linux-kernel - Re: [PATCH v4 4/6] mm: ioremap: Add ioremap/iounmap

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Date:   Tue, 7 Jun 2022 15:37:10 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <catalin.marinas@....com>, <will@...nel.org>,
        <akpm@...ux-foundation.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <hch@...radead.org>, <arnd@...db.de>, <anshuman.khandual@....com>
Subject: Re: [PATCH v4 4/6] mm: ioremap: Add ioremap/iounmap_allowed()


On 2022/6/6 23:14, Baoquan He wrote:
> On 06/06/22 at 03:48pm, Kefeng Wang wrote:
>> Add special hook for architecture to verify addr, size or prot
>> when ioremap() or iounmap(), which will make the generic ioremap
>> more useful.
>>
>>    ioremap_allowed() return an int,
>>      - NULL means continue to remap
>>      - error code means skip remap and return directly
>>    iounmap_allowed() return an int,
>>      - 0 means continue to vunmap
>>      - error code means skip vunmap and return directly
> Aren't they bool type function and better return bool value?

Ok, let's keep it simple, back to v1's version , use bool, if we want to 
extend

them,  do it later.

>
>> Acked-by: Andrew Morton <akpm@...ux-foundation.org>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>> ---
>>   include/asm-generic/io.h | 25 +++++++++++++++++++++++++
>>   mm/ioremap.c             | 13 ++++++++++---
>>   2 files changed, 35 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>> index e6ffa2519f08..9429387a3e65 100644
>> --- a/include/asm-generic/io.h
>> +++ b/include/asm-generic/io.h
>> @@ -964,6 +964,31 @@ static inline void iounmap(volatile void __iomem *addr)
>>   #elif defined(CONFIG_GENERIC_IOREMAP)
>>   #include <linux/pgtable.h>
>>   
>> +/*
>> + * Arch code can implement the following two special hooks when using GENERIC_IOREMAP
>> + * ioremap_allowed() return an int,
>> + *   - 0 means continue to remap
>> + *   - error code means skip remap and return directly
>> + * iounmap_allowed() return an int,
>> + *   - 0 means continue to vunmap
>> + *   - error code means skip vunmap and return directly
>> + */
>> +#ifndef ioremap_allowed
>> +#define ioremap_allowed ioremap_allowed
>> +static inline int ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
>> +{
>> +	return 0;
>> +}
>> +#endif
>> +
>> +#ifndef iounmap_allowed
>> +#define iounmap_allowed iounmap_allowed
>> +static inline int iounmap_allowed(void __iomem *addr)
>> +{
>> +	return 0;
>> +}
>> +#endif
>> +
>>   void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long prot);
>>   void iounmap(volatile void __iomem *addr);
>>   
>> diff --git a/mm/ioremap.c b/mm/ioremap.c
>> index 7cb9996b0c12..196c93c0beb8 100644
>> --- a/mm/ioremap.c
>> +++ b/mm/ioremap.c
>> @@ -27,8 +27,10 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, unsigned long pro
>>   	phys_addr -= offset;
>>   	size = PAGE_ALIGN(size + offset);
>>   
>> -	area = get_vm_area_caller(size, VM_IOREMAP,
>> -			__builtin_return_address(0));
>> +	if (ioremap_allowed(phys_addr, size, prot))
>> +		return NULL;
>> +
>> +	area = get_vm_area_caller(size, VM_IOREMAP, __builtin_return_address(0));
>>   	if (!area)
>>   		return NULL;
>>   	vaddr = (unsigned long)area->addr;
>> @@ -45,6 +47,11 @@ EXPORT_SYMBOL(ioremap_prot);
>>   
>>   void iounmap(volatile void __iomem *addr)
>>   {
>> -	vunmap((void *)((unsigned long)addr & PAGE_MASK));
>> +	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
>> +
>> +	if (iounmap_allowed(vaddr))
>> +		return;
>> +
>> +	vunmap((void __force *)vaddr);
>>   }
>>   EXPORT_SYMBOL(iounmap);
>> -- 
>> 2.35.3
>>
>>
> .