Segmented Stack Tests

.github/workflows/actions/build/action.yaml

@@ -157,3 +157,19 @@ runs:
         category: task
         sub-category: unwind
         test-name: deferred_nested_drop
+
+    # *** Tests for task - segmented stack ***
+
+    - name: Build test test-task-segmented_stack-function_arguments
+      uses: ./.github/workflows/actions/build-test
+      with:
+        category: task
+        sub-category: segmented_stack
+        test-name: function_arguments
+
+    - name: Build test test-task-segmented_stack-return_values
+      uses: ./.github/workflows/actions/build-test
+      with:
+        category: task
+        sub-category: segmented_stack
+        test-name: return_values

.github/workflows/segmented_stack.yaml

@@ -0,0 +1,39 @@
+name: Run Tests for Segmented Stack
+
+on:
+  workflow_call:
+    secrets:
+      cookie:
+        required: true
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  function_arguments:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Run test function_arguments
+        uses: ./.github/workflows/actions/run-test
+        with:
+          cookie: ${{ secrets.cookie }}
+          category: task
+          sub-category: segmented_stack
+          test-name: function_arguments
+
+  return_values:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Run test return_values
+        uses: ./.github/workflows/actions/run-test
+        with:
+          cookie: ${{ secrets.cookie }}
+          category: task
+          sub-category: segmented_stack
+          test-name: return_values

.github/workflows/task.yaml

@@ -19,3 +19,8 @@ jobs:
     uses: ./.github/workflows/unwind.yaml
     secrets:
       cookie: ${{ secrets.cookie }}
+
+  segmented_stack:
+    uses: ./.github/workflows/segmented_stack.yaml
+    secrets:
+      cookie: ${{ secrets.cookie }}

Cargo.toml

@@ -133,3 +133,15 @@ path = "examples/tests/task/unwind/deferred_indirect_drop.rs"
 [[example]]
 name = "test-task-unwind-deferred_nested_drop"
 path = "examples/tests/task/unwind/deferred_nested_drop.rs"
+
+[[example]]
+name = "test-task-segmented_stack-function_arguments"
+path = "examples/tests/task/segmented_stack/function_arguments.rs"
+
+[[example]]
+name = "test-task-segmented_stack-nested_functions"
+path = "examples/tests/task/segmented_stack/nested_functions.rs"
+
+[[example]]
+name = "test-task-segmented_stack-return_values"
+path = "examples/tests/task/segmented_stack/return_values.rs"

examples/tests/task/segmented_stack/function_arguments.rs

@@ -0,0 +1,133 @@
+//! Test function arguments passing via both registers and the stack when a new
+//! stacklet is allocated for a function call.
+
+#![no_std]
+#![no_main]
+#![feature(naked_functions)]
+
+extern crate alloc;
+use core::arch::asm;
+use hopter::{boot::main, debug::semihosting, hprintln, task};
+
+#[naked]
+extern "C" fn prepare_regs_stack() {
+    unsafe {
+        asm!(
+            // Segmented stack prologue.
+            // Stacklet allocation size 36, 20 for preserved values plus 16 for
+            // stack arguments.
+            // Stack argument size 0.
+            "mov.w  r12, #0x20000000",
+            "ldr.w  r12, [r12]",
+            "subs.w r12, sp, r12",
+            "cmp.w  r12, #36",
+            "bge.n  0f",
+            "svc    #255",
+            ".short 9",
+            ".short 0",
+
+            // Preserve callee-saved registers and return address.
+            "0:",
+            "push {{r4-r7, lr}}",
+
+            // Prepare arguments in registers r0-r3.
+            "mov r0, #1",
+            "mov r1, #2",
+            "mov r2, #3",
+            "mov r3, #4",
+
+            // Prepare arguments on stack.
+            "mov r4, #5",
+            "mov r5, #6",
+            "mov r6, #7",
+            "mov r7, #8",
+            "push {{r4-r7}}",
+
+            // Call `verify_arguments` function.
+            "bl {verify_arguments}",
+
+            // Discard stack arguments.
+            "add sp, #16",
+
+            // Restore callee-saved registers and return.
+            "pop {{r4-r7, pc}}",
+
+            verify_arguments = sym verify_arguments,
+            options(noreturn)
+        )
+    }
+}
+
+#[naked]
+extern "C" fn verify_arguments() {
+    unsafe {
+        asm!(
+            // Segmented stack prologue. Request a huge stack frame of size
+            // 16384 bytes, which will very likely cause a new stacklet
+            // allocation.
+            //
+            // Stacklet allocation size 16384.
+            // Stack argument size 16.
+            "mov.w  r12, #0x20000000",
+            "ldr.w  r12, [r12]",
+            "subs.w r12, sp, r12",
+            "cmp.w  r12, #16384",
+            "bge.n  0f",
+            "svc    #255",
+            ".short 4096",
+            ".short 4",
+
+            "0:",
+            // Verify register arguments.
+            "cmp r0, #1",
+            "bne {error}",
+            "cmp r1, #2",
+            "bne {error}",
+            "cmp r2, #3",
+            "bne {error}",
+            "cmp r3, #4",
+            "bne {error}",
+
+            // Verify stack arguments.
+            "ldr r0, [sp, #0]",
+            "cmp r0, #5",
+            "bne {error}",
+            "ldr r0, [sp, #4]",
+            "cmp r0, #6",
+            "bne {error}",
+            "ldr r0, [sp, #8]",
+            "cmp r0, #7",
+            "bne {error}",
+            "ldr r0, [sp, #12]",
+            "cmp r0, #8",
+            "bne {error}",
+
+            // Print success message.
+            // This also tests tail call optimization.
+            "b   {success}",
+
+            error = sym error,
+            success = sym success,
+            options(noreturn)
+        )
+    }
+}
+
+extern "C" fn success() {
+    hprintln!("Test Passed");
+}
+
+extern "C" fn error() {
+    hprintln!("Test Failed");
+    semihosting::terminate(false);
+}
+
+#[main]
+fn main(_: cortex_m::Peripherals) {
+    task::build()
+        .set_entry(|| prepare_regs_stack())
+        .spawn()
+        .unwrap();
+    task::change_current_priority(10).unwrap();
+    semihosting::terminate(true);
+}

examples/tests/task/segmented_stack/function_arguments.txt

@@ -0,0 +1 @@
+Test Passed

examples/tests/task/segmented_stack/return_values.rs

@@ -0,0 +1,106 @@
+//! Test function return values via registers.
+//!
+//! FIXME: Does return value ever get passed through stack?
+
+#![no_std]
+#![no_main]
+#![feature(naked_functions)]
+
+extern crate alloc;
+use core::arch::asm;
+use hopter::{boot::main, debug::semihosting, hprintln, task};
+
+#[naked]
+extern "C" fn callee() {
+    unsafe {
+        asm!(
+            // Segmented stack prologue. Request a huge stack frame of size
+            // 16384 bytes, which will very likely cause a new stacklet
+            // allocation.
+            //
+            // Stacklet allocation size 16384.
+            // Stack argument size 16.
+            "mov.w  r12, #0x20000000",
+            "ldr.w  r12, [r12]",
+            "subs.w r12, sp, r12",
+            "cmp.w  r12, #16384",
+            "bge.n  0f",
+            "svc    #255",
+            ".short 4096",
+            ".short 4",
+            "0:",
+            // Set r0-r3 to known values as the return values.
+            "mov r0, #25",
+            "mov r1, #26",
+            "mov r2, #27",
+            "mov r3, #28",
+            // Return.
+            "bx lr",
+            options(noreturn)
+        )
+    }
+}
+
+#[naked]
+extern "C" fn caller() {
+    unsafe {
+        asm!(
+            // Segmented stack prologue.
+            // Stacklet allocation size 4 for preserved return address.
+            // stack arguments.
+            // Stack argument size 0.
+            "mov.w  r12, #0x20000000",
+            "ldr.w  r12, [r12]",
+            "subs.w r12, sp, r12",
+            "cmp.w  r12, #4",
+            "bge.n  0f",
+            "svc    #255",
+            ".short 1",
+            ".short 0",
+
+            "0:",
+            // Preserve return address.
+            "push {{lr}}",
+
+            // Call the callee function.
+            "bl {callee}",
+
+            // verify return values in registers r0-r3
+            "cmp r0, #25",
+            "bne {error}",
+            "cmp r1, #26",
+            "bne {error}",
+            "cmp r2, #27",
+            "bne {error}",
+            "cmp r3, #28",
+            "bne {error}",
+
+            // Print success message.
+            "bl {success}",
+
+            // Return.
+            "pop {{pc}}",
+
+            callee = sym callee,
+            error = sym error,
+            success = sym success,
+            options(noreturn)
+        )
+    }
+}
+
+extern "C" fn success() {
+    hprintln!("Test Passed");
+}
+
+extern "C" fn error() {
+    hprintln!("Test Failed");
+    semihosting::terminate(false);
+}
+
+#[main]
+fn main(_: cortex_m::Peripherals) {
+    task::build().set_entry(|| caller()).spawn().unwrap();
+    task::change_current_priority(10).unwrap();
+    semihosting::terminate(true);
+}

examples/tests/task/segmented_stack/return_values.txt

@@ -0,0 +1 @@
+Test Passed