[PATCH-next] arm: fix clang build warning in include/asm/memory.h

[Yipeng Zou]

在 2024/3/15 15:40, Linus Walleij 写道:
> On Fri, Mar 15, 2024 at 1:43 AM Nathan Chancellor <nathan at kernel.org> wrote:
>> On Thu, Mar 14, 2024 at 03:54:09PM +0800, Yipeng Zou wrote:
>>> There is a build error has been founded with build in clang-15.0.4:
>>>
>>> ./arch/arm/include/asm/memory.h:358:12: error: result of comparison "phys addr_t’ (aka 'unsigned int’) > 4294967295 is always false [-Werror, -Wtautological-type-limit-compare]
>>>                               if (addr > (u32)~0)
>>>                                   ~~~~ ^ ~~~~~~~
>>>
>>> It will be always goes fail without CONFIG_PHYS_ADDR_T_64BIT.
>>>
>>> Directly silence it by Use CONFIG_PHYS_ADDR_T_64BIT.
>>>
>>> Fixes: 981b6714dbd2 ("ARM: provide improved virt_to_idmap() functionality")
>>> Signed-off-by: Yipeng Zou <zouyipeng at huawei.com>
>>> ---
>>>   arch/arm/include/asm/memory.h | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>>> index ef2aa79ece5a..64ced9eb42ff 100644
>>> --- a/arch/arm/include/asm/memory.h
>>> +++ b/arch/arm/include/asm/memory.h
>>> @@ -347,14 +347,18 @@ static inline bool arm_has_idmap_alias(void)
>>>        return IS_ENABLED(CONFIG_MMU) && arch_phys_to_idmap_offset != 0;
>>>   }
>>>
>>> +#ifdef CONFIG_PHYS_ADDR_T_64BIT
>>>   #define IDMAP_INVALID_ADDR ((u32)~0)
>>> +#endif
>>>
>>>   static inline unsigned long phys_to_idmap(phys_addr_t addr)
>>>   {
>>>        if (IS_ENABLED(CONFIG_MMU) && arch_phys_to_idmap_offset) {
>>>                addr += arch_phys_to_idmap_offset;
>>> +#ifdef CONFIG_PHYS_ADDR_T_64BIT
>>>                if (addr > (u32)~0)
>>>                        addr = IDMAP_INVALID_ADDR;
>>> +#endif
>>>        }
>>>        return addr;
>>>   }
>>> --
>>> 2.34.1
>>>
>> Would it be better to avoid the ifdef's here and just use IS_ENABLED()?
>> I can't see why this would not work for avoiding that warning.
>>
>> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>> index ef2aa79ece5a..fbff07bc3b28 100644
>> --- a/arch/arm/include/asm/memory.h
>> +++ b/arch/arm/include/asm/memory.h
>> @@ -353,7 +353,7 @@ static inline unsigned long phys_to_idmap(phys_addr_t addr)
>>   {
>>          if (IS_ENABLED(CONFIG_MMU) && arch_phys_to_idmap_offset) {
>>                  addr += arch_phys_to_idmap_offset;
>> -               if (addr > (u32)~0)
>> +               if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT) && addr > (u32)~0)
>>                          addr = IDMAP_INVALID_ADDR;
> +1 and I would probably use this as well:
>
> <linux/limits.h>
>
> #define IDMAP_INVALID_ADDR    PHYS_ADDR_MAX
>
> if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT) && addr > PHYS_ADDR_MAX)
>      addr = IDMAP_INVALID_ADDR;
>
> Because then it is clear what is going on: we are capping to the max physical
> address.

Yes, indeed, It's clearer to indicate what is going on.

Will fix it in that way.

> PHYS_ADDR_MAX is defined to (~(phys_addr_t)0) which on
> ARM is (~(u32)0).
>
> Yours,
> Linus Walleij
>
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-- 
Regards,
Yipeng Zou