linux-kernel - [PATCH] x86/gpu: Fix sign extension issue in Intel graphics stolen memory quirks

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Message-Id: <1397382303-17525-1-git-send-email-ville.syrjala@linux.intel.com>
Date:	Sun, 13 Apr 2014 12:45:03 +0300
From:	ville.syrjala@...ux.intel.com
To:	linux-kernel@...r.kernel.org
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] x86/gpu: Fix sign extension issue in Intel graphics stolen memory quirks

From: Ville Syrjälä <ville.syrjala@...ux.intel.com>

Have the KB(),MB(),GB() macros produce unsigned longs to avoid
uninteded sign extension issues with the gen2 memory size detection.

What happens is first the uint8_t returned by read_pci_config_byte()
gets promoted to an int which gets multiplied by another int from the
MB() macro, and finally the result gets sign extended to size_t.

Although this shouldn't be a problem in practice as all affected gen2
platforms are 32bit AFAIK, so size_t will be 32 bits.

Cc: H. Peter Anvin <hpa@...or.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
---
 arch/x86/kernel/early-quirks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
index b0cc380..6e2537c 100644
--- a/arch/x86/kernel/early-quirks.c
+++ b/arch/x86/kernel/early-quirks.c
@@ -240,7 +240,7 @@ static u32 __init intel_stolen_base(int num, int slot, int func, size_t stolen_s
 	return base;
 }
 
-#define KB(x)	((x) * 1024)
+#define KB(x)	((x) * 1024UL)
 #define MB(x)	(KB (KB (x)))
 #define GB(x)	(MB (KB (x)))
 
-- 
1.8.3.2

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