Tiny sched-ext improvements

Author: parttimenerd

README.md

@@ -89,7 +89,8 @@ limactl shell hello-ebpf
 sudo -s PATH=$PATH
 ```
 
-The scheduler examples require a patched 6.11 kernel with the scheduler extensions, you can get it from 
+The scheduler examples require a 6.12+ kernel (install on ubuntu via the [mainline](https://github.com/bkw777/mainline) tool)
+or a patched 6.11 kernel with the scheduler extensions, you can get it from
 [here](https://launchpad.net/~arighi/+archive/ubuntu/sched-ext-unstable).
 You might also be able to run [CachyOS](https://cachyos.org/) and install a patched kernel from there.
 

bpf/src/main/java/me/bechberger/ebpf/bpf/BPFJ.java

@@ -125,6 +125,16 @@ public static void bpf_probe_read_kernel_str(char[] dest, String source) {
         throw new MethodIsBPFRelatedFunction();
     }
 
+    /**
+     * Read the source string from the kernel and write it to the destination
+     * @see BPFHelpers#bpf_probe_read_kernel_str(Ptr, int, Ptr)
+     */
+    @BuiltinBPFFunction("bpf_probe_read_kernel_str($arg1, sizeof($arg1), $arg2)")
+    @NotUsableInJava
+    public static void bpf_probe_read_kernel_str(String dest, char[] source) {
+        throw new MethodIsBPFRelatedFunction();
+    }
+
     /**
      * Read the source string from the kernel and write it to the destination
      * @see BPFHelpers#bpf_probe_read_kernel_str(Ptr, int, Ptr)

bpf/src/main/java/me/bechberger/ebpf/bpf/Scheduler.java

@@ -131,7 +131,7 @@
                 	       .disable         = (void *)simple_disable,
                 	       .stopping        = (void *)simple_stopping,
                 	       .dequeue         = (void *)simple_dequeue,
-                	       .tick            = (void *)sched_tick,
+                	       .tick            = (void *)simple_tick,
                 	       .flags			= SCX_OPS_ENQ_LAST | SCX_OPS_KEEP_BUILTIN_IDLE,
                 	       .name			= "__property_sched_name");
                 """
@@ -407,7 +407,7 @@ default void stopping(Ptr<TaskDefinitions.task_struct> p, boolean runnable) {
      * scheduling position not being updated across a priority change.
      */
     @BPFFunction(
-            headerTemplate = "void BPF_STRUCT_OPS(simple_dequeue, struct task_struct *p, u64 deq_flags)",
+            headerTemplate = "int BPF_STRUCT_OPS(simple_dequeue, struct task_struct *p, u64 deq_flags)",
             addDefinition = false
     )
     default void dequeue(Ptr<TaskDefinitions.task_struct> p, @Unsigned long deq_flags) {
@@ -422,7 +422,12 @@ default void dequeue(Ptr<TaskDefinitions.task_struct> p, @Unsigned long deq_flag
      * executing an SCX task. Setting {@code p->scx.slice} to 0 will trigger an
      * immediate dispatch cycle on the CPU.
      */
-    void tick(Ptr<TaskDefinitions.task_struct> p);
+    @BPFFunction(
+            headerTemplate = "int BPF_STRUCT_OPS(simple_tick, struct task_struct *p)",
+            addDefinition = false)
+    default void tick(Ptr<TaskDefinitions.task_struct> p) {
+        return;
+    }
 
     final int SCHED_EXT_UAPI_ID = 7;