Dynamic memory allocation added:

lesson-04-memory-management/mm/.gitignore

@@ -0,0 +1,2 @@
+/Makefile~
+*.c~

lesson-04-memory-management/mm/Makefile

@@ -5,6 +5,7 @@
 ifneq ($(KERNELRELEASE),)
 
 obj-m += xxx.o
+obj-m += xxx_dynamic.o
 
 else
 

lesson-04-memory-management/mm/xxx_dynamic.c

@@ -0,0 +1,153 @@
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <asm/uaccess.h>
+#include <linux/pci.h>
+#include <linux/version.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+#define BUF_SIZE_MAX 256
+
+static enum { ALLOC_TYPE_KMALLOC = 0, ALLOC_TYPE_KVMALLOC, ALLOC_TYPE_KCACHE} alloc_type = ALLOC_TYPE_KMALLOC;
+static struct kmem_cache* pmem_cache = 0;
+static size_t buf_size = 0;
+struct KCACHE_STRUCT {
+    char buf[BUF_SIZE_MAX];
+};
+
+static char* buf_msg = 0;
+
+const char* get_alloc_type(int type)
+{
+    switch (type) {
+        case ALLOC_TYPE_KMALLOC:
+            return "ALLOC_TYPE_KMALLOC";
+        case ALLOC_TYPE_KVMALLOC:
+            return "ALLOC_TYPE_KVMALLOC";
+        case ALLOC_TYPE_KCACHE:
+            return "ALLOC_TYPE_KCACHE";
+    }
+    return "ALLOC_TYPE_UNKNOWN";
+}
+
+static void* mem_alloc(int type, size_t size)
+{
+    void* buf = 0;
+    switch (type) {
+        case ALLOC_TYPE_KMALLOC:
+            buf = kmalloc(size, GFP_KERNEL);
+            break;
+        case ALLOC_TYPE_KVMALLOC:
+            buf = vmalloc(size);
+            break;
+        case ALLOC_TYPE_KCACHE:
+            buf = kmem_cache_alloc( pmem_cache, GFP_KERNEL );
+            break;
+    }
+
+    if (buf) buf_size = size;
+
+    printk(KERN_INFO "[%s:%s] {%s} %zu bytes --> %p\n", THIS_MODULE->name, __FUNCTION__, get_alloc_type(type), size, buf);
+    return buf;
+}
+
+static void mem_free(int type, void* buf)
+{
+    if (!buf) {
+        printk(KERN_INFO "[%s:%s] Wrong parameter %p\n", THIS_MODULE->name, __FUNCTION__, buf);
+        return;
+    }
+    switch (type) {
+       case ALLOC_TYPE_KMALLOC:
+            kfree(buf);
+            break;
+        case ALLOC_TYPE_KVMALLOC:
+            vfree(buf);
+            break;
+        case ALLOC_TYPE_KCACHE:
+            kmem_cache_free( pmem_cache, buf );
+            break;
+   }
+    printk(KERN_INFO "[%s:%s] {%s} bytes --> %p\n", THIS_MODULE->name, __FUNCTION__, get_alloc_type(type), buf);
+}
+
+void init_kcache(void) 
+{
+    if (alloc_type != ALLOC_TYPE_KCACHE) return;
+    pmem_cache = KMEM_CACHE(KCACHE_STRUCT, 0);
+    printk(KERN_INFO "[%s:%s] pmem_cache: %p\n", THIS_MODULE->name, __FUNCTION__, pmem_cache);
+}
+
+void deinit_kcache(void)
+{
+    if (alloc_type != ALLOC_TYPE_KCACHE) {
+        mem_free(alloc_type, buf_msg);
+        return;
+    }
+    kmem_cache_destroy( pmem_cache );
+}
+
+static ssize_t xxx_show( struct class *class, struct class_attribute *attr, char *buf ) {
+	if (!buf_msg) {
+		printk(KERN_INFO "[%s:%s] Buffer is empty\n", THIS_MODULE->name, __FUNCTION__);
+		return 0; 
+	}
+	strcpy( buf, buf_msg );
+	printk(KERN_INFO "[%s:%s] read %ld\n", THIS_MODULE->name, __FUNCTION__, (long)strlen( buf ) );
+	return strlen( buf );	
+}
+
+static ssize_t xxx_store( struct class *class, struct class_attribute *attr, const char *buf, size_t count ) {
+	if (buf_msg) {
+		mem_free(alloc_type, buf_msg);
+		buf_msg = 0;
+	}
+
+	if (count >= BUF_SIZE_MAX) {
+		printk(KERN_INFO "[%s:%s] Buffer size exceeded! \n", THIS_MODULE->name, __FUNCTION__);
+		return 0;
+	}
+	buf_msg = mem_alloc(alloc_type, count + 1);
+	if (!buf_msg) {
+		printk(KERN_INFO "[%s:%s] Memory allocation error! \n", THIS_MODULE->name, __FUNCTION__);
+		return 0;
+	}	
+	else {
+		printk(KERN_INFO "[%s:%s] write %ld\n", THIS_MODULE->name, __FUNCTION__, (long)count );
+		strncpy( buf_msg, buf, count );
+		buf_msg[ count ] = '\0';
+		return count;
+	}
+}
+
+CLASS_ATTR_RW( xxx );
+
+static struct class *x_class;
+
+int __init x_init(void) {
+	int res;
+	printk(KERN_INFO "alloc_type is %s\n", get_alloc_type(alloc_type));
+	x_class = class_create( THIS_MODULE, "x-class" );
+	if( IS_ERR( x_class ) ) printk(KERN_INFO "bad class create\n" );
+	res = class_create_file( x_class, &class_attr_xxx );
+	init_kcache();
+	printk(KERN_INFO "'xxx' module initialized\n" );
+	return res;
+}
+
+void x_cleanup(void) {
+	class_remove_file( x_class, &class_attr_xxx );
+	class_destroy( x_class );
+	deinit_kcache();
+	printk(KERN_INFO "'xxx' module deinitialized\n" );
+	return;
+}
+
+module_param( alloc_type, int, 0444 );
+MODULE_PARM_DESC(alloc_type, "Type of memory allocation: 0 - kmalloc; 1 - vmalloc; 2 - cache");
+
+module_init( x_init );
+module_exit( x_cleanup );
+
+MODULE_LICENSE( "GPL" );