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
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.
12 use crate::spec::{LinkerFlavor, LldFlavor, PanicStrategy};
13 use crate::spec::{StackProbeType, TargetOptions};
15 pub fn opts() -> TargetOptions {
16 let mut base = super::msvc_base::opts();
18 base.add_pre_link_args(
21 // Non-standard subsystems have no default entry-point in PE+ files. We have to define
22 // one. "efi_main" seems to be a common choice amongst other implementations and the
25 // COFF images have a "Subsystem" field in their header, which defines what kind of
26 // program it is. UEFI has 3 fields reserved, which are EFI_APPLICATION,
27 // EFI_BOOT_SERVICE_DRIVER, and EFI_RUNTIME_DRIVER. We default to EFI_APPLICATION,
28 // which is very likely the most common option. Individual projects can override this
29 // with custom linker flags.
30 // The subsystem-type only has minor effects on the application. It defines the memory
31 // regions the application is loaded into (runtime-drivers need to be put into
32 // reserved areas), as well as whether a return from the entry-point is treated as
33 // exit (default for applications).
34 "/subsystem:efi_application",
40 linker_flavor: LinkerFlavor::Lld(LldFlavor::Link),
41 disable_redzone: true,
42 exe_suffix: ".efi".into(),
43 allows_weak_linkage: false,
44 panic_strategy: PanicStrategy::Abort,
45 // LLVM does not emit inline assembly because the LLVM target does not get considered as…
47 stack_probes: StackProbeType::Call,
49 linker: Some("rust-lld".into()),