[RFC,05/10] powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper
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Message ID 20190717080621.40424-6-yanaijie@huawei.com
State New
Headers show
Series
  • implement KASLR for powerpc/fsl_booke/32
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Commit Message

Jason Yan July 17, 2019, 8:06 a.m. UTC
Add a new helper reloc_kernel_entry() to jump back to the start of the
new kernel. After we put the new kernel in a randomized place we can use
this new helper to enter the kernel and begin to relocate again.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
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_fsl_booke.S | 16 ++++++++++++++++
 arch/powerpc/mm/mmu_decl.h           |  1 +
 2 files changed, 17 insertions(+)

Comments

Christophe Leroy July 29, 2019, 11:08 a.m. UTC | #1
Le 17/07/2019 à 10:06, Jason Yan a écrit :
> Add a new helper reloc_kernel_entry() to jump back to the start of the
> new kernel. After we put the new kernel in a randomized place we can use
> this new helper to enter the kernel and begin to relocate again.
> 
> Signed-off-by: Jason Yan <yanaijie@huawei.com>
> 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_fsl_booke.S | 16 ++++++++++++++++
>   arch/powerpc/mm/mmu_decl.h           |  1 +
>   2 files changed, 17 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
> index a57d44638031..ce40f96dae20 100644
> --- a/arch/powerpc/kernel/head_fsl_booke.S
> +++ b/arch/powerpc/kernel/head_fsl_booke.S
> @@ -1144,6 +1144,22 @@ _GLOBAL(create_tlb_entry)
>   	sync
>   	blr
>   
> +/*
> + * Return to the start of the relocated kernel and run again
> + * r3 - virtual address of fdt
> + * r4 - entry of the kernel
> + */
> +_GLOBAL(reloc_kernel_entry)
> +	mfmsr	r7
> +	li	r8,(MSR_IS | MSR_DS)
> +	andc	r7,r7,r8

Instead of the li/andc, what about the following:

rlwinm r7, r7, 0, ~(MSR_IS | MSR_DS)

> +
> +	mtspr	SPRN_SRR0,r4
> +	mtspr	SPRN_SRR1,r7
> +	isync
> +	sync
> +	rfi

Are the isync/sync really necessary ? AFAIK, rfi is context synchronising.

> +
>   /*
>    * Create a tlb entry with the same effective and physical address as
>    * the tlb entry used by the current running code. But set the TS to 1.
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index d7737cf97cee..dae8e9177574 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -143,6 +143,7 @@ extern void adjust_total_lowmem(void);
>   extern int switch_to_as1(void);
>   extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
>   extern void create_tlb_entry(phys_addr_t phys, unsigned long virt, int entry);
> +extern void reloc_kernel_entry(void *fdt, int addr);

No new 'extern' please, see 
https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/8125//artifact/linux/checkpatch.log


>   #endif
>   extern void loadcam_entry(unsigned int index);
>   extern void loadcam_multi(int first_idx, int num, int tmp_idx);
> 

Christophe
Jason Yan July 29, 2019, 1:35 p.m. UTC | #2
On 2019/7/29 19:08, Christophe Leroy wrote:
> 
> 
> Le 17/07/2019 à 10:06, Jason Yan a écrit :
>> Add a new helper reloc_kernel_entry() to jump back to the start of the
>> new kernel. After we put the new kernel in a randomized place we can use
>> this new helper to enter the kernel and begin to relocate again.
>>
>> Signed-off-by: Jason Yan <yanaijie@huawei.com>
>> 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_fsl_booke.S | 16 ++++++++++++++++
>>   arch/powerpc/mm/mmu_decl.h           |  1 +
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/head_fsl_booke.S 
>> b/arch/powerpc/kernel/head_fsl_booke.S
>> index a57d44638031..ce40f96dae20 100644
>> --- a/arch/powerpc/kernel/head_fsl_booke.S
>> +++ b/arch/powerpc/kernel/head_fsl_booke.S
>> @@ -1144,6 +1144,22 @@ _GLOBAL(create_tlb_entry)
>>       sync
>>       blr
>> +/*
>> + * Return to the start of the relocated kernel and run again
>> + * r3 - virtual address of fdt
>> + * r4 - entry of the kernel
>> + */
>> +_GLOBAL(reloc_kernel_entry)
>> +    mfmsr    r7
>> +    li    r8,(MSR_IS | MSR_DS)
>> +    andc    r7,r7,r8
> 
> Instead of the li/andc, what about the following:
> 
> rlwinm r7, r7, 0, ~(MSR_IS | MSR_DS)
> 

Good idea.

>> +
>> +    mtspr    SPRN_SRR0,r4
>> +    mtspr    SPRN_SRR1,r7
>> +    isync
>> +    sync
>> +    rfi
> 
> Are the isync/sync really necessary ? AFAIK, rfi is context synchronising.
> 

I see some code with sync before rfi so I'm not sure. I will check this
and drop the isync/sync if it's true.

Thanks.

>> +
>>   /*
>>    * Create a tlb entry with the same effective and physical address as
>>    * the tlb entry used by the current running code. But set the TS to 1.
>> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
>> index d7737cf97cee..dae8e9177574 100644
>> --- a/arch/powerpc/mm/mmu_decl.h
>> +++ b/arch/powerpc/mm/mmu_decl.h
>> @@ -143,6 +143,7 @@ extern void adjust_total_lowmem(void);
>>   extern int switch_to_as1(void);
>>   extern void restore_to_as0(int esel, int offset, void *dt_ptr, int 
>> bootcpu);
>>   extern void create_tlb_entry(phys_addr_t phys, unsigned long virt, 
>> int entry);
>> +extern void reloc_kernel_entry(void *fdt, int addr);
> 
> No new 'extern' please, see 
> https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/8125//artifact/linux/checkpatch.log 
> 
> 
> 
>>   #endif
>>   extern void loadcam_entry(unsigned int index);
>>   extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>>
> 
> Christophe
> 
> .
>

Patch
diff mbox series

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index a57d44638031..ce40f96dae20 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1144,6 +1144,22 @@  _GLOBAL(create_tlb_entry)
 	sync
 	blr
 
+/*
+ * Return to the start of the relocated kernel and run again
+ * r3 - virtual address of fdt
+ * r4 - entry of the kernel
+ */
+_GLOBAL(reloc_kernel_entry)
+	mfmsr	r7
+	li	r8,(MSR_IS | MSR_DS)
+	andc	r7,r7,r8
+
+	mtspr	SPRN_SRR0,r4
+	mtspr	SPRN_SRR1,r7
+	isync
+	sync
+	rfi
+
 /*
  * Create a tlb entry with the same effective and physical address as
  * the tlb entry used by the current running code. But set the TS to 1.
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index d7737cf97cee..dae8e9177574 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -143,6 +143,7 @@  extern void adjust_total_lowmem(void);
 extern int switch_to_as1(void);
 extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
 extern void create_tlb_entry(phys_addr_t phys, unsigned long virt, int entry);
+extern void reloc_kernel_entry(void *fdt, int addr);
 #endif
 extern void loadcam_entry(unsigned int index);
 extern void loadcam_multi(int first_idx, int num, int tmp_idx);