Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Florian Weimer
On 05/19/2018 02:52 AM, Ram Pai wrote: The POWER semantics make it very hard for a multithreaded program to meaningfully use protection keys to prevent accidental access to important memory. And you can change access rights for unallocated keys (unallocated at thread start time, allocated

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Ram Pai
On Fri, May 18, 2018 at 11:13:30PM +0200, Florian Weimer wrote: > On 05/18/2018 09:39 PM, Andy Lutomirski wrote: > >The difference is that x86 starts out with deny-all instead of allow-all. Ah!. this explains the discrepency. But still does not explain one thing.. see below. > >The POWER

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Florian Weimer
On 05/18/2018 09:39 PM, Andy Lutomirski wrote: The difference is that x86 starts out with deny-all instead of allow-all. The POWER semantics make it very hard for a multithreaded program to meaningfully use protection keys to prevent accidental access to important memory. And you can change

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Florian Weimer
On 05/18/2018 07:44 PM, Ram Pai wrote: Florian, is the behavior on x86 any different? A key allocated in the context off one thread is not meaningful in the context of any other thread. Since thread B was created prior to the creation of the key, and the key was created in the context of thread

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Andy Lutomirski
On Fri, May 18, 2018 at 10:45 AM Ram Pai wrote: > On Fri, May 18, 2018 at 03:17:14PM +0200, Florian Weimer wrote: > > I'm working on adding POWER pkeys support to glibc. The coding work > > is done, but I'm faced with some test suite failures. > > > > Unlike the default x86

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Ram Pai
On Fri, May 18, 2018 at 03:17:14PM +0200, Florian Weimer wrote: > I'm working on adding POWER pkeys support to glibc. The coding work > is done, but I'm faced with some test suite failures. > > Unlike the default x86 configuration, on POWER, existing threads > have full access to newly allocated

Re: pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Andy Lutomirski
On Fri, May 18, 2018 at 6:17 AM Florian Weimer wrote: > I'm working on adding POWER pkeys support to glibc. The coding work is > done, but I'm faced with some test suite failures. > Unlike the default x86 configuration, on POWER, existing threads have > full access to newly

pkeys on POWER: Default AMR, UAMOR values

2018-05-18 Thread Florian Weimer
I'm working on adding POWER pkeys support to glibc. The coding work is done, but I'm faced with some test suite failures. Unlike the default x86 configuration, on POWER, existing threads have full access to newly allocated keys. Or, more precisely, in this scenario: * Thread A launches