Re: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left shift
Star and Paolo, Thanks for the feedbacks. I will refine the patch according to your suggestions. Best Regards, Hao Wu > -Original Message- > From: Zeng, Star > Sent: Thursday, September 21, 2017 10:57 AM > To: Paolo Bonzini; Wu, Hao A; edk2-devel@lists.01.org > Cc: Dong, Eric; Zeng, Star > Subject: RE: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left > shift > > There is a case must be considered that gEventPending is 0, HighBitSet64 will > return -1, then the code will be wrong. > The code maybe: > > while (gEventPending != 0) { > PendingTpl = (UINTN) HighBitSet64 (gEventPending); > if (NewTpl >= PendingTpl) { > break; > } > gEfiCurrentTpl = PendingTpl; > > ... > > } > > > Thanks, > Star > -Original Message- > From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of Paolo > Bonzini > Sent: Wednesday, September 20, 2017 1:03 AM > To: Wu, Hao A <hao.a...@intel.com>; edk2-devel@lists.01.org > Cc: Dong, Eric <eric.d...@intel.com>; Zeng, Star <star.z...@intel.com> > Subject: Re: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left > shift > > On 19/09/2017 13:43, Hao Wu wrote: > > 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 <steven@intel.com> > > Cc: Star Zeng <star.z...@intel.com> > > Cc: Eric Dong <eric.d...@intel.com> > > Contributed-under: TianoCore Contribution Agreement 1.1 > > Signed-off-by: Hao Wu <hao.a...@intel.com> > > --- > > 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); > > > > Maybe: > > for (;;) { > PendingTpl = (UINTN) HighBitSet64 (gEventPending); > if (NewTpl >= PendingTpl) { > break; > } > gEfiCurrentTpl = PendingTpl; > } > > This is much more readable, and HighBitSet64 should be efficient on most > modern processors. > > Paolo > ___ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left shift
There is a case must be considered that gEventPending is 0, HighBitSet64 will return -1, then the code will be wrong. The code maybe: while (gEventPending != 0) { PendingTpl = (UINTN) HighBitSet64 (gEventPending); if (NewTpl >= PendingTpl) { break; } gEfiCurrentTpl = PendingTpl; ... } Thanks, Star -Original Message- From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of Paolo Bonzini Sent: Wednesday, September 20, 2017 1:03 AM To: Wu, Hao A <hao.a...@intel.com>; edk2-devel@lists.01.org Cc: Dong, Eric <eric.d...@intel.com>; Zeng, Star <star.z...@intel.com> Subject: Re: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left shift On 19/09/2017 13:43, Hao Wu wrote: > 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 <steven@intel.com> > Cc: Star Zeng <star.z...@intel.com> > Cc: Eric Dong <eric.d...@intel.com> > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Hao Wu <hao.a...@intel.com> > --- > 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); > Maybe: for (;;) { PendingTpl = (UINTN) HighBitSet64 (gEventPending); if (NewTpl >= PendingTpl) { break; } gEfiCurrentTpl = PendingTpl; } This is much more readable, and HighBitSet64 should be efficient on most modern processors. Paolo ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 3/6] MdeModulePkg/Tpl: Fix negative value left shift
On 19/09/2017 13:43, Hao Wu wrote: > 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> Cc: Star Zeng > Cc: Eric Dong > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Hao Wu > --- > 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); > Maybe: for (;;) { PendingTpl = (UINTN) HighBitSet64 (gEventPending); if (NewTpl >= PendingTpl) { break; } gEfiCurrentTpl = PendingTpl; } This is much more readable, and HighBitSet64 should be efficient on most modern processors. Paolo ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
[edk2] [PATCH 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 explicitly cast '-2' with UINTN to resolve this issue. Cc: Steven ShiCc: Star Zeng Cc: Eric Dong Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- 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 ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel