Add pie as another relocation-model value

Author: hlopko

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -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,

compiler/rustc_codegen_llvm/src/context.rs

@@ -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);
         }
     }

compiler/rustc_codegen_llvm/src/lib.rs

@@ -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!();

compiler/rustc_codegen_llvm/src/mono_item.rs

@@ -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;
     }
 }

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -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,

compiler/rustc_target/src/spec/mod.rs

@@ -287,6 +287,7 @@ impl ToJson for MergeFunctions {
 pub enum RelocModel {
     Static,
     Pic,
+    Pie,
     DynamicNoPic,
     Ropi,
     Rwpi,
@@ -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,
@@ -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",

src/doc/rustc/src/codegen-options/index.md

@@ -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.  \

src/test/assembly/pic-relocation-model.rs

@@ -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;}

src/test/assembly/pie-relocation-model.rs

@@ -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;}

src/test/codegen/pic-relocation-model.rs

@@ -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}

src/test/codegen/pie-relocation-model.rs

@@ -0,0 +1,22 @@
+// compile-flags: -C relocation-model=pie
+// only-x86_64-unknown-linux-gnu
+
+#![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}