diff mbox series

[v13,3/3] kasan: define and use MAX_PTRS_PER_* for early shadow tables

Message ID 20210616080244.51236-4-dja@axtens.net (mailing list archive)
State New, archived
Headers show
Series KASAN core changes for ppc64 radix KASAN | expand

Commit Message

Daniel Axtens June 16, 2021, 8:02 a.m. UTC 
powerpc has a variable number of PTRS_PER_*, set at runtime based
on the MMU that the kernel is booted under.

This means the PTRS_PER_* are no longer constants, and therefore
breaks the build.

Define default MAX_PTRS_PER_*s in the same style as MAX_PTRS_PER_P4D.
As KASAN is the only user at the moment, just define them in the kasan
header, and have them default to PTRS_PER_* unless overridden in arch
code.

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Suggested-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 include/linux/kasan.h | 18 +++++++++++++++---
 mm/kasan/init.c       |  6 +++---
 2 files changed, 18 insertions(+), 6 deletions(-)

Comments

Marco Elver June 16, 2021, 9:07 a.m. UTC | #1 
On Wed, 16 Jun 2021 at 10:03, Daniel Axtens <dja@axtens.net> wrote:
[...]
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 768d7d342757..fd65f477ac92 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -40,10 +40,22 @@ struct kunit_kasan_expectation {
>  #define PTE_HWTABLE_PTRS 0
>  #endif
>
> +#ifndef MAX_PTRS_PER_PTE
> +#define MAX_PTRS_PER_PTE PTRS_PER_PTE
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PMD
> +#define MAX_PTRS_PER_PMD PTRS_PER_PMD
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PUD
> +#define MAX_PTRS_PER_PUD PTRS_PER_PUD
> +#endif

This is introducing new global constants in a <linux/..> header. It
feels like this should be in <linux/pgtable.h> together with a
comment. Because <linux/kasan.h> is actually included in
<linux/slab.h>, most of the kernel will get these new definitions.
That in itself is fine, but it feels wrong that the KASAN header
introduces these.

Thoughts?

Sorry for only realizing this now.

Thanks,
-- Marco

>  extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
> -extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS];
> -extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
> -extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
> +extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS];
> +extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
> +extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
>  extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
>
>  int kasan_populate_early_shadow(const void *shadow_start,
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index 348f31d15a97..cc64ed6858c6 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -41,7 +41,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
>  }
>  #endif
>  #if CONFIG_PGTABLE_LEVELS > 3
> -pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
> +pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
>  static inline bool kasan_pud_table(p4d_t p4d)
>  {
>         return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
> @@ -53,7 +53,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
>  }
>  #endif
>  #if CONFIG_PGTABLE_LEVELS > 2
> -pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
>  static inline bool kasan_pmd_table(pud_t pud)
>  {
>         return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
> @@ -64,7 +64,7 @@ static inline bool kasan_pmd_table(pud_t pud)
>         return false;
>  }
>  #endif
> -pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
> +pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
>         __page_aligned_bss;
>
>  static inline bool kasan_pte_table(pmd_t pmd)
> --
> 2.30.2
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210616080244.51236-4-dja%40axtens.net.
Christophe Leroy June 16, 2021, 5:23 p.m. UTC | #2 
Le 16/06/2021 à 11:07, Marco Elver a écrit :
> On Wed, 16 Jun 2021 at 10:03, Daniel Axtens <dja@axtens.net> wrote:
> [...]
>> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
>> index 768d7d342757..fd65f477ac92 100644
>> --- a/include/linux/kasan.h
>> +++ b/include/linux/kasan.h
>> @@ -40,10 +40,22 @@ struct kunit_kasan_expectation {
>>   #define PTE_HWTABLE_PTRS 0
>>   #endif
>>
>> +#ifndef MAX_PTRS_PER_PTE
>> +#define MAX_PTRS_PER_PTE PTRS_PER_PTE
>> +#endif
>> +
>> +#ifndef MAX_PTRS_PER_PMD
>> +#define MAX_PTRS_PER_PMD PTRS_PER_PMD
>> +#endif
>> +
>> +#ifndef MAX_PTRS_PER_PUD
>> +#define MAX_PTRS_PER_PUD PTRS_PER_PUD
>> +#endif
> 
> This is introducing new global constants in a <linux/..> header. It
> feels like this should be in <linux/pgtable.h> together with a
> comment. Because <linux/kasan.h> is actually included in
> <linux/slab.h>, most of the kernel will get these new definitions.
> That in itself is fine, but it feels wrong that the KASAN header
> introduces these.
> 
> Thoughts?
> 
> Sorry for only realizing this now.

My idea here was to follow the same road as MAX_PTRS_PER_P4D, added by commit 
https://github.com/linuxppc/linux/commit/c65e774f

That commit spread MAX_PTRS_PER_P4D everywhere.

Instead of doing the same, we found that it would be better to define a fallback for when the 
architecture doesn't define MAX_PTRS_PER_PxD . Now, it can be made more global in pgtable.h, in that 
case I'd suggest to also include MAX_PTRS_PER_P4D in the dance and avoid architectures like s390 
having to define it, or even not defining it either in asm-generic/pgtable-nop4d.h

Christophe

> 
> Thanks,
> -- Marco
> 
>>   extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
>> -extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS];
>> -extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
>> -extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
>> +extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS];
>> +extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
>> +extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
>>   extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
>>
>>   int kasan_populate_early_shadow(const void *shadow_start,
>> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
>> index 348f31d15a97..cc64ed6858c6 100644
>> --- a/mm/kasan/init.c
>> +++ b/mm/kasan/init.c
>> @@ -41,7 +41,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
>>   }
>>   #endif
>>   #if CONFIG_PGTABLE_LEVELS > 3
>> -pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
>> +pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
>>   static inline bool kasan_pud_table(p4d_t p4d)
>>   {
>>          return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
>> @@ -53,7 +53,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
>>   }
>>   #endif
>>   #if CONFIG_PGTABLE_LEVELS > 2
>> -pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
>> +pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
>>   static inline bool kasan_pmd_table(pud_t pud)
>>   {
>>          return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
>> @@ -64,7 +64,7 @@ static inline bool kasan_pmd_table(pud_t pud)
>>          return false;
>>   }
>>   #endif
>> -pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
>> +pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
>>          __page_aligned_bss;
>>
>>   static inline bool kasan_pte_table(pmd_t pmd)
>> --
>> 2.30.2
>>
>> --
>> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
>> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
>> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210616080244.51236-4-dja%40axtens.net.
diff mbox series

Patch

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 768d7d342757..fd65f477ac92 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -40,10 +40,22 @@  struct kunit_kasan_expectation {
 #define PTE_HWTABLE_PTRS 0
 #endif
 
+#ifndef MAX_PTRS_PER_PTE
+#define MAX_PTRS_PER_PTE PTRS_PER_PTE
+#endif
+
+#ifndef MAX_PTRS_PER_PMD
+#define MAX_PTRS_PER_PMD PTRS_PER_PMD
+#endif
+
+#ifndef MAX_PTRS_PER_PUD
+#define MAX_PTRS_PER_PUD PTRS_PER_PUD
+#endif
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
-extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS];
-extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
-extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
+extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS];
+extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
+extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
 extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
 
 int kasan_populate_early_shadow(const void *shadow_start,
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index 348f31d15a97..cc64ed6858c6 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -41,7 +41,7 @@  static inline bool kasan_p4d_table(pgd_t pgd)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
-pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
+pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
 static inline bool kasan_pud_table(p4d_t p4d)
 {
 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
@@ -53,7 +53,7 @@  static inline bool kasan_pud_table(p4d_t p4d)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
-pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
 static inline bool kasan_pmd_table(pud_t pud)
 {
 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
@@ -64,7 +64,7 @@  static inline bool kasan_pmd_table(pud_t pud)
 	return false;
 }
 #endif
-pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
+pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
 	__page_aligned_bss;
 
 static inline bool kasan_pte_table(pmd_t pmd)