uaccess: generalize access_ok()

There are many different ways that access_ok() is defined across
architectures, but in the end, they all just compare against the
user_addr_max() value or they accept anything.

Provide one definition that works for most architectures, checking
against TASK_SIZE_MAX for user processes or skipping the check inside
of uaccess_kernel() sections.

For architectures without CONFIG_SET_FS(), this should be the fastest
check, as it comes down to a single comparison of a pointer against a
compile-time constant, while the architecture specific versions tend to
do something more complex for historic reasons or get something wrong.

Type checking for __user annotations is handled inconsistently across
architectures, but this is easily simplified as well by using an inline
function that takes a 'const void __user *' argument. A handful of
callers need an extra __user annotation for this.

Some architectures had trick to use 33-bit or 65-bit arithmetic on the
addresses to calculate the overflow, however this simpler version uses
fewer registers, which means it can produce better object code in the
end despite needing a second (statically predicted) branch.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mark Rutland <mark.rutland@arm.com> [arm64, asm-generic]
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/s390/include/asm/uaccess.h

@@ -17,22 +17,10 @@
 #include <asm/ctl_reg.h>
 #include <asm/extable.h>
 #include <asm/facility.h>
+#include <asm-generic/access_ok.h>
 
 void debug_user_asce(int exit);
 
-static inline int __range_ok(unsigned long addr, unsigned long size)
-{
-	return 1;
-}
-
-#define __access_ok(addr, size)				\
-({							\
-	__chk_user_ptr(addr);				\
-	__range_ok((unsigned long)(addr), (size));	\
-})
-
-#define access_ok(addr, size) __access_ok(addr, size)
-
 unsigned long __must_check
 raw_copy_from_user(void *to, const void __user *from, unsigned long n);