Reviewed-by: Star Zeng <[email protected]> -----Original Message----- From: Wu, Hao A Sent: Thursday, September 21, 2017 2:46 PM To: [email protected] Cc: Wu, Hao A <[email protected]>; Shi, Steven <[email protected]>; Zeng, Star <[email protected]>; Dong, Eric <[email protected]>; Paolo Bonzini <[email protected]>; Kinney, Michael D <[email protected]>; Gao, Liming <[email protected]> Subject: [PATCH v2 3/6] MdeModulePkg/Tpl: Fix negative value left shift
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: Star Zeng <[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]> --- 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
