diff mbox

[1/1] ARM: compressed/head.S: fix __nop macro rept number for ARMv7M

Message ID 1493110893-21857-1-git-send-email-patrice.chotard@st.com (mailing list archive)
State New, archived
Headers show

Commit Message

Patrice CHOTARD April 25, 2017, 9:01 a.m. UTC 
From: Patrice Chotard <patrice.chotard@st.com>

In zImage, _magic_sig is located at offset 0x24.
But for ARMv7M architecture which enable CPU_THUMBONLY
and !EFI_STUB kernel flag, _magic_sig is located at offset 0x14

00000000  00 46 00 46 00 46 00 46  00 46 00 46 00 46 0f f2  |.F.F.F.F.F.F.F.ò|
00000010  15 0c 60 47 18 28 6f 01  00 00 00 00 28 5c 0e 00  |..`G.(o.....(\..|
00000020  01 02 03 04 0f 46 90 46  00 00 00 00 00 00 00 00  |.....F.F........|

Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.

To restore correct _magic_sig offset at 0x24, we add 8 additional
"mov r0, r0" instruction.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
---
 arch/arm/boot/compressed/head.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Patrice CHOTARD May 12, 2017, 7:22 a.m. UTC | #1 
Hi all

It's a gentle reminder to not forgot this patch.

Thanks

Patrice

On 04/25/2017 11:01 AM, patrice.chotard@st.com wrote:
> From: Patrice Chotard <patrice.chotard@st.com>

>

> In zImage, _magic_sig is located at offset 0x24.

> But for ARMv7M architecture which enable CPU_THUMBONLY

> and !EFI_STUB kernel flag, _magic_sig is located at offset 0x14

>

> 00000000  00 46 00 46 00 46 00 46  00 46 00 46 00 46 0f f2  |.F.F.F.F.F.F.F.ò|

> 00000010  15 0c 60 47 18 28 6f 01  00 00 00 00 28 5c 0e 00  |..`G.(o.....(\..|

> 00000020  01 02 03 04 0f 46 90 46  00 00 00 00 00 00 00 00  |.....F.F........|

>

> Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.

>

> To restore correct _magic_sig offset at 0x24, we add 8 additional

> "mov r0, r0" instruction.

>

> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

> ---

>  arch/arm/boot/compressed/head.S | 3 ++-

>  1 file changed, 2 insertions(+), 1 deletion(-)

>

> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S

> index 9150f97..5d9cda3 100644

> --- a/arch/arm/boot/compressed/head.S

> +++ b/arch/arm/boot/compressed/head.S

> @@ -127,7 +127,8 @@

>   AR_CLASS(	.arm	)

>  start:

>  		.type	start,#function

> -		.rept	7

> +   ARM(		.rept	7)

> + THUMB(		.rept	15)

>  		__nop

>  		.endr

>     ARM(		mov	r0, r0		)

>
Ard Biesheuvel May 18, 2017, 11:16 a.m. UTC | #2 
On 12 May 2017 at 08:22, Patrice CHOTARD <patrice.chotard@st.com> wrote:
> Hi all
>
> It's a gentle reminder to not forgot this patch.
>
> Thanks
>
> Patrice
>
> On 04/25/2017 11:01 AM, patrice.chotard@st.com wrote:
>> From: Patrice Chotard <patrice.chotard@st.com>
>>
>> In zImage, _magic_sig is located at offset 0x24.
>> But for ARMv7M architecture which enable CPU_THUMBONLY
>> and !EFI_STUB kernel flag, _magic_sig is located at offset 0x14
>>
>> 00000000  00 46 00 46 00 46 00 46  00 46 00 46 00 46 0f f2  |.F.F.F.F.F.F.F.ò|
>> 00000010  15 0c 60 47 18 28 6f 01  00 00 00 00 28 5c 0e 00  |..`G.(o.....(\..|
>> 00000020  01 02 03 04 0f 46 90 46  00 00 00 00 00 00 00 00  |.....F.F........|
>>
>> Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.
>>
>> To restore correct _magic_sig offset at 0x24, we add 8 additional
>> "mov r0, r0" instruction.
>>
>> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
>> ---
>>  arch/arm/boot/compressed/head.S | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
>> index 9150f97..5d9cda3 100644
>> --- a/arch/arm/boot/compressed/head.S
>> +++ b/arch/arm/boot/compressed/head.S
>> @@ -127,7 +127,8 @@
>>   AR_CLASS(   .arm    )
>>  start:
>>               .type   start,#function
>> -             .rept   7
>> +   ARM(              .rept   7)
>> + THUMB(              .rept   15)
>>

Could you try using W(mov) instead of mov in the definition of __nop ?
Patrice CHOTARD May 19, 2017, 1:41 p.m. UTC | #3 
Hi Ard

On 05/18/2017 01:16 PM, Ard Biesheuvel wrote:
> On 12 May 2017 at 08:22, Patrice CHOTARD <patrice.chotard@st.com> wrote:

>> Hi all

>>

>> It's a gentle reminder to not forgot this patch.

>>

>> Thanks

>>

>> Patrice

>>

>> On 04/25/2017 11:01 AM, patrice.chotard@st.com wrote:

>>> From: Patrice Chotard <patrice.chotard@st.com>

>>>

>>> In zImage, _magic_sig is located at offset 0x24.

>>> But for ARMv7M architecture which enable CPU_THUMBONLY

>>> and !EFI_STUB kernel flag, _magic_sig is located at offset 0x14

>>>

>>> 00000000  00 46 00 46 00 46 00 46  00 46 00 46 00 46 0f f2  |.F.F.F.F.F.F.F.ò|

>>> 00000010  15 0c 60 47 18 28 6f 01  00 00 00 00 28 5c 0e 00  |..`G.(o.....(\..|

>>> 00000020  01 02 03 04 0f 46 90 46  00 00 00 00 00 00 00 00  |.....F.F........|

>>>

>>> Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.

>>>

>>> To restore correct _magic_sig offset at 0x24, we add 8 additional

>>> "mov r0, r0" instruction.

>>>

>>> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

>>> ---

>>>   arch/arm/boot/compressed/head.S | 3 ++-

>>>   1 file changed, 2 insertions(+), 1 deletion(-)

>>>

>>> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S

>>> index 9150f97..5d9cda3 100644

>>> --- a/arch/arm/boot/compressed/head.S

>>> +++ b/arch/arm/boot/compressed/head.S

>>> @@ -127,7 +127,8 @@

>>>    AR_CLASS(   .arm    )

>>>   start:

>>>                .type   start,#function

>>> -             .rept   7

>>> +   ARM(              .rept   7)

>>> + THUMB(              .rept   15)

>>>

> 

> Could you try using W(mov) instead of mov in the definition of __nop ?


If i use W(mov) instead of mov in __nop macro, i need to add one 
additional "mov r0,r0" in THUMB case as following :


  start:
  		.type	start,#function
  		.rept	7
  		__nop
  		.endr
     ARM(		mov	r0, r0		)
     ARM(		b	1f		)
+ THUMB(		mov	r0, r0		)
   THUMB(		badr	r12, 1f		)
   THUMB(		bx	r12		)

  		.word	_magic_sig	@ Magic numbers to help the loader
  		.word	_magic_start	@ absolute load/run zImage address
  		.word	_magic_end	@ zImage end address
  		.word	0x04030201	@ endianness flag


Which implementation do you prefer ?

Thanks

Patrice
vikasm May 23, 2017, 1:06 a.m. UTC | #4 
Hi Patrice,

> -----Original Message-----

> From: Patrice CHOTARD

> Sent: Friday, May 19, 2017 6:41 AM

> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> Cc: linux@armlinux.org.uk; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Christophe PRIOUZEAU

> <christophe.priouzeau@st.com>; Christophe KERELLO <christophe.kerello@st.com>; Vikas MANOCHA <vikas.manocha@st.com>;

> Patrick DELAUNAY <patrick.delaunay@st.com>

> Subject: Re: [PATCH 1/1] ARM: compressed/head.S: fix __nop macro rept number for ARMv7M

> 

> Hi Ard

> 

> On 05/18/2017 01:16 PM, Ard Biesheuvel wrote:

> > On 12 May 2017 at 08:22, Patrice CHOTARD <patrice.chotard@st.com> wrote:

> >> Hi all

> >>

> >> It's a gentle reminder to not forgot this patch.

> >>

> >> Thanks

> >>

> >> Patrice

> >>

> >> On 04/25/2017 11:01 AM, patrice.chotard@st.com wrote:

> >>> From: Patrice Chotard <patrice.chotard@st.com>

> >>>

> >>> In zImage, _magic_sig is located at offset 0x24.

> >>> But for ARMv7M architecture which enable CPU_THUMBONLY and !EFI_STUB

> >>> kernel flag, _magic_sig is located at offset 0x14

> >>>

> >>> 00000000  00 46 00 46 00 46 00 46  00 46 00 46 00 46 0f f2

> >>> |.F.F.F.F.F.F.F.ò|

> >>> 00000010  15 0c 60 47 18 28 6f 01  00 00 00 00 28 5c 0e 00

> >>> |..`G.(o.....(\..|

> >>> 00000020  01 02 03 04 0f 46 90 46  00 00 00 00 00 00 00 00

> >>> |.....F.F........|

> >>>

> >>> Reproduced with stm32_defconfig with XIP_KERNEL flag disabled.

> >>>

> >>> To restore correct _magic_sig offset at 0x24, we add 8 additional

> >>> "mov r0, r0" instruction.

> >>>

> >>> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

> >>> ---

> >>>   arch/arm/boot/compressed/head.S | 3 ++-

> >>>   1 file changed, 2 insertions(+), 1 deletion(-)

> >>>

> >>> diff --git a/arch/arm/boot/compressed/head.S

> >>> b/arch/arm/boot/compressed/head.S index 9150f97..5d9cda3 100644

> >>> --- a/arch/arm/boot/compressed/head.S

> >>> +++ b/arch/arm/boot/compressed/head.S

> >>> @@ -127,7 +127,8 @@

> >>>    AR_CLASS(   .arm    )

> >>>   start:

> >>>                .type   start,#function

> >>> -             .rept   7

> >>> +   ARM(              .rept   7)

> >>> + THUMB(              .rept   15)

> >>>

> >

> > Could you try using W(mov) instead of mov in the definition of __nop ?

> 

> If i use W(mov) instead of mov in __nop macro, i need to add one additional "mov r0,r0" in THUMB case as following :

> 

> 

>   start:

>   		.type	start,#function

>   		.rept	7

>   		__nop

>   		.endr

>      ARM(		mov	r0, r0		)

>      ARM(		b	1f		)

> + THUMB(		mov	r0, r0		)


No need of extra THUMB instruction, compiling previous mov r0,r0 should be good for both arm & thumb :

   		__nop
   		.endr
      			mov	r0, r0		/* 32 bit for arm & 16 bit for thumb */
      ARM(		b	1f		)
     THUMB(		badr	r12, 1f		)

Cheers,
Vikas

>    THUMB(		badr	r12, 1f		)

>    THUMB(		bx	r12		)

> 

>   		.word	_magic_sig	@ Magic numbers to help the loader

>   		.word	_magic_start	@ absolute load/run zImage address

>   		.word	_magic_end	@ zImage end address

>   		.word	0x04030201	@ endianness flag

> 

> 

> Which implementation do you prefer ?

> 

> Thanks

> 

> Patrice
diff mbox

Patch

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 9150f97..5d9cda3 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -127,7 +127,8 @@ 
  AR_CLASS(	.arm	)
 start:
 		.type	start,#function
-		.rept	7
+   ARM(		.rept	7)
+ THUMB(		.rept	15)
 		__nop
 		.endr
    ARM(		mov	r0, r0		)