From fc0ab35390e98d132c810d791ff8b3d6d405a353 Mon Sep 17 00:00:00 2001
From: Stefan Lankes <slankes@eonerc.rwth-aachen.de>
Date: Fri, 15 Mar 2024 07:46:42 +0100
Subject: [PATCH] introduce feature flag `nostd` to boot the kernel without
 `std`

---
 Cargo.toml   | 1 +
 src/errno.rs | 8 ++++++--
 src/lib.rs   | 8 ++++----
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 02dd3ca2c2..a2eec32ab9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -65,6 +65,7 @@ udp = ["smoltcp", "smoltcp/socket-udp"]
 trace = []
 vga = []
 common-os = []
+nostd = []
 semihosting = ["dep:semihosting"]
 shell = ["simple-shell"]
 
diff --git a/src/errno.rs b/src/errno.rs
index 07c68b64f7..271c2afd95 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -396,11 +396,15 @@ pub const ERFKILL: i32 = 132;
 /// Robust mutexes: Memory page has hardware error
 pub const EHWPOISON: i32 = 133;
 
-#[cfg(all(not(feature = "common-os"), not(target_arch = "riscv64")))]
+#[cfg(all(
+	not(any(feature = "common-os", feature = "nostd")),
+	not(target_arch = "riscv64")
+))]
 #[thread_local]
 pub(crate) static ERRNO: core::cell::UnsafeCell<i32> = core::cell::UnsafeCell::new(0);
 
 /// Get the error number from the thread local storage
+#[cfg(not(feature = "nostd"))]
 #[no_mangle]
 pub extern "C" fn sys_get_errno() -> i32 {
 	cfg_if::cfg_if! {
@@ -423,7 +427,7 @@ pub(crate) trait ToErrno {
 	{
 		if let Some(errno) = self.to_errno() {
 			cfg_if::cfg_if! {
-				if #[cfg(any(feature = "common-os", target_arch = "riscv64"))] {
+				if #[cfg(any(feature = "common-os", feature = "nostd", target_arch = "riscv64"))] {
 					let _ = errno;
 				} else {
 					unsafe {
diff --git a/src/lib.rs b/src/lib.rs
index cd51074329..a0a6df9227 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -252,9 +252,9 @@ pub(crate) extern "C" fn __sys_free(ptr: *mut u8, size: usize, align: usize) {
 #[cfg(target_os = "none")]
 extern "C" fn initd(_arg: usize) {
 	extern "C" {
-		#[cfg(all(not(test), not(feature = "common-os")))]
+		#[cfg(all(not(test), not(any(feature = "nostd", feature = "common-os"))))]
 		fn runtime_entry(argc: i32, argv: *const *const u8, env: *const *const u8) -> !;
-		#[cfg(all(not(test), feature = "common-os"))]
+		#[cfg(all(not(test), any(feature = "nostd", feature = "common-os")))]
 		fn main(argc: i32, argv: *const *const u8, env: *const *const u8);
 		#[cfg(feature = "newlib")]
 		fn init_lwip();
@@ -298,9 +298,9 @@ extern "C" fn initd(_arg: usize) {
 	#[cfg(not(test))]
 	unsafe {
 		// And finally start the application.
-		#[cfg(all(not(test), not(feature = "common-os")))]
+		#[cfg(all(not(test), not(any(feature = "nostd", feature = "common-os"))))]
 		runtime_entry(argc, argv, environ);
-		#[cfg(all(not(test), feature = "common-os"))]
+		#[cfg(all(not(test), any(feature = "nostd", feature = "common-os")))]
 		main(argc, argv, environ);
 	}
 	#[cfg(test)]