linux-kernel - Re: [PATCH] RISC-V: Always define XIP_FIXUP

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Message-ID: <436e619a-de98-9948-9ccf-62a2f943142e@ghiti.fr>
Date:   Sun, 2 May 2021 04:14:27 -0400
From:   Alex Ghiti <alex@...ti.fr>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, akpm@...ux-foundation.org,
        Atish Patra <Atish.Patra@....com>,
        Anup Patel <Anup.Patel@....com>, wangkefeng.wang@...wei.com,
        rppt@...nel.org, vitaly.wool@...sulko.com, greentime.hu@...ive.com,
        0x7f454c46@...il.com, chenhuang5@...wei.com,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        linux@...ck-us.net
Subject: Re: [PATCH] RISC-V: Always define XIP_FIXUP

Hi Palmer,

Le 4/29/21 à 12:43 AM, Palmer Dabbelt a écrit :
> On Wed, 28 Apr 2021 01:25:55 PDT (-0700), alex@...ti.fr wrote:
>> Le 4/27/21 à 11:34 PM, Palmer Dabbelt a écrit :
>>> From: Palmer Dabbelt <palmerdabbelt@...gle.com>
>>>
>>> XIP depends on MMU, but XIP_FIXUP is defined throughout the kernel in
>>> order to avoid excessive ifdefs.  This just makes sure to always define
>>> XIP_FIXIP, which will fix MMU=n builds.
>>
>> A small typo here.
> 
> Actually two: "defined" should have been "used".  Both are fixed.
> 
>>
>>>
>>> Fixes: 44c922572952 ("RISC-V: enable XIP")
>>> Reported-by: Guenter Roeck <linux@...ck-us.net>
>>> Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
>>> ---
>>>   arch/riscv/include/asm/pgtable.h | 24 ++++++++++++------------
>>>   1 file changed, 12 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/arch/riscv/include/asm/pgtable.h 
>>> b/arch/riscv/include/asm/pgtable.h
>>> index 2f1384e14e31..fd749351f432 100644
>>> --- a/arch/riscv/include/asm/pgtable.h
>>> +++ b/arch/riscv/include/asm/pgtable.h
>>> @@ -73,18 +73,6 @@
>>>   #endif
>>>   #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>>>
>>> -#ifdef CONFIG_XIP_KERNEL
>>> -#define XIP_OFFSET        SZ_8M
>>> -#define XIP_FIXUP(addr) ({                            \
>>> -    uintptr_t __a = (uintptr_t)(addr);                    \
>>> -    (__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + 
>>> SZ_16M) ?    \
>>> -        __a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - 
>>> XIP_OFFSET :\
>>> -        __a;                                \
>>> -    })
>>> -#else
>>> -#define XIP_FIXUP(addr)        (addr)
>>> -#endif /* CONFIG_XIP_KERNEL */
>>> -
>>>   #endif
>>>
>>>   #ifndef __ASSEMBLY__
>>> @@ -101,6 +89,18 @@
>>>   #include <asm/pgtable-32.h>
>>>   #endif /* CONFIG_64BIT */
>>>
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define XIP_OFFSET        SZ_8M
>>
>>
>> XIP_OFFSET is used in head.S and then this breaks XIP_KERNEL. XIP_OFFSET
>> must live outside the ifndef __ASSEMBLY__.
> 
> Thanks, I hadn't even seen XIP_OFFSET.  This is fixed in the v2.
> 
> Do you have an XIP config that will run on QEMU, and a way to run it? If 
> so, can you post a defconfig and some instructions?  That'll make it 
> easier to test on my end.

I posted a tutorial here on how I test XIP kernel:

https://alexghiti.github.io/xip/XIP.html

If something does not work for you, please tell me.

Alex

> 
>>> +#define XIP_FIXUP(addr) ({                            \
>>> +    uintptr_t __a = (uintptr_t)(addr);                    \
>>> +    (__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + 
>>> SZ_16M) ?    \
>>> +        __a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - 
>>> XIP_OFFSET :\
>>> +        __a;                                \
>>> +    })
>>> +#else
>>> +#define XIP_FIXUP(addr)        (addr)
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> +
>>>   #ifdef CONFIG_MMU
>>>   /* Number of entries in the page global directory */
>>>   #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
>>>
>>
>> Thank you for doing that!
>>
>> Alex
> 
> _______________________________________________
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> linux-riscv@...ts.infradead.org
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