linux-kernel - Re: [PATCH v1 2/4] x86/xen: add basic KASAN support for PV kernel

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Date:   Fri, 10 Jan 2020 11:07:18 +0000
From:   Sergey Dyasli <sergey.dyasli@...rix.com>
To:     Jürgen Groß <jgross@...e.com>,
        <xen-devel@...ts.xen.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
CC:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        George Dunlap <george.dunlap@...rix.com>,
        Ross Lagerwall <ross.lagerwall@...rix.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "sergey.dyasli@...rix.com >> Sergey Dyasli" 
        <sergey.dyasli@...rix.com>
Subject: Re: [PATCH v1 2/4] x86/xen: add basic KASAN support for PV kernel

On 09/01/2020 09:15, Jürgen Groß wrote:
> On 08.01.20 16:20, Sergey Dyasli wrote:
>> This enables to use Outline instrumentation for Xen PV kernels.
>>
>> KASAN_INLINE and KASAN_VMALLOC options currently lead to boot crashes
>> and hence disabled.
>>
>> Signed-off-by: Sergey Dyasli <sergey.dyasli@...rix.com>
>> ---
>> RFC --> v1:
>> - New functions with declarations in xen/xen-ops.h
>> - Fixed the issue with free_kernel_image_pages() with the help of
>>    xen_pv_kasan_unpin_pgd()
>> ---
>>   arch/x86/mm/kasan_init_64.c | 12 ++++++++++++
>>   arch/x86/xen/Makefile       |  7 +++++++
>>   arch/x86/xen/enlighten_pv.c |  3 +++
>>   arch/x86/xen/mmu_pv.c       | 39 +++++++++++++++++++++++++++++++++++++
>>   drivers/xen/Makefile        |  2 ++
>>   include/xen/xen-ops.h       |  4 ++++
>>   kernel/Makefile             |  2 ++
>>   lib/Kconfig.kasan           |  3 ++-
>>   8 files changed, 71 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
>> index cf5bc37c90ac..902a6a152d33 100644
>> --- 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();
>
> You are breaking the build with CONFIG_XEN_PV undefined here.

Right, the following is needed:

diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 91d66520f0a3..3d20f000af12 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -241,8 +241,14 @@ static inline void xen_preemptible_hcall_end(void)

 #endif /* CONFIG_PREEMPT */

+#if defined(CONFIG_XEN_PV)
 pgd_t *xen_pv_kasan_early_init(void);
 void xen_pv_kasan_pin_pgd(pgd_t *pgd);
 void xen_pv_kasan_unpin_pgd(pgd_t *pgd);
+#else
+static inline pgd_t *xen_pv_kasan_early_init(void) { return NULL; }
+static inline void xen_pv_kasan_pin_pgd(pgd_t *pgd) { }
+static inline void xen_pv_kasan_unpin_pgd(pgd_t *pgd) { }
+#endif /* defined(CONFIG_XEN_PV) */

 #endif /* INCLUDE_XEN_OPS_H */

--
Thanks,
Sergey