linux-kernel - [PATCH 0/2] Fix truncation warnings from building test

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Date:   Mon, 24 May 2021 16:59:39 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <pmladek@...e.com>, <rostedt@...dmis.org>,
        <sergey.senozhatsky@...il.com>,
        <andriy.shevchenko@...ux.intel.com>, <linux@...musvillemoes.dk>,
        <w@....eu>, <lkml@....org>, <davem@...emloft.net>,
        <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH 0/2] Fix truncation warnings from building test_scanf.c

The kernel test robot is reporting truncation warnings when building
lib/test_scanf.c:

1) lib/test_scanf.c:250:9: sparse: sparse: cast truncates bits from
   constant value (ffff0001 becomes 1)
   Reported on several lines.

2) include/linux/prandom.h:114:45: sparse: sparse: cast truncates bits
   from constant value (4f2e5357408c3c09 becomes 408c3c09)

(1) is caused by test_scanf.c using type_min() on an unsigned type. The
type_min() macro calculates -type_max() - 1, so is only meaningful for
signed types.

(2) is caused by prandom_seed_state() storing a modified u64 seed value
into a u32 - sparse will warn that this causes a truncation. 

The two patches in this series fix these problems.

Richard Fitzgerald (2):
  lib: test_scanf: Fix incorrect use of type_min() with unsigned types
  random32: Fix implicit truncation warning in prandom_seed_state()

 include/linux/prandom.h |  2 +-
 lib/test_scanf.c        | 13 ++++++-------
 2 files changed, 7 insertions(+), 8 deletions(-)

-- 
2.20.1