linux-kernel - [PATCH v2 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access

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Date:   Fri,  2 Mar 2018 20:50:51 +0100
From:   Mathieu Malaterre <malat@...ian.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe LEROY <christophe.leroy@....fr>,
        Mathieu Malaterre <malat@...ian.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok

Rewrite function-like macro into regular static inline function to avoid a
warning during macro expansion.
Fix warning (treated as error in W=1):

  CC      arch/powerpc/kernel/signal_32.o
In file included from ./include/linux/uaccess.h:14:0,
                 from ./include/asm-generic/termios-base.h:8,
                 from ./arch/powerpc/include/asm/termios.h:20,
                 from ./include/uapi/linux/termios.h:6,
                 from ./include/linux/tty.h:7,
                 from arch/powerpc/kernel/signal_32.c:36:
./include/asm-generic/termios-base.h: In function ‘user_termio_to_kernel_termios’:
./arch/powerpc/include/asm/uaccess.h:52:35: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
   (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
                                   ^
./arch/powerpc/include/asm/uaccess.h:58:3: note: in expansion of macro ‘__access_ok’
   __access_ok((__force unsigned long)(addr), (size), get_fs()))
   ^~~~~~~~~~~
./arch/powerpc/include/asm/uaccess.h:262:6: note: in expansion of macro ‘access_ok’
  if (access_ok(VERIFY_READ, __gu_addr, (size)))   \
      ^~~~~~~~~
./arch/powerpc/include/asm/uaccess.h:80:2: note: in expansion of macro ‘__get_user_check’
  __get_user_check((x), (ptr), sizeof(*(ptr)))
  ^~~~~~~~~~~~~~~~
./include/asm-generic/termios-base.h:36:6: note: in expansion of macro ‘get_user’
  if (get_user(termios->c_line, &termio->c_line) < 0)
      ^~~~~~~~
[...]
cc1: all warnings being treated as errors

Suggested-by: Segher Boessenkool <segher@...nel.crashing.org>
Signed-off-by: Mathieu Malaterre <malat@...ian.org>
---
 arch/powerpc/include/asm/uaccess.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 51bfeb8777f0..a62ee663b2c8 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -47,9 +47,13 @@
 
 #else
 
-#define __access_ok(addr, size, segment)	\
-	(((addr) <= (segment).seg) &&		\
-	 (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
+static inline int __access_ok(unsigned long addr, unsigned long size,
+			mm_segment_t seg)
+{
+	if (addr > seg.seg)
+		return 0;
+	return (size == 0 || size - 1 <= seg.seg - addr);
+}
 
 #endif
 
-- 
2.11.0