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Subject: Re: [PATCH v7 9/9] sparc64: Add support for ADI (Application Data
 Integrity)
From: David Miller <davem@davemloft.net>
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From: Khalid Aziz <khalid.aziz@oracle.com>
Date: Wed, 30 Aug 2017 16:27:54 -0600

>>> +#define arch_calc_vm_prot_bits(prot, pkey)
>>> sparc_calc_vm_prot_bits(prot)
>>> +static inline unsigned long sparc_calc_vm_prot_bits(unsigned long
>>> prot)
>>> +{
>>> +	if (prot & PROT_ADI) {
>>> +		struct pt_regs *regs;
>>> +
>>> +		if (!current->mm->context.adi) {
>>> +			regs = task_pt_regs(current);
>>> +			regs->tstate |= TSTATE_MCDE;
>>> +			current->mm->context.adi = true;
>> If a process is multi-threaded when it enables ADI on some memory for
>> the first time, TSTATE_MCDE will only be set for the calling thread
>> and it will not be possible to enable it for the other threads.
>> One possible way to handle this is to enable TSTATE_MCDE for all user
>> threads when they are initialized if adi_capable() returns true.
>> 
> 
> Or set TSTATE_MCDE unconditionally here by removing "if
> (!current->mm->context.adi)"?

I think you have to make "ADI enabled" a property of the mm_struct.

Then you can broadcast to mm->cpu_vm_mask a per-cpu interrupt that
updates regs->tstate of a thread using 'mm' is currently executing.

And in the context switch code you set TSTATE_MCDE if it's not set
already.

That should cover all threaded case.