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Make const ptr assign as function call in clang

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- This can act as memory barrier in clang to avoid
  read before assign of a const ptr

Signed-off-by: LoveSy <shana@zju.edu.cn>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
YU Jincheng
2021-10-10 02:19:51 +08:00
committed by Denys Vlasenko
parent 04ad683bf9
commit 5156b24553
7 changed files with 38 additions and 12 deletions
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21
include/libbb.h
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@ -2280,6 +2280,7 @@ extern const char bb_PATH_root_path[] ALIGN1; /* BB_PATH_ROOT_PATH */
extern const int const_int_0;
//extern const int const_int_1;
/* This struct is deliberately not defined. */
/* See docs/keep_data_small.txt */
struct globals;
@ -2304,23 +2305,31 @@ static ALWAYS_INLINE void* not_const_pp(const void *p)
);
return pp;
}
# define ASSIGN_CONST_PTR(pptr, v) do { \
*(void**)not_const_pp(pptr) = (void*)(v); \
barrier(); \
} while (0)
/* XZALLOC_CONST_PTR() is an out-of-line function to prevent
* clang from reading pointer before it is assigned.
*/
void XZALLOC_CONST_PTR(const void *pptr, size_t size) FAST_FUNC;
#else
static ALWAYS_INLINE void* not_const_pp(const void *p) { return (void*)p; }
#endif
#define ASSIGN_CONST_PTR(p, v) do { \
*(void**)not_const_pp(&p) = (void*)(v); \
# define ASSIGN_CONST_PTR(pptr, v) do { \
*(void**)(pptr) = (void*)(v); \
/* At least gcc 3.4.6 on mipsel needs optimization barrier */ \
barrier(); \
} while (0)
# define XZALLOC_CONST_PTR(pptr, size) ASSIGN_CONST_PTR(pptr, xzalloc(size))
#endif
#define SET_PTR_TO_GLOBALS(x) ASSIGN_CONST_PTR(ptr_to_globals, x)
#define SET_PTR_TO_GLOBALS(x) ASSIGN_CONST_PTR(&ptr_to_globals, x)
#define FREE_PTR_TO_GLOBALS() do { \
if (ENABLE_FEATURE_CLEAN_UP) { \
free(ptr_to_globals); \
} \
} while (0)
/* You can change LIBBB_DEFAULT_LOGIN_SHELL, but don't use it,
* use bb_default_login_shell and following defines.
* If you change LIBBB_DEFAULT_LOGIN_SHELL,