Kernel: Add procfs that contains only pids

kernel/CMakeLists.txt

@@ -24,6 +24,8 @@ set(KERNEL_SOURCES
 	kernel/FS/Ext2/Inode.cpp
 	kernel/FS/Inode.cpp
 	kernel/FS/Pipe.cpp
+	kernel/FS/ProcFS/FileSystem.cpp
+	kernel/FS/ProcFS/Inode.cpp
 	kernel/FS/RamFS/FileSystem.cpp
 	kernel/FS/RamFS/Inode.cpp
 	kernel/FS/VirtualFileSystem.cpp

kernel/include/kernel/FS/ProcFS/FileSystem.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <kernel/FS/RamFS/FileSystem.h>
+#include <kernel/FS/RamFS/Inode.h>
+#include <kernel/Process.h>
+
+namespace Kernel
+{
+
+	class ProcFileSystem final : public RamFileSystem
+	{
+	public:
+		static void initialize();
+		static ProcFileSystem& get();
+
+		BAN::ErrorOr<void> on_process_create(Process&);
+		void on_process_delete(Process&);
+
+	private:
+		ProcFileSystem(size_t size);
+
+	private:
+		BAN::RefPtr<RamDirectoryInode> m_root_inode;
+	};
+
+}

kernel/include/kernel/FS/ProcFS/Inode.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <kernel/FS/RamFS/FileSystem.h>
+#include <kernel/FS/RamFS/Inode.h>
+#include <kernel/Process.h>
+
+namespace Kernel
+{
+
+	class ProcPidInode final : public RamDirectoryInode
+	{
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<ProcPidInode>> create(Process&, RamFileSystem&, mode_t, uid_t, gid_t);
+		~ProcPidInode() = default;
+
+	private:
+		ProcPidInode(Process&, RamFileSystem&, const FullInodeInfo&);
+
+	private:
+		Process& m_process;
+	};
+
+}

kernel/kernel/FS/ProcFS/FileSystem.cpp

@@ -0,0 +1,46 @@
+#include <kernel/FS/ProcFS/FileSystem.h>
+#include <kernel/FS/ProcFS/Inode.h>
+#include <kernel/FS/RamFS/Inode.h>
+#include <kernel/LockGuard.h>
+
+namespace Kernel
+{
+
+	static ProcFileSystem* s_instance = nullptr;
+
+	void ProcFileSystem::initialize()
+	{
+		ASSERT(s_instance == nullptr);
+		s_instance = new ProcFileSystem(1024 * 1024);
+		ASSERT(s_instance);
+
+		s_instance->m_root_inode = MUST(RamDirectoryInode::create(*s_instance, 0, 0555, 0, 0));
+		MUST(s_instance->set_root_inode(s_instance->m_root_inode));
+	}
+
+	ProcFileSystem& ProcFileSystem::get()
+	{
+		ASSERT(s_instance);
+		return *s_instance;
+	}
+
+	ProcFileSystem::ProcFileSystem(size_t size)
+		: RamFileSystem(size)
+	{
+	}
+
+	BAN::ErrorOr<void> ProcFileSystem::on_process_create(Process& process)
+	{
+		auto path = BAN::String::formatted("{}", process.pid());
+		auto inode = TRY(ProcPidInode::create(process, *this, 0555, 0, 0));
+		TRY(m_root_inode->add_inode(path, inode));
+		return {};
+	}
+
+	void ProcFileSystem::on_process_delete(Process& process)
+	{
+		auto path = BAN::String::formatted("{}", process.pid());
+		MUST(m_root_inode->delete_inode(path));
+	}
+
+}

kernel/kernel/FS/ProcFS/Inode.cpp

@@ -0,0 +1,26 @@
+#include <kernel/FS/ProcFS/Inode.h>
+
+namespace Kernel
+{
+
+	BAN::ErrorOr<BAN::RefPtr<ProcPidInode>> ProcPidInode::create(Process& process, RamFileSystem& fs, mode_t mode, uid_t uid, gid_t gid)
+	{
+		FullInodeInfo inode_info(fs, mode, uid, gid);
+
+		auto* inode_ptr = new ProcPidInode(process, fs, inode_info);
+		if (inode_ptr == nullptr)
+			return BAN::Error::from_errno(ENOMEM);
+		auto inode = BAN::RefPtr<ProcPidInode>::adopt(inode_ptr);
+
+		TRY(inode->add_inode("meminfo"sv, MUST(ProcMemInode::create(process, fs, 0755, 0, 0))));
+
+		return inode;
+	}
+
+	ProcPidInode::ProcPidInode(Process& process, RamFileSystem& fs, const FullInodeInfo& inode_info)
+		: RamDirectoryInode(fs, inode_info, fs.root_inode()->ino())
+		, m_process(process)
+	{
+	}
+
+}

kernel/kernel/FS/VirtualFileSystem.cpp

@@ -2,6 +2,7 @@
 #include <BAN/StringView.h>
 #include <kernel/FS/DevFS/FileSystem.h>
 #include <kernel/FS/Ext2/FileSystem.h>
+#include <kernel/FS/ProcFS/FileSystem.h>
 #include <kernel/FS/RamFS/FileSystem.h>
 #include <kernel/FS/RamFS/Inode.h>
 #include <kernel/FS/VirtualFileSystem.h>
@@ -28,6 +29,8 @@ namespace Kernel
 		Credentials root_creds { 0, 0, 0, 0 };
 		MUST(s_instance->mount(root_creds, &DevFileSystem::get(), "/dev"sv));
 
+		MUST(s_instance->mount(root_creds, &ProcFileSystem::get(), "/proc"sv));
+
 		auto* tmpfs = MUST(RamFileSystem::create(1024 * 1024, 0777, 0, 0));
 		MUST(s_instance->mount(root_creds, tmpfs, "/tmp"sv));
 	}

kernel/kernel/Process.cpp

@@ -2,6 +2,7 @@
 #include <BAN/StringView.h>
 #include <kernel/CriticalScope.h>
 #include <kernel/FS/DevFS/FileSystem.h>
+#include <kernel/FS/ProcFS/FileSystem.h>
 #include <kernel/FS/VirtualFileSystem.h>
 #include <kernel/IDT.h>
 #include <kernel/InterruptController.h>
@@ -81,6 +82,8 @@ namespace Kernel
 		auto* process = new Process(credentials, pid, parent, sid, pgrp);
 		ASSERT(process);
 
+		MUST(ProcFileSystem::get().on_process_create(*process));
+
 		return process;
 	}
 
@@ -194,6 +197,8 @@ namespace Kernel
 				s_processes.remove(i);
 		s_process_lock.unlock();
 
+		ProcFileSystem::get().on_process_delete(*this);
+
 		m_lock.lock();
 		m_exit_status.exited = true;
 		while (m_exit_status.waiting > 0)

kernel/kernel/kernel.cpp

@@ -2,6 +2,7 @@
 #include <kernel/Arch.h>
 #include <kernel/Debug.h>
 #include <kernel/FS/DevFS/FileSystem.h>
+#include <kernel/FS/ProcFS/FileSystem.h>
 #include <kernel/FS/VirtualFileSystem.h>
 #include <kernel/GDT.h>
 #include <kernel/IDT.h>
@@ -131,6 +132,9 @@ extern "C" void kernel_main()
 	DevFileSystem::initialize();
 	dprintln("devfs initialized");
 
+	ProcFileSystem::initialize();
+	dprintln("procfs initialized");
+
 	if (Serial::has_devices())
 	{
 		Serial::initialize_devices();