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, LldFlavor, PanicStrategy, TargetOptions};
  13
  14 pub fn opts() -> TargetOptions {
  15     let mut base = super::msvc_base::opts();
  16
  17     let pre_link_args_msvc = vec![
  18         // Non-standard subsystems have no default entry-point in PE+ files. We have to define
  19         // one. "efi_main" seems to be a common choice amongst other implementations and the
  20         // spec.
  21         "/entry:efi_main".to_string(),
  22         // COFF images have a "Subsystem" field in their header, which defines what kind of
  23         // program it is. UEFI has 3 fields reserved, which are EFI_APPLICATION,
  24         // EFI_BOOT_SERVICE_DRIVER, and EFI_RUNTIME_DRIVER. We default to EFI_APPLICATION,
  25         // which is very likely the most common option. Individual projects can override this
  26         // with custom linker flags.
  27         // The subsystem-type only has minor effects on the application. It defines the memory
  28         // regions the application is loaded into (runtime-drivers need to be put into
  29         // reserved areas), as well as whether a return from the entry-point is treated as
  30         // exit (default for applications).
  31         "/subsystem:efi_application".to_string(),
  32     ];
  33     base.pre_link_args.get_mut(&LinkerFlavor::Msvc).unwrap().extend(pre_link_args_msvc.clone());
  34     base.pre_link_args
  35         .get_mut(&LinkerFlavor::Lld(LldFlavor::Link))
  36         .unwrap()
  37         .extend(pre_link_args_msvc);
  38
  39     TargetOptions {
  40         disable_redzone: true,
  41         exe_suffix: ".efi".to_string(),
  42         allows_weak_linkage: false,
  43         panic_strategy: PanicStrategy::Abort,
  44         stack_probes: true,
  45         singlethread: true,
  46         linker: Some("rust-lld".to_string()),
  47         // FIXME: This should likely be `true` inherited from `msvc_base`
  48         // because UEFI follows Windows ABI and uses PE/COFF.
  49         // The `false` is probably causing ABI bugs right now.
  50         is_like_windows: false,
  51         // FIXME: This should likely be `true` inherited from `msvc_base`
  52         // because UEFI follows Windows ABI and uses PE/COFF.
  53         // The `false` is probably causing ABI bugs right now.
  54         is_like_msvc: false,
  55
  56         ..base
  57     }
  58 }