Add adjustable stack size and call depth (#12728)

programs/bpf/rust/call_depth/src/lib.rs

@@ -0,0 +1,27 @@
+//! @brief Example Rust-based BPF program that tests call depth and stack usage
+
+use solana_sdk::{entrypoint::SUCCESS, info};
+
+#[inline(never)]
+pub fn recurse(data: &mut [u8]) {
+    if data.len() <= 1 {
+        return;
+    }
+    recurse(&mut data[1..]);
+    info!(line!(), 0, 0, 0, data[0]);
+}
+
+/// # Safety
+#[inline(never)]
+#[no_mangle]
+pub unsafe extern "C" fn entrypoint(input: *mut u8) -> u64 {
+    info!("Call depth");
+    let depth = *(input.add(16) as *mut u8);
+    info!(line!(), 0, 0, 0, depth);
+    let mut data = Vec::with_capacity(depth as usize);
+    for i in 0_u8..depth {
+        data.push(i);
+    }
+    recurse(&mut data);
+    SUCCESS
+}