I'll post another version to fix the formatting issue in a bit, but before the
patch the issue was we applied the alignment offset before we did a space check.
-Jeff
> -----Original Message-----
> From: Ard Biesheuvel <a...@kernel.org>
> Sent: Wednesday, September 7, 2022 2:34 AM
> To: Jeff Brasen <jbra...@nvidia.com>
> Cc: devel@edk2.groups.io; quic_llind...@quicinc.com;
> ardb+tianoc...@kernel.org; abner.ch...@hpe.com; daniel.schae...@hpe.com
> Subject: Re: [PATCH] EmbeddedPkg/PrePiMemoryAllocationLib: Add check for
> space on offset allocation
>
> External email: Use caution opening links or attachments
>
>
> On Thu, 30 Jun 2022 at 21:06, Jeff Brasen <jbra...@nvidia.com> wrote:
> >
> > Update check for enough space to occur prior to alignment offset.
> > This prevents cases where EfiFreeMemoryTop < EfiFreeMemoryBottom.
> >
>
> So prior to this patch, we would
> - check for enough space
> - apply the alignment
> - potentially exceed the available space due to alignment padding?
>
> > Signed-off-by: Jeff Brasen <jbra...@nvidia.com>
>
> This patch got mangled so I cannot apply it from the list.
>
> > ---
> > .../MemoryAllocationLib.c | 53 +++++++++++--------
> > 1 file changed, 30 insertions(+), 23 deletions(-)
> >
> > diff --git
> > a/EmbeddedPkg/Library/PrePiMemoryAllocationLib/MemoryAllocationLib.c
> > b/EmbeddedPkg/Library/PrePiMemoryAllocationLib/MemoryAllocationLib.c
> > index 78f8da5e95..1956d644c3 100644
> > ---
> > a/EmbeddedPkg/Library/PrePiMemoryAllocationLib/MemoryAllocationLib.c
> > +++ b/EmbeddedPkg/Library/PrePiMemoryAllocationLib/MemoryAllocationLib
> > +++ .c
> > @@ -38,37 +38,44 @@ AllocatePages (
> >
> > Hob.Raw = GetHobList ();
> >
> > - // Check to see if on 4k boundary
> > Offset = Hob.HandoffInformationTable->EfiFreeMemoryTop & 0xFFF;
> > + //
> > + // Verify that there is sufficient memory to satisfy the allocation
> > + and padding prior to updating anything // if
> > + ((Hob.HandoffInformationTable->EfiFreeMemoryTop - ((Pages *
> EFI_PAGE_SIZE) + sizeof (EFI_HOB_MEMORY_ALLOCATION)) - Offset) <
> Hob.HandoffInformationTable->EfiFreeMemoryBottom) {
> > + if (Offset != 0) {
> > + DEBUG ((DEBUG_ERROR, "Offset applied without enough space\r\n"));
> > + } else {
> > + DEBUG ((DEBUG_ERROR, "Out of memory\r\n"));
> > + }
> > +
> > + ASSERT (FALSE);
> > + return 0;
> > + }
> > +
> > + // Check to see if on 4k boundary
> > if (Offset != 0) {
> > // If not aligned, make the allocation aligned.
> > Hob.HandoffInformationTable->EfiFreeMemoryTop -= Offset;
> > }
> >
> > //
> > - // Verify that there is sufficient memory to satisfy the allocation
> > + // Update the PHIT to reflect the memory usage
> > //
> > - if (Hob.HandoffInformationTable->EfiFreeMemoryTop - ((Pages *
> EFI_PAGE_SIZE) + sizeof (EFI_HOB_MEMORY_ALLOCATION)) <
> Hob.HandoffInformationTable->EfiFreeMemoryBottom) {
> > - return 0;
> > - } else {
> > - //
> > - // Update the PHIT to reflect the memory usage
> > - //
> > - Hob.HandoffInformationTable->EfiFreeMemoryTop -= Pages *
> EFI_PAGE_SIZE;
> > -
> > - // This routine used to create a memory allocation HOB a la PEI, but
> > that's
> not
> > - // necessary for us.
> > -
> > - //
> > - // Create a memory allocation HOB.
> > - //
> > - BuildMemoryAllocationHob (
> > - Hob.HandoffInformationTable->EfiFreeMemoryTop,
> > - Pages * EFI_PAGE_SIZE,
> > - EfiBootServicesData
> > - );
> > - return (VOID *)(UINTN)Hob.HandoffInformationTable-
> >EfiFreeMemoryTop;
> > - }
> > + Hob.HandoffInformationTable->EfiFreeMemoryTop -= Pages *
> > + EFI_PAGE_SIZE;
> > +
> > + // This routine used to create a memory allocation HOB a la PEI,
> > + but that's not // necessary for us.
> > +
> > + //
> > + // Create a memory allocation HOB.
> > + //
> > + BuildMemoryAllocationHob (
> > + Hob.HandoffInformationTable->EfiFreeMemoryTop,
> > + Pages * EFI_PAGE_SIZE,
> > + EfiBootServicesData
> > + );
> > + return (VOID
> > + *)(UINTN)Hob.HandoffInformationTable->EfiFreeMemoryTop;
> > }
> >
> > /**
> > --
> > 2.25.1
> >
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