REF: https://bugzilla.tianocore.org/show_bug.cgi?id=695
Within function CoreRestoreTpl(), left shift a negative value -2 is used
in:
"while (((-2 << NewTpl) & gEventPending) != 0) {"
which involves undefined behavior.
According to the C11 spec, Section 6.5.7:
> 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated
> bits are filled with zeros. If E1 has an unsigned type, the value
> of the result is E1 * 2^E2 , reduced modulo one more than the
> maximum value representable in the result type. If E1 has a signed
> type and nonnegative value, and E1 * 2^E2 is representable in the
> result type, then that is the resulting value; otherwise, the
> behavior is undefined.
This commit explicitly cast '-2' with UINTN to resolve this issue.
Cc: Steven Shi <[email protected]>
Cc: Star Zeng <[email protected]>
Cc: Eric Dong <[email protected]>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <[email protected]>
---
MdeModulePkg/Core/Dxe/Event/Tpl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/MdeModulePkg/Core/Dxe/Event/Tpl.c
b/MdeModulePkg/Core/Dxe/Event/Tpl.c
index 8ad0a33701..8c50f61117 100644
--- a/MdeModulePkg/Core/Dxe/Event/Tpl.c
+++ b/MdeModulePkg/Core/Dxe/Event/Tpl.c
@@ -123,7 +123,7 @@ CoreRestoreTpl (
//
// Dispatch any pending events
//
- while (((-2 << NewTpl) & gEventPending) != 0) {
+ while (((((UINTN)-2) << NewTpl) & gEventPending) != 0) {
gEfiCurrentTpl = (UINTN) HighBitSet64 (gEventPending);
if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
CoreSetInterruptState (TRUE);
--
2.12.0.windows.1
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