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, StackProbeType, TargetOptions};
13
opts() -> TargetOptions14 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.entry(LinkerFlavor::Msvc).or_default().extend(pre_link_args_msvc.clone());
34 base.pre_link_args
35 .entry(LinkerFlavor::Lld(LldFlavor::Link))
36 .or_default()
37 .extend(pre_link_args_msvc);
38
39 TargetOptions {
40 os: "uefi".to_string(),
41 linker_flavor: LinkerFlavor::Lld(LldFlavor::Link),
42 disable_redzone: true,
43 exe_suffix: ".efi".to_string(),
44 allows_weak_linkage: false,
45 panic_strategy: PanicStrategy::Abort,
46 // LLVM does not emit inline assembly because the LLVM target does not get considered as…
47 // "Windows".
48 stack_probes: StackProbeType::Call,
49 singlethread: true,
50 linker: Some("rust-lld".to_string()),
51 ..base
52 }
53 }
54