[PATCH] ARM: spectre-v2: Try to set IBE bit for Cortex-A15 and Brahma-B15

[PATCH] ARM: spectre-v2: Try to set IBE bit for Cortex-A15 and Brahma-B15

[Florian Fainelli]

Per the ARM reference manual for the Cortex-A15, The ACTLR:

 Is a read/write register.

 Common to the Secure and Non-secure states.

 Is only accessible from PL1 or higher, with access rights that depend
 on the mode:

    * Read/write in Secure PL1 modes.

    * Read-only and write-ignored in Non-secure PL1 and PL2 modes
      if NSACR.NS_SMP is 0.

    * Read/write in Non-secure PL1 and PL2 modes if NSACR.NS_SMP
      is 1. In this case, all bits are write-ignored except for the SMP bit.

We can attempt to set this bit from within the kernel, which helps
avoiding firmware side modifications to set the IBE bit when that is
impractical. We do this within __v7_ca15mp_setup and __v7_b15mp_setup
because by then we already took those labels because the processors we
run on do match.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 arch/arm/mm/proc-v7.S | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 6fe52819e014..a21cf3729efa 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -284,10 +284,16 @@ __v7_cr8mp_setup:
 	b	1f
 __v7_ca7mp_setup:
 __v7_ca12mp_setup:
+	b	2f
 __v7_ca15mp_setup:
 __v7_b15mp_setup:
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+	mrc	p15, 0, r0, c1, c0, 1
+	orr	r0, r0, #1			@ Enable IBE bit
+	mcr	p15, 0, r0, c1, c0, 1
+#endif
 __v7_ca17mp_setup:
-	mov	r10, #0
+2:	mov	r10, #0
 1:	adr	r0, __v7_setup_stack_ptr
 	ldr	r12, [r0]
 	add	r12, r12, r0			@ the local stack
-- 
2.14.1

[PATCH] ARM: spectre-v2: Try to set IBE bit for Cortex-A15 and Brahma-B15

[Marek Vasut]

On 06/08/2018 12:58 AM, Florian Fainelli wrote:
> Per the ARM reference manual for the Cortex-A15, The ACTLR:
> 
>  Is a read/write register.
> 
>  Common to the Secure and Non-secure states.
> 
>  Is only accessible from PL1 or higher, with access rights that depend
>  on the mode:
> 
>     * Read/write in Secure PL1 modes.
> 
>     * Read-only and write-ignored in Non-secure PL1 and PL2 modes
>       if NSACR.NS_SMP is 0.
> 
>     * Read/write in Non-secure PL1 and PL2 modes if NSACR.NS_SMP
>       is 1. In this case, all bits are write-ignored except for the SMP bit.
> 
> We can attempt to set this bit from within the kernel, which helps
> avoiding firmware side modifications to set the IBE bit when that is
> impractical. We do this within __v7_ca15mp_setup and __v7_b15mp_setup
> because by then we already took those labels because the processors we
> run on do match.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

I believe this would help on selected R-Car Gen2 SoCs which have CA15
cores. Those cores are released from reset by Linux directly and jump to
the reset vector set up by Linux in Secure mode.

I was looking for a generic solution after discussing how to mitigate
the spectrev2 on such SoCs with Catalin on IRC and this seems to be one
option. There was also a suggestion that Russell is working on some sort
of generic solution too. Can you comment on that please ?

> ---
>  arch/arm/mm/proc-v7.S | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 6fe52819e014..a21cf3729efa 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -284,10 +284,16 @@ __v7_cr8mp_setup:
>  	b	1f
>  __v7_ca7mp_setup:
>  __v7_ca12mp_setup:
> +	b	2f
>  __v7_ca15mp_setup:
>  __v7_b15mp_setup:
> +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> +	mrc	p15, 0, r0, c1, c0, 1
> +	orr	r0, r0, #1			@ Enable IBE bit
> +	mcr	p15, 0, r0, c1, c0, 1
> +#endif
>  __v7_ca17mp_setup:
> -	mov	r10, #0
> +2:	mov	r10, #0
>  1:	adr	r0, __v7_setup_stack_ptr
>  	ldr	r12, [r0]
>  	add	r12, r12, r0			@ the local stack
> 


-- 
Best regards,
Marek Vasut

[PATCH] ARM: spectre-v2: Try to set IBE bit for Cortex-A15 and Brahma-B15

[Marek Vasut]

On 08/11/2018 03:58 PM, Marek Vasut wrote:
> On 06/08/2018 12:58 AM, Florian Fainelli wrote:
>> Per the ARM reference manual for the Cortex-A15, The ACTLR:
>>
>>  Is a read/write register.
>>
>>  Common to the Secure and Non-secure states.
>>
>>  Is only accessible from PL1 or higher, with access rights that depend
>>  on the mode:
>>
>>     * Read/write in Secure PL1 modes.
>>
>>     * Read-only and write-ignored in Non-secure PL1 and PL2 modes
>>       if NSACR.NS_SMP is 0.
>>
>>     * Read/write in Non-secure PL1 and PL2 modes if NSACR.NS_SMP
>>       is 1. In this case, all bits are write-ignored except for the SMP bit.
>>
>> We can attempt to set this bit from within the kernel, which helps
>> avoiding firmware side modifications to set the IBE bit when that is
>> impractical. We do this within __v7_ca15mp_setup and __v7_b15mp_setup
>> because by then we already took those labels because the processors we
>> run on do match.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> 
> I believe this would help on selected R-Car Gen2 SoCs which have CA15
> cores. Those cores are released from reset by Linux directly and jump to
> the reset vector set up by Linux in Secure mode.
> 
> I was looking for a generic solution after discussing how to mitigate
> the spectrev2 on such SoCs with Catalin on IRC and this seems to be one
> option. There was also a suggestion that Russell is working on some sort
> of generic solution too. Can you comment on that please ?

Is there any feedback on this ?

>> ---
>>  arch/arm/mm/proc-v7.S | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
>> index 6fe52819e014..a21cf3729efa 100644
>> --- a/arch/arm/mm/proc-v7.S
>> +++ b/arch/arm/mm/proc-v7.S
>> @@ -284,10 +284,16 @@ __v7_cr8mp_setup:
>>  	b	1f
>>  __v7_ca7mp_setup:
>>  __v7_ca12mp_setup:
>> +	b	2f
>>  __v7_ca15mp_setup:
>>  __v7_b15mp_setup:
>> +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
>> +	mrc	p15, 0, r0, c1, c0, 1
>> +	orr	r0, r0, #1			@ Enable IBE bit
>> +	mcr	p15, 0, r0, c1, c0, 1
>> +#endif
>>  __v7_ca17mp_setup:
>> -	mov	r10, #0
>> +2:	mov	r10, #0
>>  1:	adr	r0, __v7_setup_stack_ptr
>>  	ldr	r12, [r0]
>>  	add	r12, r12, r0			@ the local stack
>>
> 
> 


-- 
Best regards,
Marek Vasut