VFS, DeviceFS: Implement a device filesystem

For now, we just have a version device. (this will allow us to get rid of sys_getversion!!)
More should be implemented soon.

apps/src/init.c

@@ -8,6 +8,39 @@
 
 typedef long ssize_t;
 
+int print_version()
+{
+    char version[4096];
+
+    FILE* verfile = fopen("/dev/version", "r");
+    if (!verfile)
+    {
+        perror("fopen");
+        return 1;
+    }
+
+    size_t nread = fread(version, 4096, 1, verfile);
+    if (ferror(verfile))
+    {
+        perror("fread");
+        return 1;
+    }
+
+    printf("Read %zd bytes\n", nread);
+
+    version[nread] = 0;
+
+    if (fclose(verfile) < 0)
+    {
+        perror("fclose");
+        return 1;
+    }
+
+    printf("Your kernel version is %s\n\n", version);
+
+    return 0;
+}
+
 int main()
 {
     if (gettid() == 0) // why are we the idle task?
@@ -21,10 +54,7 @@ int main()
 
     sleep(1);
 
-    char version[40];
-    syscall(SYS_getversion, version, sizeof(version));
-
-    printf("Your kernel version is %s\n\n", version);
+    if (print_version()) return 1;
 
     sleep(2);
 

kernel/include/fs/VFS.h

@@ -38,6 +38,7 @@ namespace VFS
     Node* resolve_path(const char* filename, Node* root = nullptr);
 
     void mount(Node* mountpoint, Node* mounted);
+    void mount(const char* pathname, Node* mounted);
 
     void unmount(Node* mountpoint);
 

kernel/include/fs/devices/DeviceFS.h

@@ -0,0 +1,9 @@
+#pragma once
+#include "fs/VFS.h"
+
+namespace DeviceFS
+{
+    VFS::Node* get();
+
+    VFS::Node* finddir(VFS::Node* node, const char* filename);
+}

kernel/include/fs/devices/Version.h

@@ -0,0 +1,9 @@
+#pragma once
+#include "fs/VFS.h"
+
+namespace VersionDevice
+{
+    VFS::Node* create_new();
+
+    ssize_t read(VFS::Node* node, size_t offset, size_t size, char* buffer);
+}

kernel/src/fs/VFS.cpp

@@ -134,6 +134,11 @@ void VFS::mount(Node* mountpoint, Node* mounted)
     mountpoint->flags |= VFS_MOUNTPOINT;
 }
 
+void VFS::mount(const char* pathname, Node* mounted)
+{
+    return mount(resolve_path(pathname), mounted);
+}
+
 void VFS::unmount(Node* mountpoint)
 {
     if (!mountpoint) return;

kernel/src/fs/devices/DeviceFS.cpp

@@ -0,0 +1,35 @@
+#include "fs/devices/DeviceFS.h"
+#include "fs/devices/Version.h"
+#include "std/stdlib.h"
+#include "std/string.h"
+
+#define DEVFS_MAX_FILES 32
+
+VFS::Node* devfs_root = nullptr;
+
+VFS::Node* devfs_files[DEVFS_MAX_FILES];
+int devfs_file_count = 0;
+
+VFS::Node* DeviceFS::get()
+{
+    if (devfs_root) return devfs_root;
+    devfs_root = new VFS::Node;
+    devfs_root->length = 0;
+    devfs_root->inode = 0;
+    devfs_root->type = VFS_DIRECTORY;
+    devfs_root->find_func = DeviceFS::finddir;
+    strncpy(devfs_root->name, "dev", sizeof(devfs_root->name));
+
+    devfs_files[devfs_file_count++] = VersionDevice::create_new();
+    return devfs_root;
+}
+
+VFS::Node* DeviceFS::finddir(VFS::Node* node, const char* filename)
+{
+    if (!node) return 0;
+    for (int i = 0; i < devfs_file_count; i++)
+    {
+        if (strncmp(devfs_files[i]->name, filename, sizeof(VFS::Node::name)) == 0) { return devfs_files[i]; }
+    }
+    return 0;
+}

kernel/src/fs/devices/Version.cpp

@@ -0,0 +1,26 @@
+#include "fs/devices/Version.h"
+#include "config.h"
+#include "std/stdio.h"
+#include "std/stdlib.h"
+#include "std/string.h"
+
+VFS::Node* VersionDevice::create_new()
+{
+    VFS::Node* dev = new VFS::Node;
+    dev->read_func = VersionDevice::read;
+    dev->inode = 0;
+    dev->length = strlen(moon_version()) + 5;
+    dev->type = VFS_FILE;
+    strncpy(dev->name, "version", sizeof(dev->name));
+    return dev;
+}
+
+ssize_t VersionDevice::read(VFS::Node* node, size_t offset, size_t size, char* buffer)
+{
+    if (!node) return -1;
+    if (offset > node->length) return -1;
+    if (offset + size > node->length) { size = node->length - offset; }
+    if (offset > 0) return -1;
+    snprintf(buffer, size + 1, "moon %s", moon_version()); // FIXME: Support offseting this read
+    return (ssize_t)size;
+}

kernel/src/main.cpp

@@ -5,6 +5,7 @@
 #include "config.h"
 #include "cpu/CPU.h"
 #include "fs/VFS.h"
+#include "fs/devices/DeviceFS.h"
 #include "gdt/GDT.h"
 #include "init/Init.h"
 #include "init/InitRD.h"
@@ -158,30 +159,13 @@ extern "C" void _start()
 
     Init::finish_kernel_boot();
 
+    VFS::mkdir("/", "dev");
+    VFS::mount("/dev", DeviceFS::get());
+
     Interrupts::enable();
 
     kinfoln("Interrupts enabled");
 
-    kinfoln("Trying VFS");
-
-    if (VFS::mkdir("/", "rootfs") < 0) { kerrorln("Unable to create directory rootfs"); }
-    else
-    {
-        VFS::mount(VFS::resolve_path("/rootfs"), VFS::root());
-        VFS::Node* node = VFS::resolve_path("/rootfs/sys/config");
-        if (!node) kerrorln("unable to find /sys/config in VFS");
-        else
-        {
-            kinfoln("Found '%s'", node->name);
-            char* buffer = (char*)kmalloc(node->length + 1);
-            buffer[node->length] = 0;
-            ssize_t nread = VFS::read(node, 0, node->length, buffer);
-            kdbgln("Read %zd bytes", nread);
-            kinfoln("Read: %s", buffer);
-            kfree(buffer);
-        }
-    }
-
     PCI::scan([](PCI::Device& dev) {
         kinfoln("Found PCI device %x:%x, %s", dev.id().vendor, dev.id().device, pci_type_name(dev.type()));
     });