linux-kernel - [PATCH] resource: Elide a conversion warning on 32-bit

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Message-ID: <20240729151652.15063-2-palmer@rivosinc.com>
Date: Mon, 29 Jul 2024 08:16:53 -0700
From: Palmer Dabbelt <palmer@...osinc.com>
To: bhelgaas@...gle.com
Cc: andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com,
  ilpo.jarvinen@...ux.intel.com, Greg KH <gregkh@...uxfoundation.org>, bhe@...hat.com,
  alison.schofield@...el.com, Palmer Dabbelt <palmer@...osinc.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] resource: Elide a conversion warning on 32-bit

From: Palmer Dabbelt <palmer@...osinc.com>

I recently ended up with a warning on some compilers along the lines of

      CC      kernel/resource.o
    In file included from include/linux/ioport.h:16,
                     from kernel/resource.c:15:
    kernel/resource.c: In function 'gfr_start':
    include/linux/minmax.h:49:37: error: conversion from 'long long unsigned int' to 'resource_size_t' {aka 'unsigned int'} changes value from '17179869183' to '4294967295' [-Werror=overflow]
       49 |         ({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
          |                                     ^
    include/linux/minmax.h:52:9: note: in expansion of macro '__cmp_once_unique'
       52 |         __cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
          |         ^~~~~~~~~~~~~~~~~
    include/linux/minmax.h:161:27: note: in expansion of macro '__cmp_once'
      161 | #define min_t(type, x, y) __cmp_once(min, type, x, y)
          |                           ^~~~~~~~~~
    kernel/resource.c:1829:23: note: in expansion of macro 'min_t'
     1829 |                 end = min_t(resource_size_t, base->end,
          |                       ^~~~~
    kernel/resource.c: In function 'gfr_continue':
    include/linux/minmax.h:49:37: error: conversion from 'long long unsigned int' to 'resource_size_t' {aka 'unsigned int'} changes value from '17179869183' to '4294967295' [-Werror=overflow]
       49 |         ({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
          |                                     ^
    include/linux/minmax.h:52:9: note: in expansion of macro '__cmp_once_unique'
       52 |         __cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
          |         ^~~~~~~~~~~~~~~~~
    include/linux/minmax.h:161:27: note: in expansion of macro '__cmp_once'
      161 | #define min_t(type, x, y) __cmp_once(min, type, x, y)
          |                           ^~~~~~~~~~
    kernel/resource.c:1847:24: note: in expansion of macro 'min_t'
     1847 |                addr <= min_t(resource_size_t, base->end,
          |                        ^~~~~
    cc1: all warnings being treated as errors

which this elides via an extra cast.

Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
---
Not sure if there's a better way to do this, but I didn't see any
reports yet and my tester is failing so I figured it'd be best to get
something on the lists.
---
 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 14777afb0a99..6459561b746e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1845,7 +1845,7 @@ static bool gfr_continue(struct resource *base, resource_size_t addr,
 	 */
 	return addr > addr - size &&
 	       addr <= min_t(resource_size_t, base->end,
-			     (1ULL << MAX_PHYSMEM_BITS) - 1);
+			     (resource_size_t)((1ULL << MAX_PHYSMEM_BITS) - 1));
 }
 
 static resource_size_t gfr_next(resource_size_t addr, resource_size_t size,
-- 
2.45.2