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Subject[PATCH v3 1/2] powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()
Date
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@csgroup.eu>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
---
v3:
- Removed the pre-update form and the <> modifier, because it seems
to be problematic with some older versions of GCC (namely 4.9) and
doesn't seems to generate much code of that form anyway. So better
to get it merged with the pre-update form than not be merged at all.
The pre-update form is added in a following patch that may then get
merged later once we have cleared the issue with it.

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

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
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 64c04ab09112..c546fb36043d 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -159,7 +159,7 @@ 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 "%X2 %1,%2 # put_user\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: li %0,%3\n" \
@@ -167,7 +167,7 @@ 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) \
@@ -175,8 +175,8 @@ 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" \
@@ -185,7 +185,7 @@ 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) \
@@ -317,7 +317,7 @@ 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"%X2 %1, %2 # get_user\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: li %0,%3\n" \
@@ -326,7 +326,7 @@ 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) \
@@ -334,8 +334,8 @@ 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" \
@@ -346,7 +346,7 @@ 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) \
@@ -356,10 +356,10 @@ 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)
--
2.25.0
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