// This defines a base target-configuration for native UEFI systems. The UEFI specification has
// quite detailed sections on the ABI of all the supported target architectures. In almost all
// cases it simply follows what Microsoft Windows does. Hence, whenever in doubt, see the MSDN
// documentation.
// UEFI uses COFF/PE32+ format for binaries. All binaries must be statically linked. No dynamic
// linker is supported. As native to COFF, binaries are position-dependent, but will be relocated
// by the loader if the pre-chosen memory location is already in use.
// UEFI forbids running code on anything but the boot-CPU. No interrupts are allowed other than
// the timer-interrupt. Device-drivers are required to use polling-based models. Furthermore, all
// code runs in the same environment, no process separation is supported.
use crate::spec::{LinkArgs, LinkerFlavor, LldFlavor, PanicStrategy, TargetOptions};
use std::default::Default;
pub fn opts() -> TargetOptions {
let mut pre_link_args = LinkArgs::new();
pre_link_args.insert(LinkerFlavor::Lld(LldFlavor::Link), vec![
// Suppress the verbose logo and authorship debugging output, which would needlessly
// clog any log files.
"/NOLOGO".to_string(),
// UEFI is fully compatible to non-executable data pages. Tell the compiler that
// non-code sections can be marked as non-executable, including stack pages. In fact,
// firmware might enforce this, so we better let the linker know about this, so it
// will fail if the compiler ever tries placing code on the stack (e.g., trampoline
// constructs and alike).
"/NXCOMPAT".to_string(),
// There is no runtime for UEFI targets, prevent them from being linked. UEFI targets
// must be freestanding.
"/nodefaultlib".to_string(),
// Non-standard subsystems have no default entry-point in PE+ files. We have to define
// one. "efi_main" seems to be a common choice amongst other implementations and the
// spec.
"/entry:efi_main".to_string(),
// COFF images have a "Subsystem" field in their header, which defines what kind of
// program it is. UEFI has 3 fields reserved, which are EFI_APPLICATION,
// EFI_BOOT_SERVICE_DRIVER, and EFI_RUNTIME_DRIVER. We default to EFI_APPLICATION,
// which is very likely the most common option. Individual projects can override this
// with custom linker flags.
// The subsystem-type only has minor effects on the application. It defines the memory
// regions the application is loaded into (runtime-drivers need to be put into
// reserved areas), as well as whether a return from the entry-point is treated as
// exit (default for applications).
"/subsystem:efi_application".to_string(),
]);
TargetOptions {
dynamic_linking: false,
executables: true,
disable_redzone: true,
exe_suffix: ".efi".to_string(),
allows_weak_linkage: false,
panic_strategy: PanicStrategy::Abort,
stack_probes: true,
singlethread: true,
emit_debug_gdb_scripts: false,
linker: Some("rust-lld".to_string()),
lld_flavor: LldFlavor::Link,
pre_link_args,
.. Default::default()
}
}