MdeModulePkg/PiSmmCore: Fix issues in Heap Guard

One issue is that macros defined in HeapGuard.h

    GUARD_HEAP_TYPE_PAGE
    GUARD_HEAP_TYPE_POOL

doesn't match the definition of PCD PcdHeapGuardPropertyMask in
MdeModulePkg.dec. This patch fixed it by exchanging the BIT0 and BIT1
of them.

Another is that method AdjustMemoryF() will return a bigger NumberOfPages than
the value passed in. This is caused by counting twice of a shared Guard page
which can be used for both head and tail Guard of the memory before it and
after it. This happens only when partially freeing just one page in the middle
of a bunch of allocated pages. The freed page should be turned into a new
Guard page.

Cc: Jie Lin <jie.lin@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

2 files changed, 76 insertions, 19 deletions

diff --git a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
index 1d5fb8c..04fa174 100644
--- a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
+++ b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
@@ -776,6 +776,7 @@ UnsetGuardForMemory (
   )

 {

   EFI_PHYSICAL_ADDRESS  GuardPage;

+  UINT64                GuardBitmap;

 

   if (NumberOfPages == 0) {

     return;

@@ -784,16 +785,29 @@ UnsetGuardForMemory (
   //

   // Head Guard must be one page before, if any.

   //

+  //          MSB-> 1     0 <-LSB

+  //          -------------------

+  //  Head Guard -> 0     1 -> Don't free Head Guard  (shared Guard)

+  //  Head Guard -> 0     0 -> Free Head Guard either (not shared Guard)

+  //                1     X -> Don't free first page  (need a new Guard)

+  //                           (it'll be turned into a Guard page later)

+  //          -------------------

+  //      Start -> -1    -2

+  //

   GuardPage = Memory - EFI_PAGES_TO_SIZE (1);

-  if (IsHeadGuard (GuardPage)) {

-    if (!IsMemoryGuarded (GuardPage - EFI_PAGES_TO_SIZE (1))) {

+  GuardBitmap = GetGuardedMemoryBits (Memory - EFI_PAGES_TO_SIZE (2), 2);

+  if ((GuardBitmap & BIT1) == 0) {

+    //

+    // Head Guard exists.

+    //

+    if ((GuardBitmap & BIT0) == 0) {

       //

       // If the head Guard is not a tail Guard of adjacent memory block,

       // unset it.

       //

       UnsetGuardPage (GuardPage);

     }

-  } else if (IsMemoryGuarded (GuardPage)) {

+  } else {

     //

     // Pages before memory to free are still in Guard. It's a partial free

     // case. Turn first page of memory block to free into a new Guard.

@@ -804,16 +818,29 @@ UnsetGuardForMemory (
   //

   // Tail Guard must be the page after this memory block to free, if any.

   //

+  //   MSB-> 1     0 <-LSB

+  //  --------------------

+  //         1     0 <- Tail Guard -> Don't free Tail Guard  (shared Guard)

+  //         0     0 <- Tail Guard -> Free Tail Guard either (not shared Guard)

+  //         X     1               -> Don't free last page   (need a new Guard)

+  //                                 (it'll be turned into a Guard page later)

+  //  --------------------

+  //        +1    +0 <- End

+  //

   GuardPage = Memory + EFI_PAGES_TO_SIZE (NumberOfPages);

-  if (IsTailGuard (GuardPage)) {

-    if (!IsMemoryGuarded (GuardPage + EFI_PAGES_TO_SIZE (1))) {

+  GuardBitmap = GetGuardedMemoryBits (GuardPage, 2);

+  if ((GuardBitmap & BIT0) == 0) {

+    //

+    // Tail Guard exists.

+    //

+    if ((GuardBitmap & BIT1) == 0) {

       //

       // If the tail Guard is not a head Guard of adjacent memory block,

       // free it; otherwise, keep it.

       //

       UnsetGuardPage (GuardPage);

     }

-  } else if (IsMemoryGuarded (GuardPage)) {

+  } else {

     //

     // Pages after memory to free are still in Guard. It's a partial free

     // case. We need to keep one page to be a head Guard.

@@ -903,6 +930,7 @@ AdjustMemoryF (
   EFI_PHYSICAL_ADDRESS  Start;

   EFI_PHYSICAL_ADDRESS  MemoryToTest;

   UINTN                 PagesToFree;

+  UINT64                GuardBitmap;

 

   if (Memory == NULL || NumberOfPages == NULL || *NumberOfPages == 0) {

     return;

@@ -914,9 +942,22 @@ AdjustMemoryF (
   //

   // Head Guard must be one page before, if any.

   //

-  MemoryToTest = Start - EFI_PAGES_TO_SIZE (1);

-  if (IsHeadGuard (MemoryToTest)) {

-    if (!IsMemoryGuarded (MemoryToTest - EFI_PAGES_TO_SIZE (1))) {

+  //          MSB-> 1     0 <-LSB

+  //          -------------------

+  //  Head Guard -> 0     1 -> Don't free Head Guard  (shared Guard)

+  //  Head Guard -> 0     0 -> Free Head Guard either (not shared Guard)

+  //                1     X -> Don't free first page  (need a new Guard)

+  //                           (it'll be turned into a Guard page later)

+  //          -------------------

+  //      Start -> -1    -2

+  //

+  MemoryToTest = Start - EFI_PAGES_TO_SIZE (2);

+  GuardBitmap = GetGuardedMemoryBits (MemoryToTest, 2);

+  if ((GuardBitmap & BIT1) == 0) {

+    //

+    // Head Guard exists.

+    //

+    if ((GuardBitmap & BIT0) == 0) {

       //

       // If the head Guard is not a tail Guard of adjacent memory block,

       // free it; otherwise, keep it.

@@ -924,10 +965,10 @@ AdjustMemoryF (
       Start       -= EFI_PAGES_TO_SIZE (1);

       PagesToFree += 1;

     }

-  } else if (IsMemoryGuarded (MemoryToTest)) {

+  } else {

     //

-    // Pages before memory to free are still in Guard. It's a partial free

-    // case. We need to keep one page to be a tail Guard.

+    // No Head Guard, and pages before memory to free are still in Guard. It's a

+    // partial free case. We need to keep one page to be a tail Guard.

     //

     Start       += EFI_PAGES_TO_SIZE (1);

     PagesToFree -= 1;

@@ -936,19 +977,32 @@ AdjustMemoryF (
   //

   // Tail Guard must be the page after this memory block to free, if any.

   //

+  //   MSB-> 1     0 <-LSB

+  //  --------------------

+  //         1     0 <- Tail Guard -> Don't free Tail Guard  (shared Guard)

+  //         0     0 <- Tail Guard -> Free Tail Guard either (not shared Guard)

+  //         X     1               -> Don't free last page   (need a new Guard)

+  //                                 (it'll be turned into a Guard page later)

+  //  --------------------

+  //        +1    +0 <- End

+  //

   MemoryToTest = Start + EFI_PAGES_TO_SIZE (PagesToFree);

-  if (IsTailGuard (MemoryToTest)) {

-    if (!IsMemoryGuarded (MemoryToTest + EFI_PAGES_TO_SIZE (1))) {

+  GuardBitmap = GetGuardedMemoryBits (MemoryToTest, 2);

+  if ((GuardBitmap & BIT0) == 0) {

+    //

+    // Tail Guard exists.

+    //

+    if ((GuardBitmap & BIT1) == 0) {

       //

       // If the tail Guard is not a head Guard of adjacent memory block,

       // free it; otherwise, keep it.

       //

       PagesToFree += 1;

     }

-  } else if (IsMemoryGuarded (MemoryToTest)) {

+  } else if (PagesToFree > 0) {

     //

-    // Pages after memory to free are still in Guard. It's a partial free

-    // case. We need to keep one page to be a head Guard.

+    // No Tail Guard, and pages after memory to free are still in Guard. It's a

+    // partial free case. We need to keep one page to be a head Guard.

     //

     PagesToFree -= 1;

   }

@@ -1146,6 +1200,9 @@ SmmInternalFreePagesExWithGuard (
 

   AdjustMemoryF (&MemoryToFree, &PagesToFree);

   UnsetGuardForMemory (Memory, NumberOfPages);

+  if (PagesToFree == 0) {

+    return EFI_SUCCESS;

+  }

 

   return SmmInternalFreePagesEx (MemoryToFree, PagesToFree, AddRegion);

 }

diff --git a/MdeModulePkg/Core/PiSmmCore/HeapGuard.h b/MdeModulePkg/Core/PiSmmCore/HeapGuard.h
index a6f92a2..3e4b2a4 100644
--- a/MdeModulePkg/Core/PiSmmCore/HeapGuard.h
+++ b/MdeModulePkg/Core/PiSmmCore/HeapGuard.h
@@ -160,8 +160,8 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 //

 // Memory type to guard (matching the related PCD definition)

 //

-#define GUARD_HEAP_TYPE_POOL        BIT2

-#define GUARD_HEAP_TYPE_PAGE        BIT3

+#define GUARD_HEAP_TYPE_PAGE        BIT2

+#define GUARD_HEAP_TYPE_POOL        BIT3

 

 //

 // Debug message level