 @@ fn exec_linker(
fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
(CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
(CrateType::Executable, false, RelocModel::Pic) => LinkOutputKind::DynamicPicExe,
(CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
LinkOutputKind::DynamicPicExe
}
(CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
(CrateType::Executable, true, RelocModel::Pic) => LinkOutputKind::StaticPicExe,
(CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
LinkOutputKind::StaticPicExe
}
(CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
(_, true, _) => LinkOutputKind::StaticDylib,
(_, false, _) => LinkOutputKind::DynamicDylib,
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3 changes: 3 additions & 0 deletions compiler/rustc_target/src/spec/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -287,6 +287,7 @@ impl ToJson for MergeFunctions {
pub enum RelocModel {
Static,
Pic,
Pie,
DynamicNoPic,
Ropi,
Rwpi,
Expand All @@ -300,6 +301,7 @@ impl FromStr for RelocModel {
Ok(match s {
"static" => RelocModel::Static,
"pic" => RelocModel::Pic,
"pie" => RelocModel::Pie,
"dynamic-no-pic" => RelocModel::DynamicNoPic,
"ropi" => RelocModel::Ropi,
"rwpi" => RelocModel::Rwpi,
Expand All @@ -314,6 +316,7 @@ impl ToJson for RelocModel {
match *self {
RelocModel::Static => "static",
RelocModel::Pic => "pic",
RelocModel::Pie => "pie",
RelocModel::DynamicNoPic => "dynamic-no-pic",
RelocModel::Ropi => "ropi",
RelocModel::Rwpi => "rwpi",
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4 changes: 4 additions & 0 deletions src/doc/rustc/src/codegen-options/index.md
Original file line number Diff line number Diff line change
Expand Up @@ -435,6 +435,10 @@ Equivalent to the "uppercase" `-fPIC` or `-fPIE` options in other compilers,
depending on the produced crate types. \
This is the default model for majority of supported targets.

- `pie` - position independent executable, relocatable code but without support for symbol
interpositioning (replacing symbols by name using `LD_PRELOAD` and similar). Equivalent to the "uppercase" `-fPIE` option in other compilers. `pie`
code cannot be linked into shared libraries (you'll get a linking error on attempt to do this).

#### Special relocation models

- `dynamic-no-pic` - relocatable external references, non-relocatable code. \
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35 changes: 35 additions & 0 deletions src/test/assembly/pic-relocation-model.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
// revisions: x64
// assembly-output: emit-asm
// [x64] compile-flags: --target x86_64-unknown-linux-gnu -Crelocation-model=pic
// [x64] needs-llvm-components: x86


#![feature(no_core, lang_items)]
#![no_core]
#![crate_type="rlib"]

#[lang = "sized"]
trait Sized {}
#[lang = "copy"]
trait Copy {}

// CHECK-LABEL: call_other_fn:
// CHECK: {{(jmpq|callq)}} *other_fn@GOTPCREL(%rip)
#[no_mangle]
pub fn call_other_fn() -> u8 {
unsafe {
other_fn()
}
}

// CHECK-LABEL: other_fn:
// CHECK: callq *foreign_fn@GOTPCREL(%rip)
#[no_mangle]
#[inline(never)]
pub fn other_fn() -> u8 {
unsafe {
foreign_fn()
}
}

extern "C" {fn foreign_fn() -> u8;}
38 changes: 38 additions & 0 deletions src/test/assembly/pie-relocation-model.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
// revisions: x64
// assembly-output: emit-asm
// [x64] compile-flags: --target x86_64-unknown-linux-gnu -Crelocation-model=pie
// [x64] needs-llvm-components: x86


#![feature(no_core, lang_items)]
#![no_core]
#![crate_type="rlib"]

#[lang = "sized"]
trait Sized {}
#[lang = "copy"]
trait Copy {}

// CHECK-LABEL: call_other_fn:
// With PIE local functions are called "directly".
// CHECK: {{(jmp|callq)}} other_fn
#[no_mangle]
pub fn call_other_fn() -> u8 {
unsafe {
other_fn()
}
}

// CHECK-LABEL: other_fn:
// External functions are still called through GOT, since we don't know if the symbol
// is defined in the binary or in the shared library.
// CHECK: callq *foreign_fn@GOTPCREL(%rip)
#[no_mangle]
#[inline(never)]
pub fn other_fn() -> u8 {
unsafe {
foreign_fn()
}
}

extern "C" {fn foreign_fn() -> u8;}
16 changes: 16 additions & 0 deletions src/test/codegen/pic-relocation-model.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
// compile-flags: -C relocation-model=pic

#![crate_type = "rlib"]

// CHECK: define i8 @call_foreign_fn()
#[no_mangle]
pub fn call_foreign_fn() -> u8 {
unsafe {
foreign_fn()
}
}

// CHECK: declare zeroext i8 @foreign_fn()
extern "C" {fn foreign_fn() -> u8;}

// CHECK: !{i32 7, !"PIC Level", i32 2}
21 changes: 21 additions & 0 deletions src/test/codegen/pie-relocation-model.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
// compile-flags: -C relocation-model=pie

#![crate_type = "rlib"]

// With PIE we know local functions cannot be interpositioned, we can mark them
// as dso_local.
// CHECK: define dso_local i8 @call_foreign_fn()
#[no_mangle]
pub fn call_foreign_fn() -> u8 {
unsafe {
foreign_fn()
}
}

// External functions are still marked as non-dso_local, since we don't know if the symbol
// is defined in the binary or in the shared library.
// CHECK: declare zeroext i8 @foreign_fn()
extern "C" {fn foreign_fn() -> u8;}

// CHECK: !{i32 7, !"PIC Level", i32 2}
// CHECK: !{i32 7, !"PIE Level", i32 2}

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