soc/amd/common/pi: Fix issue in AGESA heap allocator

The heap allocator would try to split a buffer node that
was too small for another node. In the failing case, the buffer
node was 0x140 bytes and the requested size was 0x133 bytes.
The logic would check that there was room for the header and
buffer and try to split the buffer node. The buffer node header
is 0xC bytes, so 0x13F bytes are need. The problem is that it didn't
leave room for another node header and a little space for a buffer.

BUG=b:71764350
TEST= Boot grunt.
BRANCH=none

Change-Id: Iece5e12d5787415a335bb953985331a5dc312152
Signed-off-by: Marc Jones <marcj303@gmail.com>
Reviewed-on: https://review.coreboot.org/23211
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Daniel Kurtz <djkurtz@google.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/src/soc/amd/common/block/pi/heapmanager.c b/src/soc/amd/common/block/pi/heapmanager.c
index cea3171aa5..d149e9144f 100644
--- a/src/soc/amd/common/block/pi/heapmanager.c
+++ b/src/soc/amd/common/block/pi/heapmanager.c
@@ -159,11 +159,12 @@ AGESA_STATUS agesa_AllocateBuffer (UINT32 Func, UINTN Data, VOID *ConfigPtr)
 							BestFitPrevNodeOffset);
 
 		/*
-		 * If BestFitNode is larger than the requested buffer,
-		 * fragment the node further
+		 * If BestFitNode is larger than the requested buffer and
+		 * has room for another buffer node, fragment the node further.
 		 */
-		if (BestFitNodePtr->BufferSize >
-		    (AllocParams->BufferLength + sizeof(BIOS_BUFFER_NODE))) {
+		if (BestFitNodePtr->BufferSize >=
+		    (AllocParams->BufferLength + sizeof(BIOS_BUFFER_NODE) +
+		     MIN_BUFFER_NODE_SIZE)) {
 			NextFreeOffset = BestFitNodeOffset +
 					 AllocParams->BufferLength +
 					 sizeof(BIOS_BUFFER_NODE);