feat(lab02): add ex04

doc/lab-01_02.typ

@@ -234,7 +234,7 @@ The `/proc/modules` file give us more details about the state of the module. We
 |> dmesg | tail -5
 [ 3559.279143]   number: 1
 [ 3581.198562] Linux module skeleton unloaded
-[ 3583.616662] Linux module skeleton ex02 loaded
+[ 3583.616662] Linux module skeleton ex03 loaded
 [ 3583.621085]   text: The answer to the Ultimate Question of Life, The Universe, and Everything
 [ 3583.621085]   number: 42
 |> modprobe -r mymodule
@@ -297,6 +297,22 @@ This number matches with this table (#link("https://www.kernel.org/doc/html/late
   ]
 )
 
+To allocate memory in the kernel, we can use the `kcalloc` function. It allows to allocate directly the memory for all element. It's also possible to use `kzalloc` in a loop to allocate memory for each element. We prefer allocate all the memory at once to avoid fragmentation and to be sure all the memory can be allocated.
+
+```bash
+struct element* element_ptr = kcalloc(elements, sizeof(struct element), GFP_KERNEL);
+
+for (int i = 0; i < elements; i++) {
+  struct element* e = element_ptr + i;
+      if (e != 0) {
+          strncpy(e->text, text, TEXT_LENGTH_MAX - 1);
+          e->unique_number = i;
+          list_add_tail(&e->node, &list_unique_elements);
+    pr_info ("add element %d: %s\n", e->unique_number, e->text);
+      }
+  }
+```
+
 //-------------------
 // Exercise 5: Display the processor chip ID, CPU temperature and the MAC adress of the Ethernet controller
 //-------------------

src/01-skeleton/skeleton.c

@@ -5,27 +5,65 @@
 
 #include <linux/moduleparam.h>	// needed for module parameters
 
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/string.h>
+
+#define TEXT_LENGTH_MAX 255
+
 static char* text = "dummy text";
 module_param(text, charp, 0664);
-static int  number = 1;
+static int elements = 1;
-module_param(number, int, 0);
+module_param(elements, int, 0);
 
-static int __init skeleton_init(void)
+struct element {
-{
+    char text[TEXT_LENGTH_MAX];
-	pr_info ("Linux module skeleton ex02 loaded\n");
+    int unique_number;
-	pr_debug ("  text: %s\n  number: %d\n", text, number);
+    struct list_head node;
+};
+
+static LIST_HEAD (list_unique_elements);
+
+static int __init skeleton_init(void) {
+	pr_info("Linux module skeleton ex04 loaded\n");
+	pr_debug("  text: %s\n  elements: %d\n", text, elements);
+	
+	struct element* element_ptr = kcalloc(elements, sizeof(struct element), GFP_KERNEL);
+	if (element_ptr == 0) {
+		pr_err("Failed to allocate memory for %d elements\n", elements);
+		return -ENOMEM;
+	}
+	
+	int i;
+	const int length = TEXT_LENGTH_MAX - 1;
+	for (i = 0; i < elements; i++) {
+		struct element* e = element_ptr + i;
+        if (e != 0) {
+            strncpy(e->text, text, length);
+            e->unique_number = i;
+            list_add_tail(&e->node, &list_unique_elements);
+			pr_info ("add element %d: %s\n", e->unique_number, e->text);
+        }
+    }
 	return 0;
 }
 
-static void __exit skeleton_exit(void)
+static void __exit skeleton_exit(void) {
-{
+	struct element* e;
-	pr_info ("Linux module skeleton unloaded\n");
+
+    while (!list_empty(&list_unique_elements)) {
+        e = list_entry(list_unique_elements.next, struct element, node);
+		pr_info ("delete element %d: %s\n", e->unique_number, e->text);
+        list_del(&e->node);
+        kfree(e);
+    }
+    pr_info ("Linux module skeleton unloaded\n");
 }
 
-module_init (skeleton_init);
+module_init(skeleton_init);
-module_exit (skeleton_exit);
+module_exit(skeleton_exit);
 
-MODULE_AUTHOR ("Fastium <fastium.pro@proton.me>");
+MODULE_AUTHOR("Fastium <fastium.pro@proton.me>");
-MODULE_AUTHOR ("Klagarge <remi@heredero.ch>");
+MODULE_AUTHOR("Klagarge <remi@heredero.ch>");
-MODULE_DESCRIPTION ("Module skeleton");
+MODULE_DESCRIPTION("Module skeleton");
-MODULE_LICENSE ("GPL");
+MODULE_LICENSE("GPL");

src/01-skeleton/skeleton.conf

@@ -1 +1 @@
-options mymodule number=42 text="The answer to the Ultimate Question of Life, The Universe, and Everything"
+options mymodule elements=5 text="Some element"