From 7bf03e7504e433da274963c447648876902b86df Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Thu, 13 Feb 2020 22:47:07 -0700 Subject: [PATCH] drm/i915: Cast remain to unsigned long in eb_relocate_vma MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. Closes: https://github.com/ClangBuiltLinux/linux/issues/778 Suggested-by: Michel Dänzer Reviewed-by: Jani Nikula Signed-off-by: Nathan Chancellor Signed-off-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/20200214054706.33870-1-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 c643eec4dca0..f347e595a773 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -1455,7 +1455,7 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev) 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; /*