Messages in this thread | | | From | Thomas Schlichter <> | Subject | Re: Pinning kernel memory | Date | Thu, 12 Dec 2002 22:04:15 +0100 |
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Thanks, Oliver Neukum mailed me a similar answer, too.
So it looks as my problem was an other one, but setting the pages reserved solved it. The problem was that I remapped these kernel pages into user space and accessing this remapped memory always leaded to a SIGBUS. And since setting the pages reserved "pins" them, I thought they were swapped out...
I don't know if that is the correct way I do it, and if anyone can tell me how it should be done I'll be interested...
Thomas Schlichter
P.S.: Here are some of the lines from the code I wrote that should show what I mean... ;-)
int mem_init_module(void) { struct page *page;
~~~ cut ~~~
// allocate mem_size bytes of physical continuous kernel memory page = alloc_pages( GFP_KERNEL, order ); if( !page ) { printk( "<1>kernel_mem.o: could not get %d bytes of kernel memory\n", mem_size ); return -ENOMEM; } mem_addr = page_address( page );
// pin the memory while( page < virt_to_page(mem_addr + mem_size) ) SetPageReserved( page++ );
~~~ cut ~~~
return 0; // initialization successful }
int mem_mmap( struct file *filp, struct vm_area_struct *vma ) { unsigned long offset; // byte offset from start address unsigned long physical; // physical start address unsigned long vsize; // size in virtual address space unsigned long psize; // size in physical address space
offset = vma->vm_pgoff << PAGE_SHIFT; physical = virt_to_bus(mem_addr) + offset; vsize = vma->vm_end - vma->vm_start; psize = mem_size - offset;
printk( "<1>kernel_mem.o: mmap offset %lu, physical %#010lx, vsize %lu, psize %lu\n", offset, physical, vsize, psize );
// virtual range is fully mapped to physical address space ? if ( vsize > psize ) { printk("<1>kernel_mem.o: mmap failed as vsize > psize\n"); return -EINVAL; }
// do the remapping remap_page_range( vma->vm_start, physical, vsize, vma->vm_page_prot );
// register memory operations to the kernel tables (like file operations) vma->vm_ops = &mem_vm_ops;
// invoke the vma_open routine (which actually does nothing) mem_vma_open( vma );
return 0; }
Am Donnerstag, 12. Dezember 2002 21:15 schrieb Rik van Riel: > On Thu, 12 Dec 2002, Thomas Schlichter wrote: > > I want to create a big area of unswappable, physical continuous kernel > > memory for hardware testing purposes. Currently I allocate the memory > > using alloc_pages(GFP_KERNEL, order) and after this I pin it using > > SetPageReserved(page) for each page. > > Kernel memory is never swappable, so there is no need to "pin it". > > > Rik
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