On Tue, 2017-06-20 at 15:10 +1000, Balbir Singh wrote: > On Fri, 2017-06-16 at 20:52 -0700, Ram Pai wrote: > > Memory protection keys enable applications to protect its > > address space from inadvertent access or corruption from > > itself. > > I presume by itself you mean protection between threads?
Not necessarily. You could have for example a JIT that when it runs the JITed code, only "opens" the keys for the VM itself, preventing the JITed code from "leaking out" There are plenty of other usages... > > > The overall idea: > > > > A process allocates a key and associates it with > > a address range within its address space. > > OK, so this is per VMA? > > > The process than can dynamically set read/write > > permissions on the key without involving the > > kernel. > > This bit is not clear, how can the key be set without > involving the kernel? I presume you mean the key is set > in the PTE's and the access protection values can be > set without involving the kernel? > > Any code that violates the permissions > > off the address space; as defined by its associated > > key, will receive a segmentation fault. > > > > This patch series enables the feature on PPC64. > > It is enabled on HPTE 64K-page platform. > > > > ISA3.0 section 5.7.13 describes the detailed specifications. > > > > > > Testing: > > This patch series has passed all the protection key > > tests available in the selftests directory. > > The tests are updated to work on both x86 and powerpc. > > Balbir
