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linux-user: Rewrite __get_user/__put_user with __builtin_choose_expr
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 <rth@twiddle.net> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
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1 changed files with 32 additions and 29 deletions
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@ -287,36 +287,39 @@ static inline int access_ok(int type, abi_ulong addr, abi_ulong size)
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(type == VERIFY_READ) ? PAGE_READ : (PAGE_READ | PAGE_WRITE)) == 0;
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}
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/* NOTE __get_user and __put_user use host pointers and don't check access. */
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/* These are usually used to access struct data members once the
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* struct has been locked - usually with lock_user_struct().
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*/
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#define __put_user(x, hptr)\
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({ __typeof(*hptr) pu_ = (x);\
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switch(sizeof(*hptr)) {\
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case 1: break;\
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case 2: pu_ = tswap16(pu_); break; \
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case 4: pu_ = tswap32(pu_); break; \
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case 8: pu_ = tswap64(pu_); break; \
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default: abort();\
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}\
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memcpy(hptr, &pu_, sizeof(pu_)); \
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0;\
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})
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/* NOTE __get_user and __put_user use host pointers and don't check access.
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These are usually used to access struct data members once the struct has
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been locked - usually with lock_user_struct. */
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#define __get_user(x, hptr) \
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({ __typeof(*hptr) gu_; \
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memcpy(&gu_, hptr, sizeof(gu_)); \
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switch(sizeof(*hptr)) {\
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case 1: break; \
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case 2: gu_ = tswap16(gu_); break; \
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case 4: gu_ = tswap32(gu_); break; \
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case 8: gu_ = tswap64(gu_); break; \
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default: abort();\
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}\
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(x) = gu_; \
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0;\
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})
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/* Tricky points:
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- Use __builtin_choose_expr to avoid type promotion from ?:,
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- Invalid sizes result in a compile time error stemming from
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the fact that abort has no parameters.
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- It's easier to use the endian-specific unaligned load/store
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functions than host-endian unaligned load/store plus tswapN. */
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#define __put_user_e(x, hptr, e) \
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(__builtin_choose_expr(sizeof(*(hptr)) == 1, stb_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 2, stw_##e##_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 4, stl_##e##_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 8, stq_##e##_p, abort)))) \
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((hptr), (x)), 0)
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#define __get_user_e(x, hptr, e) \
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((x) = \
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__builtin_choose_expr(sizeof(*(hptr)) == 1, ldub_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 2, lduw_##e##_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 4, ldl_##e##_p, \
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__builtin_choose_expr(sizeof(*(hptr)) == 8, ldq_##e##_p, abort)))) \
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(hptr), 0)
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#ifdef TARGET_WORDS_BIGENDIAN
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# define __put_user(x, hptr) __put_user_e(x, hptr, be)
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# define __get_user(x, hptr) __get_user_e(x, hptr, be)
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#else
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# define __put_user(x, hptr) __put_user_e(x, hptr, le)
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# define __get_user(x, hptr) __get_user_e(x, hptr, le)
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#endif
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/* put_user()/get_user() take a guest address and check access */
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/* These are usually used to access an atomic data type, such as an int,
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