compiler/rustc_target/src/spec/x86_64_unknown_uefi.rs

   1 // This defines the amd64 target for UEFI systems as described in the UEFI specification. See the
   2 // uefi-base module for generic UEFI options. On x86_64 systems (mostly called "x64" in the spec)
   3 // UEFI systems always run in long-mode, have the interrupt-controller pre-configured and force a
   4 // single-CPU execution.
   5 // The win64 ABI is used. It differs from the sysv64 ABI, so we must use a windows target with
   6 // LLVM. "x86_64-unknown-windows" is used to get the minimal subset of windows-specific features.
   7
   8 use crate::spec::{CodeModel, LinkerFlavor, LldFlavor, Target, TargetResult};
   9
  10 pub fn target() -> TargetResult {
  11     let mut base = super::uefi_msvc_base::opts();
  12     base.cpu = "x86-64".to_string();
  13     base.max_atomic_width = Some(64);
  14
  15     // We disable MMX and SSE for now, even though UEFI allows using them. Problem is, you have to
  16     // enable these CPU features explicitly before their first use, otherwise their instructions
  17     // will trigger an exception. Rust does not inject any code that enables AVX/MMX/SSE
  18     // instruction sets, so this must be done by the firmware. However, existing firmware is known
  19     // to leave these uninitialized, thus triggering exceptions if we make use of them. Which is
  20     // why we avoid them and instead use soft-floats. This is also what GRUB and friends did so
  21     // far.
  22     // If you initialize FP units yourself, you can override these flags with custom linker
  23     // arguments, thus giving you access to full MMX/SSE acceleration.
  24     base.features = "-mmx,-sse,+soft-float".to_string();
  25
  26     // UEFI systems run without a host OS, hence we cannot assume any code locality. We must tell
  27     // LLVM to expect code to reference any address in the address-space. The "large" code-model
  28     // places no locality-restrictions, so it fits well here.
  29     base.code_model = Some(CodeModel::Large);
  30
  31     Ok(Target {
  32         llvm_target: "x86_64-unknown-windows".to_string(),
  33         target_endian: "little".to_string(),
  34         target_pointer_width: "64".to_string(),
  35         target_c_int_width: "32".to_string(),
  36         data_layout: "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  37             .to_string(),
  38         target_os: "uefi".to_string(),
  39         target_env: "".to_string(),
  40         target_vendor: "unknown".to_string(),
  41         arch: "x86_64".to_string(),
  42         linker_flavor: LinkerFlavor::Lld(LldFlavor::Link),
  43
  44         options: base,
  45     })
  46 }