user app can invoke kernel syscall!!!!

user-apps/calculator/build.rs

@@ -0,0 +1,28 @@
+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("../memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    println!("cargo:rerun-if-changed=memory.x");
+    println!("cargo:rustc-link-arg-bins=-Tmemory.x");
+}

user-apps/calculator/src/main.rs

@@ -10,17 +10,15 @@ fn panic(_info: &PanicInfo) -> ! {
 }
 
 #[unsafe(no_mangle)]
-pub extern "C" fn _start() -> ! {
-    loop {
-        for i in 0..300 {
-            for o in 0..300 {
-                let call = Syscall::DrawPixel {
-                    x: i,
-                    y: o,
-                    color: 0,
-                };
-                unsafe { call_abi(&call) };
-            }
+pub extern "C" fn _start() {
+    for i in 0..300 {
+        for o in 0..300 {
+            let call = Syscall::DrawPixel {
+                x: i,
+                y: o,
+                color: 0,
+            };
+            unsafe { call_abi(&call) };
         }
     }
 }

user-apps/link.x

@@ -1,21 +0,0 @@
-MEMORY
-{
-  RAM : ORIGIN = 0x00000000, LENGTH = 256K
-}
-
-SECTIONS
-{
-  .text : {
-    *(.text .text.*);
-    *(.rodata .rodata.*);
-  } > RAM
-
-  .data : {
-    *(.data .data.*);
-  } > RAM
-
-  .bss : {
-    *(.bss .bss.*);
-    *(COMMON);
-  } > RAM
-}

user-apps/memory.x

@@ -0,0 +1,33 @@
+MEMORY
+{
+  /* Must match the USERAPP region in the kernel linker script */
+  RAM : ORIGIN = 0x20010000, LENGTH = 192K
+}
+
+SECTIONS
+{
+  /* Reserve first 1KB for patchable symbols */
+  .user_reloc (NOLOAD) : ALIGN(4)
+  {
+      __user_reloc_start = .;
+      KEEP(*(.user_reloc*));
+      __user_reloc_end = .;
+  } > RAM
+
+  .text : ALIGN(4)
+  {
+      *(.text .text.*);
+      *(.rodata .rodata.*);
+  } > RAM
+
+  .data : ALIGN(4)
+  {
+      *(.data .data.*);
+  } > RAM
+
+  .bss : ALIGN(4)
+  {
+      *(.bss .bss.*);
+      *(COMMON);
+  } > RAM
+}