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 refines the code logic to avoid left shifting the negative
value.
Cc: Steven Shi <[email protected]>
Cc: Eric Dong <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Michael Kinney <[email protected]>
Cc: Liming Gao <[email protected]>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <[email protected]>
Reviewed-by: Star Zeng <[email protected]>
---
MdeModulePkg/Core/Dxe/Event/Tpl.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/MdeModulePkg/Core/Dxe/Event/Tpl.c
b/MdeModulePkg/Core/Dxe/Event/Tpl.c
index 8ad0a33701..e3caf832b8 100644
--- a/MdeModulePkg/Core/Dxe/Event/Tpl.c
+++ b/MdeModulePkg/Core/Dxe/Event/Tpl.c
@@ -1,7 +1,7 @@
/** @file
Task priority (TPL) functions.
-Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD
License
which accompanies this distribution. The full text of the license may be
found at
@@ -103,6 +103,7 @@ CoreRestoreTpl (
)
{
EFI_TPL OldTpl;
+ EFI_TPL PendingTpl;
OldTpl = gEfiCurrentTpl;
if (NewTpl > OldTpl) {
@@ -123,8 +124,13 @@ CoreRestoreTpl (
//
// Dispatch any pending events
//
- while (((-2 << NewTpl) & gEventPending) != 0) {
- gEfiCurrentTpl = (UINTN) HighBitSet64 (gEventPending);
+ while (gEventPending != 0) {
+ PendingTpl = (UINTN) HighBitSet64 (gEventPending);
+ if (PendingTpl <= NewTpl) {
+ break;
+ }
+
+ gEfiCurrentTpl = PendingTpl;
if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
CoreSetInterruptState (TRUE);
}
--
2.12.0.windows.1
_______________________________________________
edk2-devel mailing list
[email protected]
https://lists.01.org/mailman/listinfo/edk2-devel
