From 55c4164fffb8c4389727cff554dd77012c624087 Mon Sep 17 00:00:00 2001 From: Arvind Mukund Date: Mon, 19 Dec 2022 19:06:30 -0800 Subject: [PATCH 1/2] Correct ModFlagBehavior for Aarch64 on LLVM-15 When building with Fat LTO and BTI enabled on aarch64, the BTI is set to `Module::Min` for alloc shim but is set to `Module::Error` for the crate. This was fine when we were using LLVM-14 but LLVM-15 changes it's behaviour to support for compiling with different `mbranch-protection` flags. Refer: https://github.com/rust-lang/llvm-project/commit/b0343a38a5910e980bb031e4014655d77cd0c162 --- compiler/rustc_codegen_llvm/src/context.rs | 8 ++++---- compiler/rustc_codegen_llvm/src/llvm/ffi.rs | 1 + 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs index f3bff5d57161..9c7d3dabd6fb 100644 --- a/compiler/rustc_codegen_llvm/src/context.rs +++ b/compiler/rustc_codegen_llvm/src/context.rs @@ -283,26 +283,26 @@ pub unsafe fn create_module<'ll>( if sess.target.arch == "aarch64" { llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Error, + llvm::LLVMModFlagBehavior::Min, "branch-target-enforcement\0".as_ptr().cast(), bti.into(), ); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Error, + llvm::LLVMModFlagBehavior::Min, "sign-return-address\0".as_ptr().cast(), pac_ret.is_some().into(), ); let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A }); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Error, + llvm::LLVMModFlagBehavior::Min, "sign-return-address-all\0".as_ptr().cast(), pac_opts.leaf.into(), ); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Error, + llvm::LLVMModFlagBehavior::Min, "sign-return-address-with-bkey\0".as_ptr().cast(), u32::from(pac_opts.key == PAuthKey::B), ); diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs index e61dbe8b8fc5..6c78966a98d8 100644 --- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs +++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs @@ -79,6 +79,7 @@ pub enum LLVMModFlagBehavior { Append = 5, AppendUnique = 6, Max = 7, + Min = 8, } // Consts for the LLVM CallConv type, pre-cast to usize. From 5480ac540cdb88a1512334c5680ccf7cd76a38c8 Mon Sep 17 00:00:00 2001 From: Arvind Mukund Date: Tue, 20 Dec 2022 11:44:12 -0800 Subject: [PATCH 2/2] Use `Error` behavior for LLVM versions prior to 15 CI fails when building with LLVM-13. This raises unknown behavior constant `8` from IRVerifier. --- compiler/rustc_codegen_llvm/src/context.rs | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs index 9c7d3dabd6fb..d9ccba07a346 100644 --- a/compiler/rustc_codegen_llvm/src/context.rs +++ b/compiler/rustc_codegen_llvm/src/context.rs @@ -280,29 +280,35 @@ pub unsafe fn create_module<'ll>( } if let Some(BranchProtection { bti, pac_ret }) = sess.opts.unstable_opts.branch_protection { + let behavior = if llvm_version >= (15, 0, 0) { + llvm::LLVMModFlagBehavior::Min + } else { + llvm::LLVMModFlagBehavior::Error + }; + if sess.target.arch == "aarch64" { llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Min, + behavior, "branch-target-enforcement\0".as_ptr().cast(), bti.into(), ); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Min, + behavior, "sign-return-address\0".as_ptr().cast(), pac_ret.is_some().into(), ); let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A }); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Min, + behavior, "sign-return-address-all\0".as_ptr().cast(), pac_opts.leaf.into(), ); llvm::LLVMRustAddModuleFlag( llmod, - llvm::LLVMModFlagBehavior::Min, + behavior, "sign-return-address-with-bkey\0".as_ptr().cast(), u32::from(pac_opts.key == PAuthKey::B), );