From 4741f4496392976b014b76d4d14cfcb6bbc15d73 Mon Sep 17 00:00:00 2001 From: "Jonathan Pallant (Ferrous Systems)" Date: Mon, 20 Nov 2023 16:25:58 +0000 Subject: [PATCH] Enable the Arm Cortex-A53 errata mitigation on aarch64-unknown-none Arm Cortex-A53 CPUs have an errata related to a specific sequence of instructions - errata number 843419 (https://documentation-service.arm.com/static/5fa29fddb209f547eebd361d). There is a mitigation that can be applied at link-time which detects the when sequence of instructions exists at a specific alignment. When detected, the linker re-writes those instructions and either changes an ADRP to an ADR, or bounces to a veneer to break the sequence. The linker argument to enable the mitigation is "--fix-cortex-a53-843419", and this is supported by GNU ld and LLVM lld. The gcc argument to enable the flag is "-mfix-cortex-a53-843419". Because the aarch64-unknown-none target uses rust-lld directly, this patch causes rustc to emit the "--fix-cortex-a53-843419" argument when calling the linker, just like aarch64-linux-gnu-gcc on Ubuntu 22.04 does. Failure to enable this mitigation in the linker can cause the production of instruction sequences that do not execute correctly on Arm Cortex-A53. --- .../rustc_target/src/spec/targets/aarch64_unknown_none.rs | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/compiler/rustc_target/src/spec/targets/aarch64_unknown_none.rs b/compiler/rustc_target/src/spec/targets/aarch64_unknown_none.rs index 88fa6d5a762f..63a8144f69fb 100644 --- a/compiler/rustc_target/src/spec/targets/aarch64_unknown_none.rs +++ b/compiler/rustc_target/src/spec/targets/aarch64_unknown_none.rs @@ -14,6 +14,11 @@ pub fn target() -> Target { let opts = TargetOptions { linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes), linker: Some("rust-lld".into()), + // Enable the Cortex-A53 errata 843419 mitigation by default + pre_link_args: TargetOptions::link_args( + LinkerFlavor::Gnu(Cc::No, Lld::No), + &["--fix-cortex-a53-843419"], + ), features: "+v8a,+strict-align,+neon,+fp-armv8".into(), supported_sanitizers: SanitizerSet::KCFI | SanitizerSet::KERNELADDRESS, relocation_model: RelocModel::Static,