From: Laszlo Ersek <lersek@redhat.com>
Date: Tue, 3 Mar 2015 08:13:40 +0000 (+0000)
Subject: OvmfPkg: replace strict XenHypercallLib construction with explicit query
X-Git-Tag: edk2-stable201903~10184
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=48b3ff047929aa5bd4f94128c9a3ac04d6b3b31b

OvmfPkg: replace strict XenHypercallLib construction with explicit query

XenHypercallLib has two clients at the moment: XenBusDxe and
XenConsoleSerialPortLib. Currently, when XenBusDxe starts on a non-Xen X86
platform (ie. as part of OVMF not running on Xen), the X86XenHypercallLib
instance built into it fails to initialize, which triggers an ASSERT() in
auto-generated code.

Instead, let's call XenHypercallIsAvailable() in the driver's entry point,
and exit cleanly when the driver is started on a non-Xen platform.

Modify the constructor of XenConsoleSerialPortLib similarly; we shouldn't
proceed if Xen is not available. In practice this check should never fail,
because XenConsoleSerialPortLib is only used on ARM, and
ArmXenHypercallLib is always available; but nonetheless we should be
pedantic.

Reported-by: Gabriel L. Somlo <gsomlo@gmail.com>
Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17001 6f19259b-4bc3-4df7-8a09-765794883524
---

diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
index 98022354cf..467cb27a30 100644
--- a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
+++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c
@@ -40,6 +40,10 @@ SerialPortInitialize (
   VOID
   )
 {
+  if (! XenHypercallIsAvailable ()) {
+    return RETURN_NOT_FOUND;
+  }
+
   if (!mXenConsoleInterface) {
     mXenConsoleEventChain.port = (UINT32)XenHypercallHvmGetParam (HVM_PARAM_CONSOLE_EVTCHN);
     mXenConsoleInterface = (struct xencons_interface *)(UINTN)
diff --git a/OvmfPkg/Library/XenHypercallLib/X86XenHypercall.c b/OvmfPkg/Library/XenHypercallLib/X86XenHypercall.c
index 67892bcf37..7cb7f46c9b 100644
--- a/OvmfPkg/Library/XenHypercallLib/X86XenHypercall.c
+++ b/OvmfPkg/Library/XenHypercallLib/X86XenHypercall.c
@@ -65,7 +65,13 @@ XenHypercallLibInit (
 
   GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
   if (GuidHob == NULL) {
-    return RETURN_NOT_FOUND;
+    //
+    // We don't fail library construction, since that has catastrophic
+    // consequences for client modules (whereas those modules may easily be
+    // running on a non-Xen platform). Instead, XenHypercallIsAvailable() above
+    // will return FALSE.
+    //
+    return RETURN_SUCCESS;
   }
   XenInfo = (EFI_XEN_INFO *) GET_GUID_HOB_DATA (GuidHob);
   HyperPage = XenInfo->HyperPages;
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.c b/OvmfPkg/XenBusDxe/XenBusDxe.c
index 2c4a08673c..439b060ddc 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.c
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.c
@@ -165,6 +165,7 @@ XenBusDxeUnload (
   @param  SystemTable           A pointer to the EFI System Table.
 
   @retval EFI_SUCCESS           The operation completed successfully.
+  @retval EFI_ABORTED           Xen hypercalls are not available.
   @retval Others                An unexpected error occurred.
 **/
 EFI_STATUS
@@ -176,6 +177,10 @@ XenBusDxeDriverEntryPoint (
 {
   EFI_STATUS  Status;
 
+  if (! XenHypercallIsAvailable ()) {
+    return EFI_ABORTED;
+  }
+
   //
   // Install UEFI Driver Model protocol(s).
   //