Re: [edk2] [PATCH 3/5] ArmPkg/ArmMmuLib AARCH64: implement support for EFI_MEMORY_RP permissions
On Mon, Jan 14, 2019 at 03:59:08PM +0100, Ard Biesheuvel wrote: > On Mon, 14 Jan 2019 at 15:29, Leif Lindholm wrote: > > > > On Mon, Jan 07, 2019 at 08:15:02AM +0100, Ard Biesheuvel wrote: > > > Wire up the access flag (AF) page table attribute to the EFI_MEMORY_RP > > > permission attribute, so that attempts to read from such a region will > > > trigger an access flag fault. > > > > > > Note that this is a stronger notion than just read protection, since > > > it now implies that any write or execute attempt is trapped as well. > > > However, this does not really matter in practice since we never assume > > > that a read protected page is writable or executable, and StackGuard > > > and HeapGuard (which are the primary users of this facility) certainly > > > don't care. > > > > So ... I'm cautiously positive to this patch. > > But this use does contradict the UEFI spec (2.7a, 2.3.6.1 Memory > > types), which says EFI_MEMORY_RP is "not used or defined" for AArch64. > > > > Charles? > > Not defined by the spec means we can use it do whatever we bloody want > with it, at least that is what a typical compiler engineer will tell > you :-) Not defined, yes. Not used, less so. For a reciprocal compiler engineer analogy, think pointer tagging :) > I think there was a pending ECR to update the AArch64 binding code to > reflect reality, but I don't think we included EFI_MEMORY_RP. Right. Anyway, I'm reasonably happy with stretching the rules slightly here, and I believe it to be safe, but I do want Charles' take on it. / Leif > > > Contributed-under: TianoCore Contribution Agreement 1.1 > > > Signed-off-by: Ard Biesheuvel > > > --- > > > ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c | 5 +++-- > > > ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 14 +++--- > > > 2 files changed, 14 insertions(+), 5 deletions(-) > > > > > > diff --git a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > > b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > > index 3e216c7cb235..e62e3fa87112 100644 > > > --- a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > > +++ b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > > @@ -223,8 +223,9 @@ EfiAttributeToArmAttribute ( > > > ArmAttributes = TT_ATTR_INDX_MASK; > > >} > > > > > > - // Set the access flag to match the block attributes > > > - ArmAttributes |= TT_AF; > > > + if ((EfiAttributes & EFI_MEMORY_RP) == 0) { > > > +ArmAttributes |= TT_AF; > > > + } > > > > > >// Determine protection attributes > > >if (EfiAttributes & EFI_MEMORY_RO) { > > > diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > > b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > > index e1fabfcbea14..b59c081a7e49 100644 > > > --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > > +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > > @@ -102,6 +102,10 @@ PageAttributeToGcdAttribute ( > > > GcdAttributes |= EFI_MEMORY_XP; > > >} > > > > > > + if ((PageAttributes & TT_AF) == 0) { > > > +GcdAttributes |= EFI_MEMORY_RP; > > > + } > > > + > > >return GcdAttributes; > > > } > > > > > > @@ -451,7 +455,11 @@ GcdAttributeToPageAttribute ( > > > PageAttributes |= TT_AP_RO_RO; > > >} > > > > > > - return PageAttributes | TT_AF; > > > + if ((GcdAttributes & EFI_MEMORY_RP) == 0) { > > > +PageAttributes |= TT_AF; > > > + } > > > + > > > + return PageAttributes; > > > } > > > > > > EFI_STATUS > > > @@ -474,9 +482,9 @@ ArmSetMemoryAttributes ( > > > // No memory type was set in Attributes, so we are going to update > > > the > > > // permissions only. > > > // > > > -PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK; > > > +PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK | TT_AF; > > > PageAttributeMask = ~(TT_ADDRESS_MASK_BLOCK_ENTRY | TT_AP_MASK | > > > - TT_PXN_MASK | TT_XN_MASK); > > > + TT_PXN_MASK | TT_XN_MASK | TT_AF); > > >} > > > > > >TranslationTable = ArmGetTTBR0BaseAddress (); > > > -- > > > 2.20.1 > > > ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 3/5] ArmPkg/ArmMmuLib AARCH64: implement support for EFI_MEMORY_RP permissions
On Mon, 14 Jan 2019 at 15:29, Leif Lindholm wrote: > > On Mon, Jan 07, 2019 at 08:15:02AM +0100, Ard Biesheuvel wrote: > > Wire up the access flag (AF) page table attribute to the EFI_MEMORY_RP > > permission attribute, so that attempts to read from such a region will > > trigger an access flag fault. > > > > Note that this is a stronger notion than just read protection, since > > it now implies that any write or execute attempt is trapped as well. > > However, this does not really matter in practice since we never assume > > that a read protected page is writable or executable, and StackGuard > > and HeapGuard (which are the primary users of this facility) certainly > > don't care. > > So ... I'm cautiously positive to this patch. > But this use does contradict the UEFI spec (2.7a, 2.3.6.1 Memory > types), which says EFI_MEMORY_RP is "not used or defined" for AArch64. > > Charles? > Not defined by the spec means we can use it do whatever we bloody want with it, at least that is what a typical compiler engineer will tell you :-) I think there was a pending ECR to update the AArch64 binding code to reflect reality, but I don't think we included EFI_MEMORY_RP. > > Contributed-under: TianoCore Contribution Agreement 1.1 > > Signed-off-by: Ard Biesheuvel > > --- > > ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c | 5 +++-- > > ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 14 +++--- > > 2 files changed, 14 insertions(+), 5 deletions(-) > > > > diff --git a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > index 3e216c7cb235..e62e3fa87112 100644 > > --- a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > +++ b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > > @@ -223,8 +223,9 @@ EfiAttributeToArmAttribute ( > > ArmAttributes = TT_ATTR_INDX_MASK; > >} > > > > - // Set the access flag to match the block attributes > > - ArmAttributes |= TT_AF; > > + if ((EfiAttributes & EFI_MEMORY_RP) == 0) { > > +ArmAttributes |= TT_AF; > > + } > > > >// Determine protection attributes > >if (EfiAttributes & EFI_MEMORY_RO) { > > diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > index e1fabfcbea14..b59c081a7e49 100644 > > --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > > @@ -102,6 +102,10 @@ PageAttributeToGcdAttribute ( > > GcdAttributes |= EFI_MEMORY_XP; > >} > > > > + if ((PageAttributes & TT_AF) == 0) { > > +GcdAttributes |= EFI_MEMORY_RP; > > + } > > + > >return GcdAttributes; > > } > > > > @@ -451,7 +455,11 @@ GcdAttributeToPageAttribute ( > > PageAttributes |= TT_AP_RO_RO; > >} > > > > - return PageAttributes | TT_AF; > > + if ((GcdAttributes & EFI_MEMORY_RP) == 0) { > > +PageAttributes |= TT_AF; > > + } > > + > > + return PageAttributes; > > } > > > > EFI_STATUS > > @@ -474,9 +482,9 @@ ArmSetMemoryAttributes ( > > // No memory type was set in Attributes, so we are going to update the > > // permissions only. > > // > > -PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK; > > +PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK | TT_AF; > > PageAttributeMask = ~(TT_ADDRESS_MASK_BLOCK_ENTRY | TT_AP_MASK | > > - TT_PXN_MASK | TT_XN_MASK); > > + TT_PXN_MASK | TT_XN_MASK | TT_AF); > >} > > > >TranslationTable = ArmGetTTBR0BaseAddress (); > > -- > > 2.20.1 > > ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 3/5] ArmPkg/ArmMmuLib AARCH64: implement support for EFI_MEMORY_RP permissions
On Mon, Jan 07, 2019 at 08:15:02AM +0100, Ard Biesheuvel wrote: > Wire up the access flag (AF) page table attribute to the EFI_MEMORY_RP > permission attribute, so that attempts to read from such a region will > trigger an access flag fault. > > Note that this is a stronger notion than just read protection, since > it now implies that any write or execute attempt is trapped as well. > However, this does not really matter in practice since we never assume > that a read protected page is writable or executable, and StackGuard > and HeapGuard (which are the primary users of this facility) certainly > don't care. So ... I'm cautiously positive to this patch. But this use does contradict the UEFI spec (2.7a, 2.3.6.1 Memory types), which says EFI_MEMORY_RP is "not used or defined" for AArch64. Charles? / Leif > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Ard Biesheuvel > --- > ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c | 5 +++-- > ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 14 +++--- > 2 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > index 3e216c7cb235..e62e3fa87112 100644 > --- a/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > +++ b/ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c > @@ -223,8 +223,9 @@ EfiAttributeToArmAttribute ( > ArmAttributes = TT_ATTR_INDX_MASK; >} > > - // Set the access flag to match the block attributes > - ArmAttributes |= TT_AF; > + if ((EfiAttributes & EFI_MEMORY_RP) == 0) { > +ArmAttributes |= TT_AF; > + } > >// Determine protection attributes >if (EfiAttributes & EFI_MEMORY_RO) { > diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > index e1fabfcbea14..b59c081a7e49 100644 > --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c > @@ -102,6 +102,10 @@ PageAttributeToGcdAttribute ( > GcdAttributes |= EFI_MEMORY_XP; >} > > + if ((PageAttributes & TT_AF) == 0) { > +GcdAttributes |= EFI_MEMORY_RP; > + } > + >return GcdAttributes; > } > > @@ -451,7 +455,11 @@ GcdAttributeToPageAttribute ( > PageAttributes |= TT_AP_RO_RO; >} > > - return PageAttributes | TT_AF; > + if ((GcdAttributes & EFI_MEMORY_RP) == 0) { > +PageAttributes |= TT_AF; > + } > + > + return PageAttributes; > } > > EFI_STATUS > @@ -474,9 +482,9 @@ ArmSetMemoryAttributes ( > // No memory type was set in Attributes, so we are going to update the > // permissions only. > // > -PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK; > +PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK | TT_AF; > PageAttributeMask = ~(TT_ADDRESS_MASK_BLOCK_ENTRY | TT_AP_MASK | > - TT_PXN_MASK | TT_XN_MASK); > + TT_PXN_MASK | TT_XN_MASK | TT_AF); >} > >TranslationTable = ArmGetTTBR0BaseAddress (); > -- > 2.20.1 > ___ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel