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Date: Tue, 14 Apr 2020 17:00:43 +0000 (UTC)
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'
unsafe_put_user() is designed to take benefit of 'asm goto'.
Instead of using the standard __put_user() approach and branch
based on the returned error, use 'asm goto' to branch directly
to the error label from the .fixup code.
This change significantly simplifies functions using
unsafe_put_user()
Small exemple of the benefit with the following code:
struct test {
unsigned long item1;
unsigned long item2;
unsigned long item3;
};
int set_test_to_user(struct test __user *test, unsigned long item1,
unsigned long item2, unsigned long item3)
{
unsafe_put_user(item1, &test->item1, failed);
unsafe_put_user(item2, &test->item2, failed);
unsafe_put_user(item3, &test->item3, failed);
return 0;
failed:
return -EFAULT;
}
Before the patch:
00000d94 <set_test_to_user>:
d94: 39 20 00 00 li r9,0
d98: 90 83 00 00 stw r4,0(r3)
d9c: 2f 89 00 00 cmpwi cr7,r9,0
da0: 40 9e 00 30 bne cr7,dd0 <set_test_to_user+0x3c>
da4: 39 43 00 04 addi r10,r3,4
da8: 90 aa 00 00 stw r5,0(r10)
dac: 2f 89 00 00 cmpwi cr7,r9,0
db0: 40 9e 00 20 bne cr7,dd0 <set_test_to_user+0x3c>
db4: 38 63 00 08 addi r3,r3,8
db8: 90 c3 00 00 stw r6,0(r3)
dbc: 21 29 00 00 subfic r9,r9,0
dc0: 7d 29 49 10 subfe r9,r9,r9
dc4: 38 60 ff f2 li r3,-14
dc8: 7d 23 18 38 and r3,r9,r3
dcc: 4e 80 00 20 blr
dd0: 38 60 ff f2 li r3,-14
dd4: 4e 80 00 20 blr
00000000 <.fixup>:
...
b8: 39 20 ff f2 li r9,-14
bc: 48 00 00 00 b bc <.fixup+0xbc>
bc: R_PPC_REL24 .text+0xd9c
c0: 39 20 ff f2 li r9,-14
c4: 48 00 00 00 b c4 <.fixup+0xc4>
c4: R_PPC_REL24 .text+0xdac
c8: 39 20 ff f2 li r9,-14
cc: 48 00 00 00 b cc <.fixup+0xcc>
cc: R_PPC_REL24 .text+0xdbc
After the patch:
00000d94 <set_test_to_user>:
d94: 90 83 00 00 stw r4,0(r3)
d98: 39 23 00 04 addi r9,r3,4
d9c: 90 a9 00 00 stw r5,0(r9)
da0: 38 63 00 08 addi r3,r3,8
da4: 90 c3 00 00 stw r6,0(r3)
da8: 38 60 00 00 li r3,0
dac: 4e 80 00 20 blr
db0: 38 60 ff f2 li r3,-14
db4: 4e 80 00 20 blr
00000000 <.fixup>:
...
b8: 48 00 00 00 b b8 <.fixup+0xb8>
b8: R_PPC_REL24 .text+0xdb0
bc: 48 00 00 00 b bc <.fixup+0xbc>
bc: R_PPC_REL24 .text+0xdb0
c0: 48 00 00 00 b c0 <.fixup+0xc0>
c0: R_PPC_REL24 .text+0xdb0
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
arch/powerpc/include/asm/uaccess.h | 63 +++++++++++++++++++++++++-----
1 file changed, 54 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 2f500debae21..b904f3c56463 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -93,12 +93,10 @@ static inline int __access_ok(unsigned long addr, unsigned long size,
#define __get_user(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)), true)
#define __put_user(x, ptr) \
- __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), true)
+ __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
#define __get_user_allowed(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)), false)
-#define __put_user_allowed(x, ptr) \
- __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), false)
#define __get_user_inatomic(x, ptr) \
__get_user_nosleep((x), (ptr), sizeof(*(ptr)))
@@ -124,9 +122,24 @@ extern long __put_user_bad(void);
: "=r" (err) \
: "r" (x), "b" (addr), "i" (-EFAULT), "0" (err))
+#define __put_user_asm_goto(x, addr, label, op) \
+ asm volatile goto( \
+ "1: " op " %0,0(%1) # put_user\n" \
+ "2:\n" \
+ ".section .fixup,\"ax\"\n" \
+ "3: b %l2\n" \
+ ".previous\n" \
+ EX_TABLE(1b, 3b) \
+ : \
+ : "r" (x), "b" (addr) \
+ : \
+ : label)
+
#ifdef __powerpc64__
#define __put_user_asm2(x, ptr, retval) \
__put_user_asm(x, ptr, retval, "std")
+#define __put_user_asm2_goto(x, ptr, label) \
+ __put_user_asm_goto(x, ptr, label, "std")
#else /* __powerpc64__ */
#define __put_user_asm2(x, addr, err) \
__asm__ __volatile__( \
@@ -141,6 +154,20 @@ extern long __put_user_bad(void);
EX_TABLE(2b, 4b) \
: "=r" (err) \
: "r" (x), "b" (addr), "i" (-EFAULT), "0" (err))
+#define __put_user_asm2_goto(x, addr, label) \
+ asm volatile goto( \
+ "1: stw %0,0(%1)\n" \
+ "2: stw %L0,4(%1)\n" \
+ "3:\n" \
+ ".section .fixup,\"ax\"\n" \
+ "4: b %l2\n" \
+ ".previous\n" \
+ EX_TABLE(1b, 4b) \
+ EX_TABLE(2b, 4b) \
+ : \
+ : "r" (x), "b" (addr) \
+ : \
+ : label)
#endif /* __powerpc64__ */
#define __put_user_size_allowed(x, ptr, size, retval) \
@@ -155,6 +182,17 @@ do { \
} \
} while (0)
+#define __put_user_size_goto(x, ptr, size, label) \
+do { \
+ switch (size) { \
+ case 1: __put_user_asm_goto(x, ptr, label, "stb"); break; \
+ case 2: __put_user_asm_goto(x, ptr, label, "sth"); break; \
+ case 4: __put_user_asm_goto(x, ptr, label, "stw"); break; \
+ case 8: __put_user_asm2_goto(x, ptr, label); break; \
+ default: __put_user_bad(); \
+ } \
+} while (0)
+
#define __put_user_size(x, ptr, size, retval) \
do { \
allow_write_to_user(ptr, size); \
@@ -162,20 +200,26 @@ do { \
prevent_write_to_user(ptr, size); \
} while (0)
-#define __put_user_nocheck(x, ptr, size, do_allow) \
+#define __put_user_nocheck(x, ptr, size) \
({ \
long __pu_err; \
__typeof__(*(ptr)) __user *__pu_addr = (ptr); \
if (!is_kernel_addr((unsigned long)__pu_addr)) \
might_fault(); \
__chk_user_ptr(ptr); \
- if (do_allow) \
- __put_user_size((x), __pu_addr, (size), __pu_err); \
- else \
- __put_user_size_allowed((x), __pu_addr, (size), __pu_err); \
+ __put_user_size((x), __pu_addr, (size), __pu_err); \
__pu_err; \
})
+#define __put_user_goto(x, ptr, size, label) \
+do { \
+ __typeof__(*(ptr)) __user *__pu_addr = (ptr); \
+ if (!is_kernel_addr((unsigned long)__pu_addr)) \
+ might_fault(); \
+ __chk_user_ptr(ptr); \
+ __put_user_size_goto((x), __pu_addr, (size), label); \
+} while (0)
+
#define __put_user_check(x, ptr, size) \
({ \
long __pu_err = -EFAULT; \
@@ -470,7 +514,8 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t
#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
-#define unsafe_put_user(x, p, e) unsafe_op_wrap(__put_user_allowed(x, p), e)
+#define unsafe_put_user(x, p, e) \
+ __put_user_goto((__typeof__(*(p)))(x), (p), sizeof(*(p)), e)
#define unsafe_copy_to_user(d, s, l, e) \
unsafe_op_wrap(raw_copy_to_user_allowed(d, s, l), e)
--
2.25.0
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