s390/unwind: cleanup unused READ_ONCE_TASK_STACK

Kasan instrumentation of backchain unwinder stack reads is disabled
completely and simply uses READ_ONCE_NOCHECK now.
READ_ONCE_TASK_STACK macro is unused and could be removed.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h
index 6eb2ef1..d827b5b 100644 (file)
--- a/arch/s390/include/asm/unwind.h
+++ b/arch/s390/include/asm/unwind.h
@@ -79,23 +79,4 @@ static inline void unwind_module_init(struct module *mod, void *orc_ip,
                                      size_t orc_ip_size, void *orc,
                                      size_t orc_size) {}
 
-#ifdef CONFIG_KASAN
-/*
- * This disables KASAN checking when reading a value from another task's stack,
- * since the other task could be running on another CPU and could have poisoned
- * the stack in the meantime.
- */
-#define READ_ONCE_TASK_STACK(task, x)                  \
-({                                                     \
-       unsigned long val;                              \
-       if (task == current)                            \
-               val = READ_ONCE(x);                     \
-       else                                            \
-               val = READ_ONCE_NOCHECK(x);             \
-       val;                                            \
-})
-#else
-#define READ_ONCE_TASK_STACK(task, x) READ_ONCE(x)
-#endif
-
 #endif /* _ASM_S390_UNWIND_H */