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[Qemu-devel] [PATCH 4/6] linux-user: Rewrite __get_user/__put_user with
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 4/6] linux-user: Rewrite __get_user/__put_user with __builtin_choose_expr |
Date: |
Thu, 11 Oct 2012 12:22:14 -0700 |
The previous formuation with multiple assignments to __typeof(*hptr) falls
down when hptr is qualified const. E.g. with const struct S *p, p->f is
also qualified const.
With this formulation, there's no assignment to any local variable.
Signed-off-by: Richard Henderson <address@hidden>
---
linux-user/qemu.h | 50 ++++++++++++++++++++------------------------------
1 file changed, 20 insertions(+), 30 deletions(-)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index fc4cc00..39b2c9c 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -284,36 +284,26 @@ static inline int access_ok(int type, abi_ulong addr,
abi_ulong size)
(type == VERIFY_READ) ? PAGE_READ : (PAGE_READ |
PAGE_WRITE)) == 0;
}
-/* NOTE __get_user and __put_user use host pointers and don't check access. */
-/* These are usually used to access struct data members once the
- * struct has been locked - usually with lock_user_struct().
- */
-#define __put_user(x, hptr)\
-({ __typeof(*hptr) pu_ = (x);\
- switch(sizeof(*hptr)) {\
- case 1: break;\
- case 2: pu_ = tswap16(pu_); break; \
- case 4: pu_ = tswap32(pu_); break; \
- case 8: pu_ = tswap64(pu_); break; \
- default: abort();\
- }\
- memcpy(hptr, &pu_, sizeof(pu_)); \
- 0;\
-})
-
-#define __get_user(x, hptr) \
-({ __typeof(*hptr) gu_; \
- memcpy(&gu_, hptr, sizeof(gu_)); \
- switch(sizeof(*hptr)) {\
- case 1: break; \
- case 2: gu_ = tswap16(gu_); break; \
- case 4: gu_ = tswap32(gu_); break; \
- case 8: gu_ = tswap64(gu_); break; \
- default: abort();\
- }\
- (x) = gu_; \
- 0;\
-})
+/* NOTE __get_user and __put_user use host pointers and don't check access.
+ These are usually used to access struct data members once the struct has
+ been locked - usually with lock_user_struct. */
+#define __put_user(x, hptr) \
+(*(hptr) = \
+ __builtin_choose_expr(sizeof(*(hptr)) == 1, (uint8_t)(x), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 2, tswap16((uint16_t)(x)), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 4, tswap32((uint32_t)(x)), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 8, tswap64((uint64_t)(x)), \
+ abort())))), \
+ 0)
+
+#define __get_user(x, hptr) \
+((x) = \
+ __builtin_choose_expr(sizeof(*(hptr)) == 1, *(hptr), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 2, tswap16(*(hptr)), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 4, tswap32(*(hptr)), \
+ __builtin_choose_expr(sizeof(*(hptr)) == 8, tswap64(*(hptr)), \
+ abort())))), \
+ 0)
/* put_user()/get_user() take a guest address and check access */
/* These are usually used to access an atomic data type, such as an int,
--
1.7.11.4