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| author | Laszlo Ersek <lersek@redhat.com> | 2019-09-07 00:19:29 +0200 |
|---|---|---|
| committer | Laszlo Ersek <lersek@redhat.com> | 2019-10-09 09:40:10 +0200 |
| commit | 7eb6160d4fdff25ca623a4006e6f93e5e81038bf (patch) | |
| tree | f104aa10b980c09e8adbc94e92dc553cc3585edd | |
| parent | d5e35fddec9389b50b362c84eda6b47975b99fa0 (diff) | |
| download | edk2-7eb6160d4fdff25ca623a4006e6f93e5e81038bf.tar.gz edk2-7eb6160d4fdff25ca623a4006e6f93e5e81038bf.tar.bz2 edk2-7eb6160d4fdff25ca623a4006e6f93e5e81038bf.zip | |
ShellPkg/UefiShellLib: clarify workaround for unfixable EdkShell bug
The EDK 1 Shell (available at <https://github.com/tianocore/edk-Shell>)
has a bug in its EFI_SHELL_ENVIRONMENT2.Execute() implementation that
edk2's UefiShellLib has no choice but to work around.
Improve the explanation in the code. Also, document the implicit
EFI_HANDLE -> (EFI_HANDLE*) conversion, which happens implicitly after
dereferencing ParentHandle, with an explicit cast.
In practice, this patch is a no-op.
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
| -rw-r--r-- | ShellPkg/Library/UefiShellLib/UefiShellLib.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/ShellPkg/Library/UefiShellLib/UefiShellLib.c b/ShellPkg/Library/UefiShellLib/UefiShellLib.c index 835d0f88ca..9f07a58eb2 100644 --- a/ShellPkg/Library/UefiShellLib/UefiShellLib.c +++ b/ShellPkg/Library/UefiShellLib/UefiShellLib.c @@ -1291,9 +1291,27 @@ ShellExecute ( if (mEfiShellEnvironment2 != NULL) {
//
// Call EFI Shell version.
- // Due to oddity in the EFI shell we want to dereference the ParentHandle here
//
- CmdStatus = (mEfiShellEnvironment2->Execute(*ParentHandle,
+ // Due to an unfixable bug in the EdkShell implementation, we must
+ // dereference "ParentHandle" here:
+ //
+ // 1. The EFI shell installs the EFI_SHELL_ENVIRONMENT2 protocol,
+ // identified by gEfiShellEnvironment2Guid.
+ // 2. The Execute() member function takes "ParentImageHandle" as first
+ // parameter, with type (EFI_HANDLE*).
+ // 3. In the EdkShell implementation, SEnvExecute() implements the
+ // Execute() member function. It passes "ParentImageHandle" correctly to
+ // SEnvDoExecute().
+ // 4. SEnvDoExecute() takes the (EFI_HANDLE*), and passes it directly --
+ // without de-referencing -- to the HandleProtocol() boot service.
+ // 5. But HandleProtocol() takes an EFI_HANDLE.
+ //
+ // Therefore we must
+ // - de-reference "ParentHandle" here, to mask the bug in
+ // SEnvDoExecute(), and
+ // - pass the resultant EFI_HANDLE as an (EFI_HANDLE*).
+ //
+ CmdStatus = (mEfiShellEnvironment2->Execute((EFI_HANDLE *)*ParentHandle,
CommandLine,
Output));
//
|