From c3f668a758addcf80154d42e95a701edce4bbe59 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Fri, 6 Aug 2021 15:12:33 +0300
Subject: [PATCH] Kernel: Make Process's m_promises & m_execpromises fields
 atomic

This is essentially free on x86 and allows us to not hold the big
process lock just to check the required promises for a syscall.
---
 Kernel/Process.h           | 8 ++++----
 Kernel/Syscalls/execve.cpp | 4 ++--
 Kernel/Syscalls/fork.cpp   | 8 ++++----
 Kernel/Syscalls/pledge.cpp | 4 ++--
 4 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/Kernel/Process.h b/Kernel/Process.h
index a7deaef04e..9a197e5ce1 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -92,10 +92,10 @@ protected:
     gid_t m_sgid { 0 };
     Vector<gid_t> m_extra_gids;
     bool m_dumpable { false };
-    bool m_has_promises { false };
-    u32 m_promises { 0 };
-    bool m_has_execpromises { false };
-    u32 m_execpromises { 0 };
+    Atomic<bool> m_has_promises { false };
+    Atomic<u32> m_promises { 0 };
+    Atomic<bool> m_has_execpromises { false };
+    Atomic<u32> m_execpromises { 0 };
     mode_t m_umask { 022 };
     VirtualAddress m_signal_trampoline;
     Atomic<u32> m_thread_count { 0 };
diff --git a/Kernel/Syscalls/execve.cpp b/Kernel/Syscalls/execve.cpp
index ec4991a493..5ee3589dab 100644
--- a/Kernel/Syscalls/execve.cpp
+++ b/Kernel/Syscalls/execve.cpp
@@ -639,8 +639,8 @@ KResult Process::do_exec(NonnullRefPtr<FileDescription> main_program_description
 
     {
         ProtectedDataMutationScope scope { *this };
-        m_promises = m_execpromises;
-        m_has_promises = m_has_execpromises;
+        m_promises = m_execpromises.load();
+        m_has_promises = m_has_execpromises.load();
 
         m_execpromises = 0;
         m_has_execpromises = false;
diff --git a/Kernel/Syscalls/fork.cpp b/Kernel/Syscalls/fork.cpp
index 038d48b666..cab53f8a19 100644
--- a/Kernel/Syscalls/fork.cpp
+++ b/Kernel/Syscalls/fork.cpp
@@ -30,10 +30,10 @@ KResultOr<FlatPtr> Process::sys$fork(RegisterState& regs)
 
     {
         ProtectedDataMutationScope scope { *child };
-        child->m_promises = m_promises;
-        child->m_execpromises = m_execpromises;
-        child->m_has_promises = m_has_promises;
-        child->m_has_execpromises = m_has_execpromises;
+        child->m_promises = m_promises.load();
+        child->m_execpromises = m_execpromises.load();
+        child->m_has_promises = m_has_promises.load();
+        child->m_has_execpromises = m_has_execpromises.load();
         child->m_sid = m_sid;
         child->m_extra_gids = m_extra_gids;
         child->m_umask = m_umask;
diff --git a/Kernel/Syscalls/pledge.cpp b/Kernel/Syscalls/pledge.cpp
index 885b1317a1..f021f718b1 100644
--- a/Kernel/Syscalls/pledge.cpp
+++ b/Kernel/Syscalls/pledge.cpp
@@ -74,13 +74,13 @@ KResultOr<FlatPtr> Process::sys$pledge(Userspace<const Syscall::SC_pledge_params
     // leave the caller in an unexpected state.
 
     if (promises) {
-        m_has_promises = true;
         m_promises = new_promises;
+        m_has_promises = true;
     }
 
     if (execpromises) {
-        m_has_execpromises = true;
         m_execpromises = new_execpromises;
+        m_has_execpromises = true;
     }
 
     return 0;