From a511441f7e2f055048443d9f4773f7733bd0ab48 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Sat, 30 Sep 2023 21:20:18 +0300
Subject: [PATCH] Kernel: /proc/{pid}/meminfo now reports per process memory
 usage

---
 kernel/include/kernel/FS/ProcFS/Inode.h | 21 ++++++++++++++++
 kernel/include/kernel/Process.h         |  3 +++
 kernel/kernel/FS/ProcFS/Inode.cpp       | 32 +++++++++++++++++++++++++
 kernel/kernel/Process.cpp               | 15 ++++++++++++
 libc/include/sys/banan-os.h             |  9 +++++++
 5 files changed, 80 insertions(+)

diff --git a/kernel/include/kernel/FS/ProcFS/Inode.h b/kernel/include/kernel/FS/ProcFS/Inode.h
index 87226ba9..a71164c4 100644
--- a/kernel/include/kernel/FS/ProcFS/Inode.h
+++ b/kernel/include/kernel/FS/ProcFS/Inode.h
@@ -20,4 +20,25 @@ namespace Kernel
 		Process& m_process;
 	};
 
+	class ProcMemInode final : public RamInode
+	{
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<ProcMemInode>> create(Process&, RamFileSystem&, mode_t, uid_t, gid_t);
+		~ProcMemInode() = default;
+
+	protected:
+		virtual BAN::ErrorOr<size_t> read_impl(off_t, void*, size_t) override;
+
+		// You may not write here and this is always non blocking
+		virtual BAN::ErrorOr<size_t> write_impl(off_t, const void*, size_t)	override	{ return BAN::Error::from_errno(EINVAL); }
+		virtual BAN::ErrorOr<void> truncate_impl(size_t) override						{ return BAN::Error::from_errno(EINVAL); }
+		virtual bool has_data_impl() const override										{ return true; }
+
+	private:
+		ProcMemInode(Process&, RamFileSystem&, const FullInodeInfo&);
+	
+	private:
+		Process& m_process;
+	};
+
 }
diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 6e7b04bc..625d34c6 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -13,6 +13,7 @@
 #include <kernel/Terminal/TTY.h>
 #include <kernel/Thread.h>
 
+#include <sys/banan-os.h>
 #include <sys/mman.h>
 #include <termios.h>
 
@@ -138,6 +139,8 @@ namespace Kernel
 
 		PageTable& page_table() { return m_page_table ? *m_page_table : PageTable::kernel(); }
 
+		void get_meminfo(proc_meminfo_t*) const;
+
 		bool is_userspace() const { return m_is_userspace; }
 		const userspace_info_t& userspace_info() const { return m_userspace_info; }
 
diff --git a/kernel/kernel/FS/ProcFS/Inode.cpp b/kernel/kernel/FS/ProcFS/Inode.cpp
index 6fccc23b..fdba47e3 100644
--- a/kernel/kernel/FS/ProcFS/Inode.cpp
+++ b/kernel/kernel/FS/ProcFS/Inode.cpp
@@ -23,4 +23,36 @@ namespace Kernel
 	{
 	}
 
+	BAN::ErrorOr<BAN::RefPtr<ProcMemInode>> ProcMemInode::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 ProcMemInode(process, fs, inode_info);
+		if (inode_ptr == nullptr)
+			return BAN::Error::from_errno(ENOMEM);
+		return BAN::RefPtr<ProcMemInode>::adopt(inode_ptr);
+	}
+
+	ProcMemInode::ProcMemInode(Process& process, RamFileSystem& fs, const FullInodeInfo& inode_info)
+		: RamInode(fs, inode_info)
+		, m_process(process)
+	{
+		m_inode_info.mode |= Inode::Mode::IFREG;
+	}
+
+	BAN::ErrorOr<size_t> ProcMemInode::read_impl(off_t offset, void* buffer, size_t buffer_size)
+	{
+		ASSERT(offset >= 0);
+		if ((size_t)offset >= sizeof(proc_meminfo_t))
+			return 0;
+
+		proc_meminfo_t meminfo;
+		m_process.get_meminfo(&meminfo);
+
+		size_t bytes = BAN::Math::min<size_t>(buffer_size, sizeof(meminfo) - offset);
+		memcpy(buffer, &meminfo, bytes);
+		
+		return bytes;
+	}
+
 }
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 1ca4b213..7e237b9a 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -252,6 +252,21 @@ namespace Kernel
 			thread->set_terminating();
 	}
 
+	void Process::get_meminfo(proc_meminfo_t* out) const
+	{
+		LockGuard _(m_lock);
+
+		out->page_size = PAGE_SIZE;
+
+		out->virt_pages = 0;
+		for (auto* thread : m_threads)
+			out->virt_pages += thread->virtual_page_count();
+		for (auto& region : m_mapped_regions)
+			out->virt_pages += region->virtual_page_count();
+		if (m_loadable_elf)
+			out->virt_pages += m_loadable_elf->virtual_page_count();
+	}
+
 	BAN::ErrorOr<long> Process::sys_exit(int status)
 	{
 		exit(status, 0);
diff --git a/libc/include/sys/banan-os.h b/libc/include/sys/banan-os.h
index 08fe6a38..f514f829 100644
--- a/libc/include/sys/banan-os.h
+++ b/libc/include/sys/banan-os.h
@@ -5,6 +5,9 @@
 
 __BEGIN_DECLS
 
+#define __need_size_t 1
+#include <stddef.h>
+
 #define TTY_CMD_SET		0x01
 #define TTY_CMD_UNSET	0x02
 
@@ -14,6 +17,12 @@ __BEGIN_DECLS
 #define POWEROFF_SHUTDOWN 0
 #define POWEROFF_REBOOT 1
 
+struct proc_meminfo_t
+{
+	size_t page_size;
+	size_t virt_pages;
+};
+
 /*
 fildes:		refers to valid tty device
 command:	one of TTY_CMD_* definitions