[v3,4/6] powerpc/fsl_booke/64: do not clear the BSS for the second pass
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Message ID 20200206025825.22934-5-yanaijie@huawei.com
State New
Headers show
Series
  • implement KASLR for powerpc/fsl_booke/64
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Commit Message

Jason Yan Feb. 6, 2020, 2:58 a.m. UTC
The BSS section has already cleared out in the first pass. No need to
clear it again. This can save some time when booting with KASLR
enabled.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Cc: Scott Wood <oss@buserror.net>
Cc: Diana Craciun <diana.craciun@nxp.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
---
 arch/powerpc/kernel/head_64.S | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Scott Wood March 4, 2020, 9:49 p.m. UTC | #1
On Thu, 2020-02-06 at 10:58 +0800, Jason Yan wrote:
> The BSS section has already cleared out in the first pass. No need to
> clear it again. This can save some time when booting with KASLR
> enabled.
> 
> Signed-off-by: Jason Yan <yanaijie@huawei.com>
> Cc: Scott Wood <oss@buserror.net>
> Cc: Diana Craciun <diana.craciun@nxp.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> ---
>  arch/powerpc/kernel/head_64.S | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
> index 744624140fb8..8c644e7c3eaf 100644
> --- a/arch/powerpc/kernel/head_64.S
> +++ b/arch/powerpc/kernel/head_64.S
> @@ -914,6 +914,13 @@ start_here_multiplatform:
>  	bl      relative_toc
>  	tovirt(r2,r2)
>  
> +	/* Do not clear the BSS for the second pass if randomized */
> +	LOAD_REG_ADDR(r3, kernstart_virt_addr)
> +	lwz     r3,0(r3)
> +	LOAD_REG_IMMEDIATE(r4, KERNELBASE)
> +	cmpw	r3,r4
> +	bne	4f

These are 64-bit values.

-Scott
Jason Yan March 5, 2020, 3:14 a.m. UTC | #2
在 2020/3/5 5:49, Scott Wood 写道:
> On Thu, 2020-02-06 at 10:58 +0800, Jason Yan wrote:
>> The BSS section has already cleared out in the first pass. No need to
>> clear it again. This can save some time when booting with KASLR
>> enabled.
>>
>> Signed-off-by: Jason Yan <yanaijie@huawei.com>
>> Cc: Scott Wood <oss@buserror.net>
>> Cc: Diana Craciun <diana.craciun@nxp.com>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> Cc: Paul Mackerras <paulus@samba.org>
>> Cc: Nicholas Piggin <npiggin@gmail.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> ---
>>   arch/powerpc/kernel/head_64.S | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
>> index 744624140fb8..8c644e7c3eaf 100644
>> --- a/arch/powerpc/kernel/head_64.S
>> +++ b/arch/powerpc/kernel/head_64.S
>> @@ -914,6 +914,13 @@ start_here_multiplatform:
>>   	bl      relative_toc
>>   	tovirt(r2,r2)
>>   
>> +	/* Do not clear the BSS for the second pass if randomized */
>> +	LOAD_REG_ADDR(r3, kernstart_virt_addr)
>> +	lwz     r3,0(r3)
>> +	LOAD_REG_IMMEDIATE(r4, KERNELBASE)
>> +	cmpw	r3,r4
>> +	bne	4f
> 
> These are 64-bit values.
> 

Oh yes, will fix. Thanks.

> -Scott
> 
> 
> 
> .
>

Patch
diff mbox series

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 744624140fb8..8c644e7c3eaf 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -914,6 +914,13 @@  start_here_multiplatform:
 	bl      relative_toc
 	tovirt(r2,r2)
 
+	/* Do not clear the BSS for the second pass if randomized */
+	LOAD_REG_ADDR(r3, kernstart_virt_addr)
+	lwz     r3,0(r3)
+	LOAD_REG_IMMEDIATE(r4, KERNELBASE)
+	cmpw	r3,r4
+	bne	4f
+
 	/* Clear out the BSS. It may have been done in prom_init,
 	 * already but that's irrelevant since prom_init will soon
 	 * be detached from the kernel completely. Besides, we need