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ShellPkg/Shell: clean up bogus member types in SPLIT_LIST 

The "SPLIT_LIST.SplitStdOut" and "SPLIT_LIST.SplitStdIn" members currently
have type (SHELL_FILE_HANDLE *). This is wrong; SHELL_FILE_HANDLE is
already a pointer, there's no need to store a pointer to a pointer.

The error is obvious if we check where and how these members are used:

- In the RunSplitCommand() function, these members are used (populated)
  extensively; this function has to be updated in sync.

  ConvertEfiFileProtocolToShellHandle() already returns the temporary
  memory file created with CreateFileInterfaceMem() as SHELL_FILE_HANDLE,
  not as (SHELL_FILE_HANDLE *).

- In particular, the ConvertShellHandleToEfiFileProtocol() calls need to
  be dropped as well in RunSplitCommand(), since
  EFI_SHELL_PROTOCOL.SetFilePosition() and EFI_SHELL_PROTOCOL.CloseFile()
  take SHELL_FILE_HANDLE parameters, not (EFI_FILE_PROTOCOL *).

  Given that ConvertShellHandleToEfiFileProtocol() only performs a
  type-cast (it does not adjust any pointer values), *and*
  SHELL_FILE_HANDLE -- taken by EFI_SHELL_PROTOCOL member functions -- is
  actually a typedef to (VOID *) -- see more on this later --, this
  conversion error hasn't been caught by compilers.

- In the ProcessNewSplitCommandLine() function, RunSplitCommand() is
  called either initially (passing in NULL / NULL; no update needed), or
  recursively (passing in Split->SplitStdIn / Split->SplitStdOut; again no
  update is necessary beyond the RunSplitCommand() modification above).

- In the UpdateStdInStdOutStdErr() and RestoreStdInStdOutStdErr()
  functions, said structure members are compared and assigned to
  "EFI_SHELL_PARAMETERS_PROTOCOL.StdIn" and
  "EFI_SHELL_PARAMETERS_PROTOCOL.StdOut", both of which have type
  SHELL_FILE_HANDLE, *not* (SHELL_FILE_HANDLE *).

  The compiler hasn't caught this error because of the fatally flawed type
  definition of SHELL_FILE_HANDLE, namely

    typedef VOID *SHELL_FILE_HANDLE;

  Pointer-to-void silently converts to and from most other pointer types;
  among them, pointer-to-pointer-to-void. That is also why no update is
  necessary for UpdateStdInStdOutStdErr() and RestoreStdInStdOutStdErr()
  in this fix.

(

Generally speaking, using (VOID *) typedefs for opaque handles is a tragic
mistake in all of the UEFI-related specifications; this practice defeats
any type checking that compilers might help programmers with. The right
way to define an opaque handle is as follows:

  //
  // Introduce the incomplete structure type, and the derived pointer
  // type, in both the specification and the public edk2 headers. Note
  // that the derived pointer type itself is a complete type, and it can
  // be used freely by client code.
  //
  typedef struct SHELL_FILE *SHELL_FILE_HANDLE;

  //
  // Complete the structure type in the edk2 internal C source files.
  //
  struct SHELL_FILE {
    //
    // list fields
    //
  };

This way the structure size and members remain hidden from client code,
but the C compiler can nonetheless catch any invalid conversions between
incompatible XXX_HANDLE types.

)

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Marvin Häuser <Marvin.Haeuser@outlook.com>
Cc: Qiu Shumin <shumin.qiu@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
This commit is contained in:
Laszlo Ersek 2017-04-25 14:03:32 +02:00
parent 6bbd4a8f5f
commit 1bd0bf153e
2 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
ShellPkg/Application/Shell/Shell.c
View File

@ -1714,8 +1714,8 @@ ShellConvertVariables (
EFI_STATUS
RunSplitCommand(
IN CONST CHAR16 *CmdLine,
IN SHELL_FILE_HANDLE *StdIn,
IN SHELL_FILE_HANDLE *StdOut
IN SHELL_FILE_HANDLE StdIn,
IN SHELL_FILE_HANDLE StdOut
)
{
EFI_STATUS Status;
@ -1724,7 +1724,7 @@ RunSplitCommand(
UINTN Size1;
UINTN Size2;
SPLIT_LIST *Split;
SHELL_FILE_HANDLE *TempFileHandle;
SHELL_FILE_HANDLE TempFileHandle;
BOOLEAN Unicode;
ASSERT(StdOut == NULL);
@ -1790,7 +1790,7 @@ RunSplitCommand(
Split->SplitStdOut = Split->SplitStdIn;
}
Split->SplitStdIn = TempFileHandle;
ShellInfoObject.NewEfiShellProtocol->SetFilePosition(ConvertShellHandleToEfiFileProtocol(Split->SplitStdIn), 0);
ShellInfoObject.NewEfiShellProtocol->SetFilePosition (Split->SplitStdIn, 0);
if (!EFI_ERROR(Status)) {
Status = RunCommand(NextCommandLine);
@ -1806,10 +1806,10 @@ RunSplitCommand(
// Note that the original StdIn is now the StdOut...
//
if (Split->SplitStdOut != NULL) {
ShellInfoObject.NewEfiShellProtocol->CloseFile(ConvertShellHandleToEfiFileProtocol(Split->SplitStdOut));
ShellInfoObject.NewEfiShellProtocol->CloseFile (Split->SplitStdOut);
}
if (Split->SplitStdIn != NULL) {
ShellInfoObject.NewEfiShellProtocol->CloseFile(ConvertShellHandleToEfiFileProtocol(Split->SplitStdIn));
ShellInfoObject.NewEfiShellProtocol->CloseFile (Split->SplitStdIn);
FreePool (Split->SplitStdIn);
}

4
ShellPkg/Application/Shell/Shell.h
View File

@ -63,8 +63,8 @@ extern CONST CHAR16 mNoNestingFalse[];
typedef struct {
LIST_ENTRY Link; ///< Standard linked list handler.
SHELL_FILE_HANDLE *SplitStdOut; ///< ConsoleOut for use in the split.
SHELL_FILE_HANDLE *SplitStdIn; ///< ConsoleIn for use in the split.
SHELL_FILE_HANDLE SplitStdOut; ///< ConsoleOut for use in the split.
SHELL_FILE_HANDLE SplitStdIn; ///< ConsoleIn for use in the split.
} SPLIT_LIST;
typedef struct {