From: David Laight David.Laight@ACULAB.COM

commit 867046cc7027703f60a46339ffde91a1970f2901 upstream.

Allow (for example) min(unsigned_var, 20).

The opposite min(signed_var, 20u) is still errored.

Since a comparison between signed and unsigned never makes the unsigned value negative it is only necessary to adjust the __types_ok() test.

Link: https://lkml.kernel.org/r/633b64e2f39e46bb8234809c5595b8c7@AcuMS.aculab.com Signed-off-by: David Laight david.laight@aculab.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Christoph Hellwig hch@infradead.org Cc: Jason A. Donenfeld Jason@zx2c4.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 867046cc7027703f60a46339ffde91a1970f2901) Signed-off-by: SeongJae Park sj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Eliav Farber farbere@amazon.com --- include/linux/minmax.h | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h index f76b7145fc11..dd52969698f7 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -9,13 +9,18 @@ /* * min()/max()/clamp() macros must accomplish three things: * - * - avoid multiple evaluations of the arguments (so side-effects like + * - Avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - perform signed v unsigned type-checking (to generate compile - * errors instead of nasty runtime surprises). - * - retain result as a constant expressions when called with only + * - Retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). + * - Perform signed v unsigned type-checking (to generate compile + * errors instead of nasty runtime surprises). + * - Unsigned char/short are always promoted to signed int and can be + * compared against signed or unsigned arguments. + * - Unsigned arguments can be compared against non-negative signed constants. + * - Comparison of a signed argument against an unsigned constant fails + * even if the constant is below __INT_MAX__ and could be cast to int. */ #define __typecheck(x, y) \ (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) @@ -25,9 +30,14 @@ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ is_signed_type(typeof(x)), 0)

-#define __types_ok(x, y) \ - (__is_signed(x) == __is_signed(y) || \ - __is_signed((x) + 0) == __is_signed((y) + 0)) +/* True for a non-negative signed int constant */ +#define __is_noneg_int(x) \ + (__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0) + +#define __types_ok(x, y) \ + (__is_signed(x) == __is_signed(y) || \ + __is_signed((x) + 0) == __is_signed((y) + 0) || \ + __is_noneg_int(x) || __is_noneg_int(y))

#define __cmp_op_min < #define __cmp_op_max >