Do not copy whole isochronous IN buffer

Instead of allocating buffer to hold copy of the isochronous IN transfer, allocate array of payload entries and fill it with pointers to the transfer buffer. This reduces the NonPagedPool memory usage.
desowin · Jun 15, 2019 · aac8d91 · aac8d91
1 parent 5bb27d7
commit aac8d91
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Showing 2 changed files with 37 additions and 32 deletions.
diff --git a/USBPcapDriver/USBPcapBuffer.c b/USBPcapDriver/USBPcapBuffer.c
@@ -601,9 +601,12 @@ USBPcapBufferStorePacket(PUSBPCAP_ROOTHUB_DATA pRootData,
     for (i = 0; (bytes > 0) && (payloadEntries[i].buffer); i++)
     {
         tmp = min(bytes, payloadEntries[i].size);
-        USBPcapBufferWriteUnsafe(pRootData,
-                                 payloadEntries[i].buffer,
-                                 tmp);
+        if (tmp > 0)
+        {
+            USBPcapBufferWriteUnsafe(pRootData,
+                                     payloadEntries[i].buffer,
+                                     tmp);
+        }
         bytes -= tmp;
     }
 

diff --git a/USBPcapDriver/USBPcapURB.c b/USBPcapDriver/USBPcapURB.c
@@ -750,8 +750,7 @@ VOID USBPcapAnalyzeURB(PIRP pIrp, PURB pUrb, BOOLEAN post,
             USBPCAP_ENDPOINT_INFO         info;
             BOOLEAN                       epFound;
             PUSBPCAP_BUFFER_ISOCH_HEADER  packetHeader;
-            PVOID                         transferBuffer;
-            PUCHAR                        compactedBuffer;
+            PUSBPCAP_PAYLOAD_ENTRY        compactedPayloadEntries;
             PVOID                         captureBuffer;
             USHORT                        headerLen;
             ULONG                         i;
@@ -816,8 +815,7 @@ VOID USBPcapAnalyzeURB(PIRP pIrp, PURB pUrb, BOOLEAN post,
 
             /* Default to no data, will be changed later if data is to be attached to packet */
             packetHeader->header.dataLength = 0;
-            compactedBuffer = NULL;
-            transferBuffer = NULL;
+            compactedPayloadEntries = NULL;
             captureBuffer = NULL;
 
             /* Copy the packet headers untouched */
@@ -834,7 +832,7 @@ VOID USBPcapAnalyzeURB(PIRP pIrp, PURB pUrb, BOOLEAN post,
              */
             if (transfer->TransferBufferLength != 0)
             {
-                transferBuffer =
+                PUCHAR transferBuffer =
                         USBPcapURBGetBufferPointer(transfer->TransferBufferLength,
                                                    transfer->TransferBuffer,
                                                    transfer->TransferBufferMDL);
@@ -863,39 +861,35 @@ VOID USBPcapAnalyzeURB(PIRP pIrp, PURB pUrb, BOOLEAN post,
                     /* Compact the data to minimize the capture size */
                     packetHeader->header.dataLength = (UINT32)compactedLength;
 
-                    /* Allocate a buffer for the compacted results */
-                    /* The original data must remain untouched */
-                    compactedBuffer = ExAllocatePoolWithTag(NonPagedPool,
-                        (SIZE_T)compactedLength,
-                            'COSI');
-
-                    if (compactedBuffer == NULL)
+                    /* Allocate array of payload entries that will point to original data */
+                    compactedPayloadEntries = ExAllocatePoolWithTag(NonPagedPool,
+                        (SIZE_T)(transfer->NumberOfPackets + 1) * sizeof(USBPCAP_PAYLOAD_ENTRY),
+                        'COSI');
+                    if (compactedPayloadEntries == NULL)
                     {
                         DkDbgStr("Insufficient resources for isochronous transfer");
                         ExFreePool((PVOID)packetHeader);
                         break;
                     }
 
-                    /* Loop through all the isoch packets in the transfer buffer */
-                    /* Copy data from transfer buffer to compacted buffer, removing empty gaps */
+                    /* Loop through all the isoch packets in the transfer buffer
+                     * Store offset and length in payload entries array in a way
+                     * that there won't be gaps in the resulting packet.
+                     */
                     compactedOffset = 0;
                     for (i = 0; i < transfer->NumberOfPackets; i++)
                     {
-                        /* Copy the packet header, adjusting the offsets */
+                        /* Adjust the offsets */
                         packetHeader->packet[i].offset = compactedOffset;
                         packetHeader->packet[i].length = transfer->IsoPacket[i].Length;
                         packetHeader->packet[i].status = transfer->IsoPacket[i].Status;
 
-                        if (transfer->IsoPacket[i].Length > 0)
-                        {
-                            RtlCopyMemory((PVOID)(compactedBuffer + compactedOffset),
-                                (PVOID)((PUCHAR)transferBuffer + transfer->IsoPacket[i].Offset),
-                                transfer->IsoPacket[i].Length);
-                            compactedOffset += transfer->IsoPacket[i].Length;
-                        }
+                        compactedPayloadEntries[i].size = transfer->IsoPacket[i].Length;
+                        compactedPayloadEntries[i].buffer = &transferBuffer[transfer->IsoPacket[i].Offset];
+                        compactedOffset += transfer->IsoPacket[i].Length;
                     }
-
-                    captureBuffer = compactedBuffer;
+                    compactedPayloadEntries[i].size = 0;
+                    compactedPayloadEntries[i].buffer = NULL;
                 }
                 else if (((transfer->TransferFlags & USBD_TRANSFER_DIRECTION_IN) == USBD_TRANSFER_DIRECTION_OUT) && (post == FALSE))
                 {
@@ -912,12 +906,20 @@ VOID USBPcapAnalyzeURB(PIRP pIrp, PURB pUrb, BOOLEAN post,
             packetHeader->numberOfPackets = transfer->NumberOfPackets;
             packetHeader->errorCount      = transfer->ErrorCount;
 
-            USBPcapBufferWritePacket(pDeviceData->pRootData,
-                                     (PUSBPCAP_BUFFER_PACKET_HEADER)packetHeader,
-                                     captureBuffer);
+            if (compactedPayloadEntries)
+            {
+                USBPcapBufferWritePayload(pDeviceData->pRootData,
+                                          (PUSBPCAP_BUFFER_PACKET_HEADER)packetHeader,
+                                          compactedPayloadEntries);
+                ExFreePool((PVOID)compactedPayloadEntries);
+            }
+            else
+            {
+                USBPcapBufferWritePacket(pDeviceData->pRootData,
+                                         (PUSBPCAP_BUFFER_PACKET_HEADER)packetHeader,
+                                         captureBuffer);
+            }
 
-            if (compactedBuffer)
-                ExFreePool((PVOID)compactedBuffer);
             ExFreePool((PVOID)packetHeader);
             break;
         }