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117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
/*
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* procfs4.c - create a "file" in /proc
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* This program uses the seq_file library to manage the /proc file.
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*/
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#include <linux/kernel.h> /* We are doing kernel work */
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#include <linux/module.h> /* Specifically, a module */
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#include <linux/proc_fs.h> /* Necessary because we use proc fs */
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#include <linux/seq_file.h> /* for seq_file */
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#include <linux/version.h>
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
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#define HAVE_PROC_OPS
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#endif
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#define PROC_NAME "iter"
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MODULE_LICENSE("GPL");
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/* This function is called at the beginning of a sequence.
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* ie, when:
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* - the /proc file is read (first time)
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* - after the function stop (end of sequence)
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*/
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static void *my_seq_start(struct seq_file *s, loff_t *pos)
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{
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static unsigned long counter = 0;
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/* beginning a new sequence? */
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if (*pos == 0) {
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/* yes => return a non null value to begin the sequence */
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return &counter;
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}
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/* no => it is the end of the sequence, return end to stop reading */
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*pos = 0;
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return NULL;
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}
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/* This function is called after the beginning of a sequence.
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* It is called untill the return is NULL (this ends the sequence).
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*/
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static void *my_seq_next(struct seq_file *s, void *v, loff_t *pos)
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{
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unsigned long *tmp_v = (unsigned long *) v;
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(*tmp_v)++;
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(*pos)++;
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return NULL;
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}
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/* This function is called at the end of a sequence. */
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static void my_seq_stop(struct seq_file *s, void *v)
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{
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/* nothing to do, we use a static value in start() */
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}
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/* This function is called for each "step" of a sequence. */
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static int my_seq_show(struct seq_file *s, void *v)
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{
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loff_t *spos = (loff_t *) v;
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seq_printf(s, "%Ld\n", *spos);
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return 0;
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}
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/* This structure gather "function" to manage the sequence */
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static struct seq_operations my_seq_ops = {
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.start = my_seq_start,
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.next = my_seq_next,
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.stop = my_seq_stop,
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.show = my_seq_show,
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};
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/* This function is called when the /proc file is open. */
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static int my_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &my_seq_ops);
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};
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/* This structure gather "function" that manage the /proc file */
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#ifdef HAVE_PROC_OPS
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static const struct proc_ops my_file_ops = {
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.proc_open = my_open,
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.proc_read = seq_read,
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.proc_lseek = seq_lseek,
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.proc_release = seq_release,
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};
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#else
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static const struct file_operations my_file_ops = {
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.open = my_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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#endif
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/* This function is called when the module is loaded. */
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int init_module(void)
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{
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struct proc_dir_entry *entry;
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entry = proc_create(PROC_NAME, 0, NULL, &my_file_ops);
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if (entry == NULL) {
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remove_proc_entry(PROC_NAME, NULL);
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pr_debug("Error: Could not initialize /proc/%s\n", PROC_NAME);
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return -ENOMEM;
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}
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return 0;
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}
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/* This function is called when the module is unloaded. */
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void cleanup_module(void)
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{
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remove_proc_entry(PROC_NAME, NULL);
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pr_debug("/proc/%s removed\n", PROC_NAME);
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}
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