checkpoint of tasks; gonna need cpu drivers

Signed-off-by: Amy Ringo <me@remexre.com>

Author: remexre

src/kernel/arch/riscv64/hart_locals.c

@@ -1,11 +1,13 @@
 /*
- * SPDX-FileCopyrightText: 2025 ukoOS Contributors
+ * SPDX-FileCopyrightText: 2025-2026 ukoOS Contributors
  *
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
 
 #include <arch/riscv64/insns.h>
 #include <hart_locals.h>
+#include <mm/alloc.h>
+#include <task.h>
 
 /**
  * Storage for the boothart's hart-locals.
@@ -16,13 +18,24 @@ struct hart_locals *get_hart_locals(void) {
   return (struct hart_locals *)csrr(RISCV64_CSR_SSCRATCH);
 }
 
-void init_boothart_hart_locals(u64 hart_id) {
+void init_boothart_hart_locals_early(u64 hart_id) {
   csrw(RISCV64_CSR_SSCRATCH, (u64)&boothart_hart_locals);
   boothart_hart_locals = (struct hart_locals){
       .hart_id = hart_id,
+      .task = nullptr,
       .heap = nullptr,
       .rng = {},
   };
 }
 
+void init_boothart_hart_locals_late(void) {
+  // Reallocate the hart-locals to be heap-allocated.
+  struct hart_locals *hart_locals = alloc(sizeof(struct hart_locals));
+  memcpy(hart_locals, &boothart_hart_locals, sizeof(struct hart_locals));
+  csrw(RISCV64_CSR_SSCRATCH, (u64)hart_locals);
+
+  // Create a task object for the current task.
+  hart_locals->task = alloc(sizeof(struct task));
+}
+
 void init_hart_locals(u64 hart_id);

src/kernel/arch/riscv64/include.mak

@@ -15,6 +15,7 @@ kernel-objs-c += arch/riscv64/panic
 kernel-objs-c += arch/riscv64/physical
 kernel-objs-c += arch/riscv64/random
 kernel-objs-c += arch/riscv64/sbi
+kernel-objs-c += arch/riscv64/task
 
 $(eval $(call compute_component_variables,kernel))
 

src/kernel/arch/riscv64/task.S

@@ -0,0 +1,17 @@
+/*
+ * SPDX-FileCopyrightText: 2026 ukoOS Contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+.section .text
+
+/**
+ * Switches tasks.
+ */
+.p2align 2
+.global switch_to_task
+.type switch_to_task, @function
+switch_to_task:
+	ebreak
+	ret

src/kernel/include.mak

@@ -49,7 +49,6 @@ kernel-objs-c += random
 kernel-objs-c += selftest
 kernel-objs-c += swar_test
 kernel-objs-c += symbolicate
-kernel-objs-c += task
 include $(srcdir)/src/kernel/drivers/include.mak
 
 # The architecture-specific file needs to be last, since it calls

src/kernel/include/hart_locals.h

@@ -18,6 +18,11 @@ struct hart_locals {
    */
   u64 hart_id;
 
+  /**
+   * The current task.
+   */
+  struct task *task;
+
   /**
    * The current heap.
    */
@@ -29,6 +34,10 @@ struct hart_locals {
   struct random_rng rng;
 };
 
+// Check that the layout that's assumed by assembly code.
+static_assert(offsetof(struct hart_locals, hart_id) == 0);
+static_assert(offsetof(struct hart_locals, task) == 8);
+
 /**
  * Returns a pointer to the current hart's locals.
  *
@@ -42,7 +51,14 @@ struct hart_locals *get_hart_locals(void);
  * This needs to be separate from `init_hart_locals`, because the allocator
  * won't be available yet.
  */
-void init_boothart_hart_locals(u64 hart_id);
+void init_boothart_hart_locals_early(u64 hart_id);
+
+/**
+ * Called during early boot to initialize the boothart's hart-local storage.
+ * This needs to be separate from `init_hart_locals`, because the allocator
+ * won't be available yet.
+ */
+void init_boothart_hart_locals_late(void);
 
 /**
  * Called during hart bring-up to allocate hart-local storage for a hart.

src/kernel/include/task.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 ukoOS Contributors
+ * SPDX-FileCopyrightText: 2025-2026 ukoOS Contributors
  *
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
@@ -80,4 +80,14 @@ struct task {
   u8 register_save[];
 };
 
+/**
+ * Allocates a new task struct and initializes it.
+ */
+struct task *task_new(void);
+
+/**
+ * TODO: This should require that a hartlock be held.
+ */
+void switch_to_task(struct task *task);
+
 #endif // UKO_OS_KERNEL__TASK_H

src/kernel/main.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 ukoOS Contributors
+ * SPDX-FileCopyrightText: 2025-2026 ukoOS Contributors
  *
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
@@ -25,8 +25,9 @@ void main(u64 hart_id, paddr devicetree_start, paddr kernel_start,
   symbolicate_init(symtab, symtab_len, strtab, strtab_len);
   entropy_pool_init();
   arch_entropy_pool_seed_early();
-  init_boothart_hart_locals(hart_id);
+  init_boothart_hart_locals_early(hart_id);
   mm_alloc_init();
+  init_boothart_hart_locals_late();
 
   // Parse the Devicetree.
   struct devicetree_node *devicetree = devicetree_parse_from_physical(

src/kernel/task.c

@@ -1 +0,0 @@
-#include <task.h>