In this case, have you tried reading and writing to the memory segment being mmap'd from userland?
Here's an example mmap'ing device driver if you need to see that: https://github.com/claudioscordino/mmap_alloc On Tue, Jan 12, 2016 at 6:10 PM, Jethro Beekman <ker...@jbeekman.nl> wrote: > I'm writing a device driver for a memory-mapped device on x86-64. I'm > mapping > the device in the kernel using ioremap_cache(). My file_operations.mmap > function > is as follows: > > static int dev_mmap(struct file *filep, struct vm_area_struct *vma) { > vma->vm_page_prot.pgprot|=_PAGE_BIT_RW; > return vm_iomap_memory(vma,START,LEN); > } > > The user process calls mmap(..,PROT_READ|PROT_WRITE|PROT_EXEC,..). The > mapping > in /proc/[pid]/maps shows the write bit. However, when looking at the > actual > page table entry does not have the RW bit set. For example: > > virtual address = 0000_0001_8000_0000 > cr3 = 0000_0000_700a_e000 > phys:0000_0000_700a_e000 = 0000_0000_7e05_5067 (P|RW|US|A|D) > phys:0000_0000_7e05_5030 = 0000_0001_66e2_9067 (P|RW|US|A|D) > phys:0000_0001_66e2_9000 = 0000_0001_69db_3067 (P|RW|US|A|D) > phys:0000_0001_69db_3000 = 0000_0000_8020_0225 (P|US|A|SOFTW1) > > Am I doing something wrong? > > Jethro > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >
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