OvmfPkg/VirtioFsDxe: implement EFI_FILE_PROTOCOL.Read() for regular files

Using the functions introduced previously, we can now implement
VirtioFsSimpleFileRead(); for regular files at first.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-34-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

diff --git a/OvmfPkg/VirtioFsDxe/SimpleFsRead.c b/OvmfPkg/VirtioFsDxe/SimpleFsRead.c
index e737d5e332042145da89a72a74092257d1a75677..c4ad07c9aec4ceaa8653f0357bccb46746859712 100644 (file)
--- a/OvmfPkg/VirtioFsDxe/SimpleFsRead.c
+++ b/OvmfPkg/VirtioFsDxe/SimpleFsRead.c
@@ -8,6 +8,69 @@
 \r
 #include "VirtioFsDxe.h"\r
 \r
 \r
 #include "VirtioFsDxe.h"\r
 \r

+/**\r
+  Read from a regular file.\r
+**/\r
+STATIC\r
+EFI_STATUS\r
+ReadRegularFile (\r
+  IN OUT VIRTIO_FS_FILE *VirtioFsFile,\r
+  IN OUT UINTN          *BufferSize,\r
+     OUT VOID           *Buffer\r
+  )\r
+{\r
+  VIRTIO_FS                          *VirtioFs;\r
+  EFI_STATUS                         Status;\r
+  VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE FuseAttr;\r
+  UINTN                              Transferred;\r
+  UINTN                              Left;\r
+\r
+  VirtioFs = VirtioFsFile->OwnerFs;\r
+  //\r
+  // The UEFI spec forbids reads that start beyond the end of the file.\r
+  //\r
+  Status = VirtioFsFuseGetAttr (VirtioFs, VirtioFsFile->NodeId, &FuseAttr);\r
+  if (EFI_ERROR (Status) || VirtioFsFile->FilePosition > FuseAttr.Size) {\r
+    return EFI_DEVICE_ERROR;\r
+  }\r
+\r
+  Status      = EFI_SUCCESS;\r
+  Transferred = 0;\r
+  Left        = *BufferSize;\r
+  while (Left > 0) {\r
+    UINT32 ReadSize;\r
+\r
+    //\r
+    // FUSE_READ cannot express a >=4GB buffer size.\r
+    //\r
+    ReadSize = (UINT32)MIN ((UINTN)MAX_UINT32, Left);\r
+    Status = VirtioFsFuseReadFileOrDir (\r
+               VirtioFs,\r
+               VirtioFsFile->NodeId,\r
+               VirtioFsFile->FuseHandle,\r
+               FALSE,                                    // IsDir\r
+               VirtioFsFile->FilePosition + Transferred,\r
+               &ReadSize,\r
+               (UINT8 *)Buffer + Transferred\r
+               );\r
+    if (EFI_ERROR (Status) || ReadSize == 0) {\r
+      break;\r
+    }\r
+    Transferred += ReadSize;\r
+    Left        -= ReadSize;\r
+  }\r
+\r
+  *BufferSize = Transferred;\r
+  VirtioFsFile->FilePosition += Transferred;\r
+  //\r
+  // If we managed to read some data, return success. If zero bytes were\r
+  // transferred due to zero-sized buffer on input or due to EOF on first read,\r
+  // return SUCCESS. Otherwise, return the error due to which zero bytes were\r
+  // transferred.\r
+  //\r
+  return (Transferred > 0) ? EFI_SUCCESS : Status;\r
+}\r
+\r

 EFI_STATUS\r
 EFIAPI\r
 VirtioFsSimpleFileRead (\r
 EFI_STATUS\r
 EFIAPI\r
 VirtioFsSimpleFileRead (\r


@@ -16,5 +79,15 @@ VirtioFsSimpleFileRead (
      OUT VOID              *Buffer\r
   )\r
 {\r
      OUT VOID              *Buffer\r
   )\r
 {\r

-  return EFI_NO_MEDIA;\r
+  VIRTIO_FS_FILE *VirtioFsFile;\r
+  EFI_STATUS     Status;\r
+\r
+  VirtioFsFile = VIRTIO_FS_FILE_FROM_SIMPLE_FILE (This);\r
+\r
+  if (VirtioFsFile->IsDirectory) {\r
+    Status = EFI_NO_MEDIA;\r
+  } else {\r
+    Status = ReadRegularFile (VirtioFsFile, BufferSize, Buffer);\r
+  }\r
+  return Status;\r

 }\r
 }\r