Add VFS diagram image

assets/css/asciidoctor.css

@@ -164,7 +164,7 @@ table thead tr th, table tfoot tr th, table tbody tr td, table tr td, table tfoo
 .clearfix:before, .clearfix:after, .float-group:before, .float-group:after { content: " "; display: table; }
 .clearfix:after, .float-group:after { clear: both; }
 
-*:not(pre) > code { font-size: 0.9375em; padding: 1px 3px 0; white-space: nowrap; background-color: #f2f2f2; border: 1px solid #cccccc; -webkit-border-radius: 4px; border-radius: 4px; text-shadow: none; }
+*:not(pre) > code { font-size: 0.9375em; padding: 1px 3px 0; white-space: nowrap; background-color: #060606; text-shadow: none; }
 
 /*pre, pre > code { line-height: 1.4; color: inherit; font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; }*/
 

assets/css/base.css

@@ -22,7 +22,7 @@ body {
   height: 60px;
 }
 #footer {
-  background-color: #f5f5f5;
+  background-color: #060606;
   padding: 0;
 }
 
@@ -49,4 +49,4 @@ body {
 
 /*code {
   font-size: 80%;
-}*/
+}*/

assets/css/prettify.css

@@ -1 +1,118 @@
-.pln{color:#000}@media screen{.str{color:#080}.kwd{color:#008}.com{color:#800}.typ{color:#606}.lit{color:#066}.pun,.opn,.clo{color:#660}.tag{color:#008}.atn{color:#606}.atv{color:#080}.dec,.var{color:#606}.fun{color:red}}@media print,projection{.str{color:#060}.kwd{color:#006;font-weight:bold}.com{color:#600;font-style:italic}.typ{color:#404;font-weight:bold}.lit{color:#044}.pun,.opn,.clo{color:#440}.tag{color:#006;font-weight:bold}.atn{color:#404}.atv{color:#060}}pre.prettyprint{padding:2px;border:1px solid #888}ol.linenums{margin-top:0;margin-bottom:0}li.L1,li.L3,li.L5,li.L7,li.L9{background:#eee}
+/*
+ * Derived from einaros's Sons of Obsidian theme at
+ * http://studiostyl.es/schemes/son-of-obsidian by
+ * Alex Ford of CodeTunnel:
+ * http://CodeTunnel.com/blog/post/71/google-code-prettify-obsidian-theme
+ */
+
+.str
+{
+    color: #EC7600;
+}
+.kwd
+{
+    color: #93C763;
+}
+.com
+{
+    color: #66747B;
+}
+.typ
+{
+    color: #678CB1;
+}
+.lit
+{
+    color: #FACD22;
+}
+.pun
+{
+    color: #F1F2F3;
+}
+.pln
+{
+    color: #F1F2F3;
+}
+.tag
+{
+    color: #8AC763;
+}
+.atn
+{
+    color: #E0E2E4;
+}
+.atv
+{
+    color: #EC7600;
+}
+.dec
+{
+    color: purple;
+}
+pre.prettyprint
+{
+    border: 0px solid #888;
+}
+ol.linenums
+{
+    margin-top: 0;
+    margin-bottom: 0;
+}
+.prettyprint {
+    background: #000;
+}
+li.L0, li.L1, li.L2, li.L3, li.L4, li.L5, li.L6, li.L7, li.L8, li.L9
+{
+    color: #555;
+    list-style-type: decimal;
+}
+li.L1, li.L3, li.L5, li.L7, li.L9 {
+    background: #111;
+}
+@media print
+{
+    .str
+    {
+        color: #060;
+    }
+    .kwd
+    {
+        color: #006;
+        font-weight: bold;
+    }
+    .com
+    {
+        color: #600;
+        font-style: italic;
+    }
+    .typ
+    {
+        color: #404;
+        font-weight: bold;
+    }
+    .lit
+    {
+        color: #044;
+    }
+    .pun
+    {
+        color: #440;
+    }
+    .pln
+    {
+        color: #000;
+    }
+    .tag
+    {
+        color: #006;
+        font-weight: bold;
+    }
+    .atn
+    {
+        color: #404;
+    }
+    .atv
+    {
+        color: #060;
+    }
+}

content/blog/MOP2/fatfs-integration.adoc

@@ -0,0 +1,191 @@
+= FAT filesystem integration into MOP2
+Kamil Kowalczyk
+2025-11-19
+:jbake-type: post
+:jbake-tags: MOP2 osdev
+:jbake-status: published
+
+Hello, World!
+
+I would like to present to you FAT filesystem integration into the MOP2 operating system! This was
+possible thanks to `fat_io_lib` library by UltraEmbedded, because there's no way I'm writing an
+entire FAT driver from scratch ;).
+
+Source for `fat_io_lib`: https://github.com/ultraembedded/fat_io_lib
+
+== Needed changes and a "contextual" system
+
+Integrating fat_io_lib wasn't so straightforward as I thought it would be. To understand the problem
+we need to first understand the current design of MOP2's VFS.
+
+=== MOP2's VFS explained
+
+image::/img/fs-design-diagram1.png["FS diagram"]
+
+The VFS (ie. Virtual File System) is a Windows/DOS-style labeled VFS. Mountpoints are identified by
+a label, like for eg. `sys:/boot/mop2` or `base:/scripts/mount.tb`, which kinda looks like
+`C:\Path\To\File` in Windows. I've chosen this style of VFS over the UNIX kind, because it makes more
+sense to me personally. A mountpoint label can point to a physical device, a virtual device (ramsd)
+or a subdevice/partition device. In the UNIX world on the other hand, we have a hierarchical VFS, so
+paths look like `/`, `/proc`, `/dev`, etc. This is a little confusing to reason about, because you'd
+think that if `/` is mounted let's say on a drive `sda0`, then `/home` would be a home directory
+within the root of that device. This is not always the case. `/` can be placed on `sda0`, but `/home`
+can be placed on `sdb0`, so now something that looks like a subdirectory, is now a pointer to an
+entirely different media. Kinda confusing, eh?
+
+=== The problem
+
+So now that we know how MOP2's VFS works, let's get into low-level implementation details. To handle
+mountpoints we use a basic hashtable. We just map the label to the proper underlying file system
+driver like so:
+
+[source]
+----
+base      ->    Little FS
+uhome     ->    Little FS
+sys       ->    FAT16
+----
+
+Through this table, we can see that we have two mountpoints (base and uhome), which both use Little
+FS, but are placed on different media entirely. Base is located on a ramsd, which is entirely virtual
+and uhome is a partition on a physical drive.
+
+To manage such setup, we need to have separate filesystem library contexts for each mountpoint.
+A context here means an object, which stores info like block size, media read/write/sync hooks,
+media capacity and so on. Luckly, with Little FS we could do this out of the box, because it blesses
+us with `lfs_t` - an instance object. We can then create this object for each Little FS mountpoint.
+
+.Internals of the VFS mountpoint structure
+[source,c]
+----
+typedef struct VfsMountPoint {
+  int _hshtbstate;
+  char label[VFS_MOUNTPOINT_LABEL_MAX];
+
+  int32_t fstype;
+  StoreDev *backingsd;
+
+  VfsObj *(*open)(struct VfsMountPoint *vmp, const char *path, uint32_t flags);
+  int32_t (*cleanup)(struct VfsMountPoint *vmp);
+  int32_t (*stat)(struct VfsMountPoint *vmp, const char *path, FsStat *statbuf);
+  int32_t (*fetchdirent)(struct VfsMountPoint *vmp, const char *path, FsDirent *direntbuf, size_t idx);
+  int32_t (*mkdir)(struct VfsMountPoint *vmp, const char *path);
+  int32_t (*delete)(struct VfsMountPoint *vmp, const char *path);
+
+  // HERE: instance objects for the underlying filesystem driver library.
+  union {
+    LittleFs littlefs;
+    FatFs fatfs;
+  } fs;
+  SpinLock spinlock;
+} VfsMountPoint;
+
+typedef struct {
+  SpinLock spinlock;
+  VfsMountPoint mountpoints[VFS_MOUNTPOINTS_MAX];
+} VfsTable;
+
+// ...
+----
+
+.Little FS init code
+[source,c]
+----
+int32_t vfs_init_littlefs(VfsMountPoint *mp, bool format) {
+  // Configure Little FS
+  struct lfs_config *cfg = dlmalloc(sizeof(*cfg));
+  memset(cfg, 0, sizeof(*cfg));
+  cfg->context = mp;
+  cfg->read = &portlfs_read; // Our read/write hooks
+  cfg->prog = &portlfs_prog;
+  cfg->erase = &portlfs_erase;
+  cfg->sync = &portlfs_sync;
+  cfg->block_size = LITTLEFS_BLOCK_SIZE;
+  cfg->block_count = mp->backingsd->capacity(mp->backingsd) / LITTLEFS_BLOCK_SIZE;
+  // left out...
+  int err = lfs_mount(&mp->fs.littlefs.instance, cfg);
+  if (err < 0) {
+    ERR("vfs", "Little FS mount failed %d\n", err);
+    return E_MOUNTERR;
+  }
+
+  // VFS hooks
+  mp->cleanup     = &littlefs_cleanup;
+  mp->open        = &littlefs_open;
+  mp->stat        = &littlefs_stat;
+  mp->fetchdirent = &littlefs_fetchdirent;
+  mp->mkdir       = &littlefs_mkdir;
+  mp->delete      = &littlefs_delete;
+  return E_OK;
+}
+----
+
+So where is the problem? It's in the fat_io_lib library. You see, the creators of Little FS thought
+this out pretty well and designed their library in such manner that we can do cool stuff like this.
+The creators of fat_io_lib on the other hand... yeah. Here are the bits of internals of fat_io_lib:
+
+[source,c]
+----
+//-----------------------------------------------------------------------------
+// Locals
+//-----------------------------------------------------------------------------
+static FL_FILE            _files[FATFS_MAX_OPEN_FILES];
+static int                _filelib_init = 0;
+static int                _filelib_valid = 0;
+static struct fatfs       _fs;
+static struct fat_list    _open_file_list;
+static struct fat_list    _free_file_list;
+----
+
+There's no concept of a "context" - everything is thrown into a bunch of global variables.
+To clarify: THIS IS NOT BAD! This is good if you need a FAT library for let's say a microcontroller,
+or some other embedded device. Less code/stuff == less memory usage and so on.
+
+When I was searching online for a FAT library, I wanted something like Little FS, but to my suprise
+there are no libraries for FAT designed like this? Unless it's a homebrew OsDev project, of course.
+I've even went on reddit to ask and got nothing, but cricket noises ;(.
+
+I've decided to modify fat_io_lib to suit my needs. I mean, most of the code is already written for
+me anyway, so I'm good.
+
+The refactoring was quite easy to my suprise! The state of the library is global, but it's all nicely
+placed in one spot, so we can then move it out into a struct:
+
+[source,c]
+----
+struct fat_ctx {
+  FL_FILE            _files[FATFS_MAX_OPEN_FILES];
+  int                _filelib_init;
+  int                _filelib_valid;
+  struct fatfs       _fs;
+  struct fat_list    _open_file_list;
+  struct fat_list    _free_file_list;
+  void *extra; // we need this to store a ref to the mountpoint to access storage device hooks
+};
+----
+
+[source,c]
+----
+// This is what our VfsMountPoint struct from earlier was referencing, BTW.
+typedef struct {
+  struct fat_ctx instance;
+} FatFs;
+----
+
+I've then gone on a compiler error hunt for about 2 hours! All I had to do is change references for
+eg. from `_fs.some_field` into `ctx->_fs.some_field`. It was all pretty much brainless work - just
+compile the code, read the error line number, edit the variable reference, repeat.
+
+== Why do I even need FAT in MOP2?
+
+I need it, because Limine (the bootloader) uses FAT16/32 (depending on what the user picks) to store
+the kernel image, resource files and the bootloader binary itself. It'd be nice to be able to view
+all of these files and manage them, to maybe in the future for eg. update the kernel image from the
+system itself (self-hosting, hello?).
+
+== Fruits of labour
+
+Here are some screenshots ;).
+
+image::/img/fatfs-showcase2.png["showcase 2"]
+image::/img/fatfs-showcase1.png["showcase 1"]

content/blog/MOP2/mbus-messaging-ipc.adoc

@@ -0,0 +1,153 @@
+= MBus - in-kernel messaging system
+Kamil Kowalczyk
+2025-11-12
+:jbake-type: post
+:jbake-tags: MOP2 osdev
+:jbake-status: published
+
+In this article I would like to present to you `MBus` - a kernel-space messaging IPC mechanism for
+the MOP2 operating system.
+
+== One-to-many messaging
+
+MBus is a one-to-many messaging system. This means that there's one sender/publisher and many
+readers/subscribers. Think of a YouTube channel - a person posts a video and their subscribers get
+a push notification that there's content to consume.
+
+image::/img/mbus-diagram1.png["One-to-many messaging diagram"]
+
+== User-space API
+
+This is the user-space API for MBus. The application can create a message bus for `objmax`
+messages of `objsize`. Message buses are indentified via a global string ID, for eg. the PS/2
+keyboard driver uses ID "ps2kb".
+
+`ipc_mbusattch` and `ipc_mbusdttch` are used for attaching/detattching a consumer to/from the
+message bus.
+
+[source,c]
+----
+int32_t ipc_mbusmake(char *name, size_t objsize, size_t objmax);
+int32_t ipc_mbusdelete(char *name);
+int32_t ipc_mbuspublish(char *name, const uint8_t *const buffer);
+int32_t ipc_mbusconsume(char *name, uint8_t *const buffer);
+int32_t ipc_mbusattch(char *name);
+int32_t ipc_mbusdttch(char *name);
+----
+
+=== Usage
+
+The usage of MBus can be found for eg. inside of TB - the MOP2's shell:
+
+.Initalizing interactive shell mode
+[source,c]
+----
+  if (CONFIG.mode == MODE_INTERACTIVE) {
+    ipc_mbusattch("ps2kb");
+    do_mode_interactive();
+    // ...
+----
+
+.Reading key presses
+[source,c]
+----
+  // ...
+      int32_t read = ipc_mbusconsume("ps2kb", &b);
+      if (read > 0) {
+        switch (b) {
+          case C('C'):
+          case 0xE9:
+            uprintf("\n");
+            goto begin;
+            break;
+          case C('L'):
+            uprintf(ANSIQ_CUR_SET(0, 0));
+            uprintf(ANSIQ_SCR_CLR_ALL);
+            goto begin;
+            break;
+        }
+  // ...
+----
+
+Previously reading the keyboard was done in a quite ugly manner via specialized functions of the
+`ps2kbdev` device object (`DEV_PS2KBDEV_ATTCHCONS` and `DEV_PS2KBDEV_READCH`). It was a one big
+hack, but the MBus API has turned out quite nicely ;).
+
+With the new MBus API, the PS/2 keyboard driver becomes way cleaner than before (you can dig
+through the commit history...).
+
+.Kernel-side code for the PS/2 keyboard driver
+[source,c]
+----
+// ...
+IpcMBus *PS2KB_MBUS;
+
+void ps2kbdev_intr(void) {
+  int32_t c = ps2kb_intr();
+  if (c >= 0) {
+    uint8_t b = c;
+    ipc_mbuspublish("ps2kb", &b);
+  }
+}
+
+void ps2kbdev_init(void) {
+  intr_attchhandler(&ps2kbdev_intr, INTR_IRQBASE+1);
+
+  Dev *ps2kbdev;
+  HSHTB_ALLOC(DEVTABLE.devs, ident, "ps2kbdev", ps2kbdev);
+  spinlock_init(&ps2kbdev->spinlock);
+  PS2KB_MBUS = ipc_mbusmake("ps2kb", 1, 0x100);
+}
+----
+
+The messaging logic is ~20 lines of code now.
+
+== The tricky part
+
+The trickiest part to figure out while implementing MBus was to implement
+cleaning up dangling/dead consumers. In the current model, a message bus
+doesn't really know if a consumer has died without explicitly detattching
+itself from the bus. This is solved by going through each message bus and
+it's corresponding consumers and deleting the ones that aren't in the list
+of currently running processes. This operation is ran every cycle of the
+scheduler - you could say it's a form of garbage collection. All of this
+is implemented inside `ipc_mbustick`:
+
+[source,c]
+----
+void ipc_mbustick(void) {
+  spinlock_acquire(&IPC_MBUSES.spinlock);
+  // Go through all message buses
+  for (size_t i = 0; i < LEN(IPC_MBUSES.mbuses); i++) {
+    IpcMBus *mbus = &IPC_MBUSES.mbuses[i];
+    // Skip unused slots
+    if (mbus->_hshtbstate != HSHTB_TAKEN) {
+      continue;
+    }
+
+    IpcMBusCons *cons, *constmp;
+    spinlock_acquire(&mbus->spinlock);
+    // Go through every consumer of this message bus
+    LL_FOREACH_SAFE(mbus->consumers, cons, constmp) {
+      spinlock_acquire(&PROCS.spinlock);
+      Proc *proc = NULL;
+      LL_FINDPROP(PROCS.procs, proc, pid, cons->pid);
+      spinlock_release(&PROCS.spinlock);
+
+      // If not on the list of processes, purge!
+      if (proc == NULL) {
+        LL_REMOVE(mbus->consumers, cons);
+        dlfree(cons->rbuf.buffer);
+        dlfree(cons);
+      }
+    }
+    spinlock_release(&mbus->spinlock);
+  }
+  spinlock_release(&IPC_MBUSES.spinlock);
+}
+----
+
+As you can see it's a quite heavy operation and thus not ideal - but still
+way ahead of what we had before. I guess the next step would be to figure out
+a way to optimize this further, although the system doesn't seem to take a
+noticable hit in performance (maybe do some benchmarks in the future?).