Question

正如this问题中所讨论的，我在引导时使用内核引导参数memmap=8G$64G

保留内存块

我编写了一个character driver内核模块，在初始化期间~~会执行此保留内存块的ioremap。~~ 正如here所解释的那样，在我的驱动程序mmap中，remap_pfn_range返回的内存块指针只需要ioremap。

我在 3.0 linux内核上运行它。我的用户空间应用程序打开此内存块作为驱动程序安装的设备。当我从使用空间应用程序中mmap时，我看到系统挂起。我的dmesg没有向我提供太多信息。

有任何输入吗？

static int __init myDev_module_init(void)
{
   int retval;

   myDev_major = register_chrdev(0, DEVICE_NAME, &myDevfops);
   if (myDev_major < 0) 
   {
       err("failed to register device: error %d\n", myDev_major);
       retval = myDev_major;
       goto FAILED_CHRDEVREG;
   }

   myDev_class = class_create(THIS_MODULE, CLASS_NAME);
   if (IS_ERR(myDev_class)) 
   {   
       err("failed to register device class '%s'\n", CLASS_NAME);
       retval = PTR_ERR(myDev_class);
       goto FAILED_CLASSREG;
   }


   myDev_device = device_create(myDev_class, NULL, MKDEV(myDev_major, 0), NULL, CLASS_NAME "_" DEVICE_NAME);
   if (IS_ERR(myDev_device)) 
   {
       err("failed to create device '%s_%s'\n", CLASS_NAME, DEVICE_NAME);
       retval = PTR_ERR(myDev_device);
       goto FAILED_DEVREG;
   }

此处myDev.startOffset初始化为#define d 64GB，myDev.memSize初始化为8GB。

 //myDev.startAddr = ioremap(myDev.startOffset,myDev.memSize);

 //memset_io(myDev.startAddr, 0, myDev.memSize);  
 return 0;

  FAILED_DEVREG:
   class_unregister(myDev_class);
   class_destroy(myDev_class);
  FAILED_CLASSREG:
   unregister_chrdev(myDev_major, DEVICE_NAME);
  FAILED_CHRDEVREG:
   return -1;
}

static int myDev_device_open(struct inode* inode, struct file* filp)
{
    dbg("");

    if ( ((filp->f_flags & O_ACCMODE) == O_WRONLY) || ((filp->f_flags & O_ACCMODE) == O_RDWR) ) 
    {
        warn(" Opening the device with write access\n");
        //return -EACCES;
    }

    info(" device Open is called\n");
    filp->private_data = &myDev;
    return 0;
 }

mmap非常直接。

static int myDev_device_mmap(struct file * f, struct vm_area_struct * vma)
{
 int retval = 0;
struct myDevDev * pDev = (struct myDevDev *)(f->private_data);

dbg("");
if(vma)
{
    if(f)
    {
        if(f->private_data)
            warn("mmap: f->private_data  : %p\n", f->private_data);
        else
            warn(" mmap :f->private_data  : NULL \n");
    }
    else
    {
        warn("mmap: f  :NULL\n");
    }
    warn(": mmap: vm start : %lu\n", vma->vm_start);
    warn(" mmap: vm end  : %lu\n", vma->vm_end);
    warn(" mmap: vm pg offset  : %lu\n", vma->vm_pgoff);



    //retval = remap_pfn_range(vma, vma->vm_start, pDev->startOffset >> PAGE_SHIFT,    pDev->memSize, PAGE_SHARED) ;
    // retval = remap_pfn_range(vma, vma->vm_start, pDev->startAddr >> PAGE_SHIFT,    pDev->memSize, PAGE_SHARED) ;
    //retval = remap_pfn_range(vma,pDev->startAddr ,pDev->startOffset >> PAGE_SHIFT,  pDev->memSize, PAGE_SHARED);
    retval = remap_pfn_range(vma,vma->vm_start ,pDev->startOffset >> PAGE_SHIFT,  pDev->memSize, PAGE_SHARED);
    if(retval <0)
    {
        warn(" ERROR : in mapping kernel virtual space to user space return value : %d \n",retval);
        return -EINVAL;
    }

    //if(0)
    {
        vma->vm_flags |=VM_LOCKED;
        vma->vm_ops = &myRemapVMOps;
        vma->vm_flags |= VM_RESERVED;

        vma->vm_private_data = f->private_data;
        myDevice_VMA_Open(vma);
    }
}
else
{
    warn ("vma is NULL");
}

dbg(" Done ");
warn("mmpaing done : \n");

return 0;
}

来自我的用户空间应用程序我正在执行以下操作：

int err, i=0;
void * mptr = NULL;
printf(" Access the reserved memory chunk \n  ");
int fd = open("/dev/myDevice", O_RDWR | O_SYNC);

if(fd <=0)
{
    printf("ERROR: my device driver is not loaded \n");
    return 1;
}

  printf("\n mmaping mem chunk size :%llu pagesize :%lu input mptr :%p\n", sz,getpagesize (), mptr);

  mptr = mmap(0, sz , PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED, fd, 0);

if(mptr == MAP_FAILED) 
{
    close(fd);
    perror("Error mmapping the file");
    printf("\nmmapped mem address %p\n",mptr);
    exit(1);
}
printf("\nmmapped mem address %p\n",mptr);

//char * ptr = (char *)mptr;
//*ptr = 'a';

//int * pInt =  (int *) (((char *) mptr)+1); 
//for(;i<10000; ++i)
{
  //  pInt[i] = 2*i;
}

 /* free the mmapped memory
 */
if (munmap(mptr, sz) == -1) 
{
    perror("Error un-mmapping the file");
}

close(fd);

观察：

我认为(vma->vm_end - vma->vm_start)中没有反映出尺寸，因为某些原因总是4K。

Answer 1

您可以分步使用标准的phram驱动程序从用户空间访问内存。不需要编码。内核重新编译最多。
你真的有超过64Gb的内存吗？你的硬件真的支持吗？

Answer 2

当我从使用空间应用程序执行mmap时，我看到系统挂起。

在使用remap_pfn_range（）API之前，请参阅mm / memory.c（内核源代码）中内联的文档，它表明您必须先保持mm信号量。

/**
 * remap_pfn_range - remap kernel memory to userspace
 * @vma: user vma to map to
 * @addr: target user address to start at
 * @pfn: physical address of kernel memory
 * @size: size of map area
 * @prot: page protection flags for this mapping
 *
 *  Note: this is only safe if the mm semaphore is held when called.
 */

如何获取信号量是通过up_read（）和down_read（）API - 只是＆＃34; grep＆＃34;对于mm目录中的up_read，有很多例子：

mempolicy.c:    up_read(&mm->mmap_sem);
migrate.c:  up_read(&mm->mmap_sem);
mincore.c:      up_read(&current->mm->mmap_sem);
mmap.c:     up_read(&mm->mmap_sem);
msync.c:            up_read(&mm->mmap_sem);
nommu.c:    up_read(&mm->mmap_sem);

将mmap内核引导参数保留的内存映射到用户空间

2 个答案: