From a02d8e57101ba643c1b9978663cd43cea3caa85a Mon Sep 17 00:00:00 2001
From: Itamar <itamar8910@gmail.com>
Date: Mon, 20 Dec 2021 22:37:19 +0200
Subject: [PATCH] LibDebug: Add optional setup_child() callback to debugger

If set, this callback gets called right after fork() in the child
process.

It can be used by the caller if it wants to perform some logic in the
child process before it starts executing the debuggee program.
---
 Userland/Libraries/LibDebug/DebugSession.cpp | 12 +++++++++++-
 Userland/Libraries/LibDebug/DebugSession.h   |  3 ++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibDebug/DebugSession.cpp b/Userland/Libraries/LibDebug/DebugSession.cpp
index 487132c2d2..b715a1620d 100644
--- a/Userland/Libraries/LibDebug/DebugSession.cpp
+++ b/Userland/Libraries/LibDebug/DebugSession.cpp
@@ -53,7 +53,9 @@ void DebugSession::for_each_loaded_library(Function<IterationDecision(LoadedLibr
     }
 }
 
-OwnPtr<DebugSession> DebugSession::exec_and_attach(String const& command, String source_root)
+OwnPtr<DebugSession> DebugSession::exec_and_attach(String const& command,
+    String source_root,
+    Function<ErrorOr<void>()> setup_child)
 {
     auto pid = fork();
 
@@ -63,6 +65,14 @@ OwnPtr<DebugSession> DebugSession::exec_and_attach(String const& command, String
     }
 
     if (!pid) {
+
+        if (setup_child) {
+            if (setup_child().is_error()) {
+                perror("DebugSession::setup_child");
+                exit(1);
+            }
+        }
+
         if (ptrace(PT_TRACE_ME, 0, 0, 0) < 0) {
             perror("PT_TRACE_ME");
             exit(1);
diff --git a/Userland/Libraries/LibDebug/DebugSession.h b/Userland/Libraries/LibDebug/DebugSession.h
index 0949ca47f7..eaffaa82c4 100644
--- a/Userland/Libraries/LibDebug/DebugSession.h
+++ b/Userland/Libraries/LibDebug/DebugSession.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Demangle.h>
+#include <AK/Function.h>
 #include <AK/HashMap.h>
 #include <AK/NonnullRefPtr.h>
 #include <AK/Optional.h>
@@ -26,7 +27,7 @@ namespace Debug {
 
 class DebugSession : public ProcessInspector {
 public:
-    static OwnPtr<DebugSession> exec_and_attach(String const& command, String source_root = {});
+    static OwnPtr<DebugSession> exec_and_attach(String const& command, String source_root = {}, Function<ErrorOr<void>()> setup_child = {});
 
     virtual ~DebugSession() override;