Add basic and chardev modules

.envrc

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+use flake

.gitignore

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+# Ignore dev env files
+.direnv
+.idea
+
+# Ignore generated files
+*.cmd
+*.mod.c
+
+# Ignore all .ko files
+*.ko
+
+# Ignore other compiled files and directories
+*.o
+*.mod
+*.symvers
+*.order

01_basic_module/Makefile

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+obj-m += test_module.o
+
+all:
+	make -C $(LINUX_MODULES_FOLDER)/build M=$(PWD) modules
+
+clean:
+	make -C $(LINUX_MODULES_FOLDER)/build M=$(PWD) clean

01_basic_module/test_module.c

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+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+static int __init basic_module_init(void) {
+    printk(KERN_INFO "Bonjour! Le module est chargé.\n");
+    return 0;
+}
+
+static void __exit basic_module_exit(void) {
+    printk(KERN_INFO "Au revoir! Le module est déchargé.\n");
+}
+
+module_init(basic_module_init);
+module_exit(basic_module_exit);
+
+MODULE_LICENSE("MIT License");
+MODULE_AUTHOR("Florian RICHER");
+MODULE_DESCRIPTION("Un module noyau qui affiche un message");
+MODULE_VERSION("1.0");

02_character_device/Makefile

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+obj-m += test_module.o
+
+all:
+	make -C $(LINUX_MODULES_FOLDER)/build M=$(PWD) modules
+
+clean:
+	make -C $(LINUX_MODULES_FOLDER)/build M=$(PWD) clean

02_character_device/README.md

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+## Additionnal informations
+
+To test character device, your need create the device.
+
+Step 1: Get major number of your module device
+
+```bash
+cat /proc/devices | grep flodev
+```
+
+Step 2: Create device (as root)
+
+```bash
+mknod /dev/[wanted name] -c <major_number> 0
+```
+
+Exemple (as root):
+
+```bash
+cat /proc/devices | grep flodev # => 236 flodev
+mknod /dev/flodev0 c 236 0
+echo "Salut" >> /dev/flodev0
+dmesg | tail # =>
+#   flodev - Ouverture du périphérique
+#   flodev - Message reçu: Salut
+#   flodev - Fermeture du périphérique
+rm /dev/flodev0
+```
+
+
+

02_character_device/test_module.c

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+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+
+#define DEVICE_NAME "flodev"
+#define CLASS_NAME "chardrv"
+
+static int major_number;
+static char msg[256] = {0};
+static short size_of_msg;
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+static struct file_operations fops = {
+    .read = device_read,
+    .write = device_write,
+    .open = device_open,
+    .release = device_release,
+};
+
+static int __init basic_module_init(void) {
+    printk(KERN_INFO "Bonjour! Le module est chargé.\n");
+    major_number = register_chrdev(0, DEVICE_NAME, &fops);
+    if (major_number < 0) {
+        printk(KERN_ALERT "Erreur lors de l'enregistrement du périphérique de caractère\n");
+        return major_number;
+    }
+    printk(KERN_INFO "Périphérique de caractère enregistré avec le numéro de majeur %d\n", major_number);
+    return 0;
+}
+
+static void __exit basic_module_exit(void) {
+    unregister_chrdev(major_number, DEVICE_NAME);
+    printk(KERN_INFO "Au revoir! Le module est déchargé.\n");
+}
+
+static int device_open(struct inode *inode, struct file *file) {
+    printk(KERN_INFO "flodev - Ouverture du périphérique\n");
+    return 0;
+}
+
+static int device_release(struct inode *inode, struct file *file) {
+    printk(KERN_INFO "flodev - Fermeture du périphérique\n");
+    return 0;
+}
+
+static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t *offset) {
+    int bytes_read = 0;
+    if (*offset >= size_of_msg) {
+        return 0;
+    }
+    if (*offset + length > size_of_msg) {
+        length = size_of_msg - *offset;
+    }
+    if (copy_to_user(buffer, msg + *offset, length)) {
+        return -EFAULT;
+    }
+    *offset += length;
+    bytes_read = length;
+    printk(KERN_INFO "flodev - Lecture de %d bytes\n", bytes_read);
+    return bytes_read;
+}
+
+static ssize_t device_write(struct file *filp, const char *buff, size_t len, loff_t *off) {
+    if (copy_from_user(msg, buff, len)) {
+        return -EFAULT;
+    }
+    size_of_msg = len;
+    printk(KERN_INFO "flodev - Message reçu: %s\n", msg);
+    return len;
+}
+
+module_init(basic_module_init);
+module_exit(basic_module_exit);
+
+MODULE_LICENSE("MIT License");
+MODULE_AUTHOR("Florian RICHER");
+MODULE_DESCRIPTION("Un module noyau avec un périphérique de caractère");
+MODULE_VERSION("1.0");

README.md

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+## Setup env
+
+On NixOS:
+
+- Ensure Linux Kernel is the same as you configuration.
+Otherwise, change linux_dev variable with you kernel variant and change flake.lock nixpkgs with your version.
+- Use direnv allow or nix develop to setup shell.
+
+
+On other distros:
+
+- You need to setup LINUX_MODULES_FOLDER to linux modules folder of your distro (ex: `/lib/modules/$(uname -r)/build`) in flake.nix
+
+## make : targets list
+
+- all : Compiling kernel
+- clean : Cleaning build folder
+
+All subfolder is configured to use LINUX_MODULES_FOLDER env variable set by flake develop
+
+## How test module
+
+Step 1: Load module
+
+```bash
+sudo insmod [module_name].ko
+```
+
+**Warning**: Can fail if secure boot is enabled
+
+Step 2: Check logs
+
+```bash
+sudo dmesg | tail
+```
+
+Step 3: Unload module
+
+```bash
+sudo rmmod [module_name].ko
+```

flake.lock

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+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1739024019,
+        "narHash": "sha256-xvTo0Aw0+veek7hvEVLzErmJyQkEcRk6PSR4zsRQFEc=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "3a228057f5b619feb3186e986dbe76278d707b6e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "Environnement de développement pour des modules noyaux Linux";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = {
+    nixpkgs,
+    flake-utils,
+    ...
+  }: flake-utils.lib.eachSystem flake-utils.lib.allSystems (system:
+    let
+      pkgs = import nixpkgs { inherit system; };
+
+      linux_dev = pkgs.linuxKernel.kernels.linux_zen.dev;
+    in {
+      devShells = {
+        default = pkgs.mkShell {
+          packages = [ linux_dev ];
+
+          LINUX_MODULES_FOLDER = "${linux_dev}/lib/modules/${linux_dev.modDirVersion}";
+
+          shellHook = ''
+            echo "Current Linux Kernel used : ${linux_dev.version}"
+          '';
+        };
+      };
+    }
+  );
+}