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CpuPageTableLib: Fix bug that wrongly requires extra size for mapping 

With following paging structure to map
  [2M-4K, 2M] as P = 1, RW = 0,
  [2M, 4M]    as P = 1, RW = 1:

PML4[0] -> PDPTE[0] -> PDE[0](RW = 0) -> PTE[255](P = 0, RW = 0)
                    -> PDE[1](RW = 1)

When a new request to map [2M-4K, 2M+4K] as P = 1, RW = 1,
CpuPageTableMap() wrongly requests 4K buffer size for the new mapping
request.

But in fact, for [2M-4K, 2M] request, PTE[255] can be changed in place,
for [2M, 2M+4K], no change is needed because PDE[1].RW = 1 already.

The change fixes the bug.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
This commit is contained in:
Ray Ni 2022-07-18 16:41:37 +08:00 committed by mergify[bot]
parent 9f53fd4ba7
commit 927113c83b
1 changed files with 5 additions and 8 deletions
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13
UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
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@ -272,6 +272,7 @@ PageTableLibMapInLevel (
IA32_MAP_ATTRIBUTE ChildAttribute;
IA32_MAP_ATTRIBUTE ChildMask;
IA32_MAP_ATTRIBUTE CurrentMask;
IA32_MAP_ATTRIBUTE LocalParentAttribute;
ASSERT (Level != 0);
ASSERT ((Attribute != NULL) && (Mask != NULL));
@ -284,6 +285,9 @@ PageTableLibMapInLevel (
NopAttribute.Bits.ReadWrite = 1;
NopAttribute.Bits.UserSupervisor = 1;
LocalParentAttribute.Uint64 = ParentAttribute->Uint64;
ParentAttribute = &LocalParentAttribute;
//
// ParentPagingEntry ONLY is deferenced for checking Present and MustBeOne bits
// when Modify is FALSE.
@ -420,7 +424,7 @@ PageTableLibMapInLevel (
}
if (IsPle (&PagingEntry[Index], Level)) {
PageTableLibSetPle (Level - 1, &PagingEntry[Index], 0, &ChildAttribute, &ChildMask);
PageTableLibSetPle (Level, &PagingEntry[Index], 0, &ChildAttribute, &ChildMask);
} else {
PageTableLibSetPnle (&PagingEntry[Index].Pnle, &ChildAttribute, &ChildMask);
}
@ -664,13 +668,6 @@ PageTableMap (
//
// Update the page table when the supplied buffer is sufficient.
//
ParentAttribute.Uint64 = 0;
ParentAttribute.Bits.PageTableBaseAddress = 1;
ParentAttribute.Bits.Present = 1;
ParentAttribute.Bits.ReadWrite = 1;
ParentAttribute.Bits.UserSupervisor = 1;
ParentAttribute.Bits.Nx = 0;
Status = PageTableLibMapInLevel (
&TopPagingEntry,
&ParentAttribute,