zadanie1.lab4.SO

#include<linux/module.h>
#include<asm/uaccess.h>
#include<linux/proc_fs.h>
#include<linux/seq_file.h>

static struct proc_dir_entry *directory_entry_pointer, *file_entry_pointer; // deklaracja dwoch wskaznikow na strukture typu struct proc_dir_example
static char *directory_name = "procfs_test", *file_name = "procfs_file"; // zmienne wskazujace na lancuch(podkatalog i plik)
static char file_buffer[PAGE_SIZE]; //bufor na dane pliku(4KiB)

static int procfsmod_show(struct seq_file *seq, void *data)
{
    char *notice = (char *)data;
    seq_printf(seq, "Pierwszy znak w pliku tekstowym o nazwie %s:  to: %c \n",*file_name, file_buffer[0]);
    return 0;
}

static void *procfsmod_seq_start(struct seq_file *s, loff_t *position)
{
    loff_t buffer_index = *position;
    return (buffer_index<PAGE_SIZE && file_buffer[buffer_index]!='\0')?(void *)&file_buffer[buffer_index]:NULL;
}

static void *procfsmod_seq_next(struct seq_file *s, void *data, loff_t *position)
{
    loff_t next_element_index = ++*position;
    return (next_element_index<PAGE_SIZE && file_buffer[next_element_index]!='\0')?(void *)&file_buffer[next_element_index]:NULL;
}

static void procfsmod_seq_stop(struct seq_file *s, void *data) // funkcja pusta bo nie potrzba stosowac zadnych finalizacji iteratora(poniewaz buffor ma pamiec jest zrobiony statycznie i nie trzeba zwalniac na niego pamieci)
{
}

static struct seq_operations procfsmod_seq_operations = {
    .start = procfsmod_seq_start,
    .next = procfsmod_seq_next,
    .stop = procfsmod_seq_stop,
    .show = procfsmod_show
};

static int procfsmod_open(struct inode *inode, struct file *file)
{
    return single_open(file, procfsmod_show, NULL); // zamiennik dla funkcji seq_open(), uzywana do odzczytania pojedynczej wartosci
}

static ssize_t procfsmod_write(struct file *file, const char __user *buffer, size_t count, loff_t *position)
{
    int length = count;
    if(count>PAGE_SIZE)
        length=PAGE_SIZE-1;
    if(copy_from_user(file_buffer,buffer,length))
        return -EFAULT; //zwrocony odpowiedni numer wyjatku, gdy kopiowanie sie nie powiedzie
    file_buffer[length]='\0';
    return length;
}

static struct file_operations procfsmod_fops = {
    .owner = THIS_MODULE,
    .open = procfsmod_open,
    .read = seq_read,
    .write = procfsmod_write,
    .llseek = seq_lseek,
    .release = single_release
};

static int __init procfsmod_init(void)
{
    directory_entry_pointer = proc_mkdir(directory_name, NULL);
    if(IS_ERR(directory_entry_pointer)) {
        pr_alert("Error creating procfs directory: %s. Error code: %ld\n",directory_name,PTR_ERR(directory_entry_pointer));
        return -1;
    }
    file_entry_pointer = proc_create_data(file_name,0666,directory_entry_pointer,&procfsmod_fops,(void *)file_buffer);
    if(IS_ERR(file_entry_pointer)) {
        pr_alert("Error creating procfs file: %s. Error code: %ld\n",file_name,PTR_ERR(file_entry_pointer));
        proc_remove(directory_entry_pointer);
        return -1;
    }

    return 0;
}

static void __exit procfsmod_exit(void)
{
    if(file_entry_pointer)
        proc_remove(file_entry_pointer);
    if(directory_entry_pointer)
        proc_remove(directory_entry_pointer);
}

module_init(procfsmod_init);
module_exit(procfsmod_exit);