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>

1 files changed, 2 insertions, 20 deletions

diff --git a/arch/sh/include/asm/uaccess.h b/arch/sh/include/asm/uaccess.h
index 8867bb04b00e..ccd219d74851 100644
--- a/arch/sh/include/asm/uaccess.h
+++ b/arch/sh/include/asm/uaccess.h
@@ -5,28 +5,10 @@
 #include <asm/segment.h>
 #include <asm/extable.h>
 
-#define __addr_ok(addr) \
-	((unsigned long __force)(addr) < current_thread_info()->addr_limit.seg)
-
-/*
- * __access_ok: Check if address with size is OK or not.
- *
- * Uhhuh, this needs 33-bit arithmetic. We have a carry..
- *
- * sum := addr + size;  carry? --> flag = true;
- * if (sum >= addr_limit) flag = true;
- */
-#define __access_ok(addr, size)	({				\
-	unsigned long __ao_a = (addr), __ao_b = (size);		\
-	unsigned long __ao_end = __ao_a + __ao_b - !!__ao_b;	\
-	__ao_end >= __ao_a && __addr_ok(__ao_end); })
-
-#define access_ok(addr, size)	\
-	(__chk_user_ptr(addr),		\
-	 __access_ok((unsigned long __force)(addr), (size)))
-
 #define user_addr_max()	(current_thread_info()->addr_limit.seg)
 
+#include <asm-generic/access_ok.h>
+
 /*
  * Uh, these should become the main single-value transfer routines ...
  * They automatically use the right size if we just have the right