Split BPF loader to match the rest of the programs (#4636)

programs/bpf_loader_api/src/allocator_system.rs

@@ -0,0 +1,40 @@
+use crate::alloc;
+
+use alloc::{Alloc, AllocErr};
+use std::alloc::{self as system_alloc, Layout};
+
+#[derive(Debug)]
+pub struct BPFAllocator {
+    allocated: usize,
+    size: usize,
+}
+
+impl BPFAllocator {
+    pub fn new(heap: Vec<u8>) -> Self {
+        Self {
+            allocated: 0,
+            size: heap.len(),
+        }
+    }
+}
+
+impl Alloc for BPFAllocator {
+    fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr> {
+        if self.allocated + layout.size() <= self.size {
+            let ptr = unsafe { system_alloc::alloc(layout) };
+            if !ptr.is_null() {
+                self.allocated += layout.size();
+                return Ok(ptr);
+            }
+        }
+        Err(AllocErr)
+    }
+
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
+    fn dealloc(&mut self, ptr: *mut u8, layout: Layout) {
+        self.allocated -= layout.size();
+        unsafe {
+            system_alloc::dealloc(ptr, layout);
+        }
+    }
+}