[Xen-users] mmap in PV xen-4.0.1

[Eric Camachat <eric.camachat@xxxxxxxxx>]

Hi,

I have a problem to map kernel memory to userspace via /dev/mem.
The mmap() succeeded, but when I try to access it, the program will
hang forever (until press ctrl-c to terminate it).

# memtest-user
memtest_vma_open: virt 0x7fbc90085000, phys 0x3eee8000
paddr = 0x3eee8000
  mem = 0x7fbc90089000
  map = 0x7fbc90085000
map[0]= 4c4c4c4c
map[1]= 4c4c4c4c
*** Hang here, it cannot (finish) access the memory mapped via /dev/mem ***

My test source below, and it runs properly on HVM, VirtualBox, QEM and
physical machines.
What mistake I did?

My kernel module look like this:
=================================================================================
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <asm/io.h>
#include <asm/page.h>

#define MEMTEST_MAJOR           886
#define MEMTEST_NAME            "memtest"

#define MEMTEST_MAGIC           'M'
#define MEMTEST_DMA_SIZE        _IO(MEMTEST_MAGIC, 0)
#define MEMTEST_DMA_PADDR       _IO(MEMTEST_MAGIC, 1)
#define MEMTEST_DMA_VADDR       _IO(MEMTEST_MAGIC, 2)

#define SIZE_ORDER              2
static uint32_t _size = (PAGE_SIZE << SIZE_ORDER);
static unsigned long _vbase = 0;
static phys_addr_t _pbase = 0;

static int
memtest_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
               unsigned long arg)
{
        int ret = -ENOIOCTLCMD;
        phys_addr_t *paddr;
        unsigned long *vaddr;
        uint32_t *size;

        switch(cmd) {
        case MEMTEST_DMA_SIZE:
                size = (uint32_t*)arg;
                *size = _size;
                ret = 0;
                break;
        case MEMTEST_DMA_PADDR:
                paddr = (phys_addr_t*)arg;
                *paddr = _pbase;
                ret = 0;
                break;
        case MEMTEST_DMA_VADDR:
                vaddr = (unsigned long*)arg;
                *vaddr = _vbase;
                ret = 0;
                break;
        }
        return ret;
}

static void memtest_vma_open(struct vm_area_struct *vma)
{
        printk("%s: virt %#lx, phys %#lx\n", __func__, vma->vm_start,
vma->vm_pgoff << PAGE_SHIFT);
}
static void memtest_vma_close(struct vm_area_struct *vma)
{
        printk("%s\n", __func__);
}
static struct vm_operations_struct memtest_vm_ops = {
        .open   = memtest_vma_open,
        .close  = memtest_vma_close,
};
static int memtest_mmap(struct file * file, struct vm_area_struct * vma)
{
        /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
        if (remap_pfn_range(vma,
                            vma->vm_start,
                            vma->vm_pgoff,
                            vma->vm_end - vma->vm_start,
                            vma->vm_page_prot)) {
                return -EAGAIN;
        }

        vma->vm_ops = &memtest_vm_ops;
        memtest_vma_open(vma);
        return 0;
}

static struct file_operations memtest_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .ioctl          = memtest_ioctl,
        .mmap           = memtest_mmap,
};

static int __init memtest_init(void)
{
        int retval;

        printk(MEMTEST_NAME ": registering /dev/" MEMTEST_NAME "
(%d)\n",MEMTEST_MAJOR );
        retval = register_chrdev(MEMTEST_MAJOR, MEMTEST_NAME, &memtest_fops);
        if (retval < 0)
        {
                printk(MEMTEST_NAME ": failed to register /dev/" MEMTEST_NAME 
"\n");
        }
        printk(MEMTEST_NAME ": size of phys_addr_t is %lu bytes\n",
sizeof(phys_addr_t));

        //_vbase = get_zeroed_page(GFP_KERNEL);
        _vbase = __get_free_pages(GFP_KERNEL, SIZE_ORDER);
        if (_vbase == 0)
        {
                printk(MEMTEST_NAME ": kmalloc(%d, GFP_KERNEL) failed\n", 
_size);
        }
        else
        {
                memset((void*)_vbase, 'L', _size);
                ((uint32_t*)_vbase)[0] = 0x1234;
                ((uint32_t*)_vbase)[1] = 0xabcd;
                ((uint32_t*)_vbase)[2] = 0xeeee;
                ((uint32_t*)_vbase)[3] = 0xffff;
                _pbase = virt_to_bus((void*)_vbase);
        }

        printk(MEMTEST_NAME ": _vbase = %#lx\n", _vbase);
        printk(MEMTEST_NAME ": _pbase = %#lx\n", (unsigned long)_pbase);
        return retval;
}

static void __exit memtest_exit(void)
{
        if (_vbase != 0)
                free_page(_vbase);
        unregister_chrdev(MEMTEST_MAJOR, MEMTEST_NAME);
}


MODULE_LICENSE("GPL");

module_init(memtest_init);
module_exit(memtest_exit);
=================================================================================

Here is my user program:

=================================================================================
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>
#include <stdint.h>

#define MEMTEST_MAGIC           'M'
#define MEMTEST_DMA_SIZE        _IO(MEMTEST_MAGIC, 0)
#define MEMTEST_DMA_PADDR       _IO(MEMTEST_MAGIC, 1)
#define MEMTEST_DMA_VADDR       _IO(MEMTEST_MAGIC, 2)

#define DEVDIAG                 "/dev/memtest"
#define DEVMEM                  "/dev/mem"
uint32_t get_size(void);
unsigned long get_paddr(void);
unsigned int * mmap_memtest(unsigned long paddr, uint32_t size);
unsigned int * mmap_mem(unsigned long paddr, uint32_t size);

uint32_t get_size(void)
{
        int diagfd, rv;
        uint32_t size;

        diagfd = open( DEVDIAG, O_RDWR | O_SYNC | O_DSYNC | O_RSYNC );
        if (diagfd < 0)
        {
                perror("Error : fail to open" DEVDIAG);
                return 0;
        }

        rv = ioctl( diagfd, MEMTEST_DMA_SIZE, &size);
        if (rv < 0)
        {
                perror("Fail to perform ioctl");
                return 0;
        }
        close(diagfd);

        return size;
}

unsigned long get_paddr(void)
{
        int diagfd, rv;
        unsigned long paddr;

        diagfd = open( DEVDIAG, O_RDWR | O_SYNC | O_DSYNC | O_RSYNC );
        if (diagfd < 0)
        {
                perror("Error : fail to open" DEVDIAG);
                return 0;
        }
        rv = ioctl( diagfd, MEMTEST_DMA_PADDR, &paddr);
        if ( rv < 0 ) {
                perror("Fail to perform ioctl");
                return 0;
        }
        close(diagfd);

        return paddr;
}

unsigned int * mmap_memtest(unsigned long paddr, uint32_t size)
{
        int diagfd;
        unsigned int page_size = getpagesize();
        unsigned int page_mask = ~(page_size - 1);
        unsigned int *vaddr = NULL;

        /** test mmap */
        if ( paddr & ~page_mask ) {
                printf("Error : not algined %#lxx & %08x\n", paddr, ~page_mask 
);
                return NULL;
        }

        diagfd = open( DEVDIAG, O_RDWR | O_SYNC | O_DSYNC | O_RSYNC );
        if (diagfd < 0)
        {
                printf("Error : fail to open "DEVDIAG);
                return NULL;
        }


        vaddr =  (unsigned int*) mmap(NULL, size, PROT_READ, MAP_SHARED,
diagfd, paddr);
        close(diagfd);

        return vaddr;
}

unsigned int * mmap_mem(unsigned long paddr, uint32_t size)
{
        int memfd;
        unsigned int page_size = getpagesize();
        unsigned int page_mask = ~(page_size - 1);
        unsigned int *vaddr = NULL;

        /** test mmap */
        if ( paddr & ~page_mask ) {
                printf("Error : not algined %#lxx & %08x\n", paddr, ~page_mask 
);
                return NULL;
        }

        memfd = open(DEVMEM, O_RDWR |  O_SYNC | O_DSYNC | O_RSYNC);
        if (memfd < 0)
        {
                perror("Error : fail to open "DEVMEM);
                return NULL;
        }

        vaddr =  (unsigned int*) mmap(NULL, size, PROT_READ, MAP_SHARED, memfd, 
paddr);
        close(memfd);

        return vaddr;
}

int main(int argc, char **argv)
{
        uint32_t size = get_size();
        unsigned long paddr = get_paddr();
        unsigned int *mem = mmap_mem(paddr, size);
        unsigned int *map = mmap_memtest(paddr, size);

        printf("paddr = %#lx\n", paddr);
        printf("  mem = %p\n", mem);
        printf("  map = %p\n", map);

        if (map)
        {
                printf("map[0]= %x\n", map[0]);
                printf("map[1]= %x\n", map[1]);
        }

        if (mem)
        {
                printf("mem[0]= %x\n", mem[0]);
                printf("mem[1]= %x\n", mem[1]);
        }

          return 0;
}
=================================================================================

memtest-module.c
Description: Text Data

memtest-user.c
Description: Text Data

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