[edk2-devel] [PATCH v5 21/38] ArmPkg: Implement ArmSetMemoryOverrideLib

[Ard Biesheuvel]

On Thu, 16 Mar 2023 at 14:27, Leif Lindholm <quic_llindhol at quicinc.com> wrote:
>
> On Mon, Mar 13, 2023 at 18:16:57 +0100, Ard Biesheuvel wrote:
> > Implement the ARM version of a NULL class library that can be overlaid
> > on top of the DXE core to equip it right from its launch with an
> > implementation of the CPU arch protocol member that sets type and
> > permission attributes on memory regions.
> >
> > This bridges the gap between dispatch of DXE core and dispatch of the
> > DXE driver that implements the CPU arch protocol, removing the need to
> > rely on memory mappings that are writable and executable at the same
> > time.
> >
> > Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
> > ---
> >  ArmPkg/ArmPkg.dsc                                                  |  1 +
> >  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c   | 78 ++++++++++++++++++++
> >  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf | 28 +++++++
> >  3 files changed, 107 insertions(+)
> >
> > diff --git a/ArmPkg/ArmPkg.dsc b/ArmPkg/ArmPkg.dsc
> > index 3fb95d1951a9..43eb0f4f463e 100644
> > --- a/ArmPkg/ArmPkg.dsc
> > +++ b/ArmPkg/ArmPkg.dsc
> > @@ -119,6 +119,7 @@ [Components.common]
> >    ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.inf
> >    ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
> >    ArmPkg/Library/ArmExceptionLib/ArmRelocateExceptionLib.inf
> > +  ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.inf
> >
> >    ArmPkg/Drivers/CpuDxe/CpuDxe.inf
> >    ArmPkg/Drivers/CpuPei/CpuPei.inf
> > diff --git a/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c
> > new file mode 100644
> > index 000000000000..866dbbdaa7d5
> > --- /dev/null
> > +++ b/ArmPkg/Library/ArmSetMemoryOverrideLib/ArmSetMemoryOverrideLib.c
> > @@ -0,0 +1,78 @@
> > +/** @file
> > +  Overlay implementation of DXE core gCpuSetMemoryAttributes for ARM.
> > +
> > +  Copyright (c) 2023, Google LLC. All rights reserved.
> > +
> > +  SPDX-License-Identifier: BSD-2-Clause-Patent
> > +**/
> > +
> > +#include <PiDxe.h>
> > +
> > +#include <Library/ArmMmuLib.h>
> > +#include <Library/DebugLib.h>
> > +#include <Protocol/Cpu.h>
> > +
> > +extern EFI_CPU_SET_MEMORY_ATTRIBUTES  gCpuSetMemoryAttributes;
>
> Could this declaration live in a global include?
>

Yes, In fact, instead of modeling this as a NULL library class, we
could actually define a library class for this, whose include file
only has this extern declaration and nothing else (and a big fat
comment, obviously, describing the point of that)


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