Kernel: Resolve clang-tidy readability-make-member-function-const

... In files included from Kernel/Thread.cpp or Kernel/Process.cpp

Some places the warning is suppressed, because we do not want a const
object do have non-const access to the returned sub-object.

Kernel/Arch/x86/DescriptorTable.h

@@ -160,7 +160,7 @@ struct [[gnu::packed]] IDTEntry
     {
     }
 
-    FlatPtr off()
+    FlatPtr off() const
     {
 #if ARCH(I386)
         return (u32)offset_2 << 16 & (u32)offset_1;
@@ -168,7 +168,7 @@ struct [[gnu::packed]] IDTEntry
         return (u64)offset_3 << 32 & (u64)offset_2 << 16 & (u64)offset_1;
 #endif
     }
-    IDTEntryType type()
+    IDTEntryType type() const
     {
         return IDTEntryType(type_attr.gate_type);
     }

Kernel/Arch/x86/IO.h

@@ -93,7 +93,7 @@ public:
     }
 
     template<typename T>
-    ALWAYS_INLINE void out(T value)
+    ALWAYS_INLINE void out(T value) const
     {
         static_assert(sizeof(T) <= 4);
         if constexpr (sizeof(T) == 4) {
@@ -111,7 +111,7 @@ public:
         VERIFY_NOT_REACHED();
     }
 
-    inline void out(u32 value, u8 bit_width)
+    inline void out(u32 value, u8 bit_width) const
     {
         if (bit_width == 32) {
             IO::out32(get(), value);

Kernel/Arch/x86/PageDirectory.h

@@ -77,7 +77,7 @@ private:
 
 class PageTableEntry {
 public:
-    PhysicalPtr physical_page_base() { return PhysicalAddress::physical_page_base(m_raw); }
+    PhysicalPtr physical_page_base() const { return PhysicalAddress::physical_page_base(m_raw); }
     void set_physical_page_base(PhysicalPtr value)
     {
         m_raw &= 0x8000000000000fffULL;

Kernel/Arch/x86/Processor.h

@@ -120,12 +120,12 @@ public:
     void detect_hypervisor();
     void detect_hypervisor_hyperv(CPUID const& hypervisor_leaf_range);
 
-    void idle_begin()
+    void idle_begin() const
     {
         s_idle_cpu_mask.fetch_or(1u << m_cpu, AK::MemoryOrder::memory_order_relaxed);
     }
 
-    void idle_end()
+    void idle_end() const
     {
         s_idle_cpu_mask.fetch_and(~(1u << m_cpu), AK::MemoryOrder::memory_order_relaxed);
     }

Kernel/FileSystem/FileSystem.h

@@ -78,7 +78,7 @@ private:
     bool m_readonly { false };
 };
 
-inline FileSystem* InodeIdentifier::fs()
+inline FileSystem* InodeIdentifier::fs() // NOLINT(readability-make-member-function-const) const InodeIdentifiers should not be able to modify the FileSystem
 {
     return FileSystem::from_fsid(m_fsid);
 }

Kernel/FileSystem/SysFS.h

@@ -34,7 +34,7 @@ class SysFSDeviceComponent final
 public:
     static NonnullRefPtr<SysFSDeviceComponent> must_create(Device const&);
 
-    bool is_block_device() { return m_block_device; }
+    bool is_block_device() const { return m_block_device; }
 
 private:
     explicit SysFSDeviceComponent(Device const&);

Kernel/PhysicalAddress.h

@@ -38,8 +38,9 @@ public:
 
     [[nodiscard]] bool is_null() const { return m_address == 0; }
 
+    // NOLINTNEXTLINE(readability-make-member-function-const) const PhysicalAddress shouldn't be allowed to modify the underlying memory
     [[nodiscard]] u8* as_ptr() { return reinterpret_cast<u8*>(m_address); }
-    [[nodiscard]] const u8* as_ptr() const { return reinterpret_cast<const u8*>(m_address); }
+    [[nodiscard]] const u8* as_ptr() const { return reinterpret_cast<u8 const*>(m_address); }
 
     [[nodiscard]] PhysicalAddress page_base() const { return PhysicalAddress(physical_page_base(m_address)); }
     [[nodiscard]] PhysicalPtr offset_in_page() const { return PhysicalAddress(m_address & 0xfff).get(); }

Kernel/Process.cpp

@@ -502,7 +502,7 @@ Time kgettimeofday()
     return TimeManagement::now();
 }
 
-siginfo_t Process::wait_info()
+siginfo_t Process::wait_info() const
 {
     siginfo_t siginfo {};
     siginfo.si_signo = SIGCHLD;
@@ -889,7 +889,7 @@ static constexpr StringView to_string(Pledge promise)
     VERIFY_NOT_REACHED();
 }
 
-void Process::require_no_promises()
+void Process::require_no_promises() const
 {
     if (!has_promises())
         return;

Kernel/Process.h

@@ -421,7 +421,7 @@ public:
     static void initialize();
 
     [[noreturn]] void crash(int signal, FlatPtr ip, bool out_of_memory = false);
-    [[nodiscard]] siginfo_t wait_info();
+    [[nodiscard]] siginfo_t wait_info() const;
 
     const TTY* tty() const { return m_tty; }
     void set_tty(TTY*);
@@ -509,7 +509,7 @@ public:
     VirtualAddress signal_trampoline() const { return m_protected_values.signal_trampoline; }
 
     void require_promise(Pledge);
-    void require_no_promises();
+    void require_no_promises() const;
 
 private:
     friend class MemoryManager;

Kernel/Thread.cpp

@@ -445,12 +445,14 @@ void Thread::relock_process(LockMode previous_locked, u32 lock_count_to_restore)
     }
 }
 
+// NOLINTNEXTLINE(readability-make-member-function-const) False positive; We call block<SleepBlocker> which is not const
 auto Thread::sleep(clockid_t clock_id, const Time& duration, Time* remaining_time) -> BlockResult
 {
     VERIFY(state() == Thread::Running);
     return Thread::current()->block<Thread::SleepBlocker>({}, Thread::BlockTimeout(false, &duration, nullptr, clock_id), remaining_time);
 }
 
+// NOLINTNEXTLINE(readability-make-member-function-const) False positive; We call block<SleepBlocker> which is not const
 auto Thread::sleep_until(clockid_t clock_id, const Time& deadline) -> BlockResult
 {
     VERIFY(state() == Thread::Running);

Kernel/VirtualAddress.h

@@ -37,6 +37,7 @@ public:
     bool operator==(const VirtualAddress& other) const { return m_address == other.m_address; }
     bool operator!=(const VirtualAddress& other) const { return m_address != other.m_address; }
 
+    // NOLINTNEXTLINE(readability-make-member-function-const) const VirtualAddress shouldn't be allowed to modify the underlying memory
     [[nodiscard]] u8* as_ptr() { return reinterpret_cast<u8*>(m_address); }
     [[nodiscard]] const u8* as_ptr() const { return reinterpret_cast<const u8*>(m_address); }