On Tue, Dec 19, 2017 at 09:31:22AM +0100, Gabriel Paubert wrote:
On Mon, Dec 18, 2017 at 03:15:51PM -0800, Ram Pai wrote:
On Mon, Dec 18, 2017 at 02:28:14PM -0800, Dave Hansen wrote:
On 12/18/2017 02:18 PM, Ram Pai wrote:
....snip...
I think on x86 you look for some hardware registers to determine which hardware features are enabled by the kernel.
No, we use CPUID. It's a part of the ISA that's designed for enumerating CPU and (sometimes) OS support for CPU features.
We do not have generic support for something like that on ppc. The kernel looks at the device tree to determine what hardware features are available. But does not have mechanism to tell the hardware to track which of its features are currently enabled/used by the kernel; atleast not for the memory-key feature.
Bummer. You're missing out.
But, you could still do this with a syscall. "Hey, kernel, do you support this feature?"
or do powerpc specific sysfs interface. or a debugfs interface.
getauxval(3) ?
With AT_HWCAP or HWCAP2 as parameter already gives information about features supported by the hardware and the kernel.
Taking one bit to expose the availability of protection keys to applications does not look impossible.
Do I miss something obvious?
No. I am told this is possible aswell.
RP
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