Messages in this thread | | | Subject | Re: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data Integrity) | From | Khalid Aziz <> | Date | Tue, 17 Jan 2017 17:14:34 -0700 |
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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
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