Extracted step-by-step inspection into own function

src/main.rs

@@ -1,63 +1,48 @@
 mod child;
 
-use nix::libc::user_regs_struct;
 use nix::sys::ptrace::*;
-use nix::sys::wait::waitpid;
-use nix::unistd::{fork, ForkResult};
+use nix::sys::wait::{waitpid, WaitStatus};
+use nix::unistd::{fork, ForkResult, Pid};
 use std::ffi::CString;
 use std::process::ExitCode;
 
+fn single_step_all(child_pid: Pid) -> ExitCode {
+    let mut instruction_number = 0;
+    loop {
+        let wait_status = waitpid(child_pid, None);
+        match wait_status {
+            Ok(WaitStatus::Stopped(_, _)) => {
+                instruction_number += 1;
+                let regs = getregs(child_pid).unwrap();
+                println!(
+                    "🔎 [==> {}] rip= 0x{:016X}, rax = 0x{rax:X} ({rax})",
+                    instruction_number,
+                    regs.rip,
+                    rax = regs.rax
+                );
+                step(child_pid, None).unwrap();
+            }
+            Ok(WaitStatus::Exited(_, exit_code)) => {
+                println!("👋 Child exited with code {exit_code}");
+                return ExitCode::SUCCESS;
+            }
+            other => {
+                println!("⚠️ Other (unexpected) wait status: {other:?}");
+                return ExitCode::FAILURE;
+            }
+        }
+    }
+}
+
 fn main() -> ExitCode {
     let child_exec_path = CString::new(env!("TEST_PROG_PATH")).unwrap();
 
     match unsafe { fork() } {
         Ok(ForkResult::Child) => child::starti(child_exec_path),
         Ok(ForkResult::Parent { child: child_pid }) => {
-            println!("✔️ Started child {child_pid}");
-
-            let mut before_instruction = 0;
-            loop {
-                use nix::sys::signal::Signal::*;
-                use nix::sys::wait::WaitStatus::*;
-                match waitpid(child_pid, None) {
-                    Err(e) => {
-                        println!("❌ Wait failed: {e}");
-                        return ExitCode::FAILURE;
-                    }
-                    Ok(status) => match status {
-                        Exited(_pid, exit_code) => {
-                            println!("👋 Child exited with code {exit_code}");
-                            return ExitCode::SUCCESS;
-                        }
-                        Signaled(_, signal, _) => match signal {
-                            SIGKILL => {
-                                println!("💀 Child killed by SIGKILL");
-                                return ExitCode::SUCCESS;
-                            }
-                            s => println!("💡 Child received signal {s:?}"),
-                        },
-                        Stopped(_pid, _signal) => {
-                            let regs = getregs(child_pid).unwrap();
-                            println!(
-                                "🔎 [{}] rip= 0x{:016X}, rax = 0x{rax:X} ({rax})",
-                                before_instruction,
-                                regs.rip,
-                                rax = regs.rax
-                            );
-                            if regs.rax == 60 {
-                                println!("Let's change a register!");
-                                let new_regs = user_regs_struct { rdi: 54, ..regs };
-                                setregs(child_pid, new_regs).unwrap();
-                            }
-                            before_instruction += 1;
-                            step(child_pid, None).unwrap();
-                        }
-                        status => {
-                            println!("⚠️ Other (unexpected) wait status: {status:?}");
-                        }
-                    },
-                }
-            }
+            println!("✔️ Created child {child_pid}");
+            return single_step_all(child_pid);
+            // todo!("Something interesting");
         }
         Err(e) => {
             println!("❌ Fork failed: {e}");