OcAppleKernelLib: Added `PatchAppleRtcChecksum` kernel quirk

Changelog.md

@@ -13,6 +13,7 @@ OpenCore Changelog
 - Added mouse drivers to the package as OVMF needs one
 - Added memory region reservation support
 - Added RtcRw tool to manipulate RTC memory
+- Added `PatchAppleRtcChecksum` kernel quirk
 
 #### v0.5.7
 - Added TimeMachine detection to picker

Docs/Configuration.tex

@@ -1975,6 +1975,21 @@ blocking.
   ACPI table and disabling VT-d in firmware preferences, which does not break
   VT-d support in other systems in case they need it.
 
+\item
+  \texttt{DisableRtcChecksum}\\
+  \textbf{Type}: \texttt{plist\ boolean}\\
+  \textbf{Failsafe}: \texttt{false}\\
+  \textbf{Description}: Disables primary checksum (\texttt{0x58}-\texttt{0x59})
+  writing in AppleRTC.
+
+  \emph{Note 1}: This option will not protect other areas from being overwritten,
+  see \href{https://github.com/acidanthera/RTCMemoryFixup}{RTCMemoryFixup}
+  kernel extension if this is desired.
+
+  \emph{Note 2}: This option will not protect areas from being overwritten
+  at firmware stage (e.g. macOS bootloader), see \texttt{RTC} (FIXME) section
+  if this is desired.
+
 \item
   \texttt{DummyPowerManagement}\\
   \textbf{Type}: \texttt{plist\ boolean}\\

Docs/Differences/Differences.tex

 \documentclass[]{article}
 %DIF LATEXDIFF DIFFERENCE FILE
 %DIF DEL PreviousConfiguration.tex   Tue Apr  7 19:32:13 2020
-%DIF ADD ../Configuration.tex        Sat Apr 18 13:12:30 2020
+%DIF ADD ../Configuration.tex        Sat Apr 18 15:39:07 2020
 
 \usepackage{lmodern}
 \usepackage{amssymb,amsmath}
@@ -2037,7 +2037,25 @@ blocking.
   VT-d support in other systems in case they need it.
 
 \item
-  \texttt{DummyPowerManagement}\\
+  \DIFaddbegin \texttt{\DIFadd{DisableRtcChecksum}}\\
+  \textbf{\DIFadd{Type}}\DIFadd{: }\texttt{\DIFadd{plist\ boolean}}\\
+  \textbf{\DIFadd{Failsafe}}\DIFadd{: }\texttt{\DIFadd{false}}\\
+  \textbf{\DIFadd{Description}}\DIFadd{: Disables primary checksum (}\texttt{\DIFadd{0x58}}\DIFadd{-}\texttt{\DIFadd{0x59}}\DIFadd{)
+  writing in AppleRTC.
+}
+
+  \emph{\DIFadd{Note 1}}\DIFadd{: This option will not protect other areas from being overwritten,
+  see }\href{https://github.com/acidanthera/RTCMemoryFixup}{RTCMemoryFixup}
+  \DIFadd{kernel extension if this is desired.
+}
+
+  \emph{\DIFadd{Note 2}}\DIFadd{: This option will not protect areas from being overwritten
+  at firmware stage (e.g. macOS bootloader), see }\texttt{\DIFadd{RTC}} \DIFadd{(FIXME) section
+  if this is desired.
+}
+
+\item
+  \DIFaddend \texttt{DummyPowerManagement}\\
   \textbf{Type}: \texttt{plist\ boolean}\\
   \textbf{Failsafe}: \texttt{false}\\
   \textbf{Description}: Disables \texttt{AppleIntelCpuPowerManagement}.

Docs/Sample.plist

@@ -462,34 +462,6 @@
 				<key>Skip</key>
 				<integer>0</integer>
 			</dict>
-			<dict>
-				<key>Base</key>
-				<string>__ZN8AppleRTC14updateChecksumEv</string>
-				<key>Comment</key>
-				<string>Disable RTC checksum update on poweroff</string>
-				<key>Count</key>
-				<integer>1</integer>
-				<key>Enabled</key>
-				<false/>
-				<key>Find</key>
-				<data></data>
-				<key>Identifier</key>
-				<string>com.apple.driver.AppleRTC</string>
-				<key>Limit</key>
-				<integer>0</integer>
-				<key>Mask</key>
-				<data></data>
-				<key>MaxKernel</key>
-				<string></string>
-				<key>MinKernel</key>
-				<string></string>
-				<key>Replace</key>
-				<data>ww==</data>
-				<key>ReplaceMask</key>
-				<data></data>
-				<key>Skip</key>
-				<integer>0</integer>
-			</dict>
 			<dict>
 				<key>Base</key>
 				<string>_AcpiOsVprintf</string>
@@ -561,6 +533,8 @@
 			<false/>
 			<key>DisableIoMapper</key>
 			<false/>
+			<key>DisableRtcChecksum</key>
+			<false/>
 			<key>DummyPowerManagement</key>
 			<false/>
 			<key>ExternalDiskIcons</key>

Docs/SampleFull.plist

@@ -462,34 +462,6 @@
 				<key>Skip</key>
 				<integer>0</integer>
 			</dict>
-			<dict>
-				<key>Base</key>
-				<string>__ZN8AppleRTC14updateChecksumEv</string>
-				<key>Comment</key>
-				<string>Disable RTC checksum update on poweroff</string>
-				<key>Count</key>
-				<integer>1</integer>
-				<key>Enabled</key>
-				<false/>
-				<key>Find</key>
-				<data></data>
-				<key>Identifier</key>
-				<string>com.apple.driver.AppleRTC</string>
-				<key>Limit</key>
-				<integer>0</integer>
-				<key>Mask</key>
-				<data></data>
-				<key>MaxKernel</key>
-				<string></string>
-				<key>MinKernel</key>
-				<string></string>
-				<key>Replace</key>
-				<data>ww==</data>
-				<key>ReplaceMask</key>
-				<data></data>
-				<key>Skip</key>
-				<integer>0</integer>
-			</dict>
 			<dict>
 				<key>Base</key>
 				<string>_AcpiOsVprintf</string>
@@ -561,6 +533,8 @@
 			<false/>
 			<key>DisableIoMapper</key>
 			<false/>
+			<key>DisableRtcChecksum</key>
+			<false/>
 			<key>DummyPowerManagement</key>
 			<false/>
 			<key>ExternalDiskIcons</key>

Include/Library/OcAppleKernelLib.h

@@ -586,4 +586,16 @@ PatchPowerStateTimeout (
   IN OUT PATCHER_CONTEXT   *Patcher
   );
 
+/**
+  Disable AppleRTC checksum writing.
+
+  @param Patcher  Patcher context.
+
+  @return  RETURN_SUCCESS on success.
+**/
+EFI_STATUS
+PatchAppleRtcChecksum (
+  IN OUT PRELINKED_CONTEXT  *Context
+  );
+
 #endif // OC_APPLE_KERNEL_LIB_H

Include/Library/OcConfigurationLib.h

@@ -243,6 +243,7 @@
   _(BOOLEAN                     , AppleXcpmForceBoost         ,     , FALSE  , ()) \
   _(BOOLEAN                     , CustomSmbiosGuid            ,     , FALSE  , ()) \
   _(BOOLEAN                     , DisableIoMapper             ,     , FALSE  , ()) \
+  _(BOOLEAN                     , DisableRtcChecksum          ,     , FALSE  , ()) \
   _(BOOLEAN                     , DummyPowerManagement        ,     , FALSE  , ()) \
   _(BOOLEAN                     , ExternalDiskIcons           ,     , FALSE  , ()) \
   _(BOOLEAN                     , IncreasePciBarSize          ,     , FALSE  , ()) \

Library/OcAppleKernelLib/CommonPatches.c

@@ -1484,3 +1484,72 @@ PatchPowerStateTimeout (
 
   return Status;
 }
+
+//
+// There currently are 2 places main RTC checksum is calculated in AppleRTC.kext
+// __ZN8AppleRTC14updateChecksumEv and __ZN8AppleRTC19rtcRecordTracePointEjjj.
+// Since we do not want to completely break RTC and/or saving tracepoints to RTC
+// we patch-out __ZN8AppleRTC8rtcWriteEjh call arguments (0x58 and 0x59) with
+// invalid (out of range) value 0xFFFF in 4 places.
+//
+
+STATIC
+UINT8
+mAppleRtcChecksumPatchFind[] = {
+  0xBE, 0x58, 0x00, 0x00, 0x00
+};
+
+STATIC
+UINT8
+mAppleRtcChecksumPatchMask[] = {
+  0xFF, 0xFE, 0xFF, 0xFF, 0xFF
+};
+
+STATIC
+UINT8
+mAppleRtcChecksumPatchReplace[] = {
+  0xBE, 0xFF, 0xFF, 0x00, 0x00
+};
+
+STATIC
+PATCHER_GENERIC_PATCH
+mAppleRtcChecksumPatch = {
+  .Comment     = DEBUG_POINTER ("DisableRtcChecksum"),
+  .Base        = NULL,
+  .Find        = mAppleRtcChecksumPatchFind,
+  .Mask        = mAppleRtcChecksumPatchMask,
+  .Replace     = mAppleRtcChecksumPatchReplace,
+  .ReplaceMask = NULL,
+  .Size        = sizeof (mAppleRtcChecksumPatchFind),
+  .Count       = 4,
+  .Skip        = 0,
+  .Limit       = 0
+};
+
+EFI_STATUS
+PatchAppleRtcChecksum (
+  IN OUT PRELINKED_CONTEXT  *Context
+  )
+{
+  RETURN_STATUS       Status;
+  PATCHER_CONTEXT     Patcher;
+
+  Status = PatcherInitContextFromPrelinked (
+    &Patcher,
+    Context,
+    "com.apple.driver.AppleRTC"
+    );
+
+  if (!EFI_ERROR (Status)) {
+    Status = PatcherApplyGenericPatch (&Patcher, &mAppleRtcChecksumPatch);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_INFO, "OCAK: Failed to apply patch com.apple.driver.AppleRTC DisableRtcChecksum - %r\n", Status));
+    } else {
+      DEBUG ((DEBUG_INFO, "OCAK: Patch success com.apple.driver.AppleRTC DisableRtcChecksum\n"));
+    }
+  } else {
+    DEBUG ((DEBUG_INFO, "OCAK: Failed to find com.apple.driver.AppleRTC for DisableRtcChecksum - %r\n", Status));
+  }
+
+  return Status;
+}

Library/OcConfigurationLib/OcConfigurationLib.c

@@ -293,6 +293,7 @@ mKernelQuirksSchema[] = {
   OC_SCHEMA_BOOLEAN_IN ("AppleXcpmForceBoost",     OC_GLOBAL_CONFIG, Kernel.Quirks.AppleXcpmForceBoost),
   OC_SCHEMA_BOOLEAN_IN ("CustomSMBIOSGuid",        OC_GLOBAL_CONFIG, Kernel.Quirks.CustomSmbiosGuid),
   OC_SCHEMA_BOOLEAN_IN ("DisableIoMapper",         OC_GLOBAL_CONFIG, Kernel.Quirks.DisableIoMapper),
+  OC_SCHEMA_BOOLEAN_IN ("DisableRtcChecksum",      OC_GLOBAL_CONFIG, Kernel.Quirks.DisableRtcChecksum),
   OC_SCHEMA_BOOLEAN_IN ("DummyPowerManagement",    OC_GLOBAL_CONFIG, Kernel.Quirks.DummyPowerManagement),
   OC_SCHEMA_BOOLEAN_IN ("ExternalDiskIcons",       OC_GLOBAL_CONFIG, Kernel.Quirks.ExternalDiskIcons),
   OC_SCHEMA_BOOLEAN_IN ("IncreasePciBarSize",      OC_GLOBAL_CONFIG, Kernel.Quirks.IncreasePciBarSize),

Platform/OpenCore/OpenCoreKernel.c

@@ -457,6 +457,10 @@ OcKernelApplyPatches (
       PatchAppleIoMapperSupport (Context);
     }
 
+    if (Config->Kernel.Quirks.DisableRtcChecksum) {
+      PatchAppleRtcChecksum (Context);
+    }
+
     if (Config->Kernel.Quirks.IncreasePciBarSize) {
       PatchIncreasePciBarSize (Context);     
     }