compiler/rustc_target/src/spec/uefi_msvc_base.rs

   1 // This defines a base target-configuration for native UEFI systems. The UEFI specification has
   2 // quite detailed sections on the ABI of all the supported target architectures. In almost all
   3 // cases it simply follows what Microsoft Windows does. Hence, whenever in doubt, see the MSDN
   4 // documentation.
   5 // UEFI uses COFF/PE32+ format for binaries. All binaries must be statically linked. No dynamic
   6 // linker is supported. As native to COFF, binaries are position-dependent, but will be relocated
   7 // by the loader if the pre-chosen memory location is already in use.
   8 // UEFI forbids running code on anything but the boot-CPU. No interrupts are allowed other than
   9 // the timer-interrupt. Device-drivers are required to use polling-based models. Furthermore, all
  10 // code runs in the same environment, no process separation is supported.
  11
  12 use crate::spec::{LinkerFlavor, Lld, PanicStrategy, StackProbeType, TargetOptions};
  13
  14 pub fn opts() -> TargetOptions {
  15     let mut base = super::msvc_base::opts();
  16
  17     base.add_pre_link_args(
  18         LinkerFlavor::Msvc(Lld::No),
  19         &[
  20             // Non-standard subsystems have no default entry-point in PE+ files. We have to define
  21             // one. "efi_main" seems to be a common choice amongst other implementations and the
  22             // spec.
  23             "/entry:efi_main",
  24             // COFF images have a "Subsystem" field in their header, which defines what kind of
  25             // program it is. UEFI has 3 fields reserved, which are EFI_APPLICATION,
  26             // EFI_BOOT_SERVICE_DRIVER, and EFI_RUNTIME_DRIVER. We default to EFI_APPLICATION,
  27             // which is very likely the most common option. Individual projects can override this
  28             // with custom linker flags.
  29             // The subsystem-type only has minor effects on the application. It defines the memory
  30             // regions the application is loaded into (runtime-drivers need to be put into
  31             // reserved areas), as well as whether a return from the entry-point is treated as
  32             // exit (default for applications).
  33             "/subsystem:efi_application",
  34         ],
  35     );
  36
  37     TargetOptions {
  38         os: "uefi".into(),
  39         linker_flavor: LinkerFlavor::Msvc(Lld::Yes),
  40         disable_redzone: true,
  41         exe_suffix: ".efi".into(),
  42         allows_weak_linkage: false,
  43         panic_strategy: PanicStrategy::Abort,
  44         // LLVM does not emit inline assembly because the LLVM target does not get considered as…
  45         // "Windows".
  46         stack_probes: StackProbeType::Call,
  47         singlethread: true,
  48         linker: Some("rust-lld".into()),
  49         ..base
  50     }
  51 }