Better user programs with a special std. Sleep and exit are calling scheduler instead of wfi.

.cargo/config.toml

@@ -6,4 +6,7 @@ build-std = ["core", "compiler_builtins", "alloc"]
 build-std-features = ["compiler-builtins-mem"]
 
 [target.riscv64]
+rustflags = [
+  "-C", "link-arg=-Tilm.ld",
+]
 runner = "qemu-system-riscv64 -machine virt -device bochs-display -bios none -m 512M -device loader,file=/home/julien/ensimag/TPs/kernel/disk.img,addr=0x90000000 -kernel"

Cargo.toml

@@ -1,6 +1,6 @@
 [workspace]
 resolver = "3"
-members = ["user/*"]
+members = ["crates/os-std", "crates/shared", "user/*"]
 
 [package]
 name = "kernel-rust"
@@ -13,3 +13,4 @@ kernel-macros = { path = "crates/kernel-macros" }
 log = "0.4"
 critical-section = { version = "1", features = ["restore-state-bool"] }
 bffs = { path = "../../../code/bffs", features = ["alloc"] }
+shared = { path = "crates/shared" }

build.rs

@@ -1,3 +0,0 @@
-fn main() {
-    println!("cargo::rustc-link-arg=-Tilm.ld");
-}

crates/os-std-macros/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "os-std-macros"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1"
+quote = "1"
+syn = { version = "2", features = ["full"] }

crates/os-std-macros/src/lib.rs

@@ -0,0 +1 @@
+

crates/os-std/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "os-std"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+os-std-macros = { path = "../os-std-macros" }
+shared = { path = "../shared" }

crates/os-std/src/lib.rs

@@ -0,0 +1,21 @@
+#![no_std]
+
+mod prelude;
+
+pub use shared::syscall;
+
+#[macro_export]
+macro_rules! custom_std_setup {
+    () => {
+        #[panic_handler]
+        fn panic(_panic_info: &core::panic::PanicInfo) -> ! {
+            // TODO print
+            loop {}
+        }
+
+        #[unsafe(no_mangle)]
+        pub extern "C" fn _start() {
+            main()
+        }
+    };
+}

crates/os-std/src/prelude.rs

@@ -0,0 +1 @@
+

crates/shared/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "shared"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

crates/shared/src/lib.rs

@@ -0,0 +1,3 @@
+#![no_std]
+
+pub mod syscall;

crates/shared/src/syscall.rs

@@ -2,6 +2,7 @@ use core::time::Duration;
 
 #[repr(u64)]
 pub enum SysCall {
+    Exit = 60,
     NanoSleep = 101,
     WriteIntTemp = 998,
     WriteTemp = 999,
@@ -11,6 +12,7 @@ pub enum SysCall {
 impl From<u64> for SysCall {
     fn from(value: u64) -> Self {
         match value {
+            60 => SysCall::Exit,
             101 => SysCall::NanoSleep,
             998 => SysCall::WriteIntTemp,
             999 => SysCall::WriteTemp,
@@ -75,6 +77,12 @@ macro_rules! syscall {
     };
 }
 
+pub fn exit() {
+    unsafe {
+        syscall!(SysCall::Exit);
+    }
+}
+
 pub fn sleep(duration: Duration) {
     unsafe {
         let (duration_secs, duration_nanos) = (duration.as_secs(), duration.subsec_nanos() as u64);

ilm.ld

@@ -2,17 +2,16 @@
  * ld directives the for barmetal RISCV
  */
 OUTPUT_ARCH(riscv)
-ENTRY(entry)
+ENTRY(_start)
 
 MEMORY {
     RAM (wxa) : ORIGIN = 0x80000000, LENGTH = 128M
 }
 
 SECTIONS {
-    /* The kernel starts at 0x80000000 */
     . = 0x80000000;
     .text : {
-        KEEP(*(.text.entry))
+        KEEP(*(.text._start))
 
         *(.text .text.*)
     } > RAM

justfile

@@ -3,16 +3,23 @@ cargo_flags := if release != "" { "--release" } else { "" }
 
 default: run
 
-build_user_prog prog:
-    cd {{ "user" / prog }} && \
-    RUSTFLAGS="-C relocation-model=pic" cargo b {{ cargo_flags }}
-    riscv64-elf-objcopy -O binary {{ "target/riscv64/debug" / prog }} {{ "user" / prog / prog + ".mem" }}
+mount_filesystem:
+    # Add some permissions to be able to do next operations without sudo
+    @mountpoint -q mnt || sudo mount -o umask=0022,gid=$(id -g $USER),uid=$(id -u $USER) disk.img mnt
 
-build: (map_dir "user" "build_user_prog")
+sync_filesystem:
+    sync
+
+build_user_prog prog:
+    RUSTFLAGS="-C relocation-model=pic -C link-arg=-Tilm.ld" cargo b {{ cargo_flags }} --package {{ prog }}
+    riscv64-elf-objcopy -O binary {{ "target/riscv64/debug" / prog }} {{ "mnt/usr/bin" / prog }}
+
+build: mount_filesystem (map_dir "user" "build_user_prog")
     cargo b {{ cargo_flags }}
+    just sync_filesystem
 
 run: build
-    cargo r {{ cargo_flags }} --bin kernel-rust
+    cargo r {{ cargo_flags }}
 
 map_dir dir recipe:
     @for file in `ls {{ dir }}`; do \

src/boot.rs

@@ -10,7 +10,7 @@ pub mod sbi;
 
 #[unsafe(naked)]
 #[unsafe(no_mangle)]
-pub extern "C" fn entry() {
+pub extern "C" fn _start() {
     naked_asm!(
         "
         la sp, _heap_end

src/fs.rs

@@ -1,7 +1,33 @@
-use bffs::io::{IoBase, Read, Seek};
+use core::{cell::UnsafeCell, ops::Deref};
+
+use bffs::{
+    io::{IoBase, Read, Seek},
+    Fat32FileSystem,
+};
 
 const DISK_ADDR: *const u8 = 0x9000_0000 as *const _;
 
+pub struct FSTemp(UnsafeCell<Option<Fat32FileSystem<Disk>>>);
+unsafe impl Sync for FSTemp {}
+
+impl FSTemp {
+    pub unsafe fn init(&self) {
+        unsafe {
+            *self.0.get() = Some(Fat32FileSystem::new(Disk::new(1024 * 1024 * 16)).unwrap());
+        }
+    }
+}
+
+impl Deref for FSTemp {
+    type Target = Fat32FileSystem<Disk>;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { (&*self.0.get()).as_ref().unwrap_unchecked() }
+    }
+}
+
+pub static FILE_SYSTEM: FSTemp = FSTemp(UnsafeCell::new(None));
+
 #[derive(Debug)]
 pub struct Disk {
     pos: u64,

src/interrupt.rs

@@ -1,15 +1,15 @@
 use alloc::str;
 use log::info;
+use shared::syscall::SysCall;
 
 use crate::{
     boot::sbi::{EextensionID, TimerFunctionID},
-    clear_csr, generate_trap_handler,
-    process::{sleep, ExecutionContext},
+    clear_csr,
+    process::{exit_process, sleep, ExecutionContext},
     read_csr,
     riscv::disable_interrupt,
-    scheduler::scheduler,
+    scheduler::scheduler_without_ret,
     set_csr,
-    syscall::SysCall,
     time::{setup_next_timer_interrupt, IRQ_M_TIMER},
     write_csr,
 };
@@ -87,7 +87,7 @@ unsafe extern "C" fn machine_trap_handler(
 
 #[unsafe(no_mangle)]
 unsafe extern "C" fn supervisor_trap_handler(
-    interrupt_state: *mut ExecutionContext,
+    mut interrupt_state: *mut ExecutionContext,
     scause: u64,
     _sie: u64,
     _sip: u64,
@@ -96,13 +96,19 @@ unsafe extern "C" fn supervisor_trap_handler(
         #[allow(clippy::single_match)]
         match scause & !(1 << 63) {
             8 => {
+                // Advance sepc to exit the ecall
+                unsafe {
+                    (*interrupt_state).mepc = (*interrupt_state).mepc.byte_add(4);
+                }
+
                 // Environment call from S-mode
                 let syscall_u64: u64 = unsafe { (*interrupt_state).a[0] };
                 let a1: u64 = unsafe { (*interrupt_state).a[1] };
                 let a2: u64 = unsafe { (*interrupt_state).a[2] };
                 let syscall: SysCall = syscall_u64.into();
                 match syscall {
-                    SysCall::NanoSleep => sleep(Duration::new(a1, a2 as u32)),
+                    SysCall::Exit => exit_process(&mut interrupt_state),
+                    SysCall::NanoSleep => sleep(Duration::new(a1, a2 as u32), &mut interrupt_state),
                     SysCall::WriteTemp => {
                         info!("Print from user space : {}", unsafe {
                             str::from_raw_parts(a1 as *const u8, a2 as usize)
@@ -115,11 +121,6 @@ unsafe extern "C" fn supervisor_trap_handler(
                         unimplemented!("Syscall {syscall_u64} is not implemented")
                     }
                 }
-
-                // Advance sepc to exit the ecall
-                unsafe {
-                    (*interrupt_state).mepc = (*interrupt_state).mepc.byte_add(4);
-                }
             }
             _ => {}
         }
@@ -137,7 +138,7 @@ unsafe extern "C" fn supervisor_trap_handler(
                     );
                 }
                 timer_interrupt();
-                return scheduler(unsafe { *interrupt_state });
+                scheduler_without_ret(&mut interrupt_state);
             }
             _ => {}
         }
@@ -207,116 +208,107 @@ unsafe extern "C" fn _machine_mode_trap() {
         mret"
     )
 }
-generate_trap_handler! {
-    _supervisor_mode_trap, supervisor_trap_handler, s
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+unsafe extern "C" fn _supervisor_mode_trap() {
+    naked_asm!(concat!(
+        "
+        // Store sp before it gets modified
+        sd sp, 8-264(sp)
+        addi sp, sp, -264
+
+        # Store the current frame
+        sd ra, 0(sp)
+        // sp
+        sd gp, 16(sp)
+        sd tp, 24(sp)
+        sd a0, 32(sp)
+        sd a1, 40(sp)
+        sd a2, 48(sp)
+        sd a3, 56(sp)
+        sd a4, 64(sp)
+        sd a5, 72(sp)
+        sd a6, 80(sp)
+        sd a7, 88(sp)
+        sd t0, 96(sp)
+        sd t1, 104(sp)
+        sd t2, 112(sp)
+        sd t3, 120(sp)
+        sd t4, 128(sp)
+        sd t5, 136(sp)
+        sd t6, 144(sp)
+        sd s0, 152(sp)
+        sd s1, 160(sp)
+        sd s2, 168(sp)
+        sd s3, 176(sp)
+        sd s4, 184(sp)
+        sd s5, 192(sp)
+        sd s6, 200(sp)
+        sd s7, 208(sp)
+        sd s8, 216(sp)
+        sd s9, 224(sp)
+        sd s10, 232(sp)
+        sd s11, 240(sp)
+        csrr t0, sepc
+        sd t0, 248(sp)
+        csrr t0, sstatus
+        sd t0, 256(sp)
+
+        mv a0, sp
+        csrr a1, scause
+        csrr a2, sie
+        csrr a3, sip
+        jal supervisor_trap_handler
+
+        # Restore registers and sret
+        jal restore_context"
+    ))
 }
 
-#[macro_export]
-macro_rules! generate_trap_handler {
-    ($name:ident, $jump_to:ident, $mode:ident) => {
-        #[unsafe(naked)]
-        #[unsafe(no_mangle)]
-        unsafe extern "C" fn $name() {
-            naked_asm!(concat!(
-                "
-            mv t0, sp
-            addi sp, sp, -264
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn restore_context(context: *const ExecutionContext) -> ! {
+    naked_asm!(concat!(
+        "
+        ld t0, 248(a0)
+        csrw sepc, t0
+        ld t0, 256(a0)
+        csrw sstatus, t0
+        ld ra, 0(a0)
+        ld sp, 8(a0)
+        ld gp, 16(a0)
+        ld tp, 24(a0)
+        ld a1, 40(a0)
+        ld a2, 48(a0)
+        ld a3, 56(a0)
+        ld a4, 64(a0)
+        ld a5, 72(a0)
+        ld a6, 80(a0)
+        ld a7, 88(a0)
+        ld t0, 96(a0)
+        ld t1, 104(a0)
+        ld t2, 112(a0)
+        ld t3, 120(a0)
+        ld t4, 128(a0)
+        ld t5, 136(a0)
+        ld t6, 144(a0)
+        ld s0, 152(a0)
+        ld s1, 160(a0)
+        ld s2, 168(a0)
+        ld s3, 176(a0)
+        ld s4, 184(a0)
+        ld s5, 192(a0)
+        ld s6, 200(a0)
+        ld s7, 208(a0)
+        ld s8, 216(a0)
+        ld s9, 224(a0)
+        ld s10, 232(a0)
+        ld s11, 240(a0)
 
-            # Store the current frame
-            sd ra, 0(sp)
-            sd t0, 8(sp) // sp
-            sd gp, 16(sp)
-            sd tp, 24(sp)
-            sd a0, 32(sp)
-            sd a1, 40(sp)
-            sd a2, 48(sp)
-            sd a3, 56(sp)
-            sd a4, 64(sp)
-            sd a5, 72(sp)
-            sd a6, 80(sp)
-            sd a7, 88(sp)
-            sd t0, 96(sp)
-            sd t1, 104(sp)
-            sd t2, 112(sp)
-            sd t3, 120(sp)
-            sd t4, 128(sp)
-            sd t5, 136(sp)
-            sd t6, 144(sp)
-            sd s0, 152(sp)
-            sd s1, 160(sp)
-            sd s2, 168(sp)
-            sd s3, 176(sp)
-            sd s4, 184(sp)
-            sd s5, 192(sp)
-            sd s6, 200(sp)
-            sd s7, 208(sp)
-            sd s8, 216(sp)
-            sd s9, 224(sp)
-            sd s10, 232(sp)
-            sd s11, 240(sp)
-            csrr t0, sepc
-            sd t0, 248(sp)
-            csrr t0, sstatus
-            sd t0, 256(sp)
+        ld a0, 32(a0)
 
-            mv a0, sp
-            csrr a1, ",
-                stringify!($mode),
-                "cause
-            csrr a2, ",
-                stringify!($mode),
-                "ie
-            csrr a3, ",
-                stringify!($mode),
-                "ip
-            jal ",
-                stringify!($jump_to),
-                "
-
-            # Restore registers
-            ld t0, 248(a0)
-            csrw sepc, t0
-            ld t0, 256(a0)
-            csrw sstatus, t0
-            ld ra, 0(a0)
-            ld sp, 8(a0)
-            ld gp, 16(a0)
-            ld tp, 24(a0)
-            ld a1, 40(a0)
-            ld a2, 48(a0)
-            ld a3, 56(a0)
-            ld a4, 64(a0)
-            ld a5, 72(a0)
-            ld a6, 80(a0)
-            ld a7, 88(a0)
-            ld t0, 96(a0)
-            ld t1, 104(a0)
-            ld t2, 112(a0)
-            ld t3, 120(a0)
-            ld t4, 128(a0)
-            ld t5, 136(a0)
-            ld t6, 144(a0)
-            ld s0, 152(a0)
-            ld s1, 160(a0)
-            ld s2, 168(a0)
-            ld s3, 176(a0)
-            ld s4, 184(a0)
-            ld s5, 192(a0)
-            ld s6, 200(a0)
-            ld s7, 208(a0)
-            ld s8, 216(a0)
-            ld s9, 224(a0)
-            ld s10, 232(a0)
-            ld s11, 240(a0)
-
-            ld a0, 32(a0)
-
-            ",
-                stringify!($mode),
-                "ret"
-            ))
-        }
-    };
+        sret"
+    ))
 }
 
 #[repr(C)]

src/io.rs

@@ -7,7 +7,7 @@ use log::{LevelFilter, SetLoggerError};
 
 use crate::uart::write_uart;
 
-fn print(content: String) {
+pub(crate) fn print(content: String) {
     write_uart(content);
 }
 

src/main.rs

@@ -10,18 +10,15 @@
     macro_metavar_expr_concat
 )]
 
-use alloc::{boxed::Box, vec::Vec};
-use bffs::{io::Read, Fat32FileSystem};
 use embedded_alloc::LlffHeap as Heap;
 use log::info;
 
 use crate::{
-    fs::Disk,
+    fs::FILE_SYSTEM,
     io::init_log,
-    process::create_process,
+    process::{create_process, create_process_from_file},
     riscv::enable_supervisor_interrupt,
     scheduler::{idle, scheduler_init},
-    tests_fat::MemoryDisk,
     user::{proc2, test},
     vga::{Color, Vga},
 };
@@ -36,14 +33,12 @@ mod panic_handler;
 mod process;
 mod riscv;
 mod scheduler;
-mod syscall;
-mod tests_fat;
 mod time;
 mod uart;
 mod user;
 mod vga;
 
-pub const HEAP_SIZE: usize = 40960;
+pub const HEAP_SIZE: usize = 1024 * 1024; // 1Mo RAM
 #[global_allocator]
 static HEAP: Heap = Heap::empty();
 
@@ -56,6 +51,7 @@ pub extern "C" fn supervisor_mode_entry() {
         embedded_alloc::init!(HEAP, HEAP_SIZE);
         init_log().unwrap();
         Vga::init();
+        FILE_SYSTEM.init();
         scheduler_init();
     }
 
@@ -65,16 +61,7 @@ pub extern "C" fn supervisor_mode_entry() {
     create_process(&test, "proc1");
     create_process(&proc2, "proc2");
 
-    let fs = Fat32FileSystem::new(Disk::new(1024 * 1024 * 16)).unwrap();
-    let mut bin = fs.open_file("/usr/bin/test").unwrap();
-    let mut content: Vec<u8> = Vec::new();
-    bin.read_to_end(&mut content).unwrap();
-    let test = unsafe { core::mem::transmute::<*const u8, extern "C" fn()>(content.as_ptr()) };
-
-    let test = Box::leak(Box::new(move || {
-        test();
-    }));
-    create_process(test, "dyn_proc");
+    create_process_from_file("/usr/bin/test_pic");
 
     enable_supervisor_interrupt();
     idle();

src/process.rs

@@ -1,9 +1,12 @@
-use core::{arch::riscv64::wfi, time::Duration};
+use core::time::Duration;
 
-use alloc::{format, string::String};
+use alloc::{boxed::Box, format, string::String, vec::Vec};
+use bffs::{io::Read, path::Path};
+use shared::syscall::exit;
 
 use crate::{
-    scheduler::{ACTIVE_PID, PROCESS_COUNT, PROCESS_TABLE},
+    fs::FILE_SYSTEM,
+    scheduler::{scheduler_without_ret, ACTIVE_PID, PROCESS_COUNT, PROCESS_TABLE},
     time::elapsed_time_since_startup,
 };
 
@@ -54,6 +57,21 @@ impl core::fmt::Debug for Process {
     }
 }
 
+pub fn create_process_from_file<'a, T: Into<Path<'a>>>(path: T) -> i64 {
+    let path = path.into();
+    let name = path.as_str();
+    let mut bin = FILE_SYSTEM.open_file(path).unwrap();
+    let mut content: Vec<u8> = Vec::new();
+    bin.read_to_end(&mut content).unwrap();
+    let test =
+        unsafe { core::mem::transmute::<*const u8, extern "C" fn()>(Vec::leak(content).as_ptr()) };
+
+    let test = Box::leak(Box::new(move || {
+        test();
+    }));
+    create_process(test, name)
+}
+
 pub fn create_process<T: Into<String>, F: Fn()>(code: &'static F, name: T) -> i64 {
     let mut next_pid = 0;
     while next_pid < PROCESS_COUNT && unsafe { PROCESS_TABLE[next_pid].state != ProcessState::Dead }
@@ -82,27 +100,21 @@ pub fn create_process<T: Into<String>, F: Fn()>(code: &'static F, name: T) -> i6
 
 extern "C" fn process_launcher(code: *const &dyn Fn()) {
     unsafe { (*code)() };
-    terminate_process();
+    // User code didn't exit before the end of its execution, so we call the exit syscall ourselves
+    exit();
 }
 
-fn terminate_process() {
+pub fn exit_process(interrupt_context: &mut *mut ExecutionContext) {
     unsafe {
         PROCESS_TABLE[ACTIVE_PID].state = ProcessState::Dead;
     }
-    loop {}
-    // unsafe {
-    //     wfi();
-    // }
-    // scheduler();
+    scheduler_without_ret(interrupt_context)
 }
 
-pub fn sleep(duration: Duration) {
+pub fn sleep(duration: Duration, interrupt_context: &mut *mut ExecutionContext) {
     unsafe {
         PROCESS_TABLE[ACTIVE_PID].wake_time = elapsed_time_since_startup() + duration;
         PROCESS_TABLE[ACTIVE_PID].state = ProcessState::Asleep;
     }
-    unsafe {
-        wfi();
-    }
-    // scheduler();
+    scheduler_without_ret(interrupt_context)
 }

src/scheduler.rs

@@ -57,11 +57,11 @@ pub fn scheduler_init() {
     }
 }
 
-pub fn scheduler(interrupt_state: ExecutionContext) -> *const ExecutionContext {
+pub fn scheduler_without_ret(interrupt_state: &mut *mut ExecutionContext) {
     // info!("scheduler");
     unsafe {
         let prev_pid = ACTIVE_PID;
-        PROCESS_TABLE[prev_pid].ctx = interrupt_state;
+        PROCESS_TABLE[prev_pid].ctx = **interrupt_state;
 
         if PROCESS_TABLE[prev_pid].state == ProcessState::Active {
             PROCESS_TABLE[prev_pid].state = ProcessState::Activable;
@@ -80,6 +80,6 @@ pub fn scheduler(interrupt_state: ExecutionContext) -> *const ExecutionContext {
         }
         PROCESS_TABLE[ACTIVE_PID].state = ProcessState::Active;
 
-        &raw const PROCESS_TABLE[ACTIVE_PID].ctx
+        *interrupt_state = &raw mut PROCESS_TABLE[ACTIVE_PID].ctx
     }
 }

src/tests_fat.rs

@@ -1,13 +0,0 @@
-use core::str;
-use log::info;
-
-const DISK_ADDR: usize = 0x9000_0000;
-
-pub struct MemoryDisk {}
-
-impl MemoryDisk {
-    pub fn test() {
-        let test = unsafe { str::from_raw_parts(DISK_ADDR as *const u8, 13) };
-        info!("{}", test);
-    }
-}

src/user.rs

@@ -1,15 +1,9 @@
 use core::time::Duration;
 
-use alloc::vec::Vec;
-use bffs::{io::Read, Fat32FileSystem};
-
-use crate::{
-    fs::Disk,
-    syscall::{sleep, write_int_temp, write_string_temp},
-};
+use shared::syscall::{sleep, write_int_temp, write_string_temp};
 
 #[repr(align(32))]
-struct Alignement([u8; 157]);
+struct Alignement([u8; include_bytes!("../user/test_pic/test_pic.mem").len()]);
 
 static PROG: Alignement = Alignement(*include_bytes!("../user/test_pic/test_pic.mem"));
 

user/test_pic/Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+os-std = { path = "../../crates/os-std" }

user/test_pic/build.rs

@@ -1,3 +0,0 @@
-fn main() {
-    println!("cargo::rustc-link-arg=-Tilm.ld");
-}

user/test_pic/src/main.rs

@@ -1,21 +1,11 @@
 #![no_std]
 #![no_main]
+os_std::custom_std_setup! {}
 
-#[panic_handler]
-fn panic(_panic_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}
+use os_std::syscall::write_string_temp;
 
-#[unsafe(no_mangle)]
-pub extern "C" fn entry() {
-    let test = "Hello from PIC program loaded dynamically";
-    unsafe {
-        core::arch::asm!(
-            "ecall",
-            in("a0") 999,
-            in("a1") test.as_ptr(),
-            in("a2") test.len(),
-            clobber_abi("system")
-        );
-    }
+fn main() {
+    write_string_temp(
+        "Hello from PIC program loaded dynamically with custom std and a better justfile, and syscalls !",
+    );
 }