[PATCH 4/6] mm/mprotect, powerpc/mm/pkeys, x86/mm/pkeys: Add sysfs interface

[Balbir Singh]

On Fri, 15 Sep 2017 18:21:08 -0700
Ram Pai <linuxram at us.ibm.com> wrote:

> From: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
> 
> Expose useful information for programs using memory protection keys.
> Provide implementation for powerpc and x86.
> 
> On a powerpc system with pkeys support, here is what is shown:
> 
> $ head /sys/kernel/mm/protection_keys/*
> ==> /sys/kernel/mm/protection_keys/disable_access_supported <==  
> true
> 
> ==> /sys/kernel/mm/protection_keys/disable_execute_supported <==  
> true
> 
> ==> /sys/kernel/mm/protection_keys/disable_write_supported <==  
> true
> 
> ==> /sys/kernel/mm/protection_keys/total_keys <==  
> 32
> 
> ==> /sys/kernel/mm/protection_keys/usable_keys <==  
> 29
> 
> And on an x86 without pkeys support:
> 
> $ head /sys/kernel/mm/protection_keys/*
> ==> /sys/kernel/mm/protection_keys/disable_access_supported <==  
> false
> 
> ==> /sys/kernel/mm/protection_keys/disable_execute_supported <==  
> false
> 
> ==> /sys/kernel/mm/protection_keys/disable_write_supported <==  
> false
> 
> ==> /sys/kernel/mm/protection_keys/total_keys <==  
> 1
> 
> ==> /sys/kernel/mm/protection_keys/usable_keys <==  
> 0
> 
> Signed-off-by: Ram Pai <linuxram at us.ibm.com>
> Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
> ---

Just curious, how do you see this being used? For debugging
or will applications parse these properties and use them?
It's hard for an application to partition its address space
among keys at runtime, would you agree?

Balbir Singh.