[PATCH] x86/mm: disable instrumentations of mm/pgprot.c

[PATCH] x86/mm: disable instrumentations of mm/pgprot.c

[Naohiro Aota]

The commit 4867fbbdd6b3 ("x86/mm: move protection_map[] inside the
platform") moved accesses to protection_map[] from mem_encrypt_amd.c to
pgprot.c. As a result, the accesses are now targets of KASAN (and other
instrumentations), leading to the crash during the boot process.

Disable the instrumentations for pgprot.c like commit 67bb8e999e0a
("x86/mm: Disable various instrumentations of mm/mem_encrypt.c and
mm/tlb.c").

Before this patch, my AMD machine cannot boot since v6.0-rc1 with KASAN
enabled, without anything printed. After the change, it successfully boots
up.

Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 arch/x86/mm/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index f8220fd2c169..829c1409ffbd 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -4,10 +4,12 @@ KCOV_INSTRUMENT_tlb.o			:= n
 KCOV_INSTRUMENT_mem_encrypt.o		:= n
 KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n
 KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n
+KCOV_INSTRUMENT_pgprot.o		:= n
 
 KASAN_SANITIZE_mem_encrypt.o		:= n
 KASAN_SANITIZE_mem_encrypt_amd.o	:= n
 KASAN_SANITIZE_mem_encrypt_identity.o	:= n
+KASAN_SANITIZE_pgprot.o		:= n
 
 # Disable KCSAN entirely, because otherwise we get warnings that some functions
 # reference __initdata sections.
@@ -17,6 +19,7 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_mem_encrypt.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
+CFLAGS_REMOVE_pgprot.o			= -pg
 endif
 
 obj-y				:=  init.o init_$(BITS).o fault.o ioremap.o extable.o mmap.o \
-- 
2.37.2

Re: [PATCH] x86/mm: disable instrumentations of mm/pgprot.c

[Naohiro Aota]

On Wed, Aug 24, 2022 at 05:47:26PM +0900, Naohiro Aota wrote:
> The commit 4867fbbdd6b3 ("x86/mm: move protection_map[] inside the
> platform") moved accesses to protection_map[] from mem_encrypt_amd.c to
> pgprot.c. As a result, the accesses are now targets of KASAN (and other
> instrumentations), leading to the crash during the boot process.
> 
> Disable the instrumentations for pgprot.c like commit 67bb8e999e0a
> ("x86/mm: Disable various instrumentations of mm/mem_encrypt.c and
> mm/tlb.c").
> 
> Before this patch, my AMD machine cannot boot since v6.0-rc1 with KASAN
> enabled, without anything printed. After the change, it successfully boots
> up.
> 
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  arch/x86/mm/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
> index f8220fd2c169..829c1409ffbd 100644
> --- a/arch/x86/mm/Makefile
> +++ b/arch/x86/mm/Makefile
> @@ -4,10 +4,12 @@ KCOV_INSTRUMENT_tlb.o			:= n
>  KCOV_INSTRUMENT_mem_encrypt.o		:= n
>  KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n
>  KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n
> +KCOV_INSTRUMENT_pgprot.o		:= n
>  
>  KASAN_SANITIZE_mem_encrypt.o		:= n
>  KASAN_SANITIZE_mem_encrypt_amd.o	:= n
>  KASAN_SANITIZE_mem_encrypt_identity.o	:= n
> +KASAN_SANITIZE_pgprot.o		:= n
>  
>  # Disable KCSAN entirely, because otherwise we get warnings that some functions
>  # reference __initdata sections.
> @@ -17,6 +19,7 @@ ifdef CONFIG_FUNCTION_TRACER
>  CFLAGS_REMOVE_mem_encrypt.o		= -pg
>  CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg
>  CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
> +CFLAGS_REMOVE_pgprot.o			= -pg
>  endif
>  
>  obj-y				:=  init.o init_$(BITS).o fault.o ioremap.o extable.o mmap.o \
> -- 
> 2.37.2
> 

Hello, maintainers.

Gentle ping on this patch. I need this patch to boot up my AMD machine with
KASAN enabled.

Re: [PATCH] x86/mm: disable instrumentations of mm/pgprot.c

[Niklas Cassel]

On Wed, Aug 24, 2022 at 05:47:26PM +0900, Naohiro Aota wrote:
> The commit 4867fbbdd6b3 ("x86/mm: move protection_map[] inside the
> platform") moved accesses to protection_map[] from mem_encrypt_amd.c to
> pgprot.c. As a result, the accesses are now targets of KASAN (and other
> instrumentations), leading to the crash during the boot process.
> 
> Disable the instrumentations for pgprot.c like commit 67bb8e999e0a
> ("x86/mm: Disable various instrumentations of mm/mem_encrypt.c and
> mm/tlb.c").
> 
> Before this patch, my AMD machine cannot boot since v6.0-rc1 with KASAN
> enabled, without anything printed. After the change, it successfully boots
> up.
> 
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---

Hello Andrew,

I see that this patch is in linux-next, but not in Linus's tree.

Since this fixes something introduced in v6.0-rc1, I think this
ought to go into v6.0 before it is released.


Kind regards,
Niklas