Subject: Re: [PATCH V2 07/10] kasan: Make INLINE KASan support arch selectable

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Sun, 30 Aug 2015 18:20:21 +0530

Andrey Ryabinin <[email-masked]> writes:

> 2015-08-26 11:26 GMT+03:00 Aneesh Kumar K.V <[email-masked]>:
>> Some of the archs, may find it difficult to support inline KASan
>> mode. Add HAVE_ARCH_KASAN_INLINE so that we can disable inline
>> support at config time.
>>
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>> ---
>>  arch/x86/Kconfig       |  1 +
>>  lib/Kconfig.kasan      |  2 ++
>>  scripts/Makefile.kasan | 28 ++++++++++++++--------------
>>  3 files changed, 17 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index b3a1a5d77d92..4416f80580fb 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -78,6 +78,7 @@ config X86
>>         select HAVE_ARCH_HUGE_VMAP              if X86_64 || X86_PAE
>>         select HAVE_ARCH_JUMP_LABEL
>>         select HAVE_ARCH_KASAN                  if X86_64 && SPARSEMEM_VMEMMAP
>> +       select HAVE_ARCH_KASAN_INLINE                   if X86_64 && SPARSEMEM_VMEMMAP
>
> This will not work because config HAVE_ARCH_KASAN_INLINE is not defined.
> Instead of you can just add following in this file:
>
> config HAVE_ARCH_KASAN_INLINE
>           def_bool y
>           depends on KASAN
>

Missed cherry-pick

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index e9d1bb1175b8..5dba03bc3f01 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -1,6 +1,9 @@
 config HAVE_ARCH_KASAN
 	bool
 
+config HAVE_ARCH_KASAN_INLINE
+	bool
+
 if HAVE_ARCH_KASAN
 
 config KASAN

>
>>         select HAVE_ARCH_KGDB
>>         select HAVE_ARCH_KMEMCHECK
>>         select HAVE_ARCH_SECCOMP_FILTER
>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
>> index 39f24d6721e5..e9d1bb1175b8 100644
>> --- a/lib/Kconfig.kasan
>> +++ b/lib/Kconfig.kasan
>> @@ -32,6 +32,7 @@ config KASAN_OUTLINE
>>           however it doesn't bloat size of kernel's .text section so
>>           much as inline does.
>>
>> +if HAVE_ARCH_KASAN_INLINE
>>  config KASAN_INLINE
>>         bool "Inline instrumentation"
>
>  depends on HAVE_ARCH_KASAN_INLINE
>
>>         help
>> @@ -40,6 +41,7 @@ config KASAN_INLINE
>>           it gives about x2 boost over outline instrumentation), but
>>           make kernel's .text size much bigger.
>>           This requires a gcc version of 5.0 or later.
>> +endif
>>
>>  endchoice
>>
>> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
>> index 3f874d24234f..c1c06e9e107a 100644
>> --- a/scripts/Makefile.kasan
>> +++ b/scripts/Makefile.kasan
>> @@ -1,29 +1,29 @@
>>  ifdef CONFIG_KASAN
>> -ifdef CONFIG_KASAN_INLINE
>> -       call_threshold := 10000
>> -else
>> -       call_threshold := 0
>> -endif
>> -
>> -CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
>>
>>  CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
>> -               -fasan-shadow-offset=$(CONFIG_KASAN_SHADOW_OFFSET) \
>> -               --param asan-stack=1 --param asan-globals=1 \
>> -               --param asan-instrumentation-with-call-threshold=$(call_threshold))
>> -
>> -ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
>> +                   --param asan-instrumentation-with-call-threshold=0)
>> +ifeq ($(CFLAGS_KASAN),)
>>     ifneq ($(CONFIG_COMPILE_TEST),y)
>>          $(warning Cannot use CONFIG_KASAN: \
>>              -fsanitize=kernel-address is not supported by compiler)
>>     endif
>>  else
>> -    ifeq ($(CFLAGS_KASAN),)
>> +
>> +   ifdef CONFIG_KASAN_INLINE
>> +   CFLAGS_KASAN_INLINE := $(call cc-option, -fsanitize=kernel-address \
>> +                        -fasan-shadow-offset=$(CONFIG_KASAN_SHADOW_OFFSET) \
>> +                        --param asan-stack=1 --param asan-globals=1 \
>> +                        --param asan-instrumentation-with-call-threshold=10000)
>> +
>> +    ifeq ($(CFLAGS_KASAN_INLINE),)
>>          ifneq ($(CONFIG_COMPILE_TEST),y)
>>              $(warning CONFIG_KASAN: compiler does not support all options.\
>>                  Trying minimal configuration)
>>          endif
>> -        CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
>> +    else
>> +        CFLAGS_KASAN := $(CFLAGS_KASAN_INLINE)
>>      endif
>> +    endif
>> +
>
> This removes stack and globals for CONFIG_KASAN_OUTLINE=y. Why?
> Those are completely separate features. So this patch shouldn't touch
> this Makefile at all.
> Depends on HAVE_ARCH_KASAN_INLINE in CONFIG_KASAN_INLINE should be enough.

Correct. I have changes that will make kasan_global and kasan_stack as
config items. I didn't add it as part of this series because I still
haven't got outline global and stack work on ppc64. Right now the split
config only applies to ppc64. Hence didn't want to make the patch more
complicated. 

>
> But you need to disable 'asan-stack' and 'asan-globals' for pcc64.
> I'd suggest to introduce CFLAGS_ARCH_KASAN.
> Define it in ppc64 Makefile:
>
> CFLAGS_ARCH_KASAN := --param asan-globals=0 --param asan-stack=0
>
> and add these flags to CFLAGS_KASAN_MINIMAL and CFLAGS_KASAN in Makefile.kasan.
>
>
>>  endif
>>  endif
>>

-aneesh