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39a313dc20
To make sure the behavior of the read and write operations are correct with offset, update it each time. Also, since it is using the offset, modify the part of read for removing unnecessary variable.
105 lines
2.8 KiB
C
105 lines
2.8 KiB
C
/*
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* procfs3.c
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/proc_fs.h>
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#include <linux/sched.h>
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#include <linux/uaccess.h>
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#include <linux/version.h>
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#include <linux/minmax.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 PROCFS_MAX_SIZE 2048UL
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#define PROCFS_ENTRY_FILENAME "buffer2k"
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static struct proc_dir_entry *our_proc_file;
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static char procfs_buffer[PROCFS_MAX_SIZE];
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static unsigned long procfs_buffer_size = 0;
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static ssize_t procfs_read(struct file *filp, char __user *buffer,
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size_t length, loff_t *offset)
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{
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if (*offset || procfs_buffer_size == 0) {
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pr_debug("procfs_read: END\n");
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*offset = 0;
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return 0;
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}
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procfs_buffer_size = min(procfs_buffer_size, length);
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if (copy_to_user(buffer, procfs_buffer, procfs_buffer_size))
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return -EFAULT;
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*offset += procfs_buffer_size;
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pr_debug("procfs_read: read %lu bytes\n", procfs_buffer_size);
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return procfs_buffer_size;
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}
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static ssize_t procfs_write(struct file *file, const char __user *buffer,
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size_t len, loff_t *off)
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{
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procfs_buffer_size = min(PROCFS_MAX_SIZE, len);
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if (copy_from_user(procfs_buffer, buffer, procfs_buffer_size))
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return -EFAULT;
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*off += procfs_buffer_size;
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pr_debug("procfs_write: write %lu bytes\n", procfs_buffer_size);
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return procfs_buffer_size;
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}
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static int procfs_open(struct inode *inode, struct file *file)
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{
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try_module_get(THIS_MODULE);
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return 0;
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}
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static int procfs_close(struct inode *inode, struct file *file)
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{
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module_put(THIS_MODULE);
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return 0;
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}
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#ifdef HAVE_PROC_OPS
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static struct proc_ops file_ops_4_our_proc_file = {
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.proc_read = procfs_read,
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.proc_write = procfs_write,
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.proc_open = procfs_open,
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.proc_release = procfs_close,
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};
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#else
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static const struct file_operations file_ops_4_our_proc_file = {
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.read = procfs_read,
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.write = procfs_write,
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.open = procfs_open,
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.release = procfs_close,
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};
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#endif
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static int __init procfs3_init(void)
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{
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our_proc_file = proc_create(PROCFS_ENTRY_FILENAME, 0644, NULL,
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&file_ops_4_our_proc_file);
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if (our_proc_file == NULL) {
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remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL);
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pr_debug("Error: Could not initialize /proc/%s\n",
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PROCFS_ENTRY_FILENAME);
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return -ENOMEM;
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}
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proc_set_size(our_proc_file, 80);
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proc_set_user(our_proc_file, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID);
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pr_debug("/proc/%s created\n", PROCFS_ENTRY_FILENAME);
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return 0;
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}
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static void __exit procfs3_exit(void)
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{
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remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL);
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pr_debug("/proc/%s removed\n", PROCFS_ENTRY_FILENAME);
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}
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module_init(procfs3_init);
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module_exit(procfs3_exit);
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MODULE_LICENSE("GPL");
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