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

I see this patch is marked as "defered" in patchwork, but I can't see
any related discussion. Is it normal ?

Christophe

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@c-s.fr>
> Reviewed-by: Segher Boessenkool <segher@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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