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[RFC,v3,17/18] kasan: allow architectures to provide an outline readiness check

Message ID 4f888b49a3c72105ef8e74997fcb2ab20ad2252d.1552428161.git.christophe.leroy@c-s.fr (mailing list archive)
State New, archived
Headers show
Series KASAN for powerpc/32 and RFC for 64bit Book3E | expand

Commit Message

Christophe Leroy March 12, 2019, 10:16 p.m. UTC 
From: Daniel Axtens <dja@axtens.net>

In powerpc (as I understand it), we spend a lot of time in boot
running in real mode before MMU paging is initialised. During
this time we call a lot of generic code, including printk(). If
we try to access the shadow region during this time, things fail.

My attempts to move early init before the first printk have not
been successful. (Both previous RFCs for ppc64 - by 2 different
people - have needed this trick too!)

So, allow architectures to define a kasan_arch_is_ready()
hook that bails out of check_memory_region_inline() unless the
arch has done all of the init.

Link: https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series
Link: https://patchwork.ozlabs.org/patch/795211/      # ppc radix series
Originally-by: Balbir Singh <bsingharora@gmail.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
[check_return_arch_not_ready() ==> static inline kasan_arch_is_ready()]
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 include/linux/kasan.h | 4 ++++
 mm/kasan/generic.c    | 3 +++
 2 files changed, 7 insertions(+)
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Patch

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index f6261840f94c..a630d53f1a36 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -14,6 +14,10 @@  struct task_struct;
 #include <asm/kasan.h>
 #include <asm/pgtable.h>
 
+#ifndef kasan_arch_is_ready
+static inline bool kasan_arch_is_ready(void)	{ return true; }
+#endif
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
 extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
 extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index a5b28e3ceacb..0336f31bbae3 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -170,6 +170,9 @@  static __always_inline void check_memory_region_inline(unsigned long addr,
 						size_t size, bool write,
 						unsigned long ret_ip)
 {
+	if (!kasan_arch_is_ready())
+		return;
+
 	if (unlikely(size == 0))
 		return;