--- David Stroupe <dstroupe@keyed-upsoftware.com> wrote:
> Usman S. Ansari wrote:
>
> >I have a driver (this is continuation of preserving memory accross reboot) whic has some memory
> >allocated and my application wants to write to it. Therefore in the application I (after open
> >call) do
> >
> > if ((ptr = (char *) mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == NULL)
> > {
> > perror("error ...");
> > }
> >
> >Now I have access to memory starting at virtual location ptr for next 4096 bytes. In my driver
> >static int ocr_mmap(struct file *file, struct vm_area_struct *vma)
> >{
> > unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
> > int minor = MINOR(file->f_dentry->d_inode->i_rdev);
> >
> > vma->vm_flags |= VM_RESERVED;
> >
> > if (offset >= __pa(high_memory) || (file->f_flags & O_SYNC))
> > vma->vm_flags |= VM_IO; /* since this driver maps different kind of segs
> */
> >
> >if (remap_page_range(vma->vm_start, __pa(dT[minor].addr), vma->vm_end - vma->vm_start,
> > vma->vm_page_prot) < 0)
> > return -EAGAIN;
> >
> > return(0);
> >}
> >
> >Following 3 are filled by kernel
> >vma->vm_start
> >vma->vm_end
> >vma->vm_start
> >
> >__pa(dT[minor].addr) ---> I have a kernel virtual address and __pa() gives me physical address.
> >
> >I hope this is helpfull.
> >
> Indeed it has been, thanks...I am to this point. I have vmalloced
> memory in the kernel, called mmap using the virt_to_phys call on the
> address returned by vmalloc and get a zero return value from
> remap_page_range. At that point, I would assume that I should be able
> to access the memory using the address that was returned from the mmap
> call. Using gdb, I am told that it cannot access the memory at the
> address that was returned. (x /256xb address is the dgb command that I
> am using). I have used the PROT_READ|PROT_WRITE as well as the
> MAP_SHARED. What am I missing?
>
> TIA
At this point I wrote a userland program and everything worked fine. Perhaps somebody else can
shed light on gdb issue.
>
> --
> Best regards,
> David Stroupe
> Keyed-Up Software
> 5307 Faireast Court
> Arlington, Texas 76018-1683
> 817/557-4903 voice
> 817/472-0408 fax
=====
Usman S. Ansari
Linux OS & Device Drivers
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