From 9965cbd424f22b35e7743c2f59ab3ee1db15142a Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Wed, 8 Feb 2017 21:53:02 +0100 Subject: OvmfPkg/AcpiPlatformDxe: implement the QEMU_LOADER_WRITE_POINTER command The QEMU_LOADER_WRITE_POINTER command instructs the firmware to write the address of a field within a previously allocated/downloaded fw_cfg blob into another (writeable) fw_cfg file at a specific offset. Put differently, QEMU_LOADER_WRITE_POINTER propagates, to QEMU, the address that QEMU_LOADER_ALLOCATE placed the designated fw_cfg blob at, as adjusted for the given field inside the allocated blob. The implementation is similar to that of QEMU_LOADER_ADD_POINTER. Since here we "patch" a pointer object in "fw_cfg file space", not guest memory space, we utilize the QemuFwCfgSkipBytes() and QemuFwCfgWriteBytes() APIs completed in commit range 465663e9f128..7fcb73541299. An interesting aspect is that QEMU_LOADER_WRITE_POINTER creates a host-level reference to a guest memory location. Therefore, if we fail to process the linker/loader script for any reason, we have to clear out those references first, before we release the guest memory allocations in response to the error. Cc: Jordan Justen Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=359 Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek Reviewed-by: Jordan Justen --- OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c | 171 +++++++++++++++++++++++++++++++- 1 file changed, 168 insertions(+), 3 deletions(-) (limited to 'OvmfPkg/AcpiPlatformDxe') diff --git a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c index 404589cad0..de827c2df2 100644 --- a/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c +++ b/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c @@ -352,6 +352,143 @@ ProcessCmdAddChecksum ( } +/** + Process a QEMU_LOADER_WRITE_POINTER command. + + @param[in] WritePointer The QEMU_LOADER_WRITE_POINTER command to process. + + @param[in] Tracker The ORDERED_COLLECTION tracking the BLOB user + structures created thus far. + + @retval EFI_PROTOCOL_ERROR Malformed fw_cfg file name(s) have been found in + WritePointer. Or, the WritePointer command + references a file unknown to Tracker or the + fw_cfg directory. Or, the pointer object to + rewrite has invalid location, size, or initial + relative value. Or, the pointer value to store + does not fit in the given pointer size. + + @retval EFI_SUCCESS The pointer object inside the writeable fw_cfg + file has been written. +**/ +STATIC +EFI_STATUS +ProcessCmdWritePointer ( + IN CONST QEMU_LOADER_WRITE_POINTER *WritePointer, + IN CONST ORDERED_COLLECTION *Tracker + ) +{ + RETURN_STATUS Status; + FIRMWARE_CONFIG_ITEM PointerItem; + UINTN PointerItemSize; + ORDERED_COLLECTION_ENTRY *PointeeEntry; + BLOB *PointeeBlob; + UINT64 PointerValue; + + if (WritePointer->PointerFile[QEMU_LOADER_FNAME_SIZE - 1] != '\0' || + WritePointer->PointeeFile[QEMU_LOADER_FNAME_SIZE - 1] != '\0') { + DEBUG ((DEBUG_ERROR, "%a: malformed file name\n", __FUNCTION__)); + return EFI_PROTOCOL_ERROR; + } + + Status = QemuFwCfgFindFile ((CONST CHAR8 *)WritePointer->PointerFile, + &PointerItem, &PointerItemSize); + PointeeEntry = OrderedCollectionFind (Tracker, WritePointer->PointeeFile); + if (RETURN_ERROR (Status) || PointeeEntry == NULL) { + DEBUG ((DEBUG_ERROR, + "%a: invalid fw_cfg file or blob reference \"%a\" / \"%a\"\n", + __FUNCTION__, WritePointer->PointerFile, WritePointer->PointeeFile)); + return EFI_PROTOCOL_ERROR; + } + + if ((WritePointer->PointerSize != 1 && WritePointer->PointerSize != 2 && + WritePointer->PointerSize != 4 && WritePointer->PointerSize != 8) || + (PointerItemSize < WritePointer->PointerSize) || + (PointerItemSize - WritePointer->PointerSize < + WritePointer->PointerOffset)) { + DEBUG ((DEBUG_ERROR, "%a: invalid pointer location or size in \"%a\"\n", + __FUNCTION__, WritePointer->PointerFile)); + return EFI_PROTOCOL_ERROR; + } + + PointeeBlob = OrderedCollectionUserStruct (PointeeEntry); + PointerValue = WritePointer->PointeeOffset; + if (PointerValue >= PointeeBlob->Size) { + DEBUG ((DEBUG_ERROR, "%a: invalid PointeeOffset\n", __FUNCTION__)); + return EFI_PROTOCOL_ERROR; + } + + // + // The memory allocation system ensures that the address of the byte past the + // last byte of any allocated object is expressible (no wraparound). + // + ASSERT ((UINTN)PointeeBlob->Base <= MAX_ADDRESS - PointeeBlob->Size); + + PointerValue += (UINT64)(UINTN)PointeeBlob->Base; + if (RShiftU64 ( + RShiftU64 (PointerValue, WritePointer->PointerSize * 8 - 1), 1) != 0) { + DEBUG ((DEBUG_ERROR, "%a: pointer value unrepresentable in \"%a\"\n", + __FUNCTION__, WritePointer->PointerFile)); + return EFI_PROTOCOL_ERROR; + } + + QemuFwCfgSelectItem (PointerItem); + QemuFwCfgSkipBytes (WritePointer->PointerOffset); + QemuFwCfgWriteBytes (WritePointer->PointerSize, &PointerValue); + + // + // Because QEMU has now learned PointeeBlob->Base, we must mark PointeeBlob + // as unreleasable, for the case when the whole linker/loader script is + // handled successfully. + // + PointeeBlob->HostsOnlyTableData = FALSE; + + DEBUG ((DEBUG_VERBOSE, "%a: PointerFile=\"%a\" PointeeFile=\"%a\" " + "PointerOffset=0x%x PointeeOffset=0x%x PointerSize=%d\n", __FUNCTION__, + WritePointer->PointerFile, WritePointer->PointeeFile, + WritePointer->PointerOffset, WritePointer->PointeeOffset, + WritePointer->PointerSize)); + return EFI_SUCCESS; +} + + +/** + Undo a QEMU_LOADER_WRITE_POINTER command. + + This function revokes (zeroes out) a guest memory reference communicated to + QEMU earlier. The caller is responsible for invoking this function only on + such QEMU_LOADER_WRITE_POINTER commands that have been successfully processed + by ProcessCmdWritePointer(). + + @param[in] WritePointer The QEMU_LOADER_WRITE_POINTER command to undo. +**/ +STATIC +VOID +UndoCmdWritePointer ( + IN CONST QEMU_LOADER_WRITE_POINTER *WritePointer + ) +{ + RETURN_STATUS Status; + FIRMWARE_CONFIG_ITEM PointerItem; + UINTN PointerItemSize; + UINT64 PointerValue; + + Status = QemuFwCfgFindFile ((CONST CHAR8 *)WritePointer->PointerFile, + &PointerItem, &PointerItemSize); + ASSERT_RETURN_ERROR (Status); + + PointerValue = 0; + QemuFwCfgSelectItem (PointerItem); + QemuFwCfgSkipBytes (WritePointer->PointerOffset); + QemuFwCfgWriteBytes (WritePointer->PointerSize, &PointerValue); + + DEBUG ((DEBUG_VERBOSE, + "%a: PointerFile=\"%a\" PointerOffset=0x%x PointerSize=%d\n", __FUNCTION__, + WritePointer->PointerFile, WritePointer->PointerOffset, + WritePointer->PointerSize)); +} + + // // We'll be saving the keys of installed tables so that we can roll them back // in case of failure. 128 tables should be enough for anyone (TM). @@ -561,6 +698,7 @@ InstallQemuFwCfgTables ( UINTN FwCfgSize; QEMU_LOADER_ENTRY *LoaderStart; CONST QEMU_LOADER_ENTRY *LoaderEntry, *LoaderEnd; + CONST QEMU_LOADER_ENTRY *WritePointerSubsetEnd; ORIGINAL_ATTRIBUTES *OriginalPciAttributes; UINTN OriginalPciAttributesCount; ORDERED_COLLECTION *Tracker; @@ -597,6 +735,11 @@ InstallQemuFwCfgTables ( // // first pass: process the commands // + // "WritePointerSubsetEnd" points one past the last successful + // QEMU_LOADER_WRITE_POINTER command. Now when we're about to start the first + // pass, no such command has been encountered yet. + // + WritePointerSubsetEnd = LoaderStart; for (LoaderEntry = LoaderStart; LoaderEntry < LoaderEnd; ++LoaderEntry) { switch (LoaderEntry->Type) { case QemuLoaderCmdAllocate: @@ -613,6 +756,14 @@ InstallQemuFwCfgTables ( Tracker); break; + case QemuLoaderCmdWritePointer: + Status = ProcessCmdWritePointer (&LoaderEntry->Command.WritePointer, + Tracker); + if (!EFI_ERROR (Status)) { + WritePointerSubsetEnd = LoaderEntry + 1; + } + break; + default: DEBUG ((EFI_D_VERBOSE, "%a: unknown loader command: 0x%x\n", __FUNCTION__, LoaderEntry->Type)); @@ -620,14 +771,14 @@ InstallQemuFwCfgTables ( } if (EFI_ERROR (Status)) { - goto FreeTracker; + goto RollbackWritePointersAndFreeTracker; } } InstalledKey = AllocatePool (INSTALLED_TABLES_MAX * sizeof *InstalledKey); if (InstalledKey == NULL) { Status = EFI_OUT_OF_RESOURCES; - goto FreeTracker; + goto RollbackWritePointersAndFreeTracker; } // @@ -658,7 +809,21 @@ InstallQemuFwCfgTables ( FreePool (InstalledKey); -FreeTracker: +RollbackWritePointersAndFreeTracker: + // + // In case of failure, revoke any allocation addresses that were communicated + // to QEMU previously, before we release all the blobs. + // + if (EFI_ERROR (Status)) { + LoaderEntry = WritePointerSubsetEnd; + while (LoaderEntry > LoaderStart) { + --LoaderEntry; + if (LoaderEntry->Type == QemuLoaderCmdWritePointer) { + UndoCmdWritePointer (&LoaderEntry->Command.WritePointer); + } + } + } + // // Tear down the tracker infrastructure. Each fw_cfg blob will be left in // place only if we're exiting with success and the blob hosts data that is -- cgit v1.2.3