linux/bits.h: fix compilation error with GENMASK
[ Upstream commit f747e6667ebb2ffb8133486c9cd19800d72b0d98 ]
GENMASK() has an input check which uses __builtin_choose_expr() to
enable a compile time sanity check of its inputs if they are known at
compile time.
However, it turns out that __builtin_constant_p() does not always return
a compile time constant [0]. It was thought this problem was fixed with
gcc 4.9 [1], but apparently this is not the case [2].
Switch to use __is_constexpr() instead which always returns a compile time
constant, regardless of its inputs.
Link: https://lore.kernel.org/lkml/[email protected] [0]
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 [1]
Link: https://lore.kernel.org/lkml/[email protected] [2]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Rikard Falkeborn <[email protected]>
Reported-by: Tetsuo Handa <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Yury Norov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
diff --git a/include/linux/bits.h b/include/linux/bits.h
index 7f475d5..87d1126 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -22,7 +22,7 @@
#include <linux/build_bug.h>
#define GENMASK_INPUT_CHECK(h, l) \
(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
- __builtin_constant_p((l) > (h)), (l) > (h), 0)))
+ __is_constexpr((l) > (h)), (l) > (h), 0)))
#else
/*
* BUILD_BUG_ON_ZERO is not available in h files included from asm files,
diff --git a/include/linux/const.h b/include/linux/const.h
index 81b8aae..435ddd7 100644
--- a/include/linux/const.h
+++ b/include/linux/const.h
@@ -3,4 +3,12 @@
#include <vdso/const.h>
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <[email protected]>
+ */
+#define __is_constexpr(x) \
+ (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
#endif /* _LINUX_CONST_H */
diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index c0f57b0..5433c08 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -2,6 +2,8 @@
#ifndef _LINUX_MINMAX_H
#define _LINUX_MINMAX_H
+#include <linux/const.h>
+
/*
* min()/max()/clamp() macros must accomplish three things:
*
@@ -17,14 +19,6 @@
#define __typecheck(x, y) \
(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <[email protected]>
- */
-#define __is_constexpr(x) \
- (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
#define __no_side_effects(x, y) \
(__is_constexpr(x) && __is_constexpr(y))
