Clean up the memory arrangement.

Now there's 32K of RAM from the top of the SRAM region (24K from the striped block, plus SRAM_BLOCK4 and SRAM_BLOCK5) and from within that is the Core 0 stack, the Core 1 stack (a static mut array) and all the other global variables.

Tested OK.

Author: thejpster

memory.x

@@ -25,40 +25,15 @@ MEMORY {
     /*
      * This is the bottom of the four striped banks of SRAM in the RP2040.
      */
-    RAM_OS : ORIGIN = 0x20000000, LENGTH = 0x39000
+    RAM_OS : ORIGIN = 0x20000000, LENGTH = 232K
     /*
-     * This is the top of the four striped banks of SRAM in the RP2040.
+     * This is the top of the four striped banks of SRAM in the RP2040, plus SRAM_BANK4 and SRAM_BANK5.
      *
-     * We give ourselves size 4K pages [0x39_000..0x3E_FFF]
+     * We give ourselves eight 4K pages [0x3A_000..0x41_FFF]
      */
-    RAM : ORIGIN = 0x20039000, LENGTH = 24K
-    /*
-     * This 4K from the top of striped RAM, plus the fifth bank - another a 4KB
-     * block. We use this for Core 0 Stack. We tried 4K but it wasn't enough.
-     */
-    RAM_CORE0_STACK : ORIGIN = 0x2003F000, LENGTH = 8K
-    /*
-     * This is the sixth bank, a 4KB block. We use this for Core 1 Stack.
-     * As of 0.5.1 Pico BIOS uses about 316 bytes of this but we give it the
-     * full 4K so it can have uncontended access to this SRAM bank.
-     */
-    RAM_CORE1_STACK : ORIGIN = 0x20041000, LENGTH = 4K
+    RAM : ORIGIN = 0x2003A000, LENGTH = 32K
 }
 
-/*
- * This is where the call stack for Core 0 will be located. The stack is of
- * the full descending type.
- */
-_stack_start = ORIGIN(RAM_CORE0_STACK) + LENGTH(RAM_CORE0_STACK);
-_stack_bottom = ORIGIN(RAM_CORE0_STACK);
-_stack_len = LENGTH(RAM_CORE0_STACK);
-
-/*
- * This is where the call stack for Core 1 will be located.
- */
-_core1_stack_bottom = ORIGIN(RAM_CORE1_STACK);
-_core1_stack_len = LENGTH(RAM_CORE1_STACK);
-
 /*
  * Export some symbols to tell the BIOS where it might find the OS.
  */

src/main.rs

@@ -249,6 +249,9 @@ pub static OS_IMAGE: [u8; include_bytes!("thumbv6m-none-eabi-flash1002-libneotro
 /// is currently active (low).
 static INTERRUPT_PENDING: AtomicBool = AtomicBool::new(false);
 
+/// Stack for Core 1
+static mut CORE1_STACK: [usize; 256] = [0; 256];
+
 /// The table of API calls we provide the OS
 static API_CALLS: common::Api = common::Api {
 	api_version_get,
@@ -342,14 +345,17 @@ fn main() -> ! {
 	{
 		// Paint the stack
 		extern "C" {
-			static mut _stack_bottom: usize;
-			static mut _stack_len: usize;
+			static mut __sheap: usize;
+			static mut _stack_start: usize;
 		}
+		let stack_len = unsafe {
+			(&_stack_start as *const usize as usize) - (&__sheap as *const usize as usize)
+		};
 		// But not the top 64 words, because we're using the stack right now!
 		let stack = unsafe {
 			core::slice::from_raw_parts_mut(
-				&mut _stack_bottom as *mut usize,
-				(&mut _stack_len as *const _ as usize / core::mem::size_of::<usize>()) - 256,
+				&mut __sheap as *mut usize,
+				(stack_len / core::mem::size_of::<usize>()) - 256,
 			)
 		};
 		info!("Painting {:?}", stack.as_ptr_range());
@@ -2120,17 +2126,21 @@ fn IO_IRQ_BANK0() {
 #[cfg(feature = "check-stack")]
 fn check_stacks() {
 	extern "C" {
-		static _stack_bottom: usize;
-		static _stack_len: usize;
-		static _core1_stack_bottom: usize;
-		static _core1_stack_len: usize;
+		static mut __sheap: usize;
+		static mut _stack_start: usize;
 	}
-	let p = unsafe { &_stack_bottom as *const usize };
-	let total_bytes = unsafe { &_stack_len as *const usize as usize };
-	check_stack(p, total_bytes, CORE0_STACK_PAINT_WORD);
-	let p = unsafe { &_core1_stack_bottom as *const usize };
-	let total_bytes = unsafe { &_core1_stack_len as *const usize as usize };
-	check_stack(p, total_bytes, CORE1_STACK_PAINT_WORD);
+	let stack_len =
+		unsafe { (&_stack_start as *const usize as usize) - (&__sheap as *const usize as usize) };
+	check_stack(
+		unsafe { &__sheap as *const usize },
+		stack_len,
+		CORE0_STACK_PAINT_WORD,
+	);
+	check_stack(
+		unsafe { CORE1_STACK.as_ptr() },
+		unsafe { CORE1_STACK.len() * core::mem::size_of::<usize>() },
+		CORE1_STACK_PAINT_WORD,
+	);
 }
 
 /// Dummy stack checker that does nothing

src/vga/mod.rs

@@ -1027,33 +1027,30 @@ pub fn init(
 	// cannot be reconfigured at a later time, but they do keep on running
 	// as-is.
 
-	let core1_stack: &'static mut [usize] = unsafe {
-		extern "C" {
-			static mut _core1_stack_bottom: usize;
-			static mut _core1_stack_len: usize;
+	unsafe {
+		for b in super::CORE1_STACK.iter_mut() {
+			*b = super::CORE1_STACK_PAINT_WORD;
 		}
-		core::slice::from_raw_parts_mut(
-			&mut _core1_stack_bottom as *mut _,
-			&mut _core1_stack_len as *const _ as usize / core::mem::size_of::<usize>(),
-		)
-	};
-
-	for b in core1_stack.iter_mut() {
-		*b = super::CORE1_STACK_PAINT_WORD;
 	}
 
 	debug!(
 		"Core 1 stack: {:08x}, {} bytes",
-		core1_stack.as_ptr(),
-		core1_stack.len()
+		unsafe { super::CORE1_STACK.as_ptr() },
+		unsafe { super::CORE1_STACK.len() * core::mem::size_of::<usize>() }
 	);
 
 	// No-one else is looking at this right now.
 	unsafe {
 		TEXT_COLOUR_LOOKUP.init(&VIDEO_PALETTE);
 	}
 
-	multicore_launch_core1_with_stack(core1_main, core1_stack, ppb, fifo, psm);
+	multicore_launch_core1_with_stack(
+		core1_main,
+		unsafe { &mut super::CORE1_STACK },
+		ppb,
+		fifo,
+		psm,
+	);
 
 	debug!("Core 1 running");
 }