Add di-sanitizer feature, allowing to disable DI sanitization

LLVM 21.1.5 contains fixes that emit correct BTF[0] without the need to
sanitize it, except from the name fixup that:

1) Is going to be fixed up in Aya:
   * aya-rs/aya#1382
2) Should be fixed in the kernel.

Introduce the `di-sanitizer` feature, that explicitly activates the use
of `DISanitizer`. Enable it by default for now, but run Aya integration
tests without it.

[0] llvm/llvm-project#165154

Author: vadorovsky

.github/workflows/ci.yml

@@ -65,11 +65,11 @@ jobs:
           - rust: nightly
             llvm-version: 21
             llvm-from: apt
-            exclude-features: llvm-19,llvm-20,rust-llvm-19,rust-llvm-20
+            exclude-features: di-sanitizer,llvm-19,llvm-20,rust-llvm-19,rust-llvm-20
           - rust: nightly
             llvm-version: 21
             llvm-from: source
-            exclude-features: llvm-19,llvm-20,rust-llvm-19,rust-llvm-20
+            exclude-features: di-sanitizer,llvm-19,llvm-20,rust-llvm-19,rust-llvm-20
     name: rustc=${{ matrix.rust }} llvm-version=${{ matrix.llvm-version }} llvm-from=${{ matrix.llvm-from }}
     needs: llvm
 
@@ -214,7 +214,10 @@ jobs:
       - uses: actions/checkout@v5
         if: matrix.rust == 'nightly'
         with:
-          repository: aya-rs/aya
+          # FIXME: Switch to upstream after https://github.com/aya-rs/aya/pull/1382
+          # is merged.
+          repository: vadorovsky/aya
+          ref: btf-sanitize-name
           path: aya
           submodules: recursive
 

Cargo.toml

@@ -48,8 +48,9 @@ workspace = true
 name = "bpf-linker"
 
 [features]
-llvm-19 = ["dep:llvm-sys-19"]
-llvm-20 = ["dep:llvm-sys-20"]
+di-sanitizer = []
+llvm-19 = ["dep:llvm-sys-19", "di-sanitizer"]
+llvm-20 = ["dep:llvm-sys-20", "di-sanitizer"]
 llvm-21 = ["dep:llvm-sys-21"]
 rust-llvm-19 = [
     "dep:aya-rustc-llvm-proxy",
@@ -69,6 +70,11 @@ rust-llvm-21 = [
 default = [
     "llvm-21",
     "rust-llvm-21",
+    # Remove once Rust nightly and Linux distributions update to LLVM 21.1.5,
+    # that contains fixes making the sanitizer obsolete[0].
+    #
+    # [0] https://github.com/llvm/llvm-project/pull/165154
+    "di-sanitizer"
 ]
 
 [workspace]

src/linker.rs

@@ -670,6 +670,10 @@ fn create_target_machine(
 
 fn optimize<'ctx, 'a, E>(
     options: &LinkerOptions,
+    #[cfg_attr(
+        not(feature = "di-sanitizer"),
+        expect(unused, reason = "used when `di-sanitizer` feature is enabled")
+    )]
     context: &'ctx LLVMContext,
     target_machine: &LLVMTargetMachine,
     module: &mut LLVMModule<'ctx>,
@@ -707,6 +711,7 @@ where
 
     if *btf {
         // if we want to emit BTF, we need to sanitize the debug information
+        #[cfg(feature = "di-sanitizer")]
         llvm::DISanitizer::new(context, module).run(&export_symbols);
     } else {
         // if we don't need BTF emission, we can strip DI

src/llvm/iter.rs

@@ -1,13 +1,20 @@
 use std::marker::PhantomData;
 
+#[cfg(feature = "di-sanitizer")]
 use llvm_sys::{
     core::{
-        LLVMGetFirstBasicBlock, LLVMGetFirstFunction, LLVMGetFirstGlobal, LLVMGetFirstGlobalAlias,
-        LLVMGetFirstInstruction, LLVMGetLastBasicBlock, LLVMGetLastFunction, LLVMGetLastGlobal,
-        LLVMGetLastGlobalAlias, LLVMGetLastInstruction, LLVMGetNextBasicBlock, LLVMGetNextFunction,
-        LLVMGetNextGlobal, LLVMGetNextGlobalAlias, LLVMGetNextInstruction,
+        LLVMGetFirstBasicBlock, LLVMGetFirstInstruction, LLVMGetLastBasicBlock,
+        LLVMGetLastInstruction, LLVMGetNextBasicBlock, LLVMGetNextInstruction,
     },
-    prelude::{LLVMBasicBlockRef, LLVMModuleRef, LLVMValueRef},
+    prelude::LLVMBasicBlockRef,
+};
+use llvm_sys::{
+    core::{
+        LLVMGetFirstFunction, LLVMGetFirstGlobal, LLVMGetFirstGlobalAlias, LLVMGetLastFunction,
+        LLVMGetLastGlobal, LLVMGetLastGlobalAlias, LLVMGetNextFunction, LLVMGetNextGlobal,
+        LLVMGetNextGlobalAlias,
+    },
+    prelude::{LLVMModuleRef, LLVMValueRef},
 };
 
 macro_rules! llvm_iterator {
@@ -90,6 +97,7 @@ llvm_iterator! {
     LLVMGetNextFunction,
 }
 
+#[cfg(feature = "di-sanitizer")]
 llvm_iterator!(
     IterBasicBlocks,
     BasicBlockIter,
@@ -101,6 +109,7 @@ llvm_iterator!(
     LLVMGetNextBasicBlock
 );
 
+#[cfg(feature = "di-sanitizer")]
 llvm_iterator!(
     IterInstructions,
     InstructionsIter,

src/llvm/mod.rs

@@ -1,3 +1,4 @@
+#[cfg(feature = "di-sanitizer")]
 mod di;
 mod iter;
 mod types;
@@ -10,16 +11,18 @@ use std::{
     ptr, slice, str,
 };
 
+#[cfg(feature = "di-sanitizer")]
 pub(crate) use di::DISanitizer;
 use iter::{IterModuleFunctions as _, IterModuleGlobalAliases as _, IterModuleGlobals as _};
+#[cfg(feature = "di-sanitizer")]
+use llvm_sys::core::LLVMGetMDString;
 use llvm_sys::{
     LLVMAttributeFunctionIndex, LLVMLinkage, LLVMVisibility,
     bit_reader::LLVMParseBitcodeInContext2,
     core::{
         LLVMCreateMemoryBufferWithMemoryRange, LLVMDisposeMemoryBuffer, LLVMDisposeMessage,
-        LLVMGetEnumAttributeKindForName, LLVMGetMDString, LLVMGetModuleInlineAsm, LLVMGetTarget,
-        LLVMGetValueName2, LLVMRemoveEnumAttributeAtIndex, LLVMSetLinkage, LLVMSetModuleInlineAsm2,
-        LLVMSetVisibility,
+        LLVMGetEnumAttributeKindForName, LLVMGetModuleInlineAsm, LLVMGetTarget, LLVMGetValueName2,
+        LLVMRemoveEnumAttributeAtIndex, LLVMSetLinkage, LLVMSetModuleInlineAsm2, LLVMSetVisibility,
     },
     error::{
         LLVMDisposeErrorMessage, LLVMGetErrorMessage, LLVMGetErrorTypeId, LLVMGetStringErrorTypeId,

src/llvm/types/mod.rs

@@ -1,5 +1,7 @@
 pub(super) mod context;
+#[cfg(feature = "di-sanitizer")]
 pub(super) mod di;
+#[cfg(feature = "di-sanitizer")]
 pub(super) mod ir;
 pub(super) mod memory_buffer;
 pub(super) mod module;

tests/sanitizer/assembly/auxiliary/dep-exports.rs

@@ -0,0 +1,14 @@
+// no-prefer-dynamic
+// compile-flags: --crate-type rlib -C debuginfo=2
+#![no_std]
+
+#[inline(never)]
+pub fn dep_public_symbol() -> u8 {
+    // read_volatile stops LTO inlining the function in the calling crate
+    unsafe { core::ptr::read_volatile(core::ptr::dangling()) }
+}
+
+#[no_mangle]
+pub fn dep_no_mangle() -> u8 {
+    dep_public_symbol()
+}

tests/sanitizer/assembly/auxiliary/loop-panic-handler.rs

@@ -0,0 +1,8 @@
+// no-prefer-dynamic
+// compile-flags: --crate-type rlib
+#![no_std]
+
+#[panic_handler]
+fn panic_impl(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}