Messages in this thread | | | Subject | Re: [PATCH 26/26] x86, pkeys: Documentation | From | Dave Hansen <> | Date | Fri, 16 Oct 2015 08:12:48 -0700 |
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On 10/03/2015 12:27 AM, Ingo Molnar wrote: > - Along similar considerations, also add a sys_pkey_query() system call to query > the mapping of a specific pkey. (returns -EBADF or so if the key is not mapped > at the moment.) This too could be vDSO accelerated in the future. > > I.e. something like: > > unsigned long sys_pkey_alloc (unsigned long flags, unsigned long init_val) > unsigned long sys_pkey_set (int pkey, unsigned long new_val) > unsigned long sys_pkey_get (int pkey) > unsigned long sys_pkey_free (int pkey)
The pkey_set() operation is going to get a wee bit interesting with signals.
pkey_set() will modify the _current_ context's PKRU which includes the register itself and the kernel XSAVE buffer (if active). But, since the PKRU state is saved/restored with the XSAVE state, we will blow away any state set during the signal.
I _think_ the right move here is to either keep a 'shadow' version of PKRU inside the kernel (for each thread) and always update the task's XSAVE PKRU state when returning from a signal handler. Or, _copy_ the signal's PKRU state in to the main process's PKRU state when returning from a signal.
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