map reserver memory at boot to user space using remap_pfn_range - linux-device-driver

Question

I am trying to map reserved memory (30M with offset of 2G) at boot time (boot kernel parameters mem=2G memmap=30M$2G) to user space using the remap_pfn_range, bellow is my driver code:
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <asm/uaccess.h>
// #include <asm/error.h>
#define MAP_MAJOR 150
#define RAW_DATA_SIZE 0x1E00000 // 30 Mo
#define RAW_DATA_OFFSET 0x80000000 //2G
int results;
static void *rawdataStart = NULL;
static int map_mmap(struct file *filp, struct vm_area_struct *vma);
struct file_operations map_fops = {
.open = nonseekable_open,
.mmap = map_mmap
};
static int map_mmap(struct file *filp, struct vm_area_struct *vma) {
if (rawdataStart == NULL) {
printk(KERN_ERR "Memory not mapped!\n");
return -EAGAIN;
}
if ((vma->vm_end - vma->vm_start) != RAW_DATA_SIZE) {
printk(KERN_ERR "Error: sizes don't match (buffer size = %d, requested size = %lu)\n", RAW_DATA_SIZE, vma->vm_end - vma->vm_start);
return -EAGAIN;
}
results = remap_pfn_range(vma, vma->vm_start, RAW_DATA_OFFSET >> PAGE_SHIFT, RAW_DATA_SIZE, PAGE_SHARED);
if (results != 0) {
printk(KERN_ERR "Error in calling remap_pfn_range: returned %d\n", results);
return -EAGAIN;
}
return 0;
}
static int __init map_init(void)
{
printk("init map module\n");
if (register_chrdev(MAP_MAJOR,"mapReserved", &map_fops) <0 )
{
printk("unable to get major for map module\n");
return -EBUSY;
}
rawdataStart = ioremap(RAW_DATA_OFFSET, RAW_DATA_SIZE);
if (rawdataStart == NULL) {
printk(KERN_ERR "Unable to remap memory\n");
return 1;
}
printk(KERN_INFO "ioremap returned %p\n", rawdataStart);
return 0;
}
void __exit map_cleanup(void)
{
printk("exit map module\n");
unregister_chrdev(MAP_MAJOR,"mapReserved");
if (rawdataStart != NULL) {
printk(KERN_INFO "Unmapping memory at %p\n", rawdataStart);
iounmap(rawdataStart);
} else {
printk(KERN_WARNING "No memory to unmap!\n");
}
return;
}
MODULE_LICENSE("GPL");
module_init( map_init);
module_exit( map_cleanup);
and my user space app is below
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#define RAW_DATA_SIZE 0x1E00000
int main(void)
{
void * data;
int fd = open("/dev/mapReserved", O_RDWR);
if (fd == -1) {
perror("open error...\n");
return -1;
}
data = mmap(NULL, RAW_DATA_SIZE, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 4096);
close(fd);
return 0;
}
when i insert the module it's return
[ 873.621763] init map module
[ 873.623175] ioremap returned fb580000
but when i am executing the user space app it's return error
open error...

Answer 1

I've resolved this problem following those references :
1- Reserve memory in Linux driver module and share it using driver mmap
2- mmap of several GB of reserved memory using
in my case i am reserving 30M from the offset 2G and bellow is the code
module:
// #include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/debugfs.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <asm/page.h>
#include <linux/cdev.h>
#include <linux/device.h>
#ifndef VM_RESERVED
# define VM_RESERVED (VM_DONTEXPAND | VM_DONTDUMP)
#endif
#define RAW_DATA_SIZE 31457280
#define RAW_DATA_OFFSET 0x80000000UL
void *rawdataStart;
struct dentry *file;
/*
* Open the device; in fact, there's nothing to do here.
*/
int simple_open (struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Closing is just as simpler.
*/
static int simple_release(struct inode *inode, struct file *filp)
{
return 0;
}
static int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma)
{
int ret;
unsigned long mapoffset;
mapoffset = RAW_DATA_OFFSET + (vma->vm_pgoff << PAGE_SHIFT);
ret = remap_pfn_range(vma, vma->vm_start, mapoffset >> PAGE_SHIFT,
vma->vm_end - vma->vm_start, PAGE_SHARED);
if ( ret != 0 ) {
printk("Error remap_pfn_range. \n");
return -EAGAIN;
}
return 0;
}
/* Device uses remap_pfn_range */
static struct file_operations simple_remap_ops = {
.owner = THIS_MODULE,
.open = simple_open,
.release = simple_release,
.mmap = simple_remap_mmap,
};
/*
* Module housekeeping.
*/
static int simple_init(void)
{
file = debugfs_create_file("mmap_example", 0644, NULL, NULL, &simple_remap_ops);
rawdataStart = ioremap(RAW_DATA_OFFSET, RAW_DATA_SIZE);
if (rawdataStart!=NULL){
printk("rawdataStart at:%p \n", rawdataStart);
memset(rawdataStart, 'c', 20971520);
memset(rawdataStart+20971520, '$', 100);
}else{
printk("rawdataStart is NULL \n");
return -1;
}
return 0;
}
static void simple_cleanup(void)
{
debugfs_remove(file);
if (rawdataStart != NULL) {
printk(KERN_INFO "Unmapping memory at %p\n", rawdataStart);
iounmap(rawdataStart);
} else {
printk(KERN_WARNING "No memory to unmap!\n");
}
}
module_init(simple_init);
module_exit(simple_cleanup);
MODULE_AUTHOR("Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
and the user space App:
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#define RAW_DATA_SIZE 31457280
int main(int argc, char **argv) {
int configfd;
char * address = NULL;
unsigned long chkSum;
FILE *fp = fopen("results.log", "w+");
configfd = open("/sys/kernel/debug/mmap_example", O_RDWR);
if (configfd < 0) {
perror("Open call failed");
return -1;
}
address = (unsigned char*) mmap(NULL, RAW_DATA_SIZE, PROT_WRITE,
MAP_PRIVATE, configfd, 0);
if (address == MAP_FAILED) {
perror("mmap operation failed");
return -1;
}
fputs(address, fp);
fclose(fp);
close(configfd);
return 0;
}