Thanks a lot for the clarification. Is that not a big hole that the kernel provides ?. If I have a root access, then I can spoil the whole system. Is there any motive for the kernel to support this ?
Thanks, Prabhu On Wed, Oct 27, 2010 at 10:04 AM, Dave Hylands <[email protected]> wrote: > Hi Prabhu, > > On Tue, Oct 26, 2010 at 9:19 PM, Prabhu nath <[email protected]> > wrote: > > Dear All, > > > > Can you please clarify my doubt on /dev/mem > > > > When I open /dev/mem, Is that entire physical address space is > > associated to /dev/mem or only the system memory ? > > * If I can mmap the kernel memory in read write mode, I can > screw > > up the whole kernel. Is that right ? > > Absolutely. > > > * Suppose I map a random memory page frame (let's assume it is a > > free page) from physical address 1abde000 to 1abdf000, > > then will the page allocator not allocate this page to to any > > other task or to the kernel ? > > Accessing through /dev/mem has no impact on the page allocator. > > Accessing memory through /dev/mem is the same thing as the kernel > accessing that memory from within kernel space. You can access > allocated pages, unallocated pages, device registers, pretty much > anything at all. Writing indiscriminantly through /dev/mem is the same > thing as writing indiscriminantly from within a driver. > > -- > Dave Hylands > Shuswap, BC, Canada > http://www.DaveHylands.com/ >
