[PATCH v2] powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()

Michael Ellerman mpe at ellerman.id.au
Mon Jun 29 21:27:56 AEST 2020


Christophe Leroy <christophe.leroy at csgroup.eu> writes:
> Hi Michael,
>
> I see this patch is marked as "defered" in patchwork, but I can't see 
> any related discussion. Is it normal ?

Because it uses the "m<>" constraint which didn't work on GCC 4.6.

https://github.com/linuxppc/issues/issues/297

So we should be able to pick it up for v5.9 hopefully.

cheers


> Le 16/04/2020 à 14:39, Christophe Leroy a écrit :
>> At the time being, __put_user()/__get_user() and friends only use
>> D-form addressing, with 0 offset. Ex:
>> 
>> 	lwz	reg1, 0(reg2)
>> 
>> Give the compiler the opportunity to use other adressing modes
>> whenever possible, to get more optimised code.
>> 
>> Hereunder is a small exemple:
>> 
>> struct test {
>> 	u32 item1;
>> 	u16 item2;
>> 	u8 item3;
>> 	u64 item4;
>> };
>> 
>> int set_test_user(struct test __user *from, struct test __user *to)
>> {
>> 	int err;
>> 	u32 item1;
>> 	u16 item2;
>> 	u8 item3;
>> 	u64 item4;
>> 
>> 	err = __get_user(item1, &from->item1);
>> 	err |= __get_user(item2, &from->item2);
>> 	err |= __get_user(item3, &from->item3);
>> 	err |= __get_user(item4, &from->item4);
>> 
>> 	err |= __put_user(item1, &to->item1);
>> 	err |= __put_user(item2, &to->item2);
>> 	err |= __put_user(item3, &to->item3);
>> 	err |= __put_user(item4, &to->item4);
>> 
>> 	return err;
>> }
>> 
>> Before the patch:
>> 
>> 00000df0 <set_test_user>:
>>   df0:	94 21 ff f0 	stwu    r1,-16(r1)
>>   df4:	39 40 00 00 	li      r10,0
>>   df8:	93 c1 00 08 	stw     r30,8(r1)
>>   dfc:	93 e1 00 0c 	stw     r31,12(r1)
>>   e00:	7d 49 53 78 	mr      r9,r10
>>   e04:	80 a3 00 00 	lwz     r5,0(r3)
>>   e08:	38 e3 00 04 	addi    r7,r3,4
>>   e0c:	7d 46 53 78 	mr      r6,r10
>>   e10:	a0 e7 00 00 	lhz     r7,0(r7)
>>   e14:	7d 29 33 78 	or      r9,r9,r6
>>   e18:	39 03 00 06 	addi    r8,r3,6
>>   e1c:	7d 46 53 78 	mr      r6,r10
>>   e20:	89 08 00 00 	lbz     r8,0(r8)
>>   e24:	7d 29 33 78 	or      r9,r9,r6
>>   e28:	38 63 00 08 	addi    r3,r3,8
>>   e2c:	7d 46 53 78 	mr      r6,r10
>>   e30:	83 c3 00 00 	lwz     r30,0(r3)
>>   e34:	83 e3 00 04 	lwz     r31,4(r3)
>>   e38:	7d 29 33 78 	or      r9,r9,r6
>>   e3c:	7d 43 53 78 	mr      r3,r10
>>   e40:	90 a4 00 00 	stw     r5,0(r4)
>>   e44:	7d 29 1b 78 	or      r9,r9,r3
>>   e48:	38 c4 00 04 	addi    r6,r4,4
>>   e4c:	7d 43 53 78 	mr      r3,r10
>>   e50:	b0 e6 00 00 	sth     r7,0(r6)
>>   e54:	7d 29 1b 78 	or      r9,r9,r3
>>   e58:	38 e4 00 06 	addi    r7,r4,6
>>   e5c:	7d 43 53 78 	mr      r3,r10
>>   e60:	99 07 00 00 	stb     r8,0(r7)
>>   e64:	7d 23 1b 78 	or      r3,r9,r3
>>   e68:	38 84 00 08 	addi    r4,r4,8
>>   e6c:	93 c4 00 00 	stw     r30,0(r4)
>>   e70:	93 e4 00 04 	stw     r31,4(r4)
>>   e74:	7c 63 53 78 	or      r3,r3,r10
>>   e78:	83 c1 00 08 	lwz     r30,8(r1)
>>   e7c:	83 e1 00 0c 	lwz     r31,12(r1)
>>   e80:	38 21 00 10 	addi    r1,r1,16
>>   e84:	4e 80 00 20 	blr
>> 
>> After the patch:
>> 
>> 00000dbc <set_test_user>:
>>   dbc:	39 40 00 00 	li      r10,0
>>   dc0:	7d 49 53 78 	mr      r9,r10
>>   dc4:	80 03 00 00 	lwz     r0,0(r3)
>>   dc8:	7d 48 53 78 	mr      r8,r10
>>   dcc:	a1 63 00 04 	lhz     r11,4(r3)
>>   dd0:	7d 29 43 78 	or      r9,r9,r8
>>   dd4:	7d 48 53 78 	mr      r8,r10
>>   dd8:	88 a3 00 06 	lbz     r5,6(r3)
>>   ddc:	7d 29 43 78 	or      r9,r9,r8
>>   de0:	7d 48 53 78 	mr      r8,r10
>>   de4:	80 c3 00 08 	lwz     r6,8(r3)
>>   de8:	80 e3 00 0c 	lwz     r7,12(r3)
>>   dec:	7d 29 43 78 	or      r9,r9,r8
>>   df0:	7d 43 53 78 	mr      r3,r10
>>   df4:	90 04 00 00 	stw     r0,0(r4)
>>   df8:	7d 29 1b 78 	or      r9,r9,r3
>>   dfc:	7d 43 53 78 	mr      r3,r10
>>   e00:	b1 64 00 04 	sth     r11,4(r4)
>>   e04:	7d 29 1b 78 	or      r9,r9,r3
>>   e08:	7d 43 53 78 	mr      r3,r10
>>   e0c:	98 a4 00 06 	stb     r5,6(r4)
>>   e10:	7d 23 1b 78 	or      r3,r9,r3
>>   e14:	90 c4 00 08 	stw     r6,8(r4)
>>   e18:	90 e4 00 0c 	stw     r7,12(r4)
>>   e1c:	7c 63 53 78 	or      r3,r3,r10
>>   e20:	4e 80 00 20 	blr
>> 
>> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
>> Reviewed-by: Segher Boessenkool <segher at kernel.crashing.org>
>> ---
>> v2:
>> - Added <> modifier in __put_user_asm() and __get_user_asm()
>> - Removed %U2 in __put_user_asm2() and __get_user_asm2()
>> - Reworded the commit log
>> ---
>>   arch/powerpc/include/asm/uaccess.h | 28 ++++++++++++++--------------
>>   1 file changed, 14 insertions(+), 14 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
>> index 7c811442b607..9365b59495a2 100644
>> --- a/arch/powerpc/include/asm/uaccess.h
>> +++ b/arch/powerpc/include/asm/uaccess.h
>> @@ -114,7 +114,7 @@ extern long __put_user_bad(void);
>>    */
>>   #define __put_user_asm(x, addr, err, op)			\
>>   	__asm__ __volatile__(					\
>> -		"1:	" op " %1,0(%2)	# put_user\n"		\
>> +		"1:	" op "%U2%X2 %1,%2	# put_user\n"	\
>>   		"2:\n"						\
>>   		".section .fixup,\"ax\"\n"			\
>>   		"3:	li %0,%3\n"				\
>> @@ -122,7 +122,7 @@ extern long __put_user_bad(void);
>>   		".previous\n"					\
>>   		EX_TABLE(1b, 3b)				\
>>   		: "=r" (err)					\
>> -		: "r" (x), "b" (addr), "i" (-EFAULT), "0" (err))
>> +		: "r" (x), "m<>" (*addr), "i" (-EFAULT), "0" (err))
>>   
>>   #ifdef __powerpc64__
>>   #define __put_user_asm2(x, ptr, retval)				\
>> @@ -130,8 +130,8 @@ extern long __put_user_bad(void);
>>   #else /* __powerpc64__ */
>>   #define __put_user_asm2(x, addr, err)				\
>>   	__asm__ __volatile__(					\
>> -		"1:	stw %1,0(%2)\n"				\
>> -		"2:	stw %1+1,4(%2)\n"			\
>> +		"1:	stw%X2 %1,%2\n"			\
>> +		"2:	stw%X2 %L1,%L2\n"			\
>>   		"3:\n"						\
>>   		".section .fixup,\"ax\"\n"			\
>>   		"4:	li %0,%3\n"				\
>> @@ -140,7 +140,7 @@ extern long __put_user_bad(void);
>>   		EX_TABLE(1b, 4b)				\
>>   		EX_TABLE(2b, 4b)				\
>>   		: "=r" (err)					\
>> -		: "r" (x), "b" (addr), "i" (-EFAULT), "0" (err))
>> +		: "r" (x), "m" (*addr), "i" (-EFAULT), "0" (err))
>>   #endif /* __powerpc64__ */
>>   
>>   #define __put_user_size_allowed(x, ptr, size, retval)		\
>> @@ -260,7 +260,7 @@ extern long __get_user_bad(void);
>>   
>>   #define __get_user_asm(x, addr, err, op)		\
>>   	__asm__ __volatile__(				\
>> -		"1:	"op" %1,0(%2)	# get_user\n"	\
>> +		"1:	"op"%U2%X2 %1, %2	# get_user\n"	\
>>   		"2:\n"					\
>>   		".section .fixup,\"ax\"\n"		\
>>   		"3:	li %0,%3\n"			\
>> @@ -269,7 +269,7 @@ extern long __get_user_bad(void);
>>   		".previous\n"				\
>>   		EX_TABLE(1b, 3b)			\
>>   		: "=r" (err), "=r" (x)			\
>> -		: "b" (addr), "i" (-EFAULT), "0" (err))
>> +		: "m<>" (*addr), "i" (-EFAULT), "0" (err))
>>   
>>   #ifdef __powerpc64__
>>   #define __get_user_asm2(x, addr, err)			\
>> @@ -277,8 +277,8 @@ extern long __get_user_bad(void);
>>   #else /* __powerpc64__ */
>>   #define __get_user_asm2(x, addr, err)			\
>>   	__asm__ __volatile__(				\
>> -		"1:	lwz %1,0(%2)\n"			\
>> -		"2:	lwz %1+1,4(%2)\n"		\
>> +		"1:	lwz%X2 %1, %2\n"			\
>> +		"2:	lwz%X2 %L1, %L2\n"		\
>>   		"3:\n"					\
>>   		".section .fixup,\"ax\"\n"		\
>>   		"4:	li %0,%3\n"			\
>> @@ -289,7 +289,7 @@ extern long __get_user_bad(void);
>>   		EX_TABLE(1b, 4b)			\
>>   		EX_TABLE(2b, 4b)			\
>>   		: "=r" (err), "=&r" (x)			\
>> -		: "b" (addr), "i" (-EFAULT), "0" (err))
>> +		: "m" (*addr), "i" (-EFAULT), "0" (err))
>>   #endif /* __powerpc64__ */
>>   
>>   #define __get_user_size_allowed(x, ptr, size, retval)		\
>> @@ -299,10 +299,10 @@ do {								\
>>   	if (size > sizeof(x))					\
>>   		(x) = __get_user_bad();				\
>>   	switch (size) {						\
>> -	case 1: __get_user_asm(x, ptr, retval, "lbz"); break;	\
>> -	case 2: __get_user_asm(x, ptr, retval, "lhz"); break;	\
>> -	case 4: __get_user_asm(x, ptr, retval, "lwz"); break;	\
>> -	case 8: __get_user_asm2(x, ptr, retval);  break;	\
>> +	case 1: __get_user_asm(x, (u8 __user *)ptr, retval, "lbz"); break;	\
>> +	case 2: __get_user_asm(x, (u16 __user *)ptr, retval, "lhz"); break;	\
>> +	case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break;	\
>> +	case 8: __get_user_asm2(x, (u64 __user *)ptr, retval);  break;	\
>>   	default: (x) = __get_user_bad();			\
>>   	}							\
>>   } while (0)
>> 


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