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List:       linux-mips
Subject:    Re: [PATCH 6/9] MIPS: Call relocate_kernel if CONFIG_RELOCATABLE=y
From:       James Hogan <james () albanarts ! com>
Date:       2015-12-03 18:54:07
Message-ID: BA73413A-D335-4692-85A4-9330D7ACAC03 () albanarts ! com
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On 3 December 2015 17:46:14 GMT+00:00, Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> wrote:
>On 12/03/2015 05:53 PM, Matt Redfearn wrote:
>
>>>> If CONFIG_RELOCATABLE is enabled, jump to relocate_kernel.
>>>>
>>>> This function will return the entry point of the relocated kernel
>if
>>>> copy/relocate is sucessful or the original entry point if not. The
>stack
>>>> pointer must then be pointed into the new image.
>>>>
>>>> Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
>>>> ---
>>>>   arch/mips/kernel/head.S | 20 ++++++++++++++++++++
>>>>   1 file changed, 20 insertions(+)
>>>>
>>>> diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
>>>> index 4e4cc5b9a771..7dc043349d66 100644
>>>> --- a/arch/mips/kernel/head.S
>>>> +++ b/arch/mips/kernel/head.S
>>>> @@ -132,7 +132,27 @@ not_found:
>>>>       set_saved_sp    sp, t0, t1
>>>>       PTR_SUBU    sp, 4 * SZREG        # init stack pointer
>>>>
>>>> +#ifdef CONFIG_RELOCATABLE
>>>> +    /* Copy kernel and apply the relocations */
>>>> +    jal        relocate_kernel
>>>> +
>>>> +    /* Repoint the sp into the new kernel image */
>>>> +    PTR_LI        sp, _THREAD_SIZE - 32 - PT_SIZE
>>>> +    PTR_ADDU    sp, $28
>>>
>>>    Can't you account for it in the previous PTR_LI?
>
>> During relocate_kernel, $28, pointer to the current thread,
>
>Ah, it's a register! I thought it was an immediate. Nevermind then. :-)

Although, it could still be reduced:
PTR_ADDU sp, gp, _THREAD_SIZE - 32 - PT_SIZE

Assuming the immediate is in range of signed 16bit.

Cheers
James

>
>[...]
>
>MBR, Sergei


-- 
James Hogan

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