OcAfterBootCompatLib: Allow specification of max slide for unavailable range (#76)

Docs/Configuration.tex

@@ -1459,6 +1459,26 @@ To view their current state use \texttt{pmset -g} command in Terminal.
   slide values are usable!} message in the debug log. If the message is present,
   this option is to be enabled.
 
+\item
+  \texttt{ProvideMaxSlide}\\
+  \textbf{Type}: \texttt{plist\ integer}\\
+  \textbf{Failsafe}: \texttt{0}\\
+  \textbf{Description}: Provide maximum KASLR slide when higher ones are unavailable.
+
+  This option overrides the maximum slide instead of \texttt{TOTAL\_SLIDE\_NUM}
+  (256) when \texttt{ProvideCustomSlide} is enabled. It is believed that modern
+  firmwares allocate pool memory from top to bottom, effectively resulting in
+  free memory at the time of slide scanning being later used as temporary
+  memory during kernel loading. In case those memory are unavailable, this
+  option can stop evaluating higher slides.
+
+  \emph{Note}: The necessity of this quirk is determined by random boot failure
+  when \texttt{ProvideCustomSlide} is enabled and the randomized slide fall
+  into the unavailable range. When \texttt{AppleDebug} is enabled, usually the
+  debug log may contain messages like \texttt{AAPL: [EB|`LD:LKC] \} Err(0x9)}.
+  To find the optimal value, manually append \texttt{slide=X} to \texttt{boot-args}
+  and log the largest one that won't cause boot failure.
+
 \item
   \texttt{RebuildAppleMemoryMap}\\
   \textbf{Type}: \texttt{plist\ boolean}\\

Include/Acidanthera/Library/OcAfterBootCompatLib.h

@@ -36,6 +36,10 @@ typedef struct OC_ABC_SETTINGS_ {
   ///
   BOOLEAN  ProvideCustomSlide;
   ///
+  /// Provide max KASLR slide for firmwares with polluted higher memory ranges.
+  ///
+  UINT8    ProvideMaxSlide;
+  ///
   /// Remove runtime flag from MMIO areas and prevent virtual address assignment for known
   /// MMIO regions. This may improve the amount of slides available, but may not work on
   /// unknown configurations.

Include/Acidanthera/Library/OcConfigurationLib.h

@@ -124,6 +124,7 @@
   _(BOOLEAN                     , ProtectSecureBoot         ,     , FALSE  , ()) \
   _(BOOLEAN                     , ProtectUefiServices       ,     , FALSE  , ()) \
   _(BOOLEAN                     , ProvideCustomSlide        ,     , FALSE  , ()) \
+  _(UINT8                       , ProvideMaxSlide           ,     , 0      , ()) \
   _(BOOLEAN                     , RebuildAppleMemoryMap     ,     , FALSE  , ()) \
   _(BOOLEAN                     , SetupVirtualMap           ,     , FALSE  , ()) \
   _(BOOLEAN                     , SignalAppleOS             ,     , FALSE  , ()) \

Library/OcAfterBootCompatLib/BootCompatInternal.h

@@ -300,6 +300,10 @@ typedef struct SLIDE_SUPPORT_STATE_ {
   ///
   UINT32                   CsrActiveConfig;
   ///
+  /// Max slide value provided.
+  ///
+  UINT8                    ProvideMaxSlide;
+  ///
   /// Valid slides to choose from when using custom slide.
   ///
   UINT8                    ValidSlides[TOTAL_SLIDE_NUM];

Library/OcAfterBootCompatLib/CustomSlide.c

@@ -91,7 +91,7 @@ GenerateSlideValue (
 
   do {
     DivU64x32Remainder (GetPseudoRandomNumber64 (), SlideSupport->ValidSlideCount, &Slide);
-  } while (Slide == 0);
+  } while (SlideSupport->ValidSlides[Slide] == 0);
 
   return SlideSupport->ValidSlides[Slide];
 }
@@ -362,6 +362,14 @@ ShouldUseCustomSlideOffset (
       FallbackSlide    = (UINT8) Slide;
     }
 
+    //
+    // Stop evalutating slides after exceeding ProvideMaxSlide, may break when
+    // no slides are available.
+    //
+    if (SlideSupport->ProvideMaxSlide > 0 && Slide > SlideSupport->ProvideMaxSlide) {
+      break;
+    }
+
     if ((StartAddr + AvailableSize) != EndAddr) {
       //
       // The slide region is not continuous.
@@ -736,6 +744,8 @@ AppleSlideGetVariable (
      OUT VOID                  *Data
   )
 {
+  BootCompat->SlideSupport.ProvideMaxSlide =  BootCompat->Settings.ProvideMaxSlide;
+
   if (VariableName != NULL && VendorGuid != NULL && DataSize != NULL
     && CompareGuid (VendorGuid, &gAppleBootVariableGuid)) {
 

Library/OcAfterBootCompatLib/OcAfterBootCompatLib.c

@@ -124,10 +124,11 @@ OcAbcInitialize (
 
   DEBUG ((
     DEBUG_INFO,
-    "OCABC: FEXITBS %d PRMRG %d CSLIDE %d PRSRV %d RBMAP %d VMAP %d APPLOS %d RTPERMS %d\n",
+    "OCABC: FEXITBS %d PRMRG %d CSLIDE %d MSLIDE %d PRSRV %d RBMAP %d VMAP %d APPLOS %d RTPERMS %d\n",
     Settings->ForceExitBootServices,
     Settings->ProtectMemoryRegions,
     Settings->ProvideCustomSlide,
+    Settings->ProvideMaxSlide,
     Settings->ProtectUefiServices,
     Settings->RebuildAppleMemoryMap,
     Settings->SetupVirtualMap,

Library/OcConfigurationLib/OcConfigurationLib.c

@@ -179,6 +179,7 @@ mBooterQuirksSchema[] = {
   OC_SCHEMA_BOOLEAN_IN ("ProtectSecureBoot",      OC_GLOBAL_CONFIG, Booter.Quirks.ProtectSecureBoot),
   OC_SCHEMA_BOOLEAN_IN ("ProtectUefiServices",    OC_GLOBAL_CONFIG, Booter.Quirks.ProtectUefiServices),
   OC_SCHEMA_BOOLEAN_IN ("ProvideCustomSlide",     OC_GLOBAL_CONFIG, Booter.Quirks.ProvideCustomSlide),
+  OC_SCHEMA_INTEGER_IN ("ProvideMaxSlide",        OC_GLOBAL_CONFIG, Booter.Quirks.ProvideMaxSlide),
   OC_SCHEMA_BOOLEAN_IN ("RebuildAppleMemoryMap",  OC_GLOBAL_CONFIG, Booter.Quirks.RebuildAppleMemoryMap),
   OC_SCHEMA_BOOLEAN_IN ("SetupVirtualMap",        OC_GLOBAL_CONFIG, Booter.Quirks.SetupVirtualMap),
   OC_SCHEMA_BOOLEAN_IN ("SignalAppleOS",          OC_GLOBAL_CONFIG, Booter.Quirks.SignalAppleOS),

Platform/OpenCore/OpenCoreUefi.c

@@ -373,6 +373,7 @@ OcLoadBooterUefiSupport (
   AbcSettings.ForceExitBootServices  = Config->Booter.Quirks.ForceExitBootServices;
   AbcSettings.ProtectMemoryRegions   = Config->Booter.Quirks.ProtectMemoryRegions;
   AbcSettings.ProvideCustomSlide     = Config->Booter.Quirks.ProvideCustomSlide;
+  AbcSettings.ProvideMaxSlide        = Config->Booter.Quirks.ProvideMaxSlide;
   AbcSettings.ProtectUefiServices    = Config->Booter.Quirks.ProtectUefiServices;
   AbcSettings.RebuildAppleMemoryMap  = Config->Booter.Quirks.RebuildAppleMemoryMap;
   AbcSettings.SetupVirtualMap        = Config->Booter.Quirks.SetupVirtualMap;