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mmap example works

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This commit is contained in:
Ciro Santilli
2017-07-30 11:23:31 +01:00
parent 5393299433
commit 46bf3f700e
4 changed files with 97 additions and 166 deletions
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196
kernel_module/mmap.c
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@@ -1,43 +1,35 @@
/*
Remember: mmap does not work with debugfs as of 4.9!
*/
Remember: mmap, like most fops, does not work with debugfs as of 4.9! https://patchwork.kernel.org/patch/9252557/
#if 0
/*
Adapted from:
https://coherentmusings.wordpress.com/2014/06/10/implementing-mmap-for-transferring-data-from-user-space-to-kernel-space/
*/
#include <asm/uaccess.h> /* copy_from_user */
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kernel.h> /* min */
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#ifndef VM_RESERVED
# define VM_RESERVED (VM_DONTEXPAND | VM_DONTDUMP)
#endif
static const char *filename = "lkmc_mmap";
static struct dentry *debugfs_file;
enum { BUFFER_SIZE = 4 };
struct mmap_info
{
struct mmap_info {
char *data;
int reference;
};
/* After unmap. */
static void vm_close(struct vm_area_struct *vma)
{
struct mmap_info *info;
pr_info("vm_close\n");
info = (struct mmap_info *)vma->vm_private_data;
info->reference--;
}
/* First page access. */
static int vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct page *page;
@@ -53,13 +45,10 @@ static int vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
return 0;
}
/* Aftr mmap. TODO vs mmap, when can this happen at a different time than mmap? */
static void vm_open(struct vm_area_struct *vma)
{
struct mmap_info *info;
pr_info("vm_open\n");
info = (struct mmap_info *)vma->vm_private_data;
info->reference++;
}
static struct vm_operations_struct vm_ops =
@@ -73,7 +62,7 @@ static int mmap(struct file *filp, struct vm_area_struct *vma)
{
pr_info("mmap\n");
vma->vm_ops = &vm_ops;
vma->vm_flags |= VM_RESERVED;
vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_private_data = filp->private_data;
vm_open(vma);
return 0;
@@ -86,11 +75,38 @@ static int open(struct inode *inode, struct file *filp)
pr_info("open\n");
info = kmalloc(sizeof(struct mmap_info), GFP_KERNEL);
info->data = (char *)get_zeroed_page(GFP_KERNEL);
memcpy(info->data, "abc", 4);
memcpy(info->data, "asdf", BUFFER_SIZE);
filp->private_data = info;
return 0;
}
static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off)
{
struct mmap_info *info;
int ret;
pr_info("read\n");
info = filp->private_data;
ret = min(len, (size_t)BUFFER_SIZE);
if (copy_to_user(buf, info->data, ret)) {
ret = -EFAULT;
}
return ret;
}
static ssize_t write(struct file *filp, const char __user *buf, size_t len, loff_t *off)
{
struct mmap_info *info;
pr_info("write\n");
info = filp->private_data;
if (copy_from_user(info->data, buf, min(len, (size_t)BUFFER_SIZE))) {
return -EFAULT;
} else {
return len;
}
}
static int release(struct inode *inode, struct file *filp)
{
struct mmap_info *info;
@@ -107,138 +123,8 @@ static const struct file_operations fops = {
.mmap = mmap,
.open = open,
.release = release,
};
static int myinit(void)
{
debugfs_file = debugfs_create_file("lkmc_mmap", S_IRWXU, NULL, NULL, &fops);
return 0;
}
static void myexit(void)
{
debugfs_remove(debugfs_file);
}
module_init(myinit);
module_exit(myexit);
MODULE_LICENSE("GPL");
/*minimized debugfs*/
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
static struct dentry *debugfs_file;
static int mmap(struct file *filp, struct vm_area_struct *vma)
{
pr_info("mmap\n");
if (remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
vma->vm_end - vma->vm_start, vma->vm_page_prot)) {
return -EAGAIN;
}
return 0;
}
struct file_operations fops =
{
.owner = THIS_MODULE,
.open = nonseekable_open,
.mmap = mmap
};
static int myinit(void)
{
debugfs_file = debugfs_create_file("lkmc_mmap", S_IRWXU, NULL, NULL, &fops);
return 0;
}
static void myexit(void)
{
debugfs_remove(debugfs_file);
}
module_init(myinit);
module_exit(myexit);
MODULE_LICENSE("GPL");
/*working chardev*/
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#define NAME "lkmc_mmap"
static int major;
static int mmap(struct file *filp, struct vm_area_struct *vma)
{
pr_info("mmap\n");
if (remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
vma->vm_end - vma->vm_start, vma->vm_page_prot)) {
return -EAGAIN;
}
return 0;
}
struct file_operations fops =
{
.owner = THIS_MODULE,
.open = nonseekable_open,
.mmap = mmap
};
static int myinit(void)
{
major = register_chrdev(0, NAME, &fops);
return 0;
}
static void myexit(void)
{
unregister_chrdev(major, NAME);
}
module_init(myinit)
module_exit(myexit)
MODULE_LICENSE("GPL");
#endif
/* proc attempt */
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
static const char *filename = "lkmc_procfs";
static int mmap(struct file *filp, struct vm_area_struct *vma)
{
pr_info("mmap\n");
return 0;
}
struct file_operations fops =
{
.owner = THIS_MODULE,
.open = nonseekable_open,
.mmap = mmap
.read = read,
.write = write,
};
static int myinit(void)