actually fix bugs.

Author: thomasw04

machine/arm/src/sched.rs

@@ -60,9 +60,9 @@ pub struct ArmStack {
     /// The top of the stack (highest address).
     /// Safety: NonNull<u32> can safely be covariant over u32.
     top: NonNull<u32>,
-    /// The current offset from the top of the stack (in 4 byte steps).
+    /// The current offset from the top of the stack
     sp: StackPtr,
-    /// The size of the stack (in 4 byte steps).
+    /// The size of the stack
     size: NonZero<usize>,
 }
 
@@ -161,15 +161,10 @@ impl ArmStack {
             Self::push(&mut write_index, EXEC_RETURN_THREAD_PSP);
 
             // R12 (dummy), R11 - R10
-            for _ in 0..3 {
+            for _ in 0..4 {
                 Self::push(&mut write_index, 0);
             }
 
-            // R9, fixed
-            let r9: u32;
-            core::arch::asm!("mov {}, r9", out(reg) r9);
-            Self::push(&mut write_index, r9);
-
             // R8 - R4
             for _ in 0..5 {
                 Self::push(&mut write_index, 0);
@@ -224,7 +219,7 @@ impl hal_api::stack::Stacklike for ArmStack {
         Err(hal_api::Error::OutOfBoundsPtr(
             ptr as usize,
             Range {
-                start: self.top.as_ptr() as usize - self.size.get() * size_of::<u32>(),
+                start: self.top.as_ptr() as usize - self.size.get(),
                 end: self.top.as_ptr() as usize,
             },
         ))