[PATCH v2 29/37] powerpc/nohash: Replace pte_user() by pte_read()

[Christophe Leroy]

Le 31/10/2023 à 11:15, Aneesh Kumar K.V a écrit :
> Christophe Leroy <christophe.leroy at csgroup.eu> writes:
> 
>> pte_user() is now only used in pte_access_permitted() to check
>> access on vmas. User flag is cleared to make a page unreadable.
>>
>> So rename it pte_read() and remove pte_user() which isn't used
>> anymore.
>>
>> For the time being it checks _PAGE_USER but in the near futur
>> all plateforms will be converted to _PAGE_READ so lets support
>> both for now.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>> ---
>>   arch/powerpc/include/asm/nohash/32/pte-8xx.h |  7 -------
>>   arch/powerpc/include/asm/nohash/pgtable.h    | 13 +++++++------
>>   arch/powerpc/mm/ioremap.c                    |  4 ----
>>   3 files changed, 7 insertions(+), 17 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
>> index 62c965a4511a..1ee38befd29a 100644
>> --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
>> +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
>> @@ -112,13 +112,6 @@ static inline pte_t pte_mkwrite_novma(pte_t pte)
>>   
>>   #define pte_mkwrite_novma pte_mkwrite_novma
>>   
>> -static inline bool pte_user(pte_t pte)
>> -{
>> -	return !(pte_val(pte) & _PAGE_SH);
>> -}
>> -
>> -#define pte_user pte_user
>> -
>>   static inline pte_t pte_mkhuge(pte_t pte)
>>   {
>>   	return __pte(pte_val(pte) | _PAGE_SPS | _PAGE_HUGE);
>> diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
>> index ee677162f9e6..aba56fe3b1c6 100644
>> --- a/arch/powerpc/include/asm/nohash/pgtable.h
>> +++ b/arch/powerpc/include/asm/nohash/pgtable.h
>> @@ -160,9 +160,6 @@ static inline int pte_write(pte_t pte)
>>   	return pte_val(pte) & _PAGE_WRITE;
>>   }
>>   #endif
>> -#ifndef pte_read
>> -static inline int pte_read(pte_t pte)		{ return 1; }
>> -#endif
>>   static inline int pte_dirty(pte_t pte)		{ return pte_val(pte) & _PAGE_DIRTY; }
>>   static inline int pte_special(pte_t pte)	{ return pte_val(pte) & _PAGE_SPECIAL; }
>>   static inline int pte_none(pte_t pte)		{ return (pte_val(pte) & ~_PTE_NONE_MASK) == 0; }
>> @@ -190,10 +187,14 @@ static inline int pte_young(pte_t pte)
>>    * and PTE_64BIT, PAGE_KERNEL_X contains _PAGE_BAP_SR which is also in
>>    * _PAGE_USER.  Need to explicitly match _PAGE_BAP_UR bit in that case too.
>>    */
>> -#ifndef pte_user
>> -static inline bool pte_user(pte_t pte)
>> +#ifndef pte_read
>> +static inline bool pte_read(pte_t pte)
>>   {
>> +#ifdef _PAGE_READ
>> +	return (pte_val(pte) & _PAGE_READ) == _PAGE_READ;
>> +#else
>>   	return (pte_val(pte) & _PAGE_USER) == _PAGE_USER;
>> +#endif
>>   }
>>   #endif
>>   
>> @@ -208,7 +209,7 @@ static inline bool pte_access_permitted(pte_t pte, bool write)
>>   	 * A read-only access is controlled by _PAGE_USER bit.
>>   	 * We have _PAGE_READ set for WRITE and EXECUTE
>>   	 */
>> -	if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
>> +	if (!pte_present(pte) || !pte_read(pte))
>>   		return false;
>>   
>>   	if (write && !pte_write(pte))
>> diff --git a/arch/powerpc/mm/ioremap.c b/arch/powerpc/mm/ioremap.c
>> index 7823c38f09de..7b0afcabd89f 100644
>> --- a/arch/powerpc/mm/ioremap.c
>> +++ b/arch/powerpc/mm/ioremap.c
>> @@ -50,10 +50,6 @@ void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long flags)
>>   	if (pte_write(pte))
>>   		pte = pte_mkdirty(pte);
>>   
>> -	/* we don't want to let _PAGE_USER leak out */
>> -	if (WARN_ON(pte_user(pte)))
>> -		return NULL;
>>
> 
> This check is still valid right? I understand that we want to remove
> _PAGE_USER. But then loosing this check is ok?

Well, we may have to think about it for book3s/64. For all others 
_PAGE_USER is gone and replaced by a check of addresses versus TASK_SIZE.

As ioremap() will map into vmalloc space that address is necesserally 
correct.

> 
>> -
>>   	if (iowa_is_active())
>>   		return iowa_ioremap(addr, size, pte_pgprot(pte), caller);
>>   	return __ioremap_caller(addr, size, pte_pgprot(pte), caller);
>> -- 
>> 2.41.0