Re: [Xen-devel] [PATCH v2 2/4] x86/xen: add basic KASAN support for PV kernel

[Sergey Dyasli <sergey.dyasli@citrix.com>]

On 17/01/2020 14:56, Boris Ostrovsky wrote:
>
>
> On 1/17/20 7:58 AM, Sergey Dyasli wrote:
>> --- a/arch/x86/mm/kasan_init_64.c
>> +++ b/arch/x86/mm/kasan_init_64.c
>> @@ -13,6 +13,9 @@
>>   #include <linux/sched/task.h>
>>   #include <linux/vmalloc.h>
>>   +#include <xen/xen.h>
>> +#include <xen/xen-ops.h>
>> +
>>   #include <asm/e820/types.h>
>>   #include <asm/pgalloc.h>
>>   #include <asm/tlbflush.h>
>> @@ -332,6 +335,11 @@ void __init kasan_early_init(void)
>>       for (i = 0; pgtable_l5_enabled() && i < PTRS_PER_P4D; i++)
>>           kasan_early_shadow_p4d[i] = __p4d(p4d_val);
>>   +    if (xen_pv_domain()) {
>> +        pgd_t *pv_top_pgt = xen_pv_kasan_early_init();
>> +        kasan_map_early_shadow(pv_top_pgt);
>> +    }
>> +
>
>
> I'd suggest replacing this with xen_kasan_early_init() and doing everything, including PV check, there. This way non-Xen code won't need to be aware of Xen-specific details such as guest types.

This would require exporting kasan_map_early_shadow() via kasan.h.
I'm fine with either approach.

>>       kasan_map_early_shadow(early_top_pgt);
>>       kasan_map_early_shadow(init_top_pgt);
>>   }
>> @@ -369,6 +377,8 @@ void __init kasan_init(void)
>>                   __pgd(__pa(tmp_p4d_table) | _KERNPG_TABLE));
>>       }
>>   +    xen_pv_kasan_pin_pgd(early_top_pgt);
>> +
>
> And drop "_pv" here (and below) for the same reason.

This is a reasonable suggestion.

>>       load_cr3(early_top_pgt);
>>       __flush_tlb_all();
>>   @@ -433,6 +443,8 @@ void __init kasan_init(void)
>>       load_cr3(init_top_pgt);
>>       __flush_tlb_all();
>>   +    xen_pv_kasan_unpin_pgd(early_top_pgt);
>> +
>>

--
Thanks,
Sergey

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