* [PATCH 1/1] x86_64: fix KASan shadow region page tables
@ 2015-05-22 16:03 Alexander Popov
2015-05-25 8:12 ` Andrey Ryabinin
0 siblings, 1 reply; 5+ messages in thread
From: Alexander Popov @ 2015-05-22 16:03 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andrey Ryabinin,
Andrey Konovalov, Denys Vlasenko, Andy Lutomirski,
Alexander Kuleshov, Alexander Popov, Sergey Kovalev, x86,
linux-kernel
Physical addresses in KASan shadow region page tables need fixup:
kernel halts without it if phys_base is not zero.
Signed-off-by: Alexander Popov <alpopov@ptsecurity.com>
---
arch/x86/kernel/head_64.S | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ae6588b..f7711bb 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -95,6 +95,20 @@ startup_64:
addq %rbp, level2_fixmap_pgt + (506*8)(%rip)
+#ifdef CONFIG_KASAN
+ xor %rax, %rax
+ leaq kasan_zero_pud(%rip), %rbx
+ leaq kasan_zero_pmd(%rip), %rcx
+ leaq kasan_zero_pte(%rip), %rdx
+1:
+ addq %rbp, (%rbx,%rax,8)
+ addq %rbp, (%rcx,%rax,8)
+ addq %rbp, (%rdx,%rax,8)
+ inc %rax
+ cmp $512, %rax
+ jne 1b
+#endif
+
/*
* Set up the identity mapping for the switchover. These
* entries should *NOT* have the global bit set! This also
--
1.9.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] x86_64: fix KASan shadow region page tables
2015-05-22 16:03 [PATCH 1/1] x86_64: fix KASan shadow region page tables Alexander Popov
@ 2015-05-25 8:12 ` Andrey Ryabinin
2015-05-25 13:43 ` Alexander Popov
0 siblings, 1 reply; 5+ messages in thread
From: Andrey Ryabinin @ 2015-05-25 8:12 UTC (permalink / raw)
To: Alexander Popov
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andrey Konovalov,
Denys Vlasenko, Andy Lutomirski, Alexander Kuleshov,
Sergey Kovalev, x86, linux-kernel
On 05/22/2015 07:03 PM, Alexander Popov wrote:
> Physical addresses in KASan shadow region page tables need fixup:
> kernel halts without it if phys_base is not zero.
>
Indeed.
Since we have to patch page tables anyway, compile-time created kasan
page tables become pointless.
So, I'd suggest to create them in runtime. This could be done in plain C
in kasan_map_early_shadow().
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] x86_64: fix KASan shadow region page tables
2015-05-25 8:12 ` Andrey Ryabinin
@ 2015-05-25 13:43 ` Alexander Popov
2015-05-26 8:52 ` Andrey Ryabinin
0 siblings, 1 reply; 5+ messages in thread
From: Alexander Popov @ 2015-05-25 13:43 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andrey Konovalov,
Denys Vlasenko, Andy Lutomirski, Alexander Kuleshov,
Sergey Kovalev, x86, linux-kernel
On 25.05.2015 11:12, Andrey Ryabinin wrote:
> On 05/22/2015 07:03 PM, Alexander Popov wrote:
>> Physical addresses in KASan shadow region page tables need fixup:
>> kernel halts without it if phys_base is not zero.
>>
>
> Indeed.
> Since we have to patch page tables anyway, compile-time created kasan
> page tables become pointless.
> So, I'd suggest to create them in runtime. This could be done in plain C
> in kasan_map_early_shadow().
>
Thanks for your reply, Andrey.
Creating kasan_zero_pud, kasan_zero_pmd and kasan_zero_pte in
kasan_map_early_shadow() doesn't look handy for me because this function
is called twice in x86_64_start_kernel().
What do you think about leaving the initialization of KASan shadow region
page tables in arch/x86/kernel/head_64.S and calling something like
kasan_fixup_early_shadow() before calling kasan_map_early_shadow()
for the first time?
Best regards,
Alexander
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] x86_64: fix KASan shadow region page tables
2015-05-25 13:43 ` Alexander Popov
@ 2015-05-26 8:52 ` Andrey Ryabinin
2015-05-28 8:56 ` Alexander Popov
0 siblings, 1 reply; 5+ messages in thread
From: Andrey Ryabinin @ 2015-05-26 8:52 UTC (permalink / raw)
To: Alexander Popov
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andrey Konovalov,
Denys Vlasenko, Andy Lutomirski, Alexander Kuleshov,
Sergey Kovalev, x86, linux-kernel
On 05/25/2015 04:43 PM, Alexander Popov wrote:
> On 25.05.2015 11:12, Andrey Ryabinin wrote:
>> On 05/22/2015 07:03 PM, Alexander Popov wrote:
>>> Physical addresses in KASan shadow region page tables need fixup:
>>> kernel halts without it if phys_base is not zero.
>>>
>>
>> Indeed.
>> Since we have to patch page tables anyway, compile-time created kasan
>> page tables become pointless.
>> So, I'd suggest to create them in runtime. This could be done in plain C
>> in kasan_map_early_shadow().
>>
>
> Thanks for your reply, Andrey.
>
> Creating kasan_zero_pud, kasan_zero_pmd and kasan_zero_pte in
> kasan_map_early_shadow() doesn't look handy for me because this function
> is called twice in x86_64_start_kernel().
>
> What do you think about leaving the initialization of KASan shadow region
> page tables in arch/x86/kernel/head_64.S and calling something like
> kasan_fixup_early_shadow() before calling kasan_map_early_shadow()
> for the first time?
>
Why do we have initialize + fixup later if we could simply initialize page tables properly?
Just move everything into kasan_init_64.c
kasan_zero_p* could be a normal C arrays (with __page_aligned_bss attribute).
Initialize these page tables in something like kasan_early_init() before kasan_map_early_shadow()
call.
> Best regards,
> Alexander
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] x86_64: fix KASan shadow region page tables
2015-05-26 8:52 ` Andrey Ryabinin
@ 2015-05-28 8:56 ` Alexander Popov
0 siblings, 0 replies; 5+ messages in thread
From: Alexander Popov @ 2015-05-28 8:56 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Andrey Konovalov,
Denys Vlasenko, Andy Lutomirski, Alexander Kuleshov,
Sergey Kovalev, x86, linux-kernel
On 26.05.2015 11:52, Andrey Ryabinin wrote:
> On 05/25/2015 04:43 PM, Alexander Popov wrote:
>> What do you think about leaving the initialization of KASan shadow region
>> page tables in arch/x86/kernel/head_64.S and calling something like
>> kasan_fixup_early_shadow() before calling kasan_map_early_shadow()
>> for the first time?
>
> Why do we have initialize + fixup later if we could simply initialize page tables properly?
>
> Just move everything into kasan_init_64.c
> kasan_zero_p* could be a normal C arrays (with __page_aligned_bss attribute).
> Initialize these page tables in something like kasan_early_init() before kasan_map_early_shadow()
> call.
Thanks, I'll do that and return with the second version.
Best regards,
Alexander
^ permalink raw reply [flat|nested] 5+ messages in thread
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2015-05-22 16:03 [PATCH 1/1] x86_64: fix KASan shadow region page tables Alexander Popov
2015-05-25 8:12 ` Andrey Ryabinin
2015-05-25 13:43 ` Alexander Popov
2015-05-26 8:52 ` Andrey Ryabinin
2015-05-28 8:56 ` Alexander Popov
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