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Date: Mon, 29 Jun 2020 21:27:56 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>, npiggin@...il.com,
segher@...nel.crashing.org
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()
Christophe Leroy <christophe.leroy@...roup.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@....fr>
>> Reviewed-by: Segher Boessenkool <segher@...nel.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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