scx_arena, scx_wd40: remove Rust 1.91 warnings

rust/scx_arena/scx_arena/src/arenalib.rs

@@ -119,7 +119,11 @@ impl<'a> ArenaLib<'a> {
             );
         }
 
-        let ptr = unsafe { std::mem::transmute::<u64, &mut [u64; MAX_CPU_SUPPORTED]>(args.bitmap) };
+        let ptr = unsafe {
+            &mut *std::ptr::with_exposed_provenance_mut::<[u64; 640]>(
+                args.bitmap.try_into().unwrap(),
+            )
+        };
 
         let (valid_mask, _) = ptr.split_at_mut(mask.len());
         valid_mask.clone_from_slice(mask);

rust/scx_arena/selftests/src/main.rs

@@ -92,7 +92,9 @@ fn setup_topology_node(skel: &mut BpfSkel<'_>, mask: &[u64]) -> Result<()> {
         );
     }
 
-    let ptr = unsafe { std::mem::transmute::<u64, &mut [u64; 10]>(args.bitmap) };
+    let ptr = unsafe {
+        &mut *std::ptr::with_exposed_provenance_mut::<[u64; 10]>(args.bitmap.try_into().unwrap())
+    };
 
     let (valid_mask, _) = ptr.split_at_mut(mask.len());
     valid_mask.clone_from_slice(mask);

scheds/rust/scx_wd40/src/load_balance.rs

@@ -154,6 +154,8 @@ use crate::stats::DomainStats;
 use crate::stats::NodeStats;
 use crate::DomainGroup;
 
+use crate::types::dom_ctx;
+
 const DEFAULT_WEIGHT: f64 = bpf_intf::consts_LB_DEFAULT_WEIGHT as f64;
 const RAVG_FRAC_BITS: u32 = bpf_intf::ravg_consts_RAVG_FRAC_BITS;
 
@@ -629,7 +631,9 @@ impl<'a, 'b> LoadBalancer<'a, 'b> {
 
         let types::topo_level(index) = types::topo_level::TOPO_LLC;
         let ptr = self.skel.maps.bss_data.as_ref().unwrap().topo_nodes[index as usize][dom.id];
-        let dom_ctx = unsafe { std::mem::transmute::<u64, &mut types::dom_ctx>(ptr) };
+        let dom_ctx = unsafe {
+            &mut *std::ptr::with_exposed_provenance_mut::<dom_ctx>(ptr.try_into().unwrap())
+        };
         let active_tasks = &mut dom_ctx.active_tasks;
 
         let (mut ridx, widx) = (active_tasks.read_idx, active_tasks.write_idx);

scheds/rust/scx_wd40/src/main.rs

@@ -61,6 +61,8 @@ use scx_utils::Topology;
 use scx_utils::UserExitInfo;
 use scx_utils::NR_CPU_IDS;
 
+use crate::types::dom_ctx;
+
 const SCHEDULER_NAME: &str = "scx_wd40";
 const MAX_DOMS: usize = bpf_intf::consts_MAX_DOMS as usize;
 const MAX_CPUS: usize = bpf_intf::consts_MAX_CPUS as usize;
@@ -477,7 +479,9 @@ impl<'a> Scheduler<'a> {
             for dom in node_domains.iter() {
                 // XXX Remove this by using the topo node's cpumask.
                 let ptr = bss_data.topo_nodes[index as usize][dom.id()];
-                let domc = unsafe { std::mem::transmute::<u64, &mut types::dom_ctx>(ptr) };
+                let domc = unsafe {
+                    &mut *std::ptr::with_exposed_provenance_mut::<dom_ctx>(ptr.try_into().unwrap())
+                };
                 update_bpf_mask(domc.cpumask, &dom.mask())?;
 
                 bss_data.dom_numa_id_map[dom.id()] =
@@ -495,7 +499,9 @@ impl<'a> Scheduler<'a> {
             let mut ctx = dom.ctx.lock().unwrap();
 
             let ptr = skel.maps.bss_data.as_mut().unwrap().topo_nodes[index as usize][*id];
-            let domc = unsafe { std::mem::transmute::<u64, &mut types::dom_ctx>(ptr) };
+            let domc = unsafe {
+                &mut *std::ptr::with_exposed_provenance_mut::<dom_ctx>(ptr.try_into().unwrap())
+            };
             *ctx = Some(domc);
         }