intel-gfx.lists.freedesktop.org archive mirror
 help / color / mirror / Atom feed
* [Intel-gfx] [PATCH] drm/i915: Cast remain to unsigned long in eb_relocate_vma
@ 2020-02-14  5:47 Nathan Chancellor
  2020-02-14  6:31 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
                   ` (3 more replies)
  0 siblings, 4 replies; 12+ messages in thread
From: Nathan Chancellor @ 2020-02-14  5:47 UTC (permalink / raw)
  To: Jani Nikula, Joonas Lahtinen, Rodrigo Vivi
  Cc: intel-gfx, linux-kernel, dri-devel, clang-built-linux,
	Nathan Chancellor, Michel Dänzer

A recent commit in clang added -Wtautological-compare to -Wall, which is
enabled for i915 after -Wtautological-compare is disabled for the rest
of the kernel so we see the following warning on x86_64:

 ../drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:1433:22: warning:
 result of comparison of constant 576460752303423487 with expression of
 type 'unsigned int' is always false
 [-Wtautological-constant-out-of-range-compare]
         if (unlikely(remain > N_RELOC(ULONG_MAX)))
            ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
 ../include/linux/compiler.h:78:42: note: expanded from macro 'unlikely'
 # define unlikely(x)    __builtin_expect(!!(x), 0)
                                            ^
 1 warning generated.

It is not wrong in the case where ULONG_MAX > UINT_MAX but it does not
account for the case where this file is built for 32-bit x86, where
ULONG_MAX == UINT_MAX and this check is still relevant.

Cast remain to unsigned long, which keeps the generated code the same
(verified with clang-11 on x86_64 and GCC 9.2.0 on x86 and x86_64) and
the warning is silenced so we can catch more potential issues in the
future.

Link: https://github.com/ClangBuiltLinux/linux/issues/778
Suggested-by: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

Round 3 :)

Previous threads/patches:

https://lore.kernel.org/lkml/20191123195321.41305-1-natechancellor@gmail.com/
https://lore.kernel.org/lkml/20200211050808.29463-1-natechancellor@gmail.com/

 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 60c984e10c4a..47f4d8ab281e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1430,7 +1430,7 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct i915_vma *vma)
 
 	urelocs = u64_to_user_ptr(entry->relocs_ptr);
 	remain = entry->relocation_count;
-	if (unlikely(remain > N_RELOC(ULONG_MAX)))
+	if (unlikely((unsigned long)remain > N_RELOC(ULONG_MAX)))
 		return -EINVAL;
 
 	/*
-- 
2.25.0

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply related	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2020-03-26 22:15 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-14  5:47 [Intel-gfx] [PATCH] drm/i915: Cast remain to unsigned long in eb_relocate_vma Nathan Chancellor
2020-02-14  6:31 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
2020-02-14  6:36 ` [Intel-gfx] [PATCH] " Jani Nikula
2020-02-14  8:32   ` Chris Wilson
2020-02-14 11:49     ` Jani Nikula
2020-02-14 15:36       ` Michel Dänzer
2020-03-16 21:41         ` Nick Desaulniers
2020-03-26 20:11           ` Nathan Chancellor
2020-03-26 22:15             ` Jani Nikula
2020-02-14 13:46     ` Nathan Chancellor
2020-02-17 17:06 ` [Intel-gfx] ✓ Fi.CI.IGT: success for " Patchwork
2020-03-17  0:13 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for drm/i915: Cast remain to unsigned long in eb_relocate_vma (rev2) Patchwork

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).