From 95a33c484eace06bb06cf5c89a6a2cf038ebdc02 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Thu, 17 Aug 2023 20:15:32 +0200
Subject: [PATCH] kernel+libc: Add a memstat() syscall

We can finally show memory usage in userspace.

This could have been done using sysfs, but I'm lazy and don't want to implement that. Maybe in the next release?
---
 kernel/CMakeLists.txt          |  1 +
 kernel/src/sys/memstat.cpp     | 21 +++++++++++++++++++++
 libc/CMakeLists.txt            |  1 +
 libc/include/bits/memstat.h    | 14 ++++++++++++++
 libc/include/sys/memstat.h     | 20 ++++++++++++++++++++
 libc/src/sys/memstat.cpp       | 13 +++++++++++++
 libluna/include/luna/Syscall.h |  2 +-
 7 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 kernel/src/sys/memstat.cpp
 create mode 100644 libc/include/bits/memstat.h
 create mode 100644 libc/include/sys/memstat.h
 create mode 100644 libc/src/sys/memstat.cpp

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index fbf11b11..e602a1c5 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -47,6 +47,7 @@ set(SOURCES
     src/sys/poll.cpp
     src/sys/alarm.cpp
     src/sys/pledge.cpp
+    src/sys/memstat.cpp
     src/fs/VFS.cpp
     src/fs/Pipe.cpp
     src/fs/Mount.cpp
diff --git a/kernel/src/sys/memstat.cpp b/kernel/src/sys/memstat.cpp
new file mode 100644
index 00000000..8d42a781
--- /dev/null
+++ b/kernel/src/sys/memstat.cpp
@@ -0,0 +1,21 @@
+#include "Pledge.h"
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include <bits/memstat.h>
+
+Result<u64> sys_memstat(Registers*, SyscallArgs args)
+{
+    auto* current = Scheduler::current();
+    TRY(check_pledge(current, Promise::p_stdio));
+
+    struct membuf buf;
+    buf.mem_total = MemoryManager::total();
+    buf.mem_used = MemoryManager::used();
+    buf.mem_free = MemoryManager::free();
+    buf.mem_reserved = MemoryManager::reserved();
+
+    if (!MemoryManager::copy_to_user_typed((struct membuf*)args[0], &buf)) return err(EFAULT);
+
+    return 0;
+}
diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 19f4e654..aef47b36 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -33,6 +33,7 @@ set(SOURCES
     src/sys/utsname.cpp
     src/sys/mount.cpp
     src/sys/pstat.cpp
+    src/sys/memstat.cpp
     src/sys/resource.cpp
     src/sys/socket.cpp
     src/sys/poll.cpp
diff --git a/libc/include/bits/memstat.h b/libc/include/bits/memstat.h
new file mode 100644
index 00000000..365f011f
--- /dev/null
+++ b/libc/include/bits/memstat.h
@@ -0,0 +1,14 @@
+/* bits/memstat.h: The membuf structure for memstat(). */
+
+#ifndef _BITS_MEMSTAT_H
+#define _BITS_MEMSTAT_H
+
+struct membuf
+{
+    unsigned long mem_total;
+    unsigned long mem_used;
+    unsigned long mem_free;
+    unsigned long mem_reserved;
+};
+
+#endif
diff --git a/libc/include/sys/memstat.h b/libc/include/sys/memstat.h
new file mode 100644
index 00000000..6980d259
--- /dev/null
+++ b/libc/include/sys/memstat.h
@@ -0,0 +1,20 @@
+/* sys/memstat.h: Memory usage querying. */
+
+#ifndef _SYS_MEMSTAT_H
+#define _SYS_MEMSTAT_H
+
+#include <bits/memstat.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Query system memory usage. */
+    int memstat(struct membuf* mem);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/libc/src/sys/memstat.cpp b/libc/src/sys/memstat.cpp
new file mode 100644
index 00000000..2d600ac1
--- /dev/null
+++ b/libc/src/sys/memstat.cpp
@@ -0,0 +1,13 @@
+#include <bits/errno-return.h>
+#include <sys/memstat.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+extern "C"
+{
+    int memstat(struct membuf* buf)
+    {
+        long rc = syscall(SYS_memstat, buf);
+        __errno_return(rc, int);
+    }
+}
diff --git a/libluna/include/luna/Syscall.h b/libluna/include/luna/Syscall.h
index d75b1ec4..55003ab4 100644
--- a/libluna/include/luna/Syscall.h
+++ b/libluna/include/luna/Syscall.h
@@ -8,7 +8,7 @@
                     _e(umount) _e(pstat) _e(getrusage) _e(symlinkat) _e(readlinkat) _e(umask) _e(linkat) _e(faccessat) \
                         _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
                             _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll) _e(msync)       \
-                                _e(truncate) _e(ftruncate) _e(utimensat) _e(alarm) _e(pledge)
+                                _e(truncate) _e(ftruncate) _e(utimensat) _e(alarm) _e(pledge) _e(memstat)
 
 enum Syscalls
 {