lkml.org 
[lkml]   [2017]   [Jan]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data Integrity)
From
Date
On 01/16/2017 09:39 PM, David Miller wrote:
> From: Khalid Aziz <khalid.aziz@oracle.com>
> Date: Wed, 11 Jan 2017 09:12:54 -0700
>
>> diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
>> index 8a6982d..68b03bf 100644
>> --- a/arch/sparc/kernel/mdesc.c
>> +++ b/arch/sparc/kernel/mdesc.c
>> @@ -20,6 +20,7 @@
>> #include <asm/uaccess.h>
>> #include <asm/oplib.h>
>> #include <asm/smp.h>
>> +#include <asm/adi.h>
>>
>> /* Unlike the OBP device tree, the machine description is a full-on
>> * DAG. An arbitrary number of ARCs are possible from one
>> @@ -1104,5 +1105,8 @@ void __init sun4v_mdesc_init(void)
>>
>> cur_mdesc = hp;
>>
>> +#ifdef CONFIG_SPARC64
>
> mdesc.c is only built on sparc64, this ifdef is superfluous.

Good point. I will fix it.

>
>> +/* Update the state of MCDPER register in current task's mm context before
>> + * dup so the dup'd task will inherit flags in this register correctly.
>> + * Current task may have updated flags since it started running.
>> + */
>> +int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>> +{
>> + if (adi_capable() && src->mm) {
>> + register unsigned long tmp_mcdper;
>> +
>> + __asm__ __volatile__(
>> + ".word 0x83438000\n\t" /* rd %mcdper, %g1 */
>> + "mov %%g1, %0\n\t"
>> + : "=r" (tmp_mcdper)
>> + :
>> + : "g1");
>> + src->mm->context.mcdper = tmp_mcdper;
>
> I don't like the idea of duplicating 'mm' state using the task struct
> copy. Why do not the MM handling interfaces handle this properly?
>
> Maybe it means you've abstracted the ADI register handling in the
> wrong place. Maybe it's a thread property which is "pushed" from
> the MM context.

I see what you are saying. This code updates mm->context.mcdper for the
source thread with the current state of MCDPER since MCDPER can be
changed by a userspace process any time. When userspace changes MCDPER,
it is not saved into mm->context.mcdper until a context switch happens.
This means during the timeslice for a thread, its mm->context.mcdper may
not reflect the current value of MCDPER. Updating it ensures dup_mm()
will copy the real current value of MCDPER into the newly forked thread.
arch_dup_mmap() looks like a more appropriate place to do this. Do you
agree?

Thanks,
Khalid

\
 
 \ /
  Last update: 2017-01-18 01:18    [W:0.070 / U:1.920 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site