Messages in this thread |  | | From | "Imran Badr" <> | Subject | RE: Calculating kernel logical address .. | Date | Mon, 9 Sep 2002 11:41:52 -0700 |
| |
-----Original Message----- From: Daniel Phillips [mailto:phillips@arcor.de] Sent: Monday, September 09, 2002 11:27 AM To: imran.badr@cavium.com; root@chaos.analogic.com Cc: 'David S. Miller'; linux-kernel@vger.kernel.org Subject: Re: Calculating kernel logical address ..
On Monday 09 September 2002 20:12, Imran Badr wrote: > But my question here still begging an answer: What would be the portable way > to calculate kernel logical address of that user buffer?
>Could you please post your code for doing the kmalloc and mmap? > >-- >Daniel
Sure, in mmap():
size = vma->vm_end - vma->vm_start; if(size % PAGE_SIZE) { printk(KERN_CRIT "mmap: size (%ld) not multiple of PAGE_SIZE.\n", size); return -ENXIO; }
offset = vma->vm_pgoff<<PAGE_SHIFT; if(offset & ~PAGE_MASK) { printk(KERN_CRIT "mmap: offset (%ld) not aligned.\n", offset); return -ENXIO; }
kmalloc_ptr = (Uint8 *)kmalloc(size+(2*PAGE_SIZE), GFP_KERNEL); if(kmalloc_ptr == NULL) { printk(KERN_CRIT "mmap: not enough memory.\n"); return -ENOMEM; }
/* align it to page boundary */ kmalloc_area = (Uint8 *)(((Uint32)kmalloc_ptr + PAGE_SIZE -1) & PAGE_MASK);
/* reserve all pages */ for(virt_addr = (Uint32)kmalloc_area; virt_addr < (Uint32)kmalloc_area + size; virt_addr +=PAGE_SIZE) { mem_map_reserve(virt_to_page(virt_addr)); }
/* lock the area*/ vma->vm_flags |=VM_LOCKED;
if(remap_page_range(vma->vm_start, virt_to_phys((void *)(Uint32)kmalloc_area), size, PAGE_SHARED)) { printk(KERN_CRIT "mmap: remap page range failed.\n"); return -ENXIO; }
vma->vm_ops = &pkp_vma_ops; vma->vm_private_data = kmalloc_ptr; return 0;
This works just fine on my i386 platform (SMP ,non-SMP). Now in my ioctl() entry I get the kernel logical address by using the following code:
adr = user_address; pgd_offset(current->mm, adr); if (!pgd_none(*pgd)) { pmd = pmd_offset(pgd, adr); if (!pmd_none(*pmd)) { ptep = pte_offset(pmd, adr); pte = *ptep; if(pte_present(pte)) { kaddr = (unsigned long) page_address(pte_page(pte)); kaddr |= (adr & (PAGE_SIZE - 1)); } } }
Now for DMA, I get bus address by using virt_to_bus(kaddr). So, is there any portablility issue in this scheme?
Thanks, Imran.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |