[SharedCache] Fix slide info parsing and complete v2 support

There seem to be a number of issues with slide info parsing. I decided the simplest fix was to largely mimick what `dyld` is doing.

Part of this process was to remove creating a vector of page starts and processing them in another loop below the one where they were read out. It wasn't clear to me the original design decision to separate it into 2 loops like that. I think this was part of the problem that was causing issues.

By adding rewrites in the same loop where page starts are being read out, it was much easier to mimick the code in `dyld` which I assume has to be correct. So as long as my copying was correct then I believe this should work as intended.

Not everything has been thoroughly tested but I'm pretty confident v3 and v5 are now working as intended. v2 should be but less testing of it has been done.

1 files changed, 141 insertions, 121 deletions

diff --git a/view/sharedcache/core/SharedCache.cpp b/view/sharedcache/core/SharedCache.cpp
index 9e438909..81b5053a 100644
--- a/view/sharedcache/core/SharedCache.cpp
+++ b/view/sharedcache/core/SharedCache.cpp
@@ -1135,33 +1135,98 @@ void SharedCache::ParseAndApplySlideInfoForFile(std::shared_ptr<MMappedFileAcces
 	for (const auto& [off, mapping] : mappings)
 	{
 		m_logger->LogDebug("Slide Info Version: %d", mapping.slideInfoVersion);
+		uint64_t extrasOffset = off;
 		uint64_t pageStartsOffset = off;
 		uint64_t pageStartCount;
 		uint64_t pageSize;
-		std::vector<uint64_t> pageStartFileOffsets;
 
 		if (mapping.slideInfoVersion == 2)
 		{
 			pageStartsOffset += mapping.slideInfoV2.page_starts_offset;
 			pageStartCount = mapping.slideInfoV2.page_starts_count;
 			pageSize = mapping.slideInfoV2.page_size;
-
-			pageStartFileOffsets.reserve(pageStartCount);
-			size_t cursor = pageStartsOffset;
+			extrasOffset += mapping.slideInfoV2.page_extras_offset;
+			auto cursor = pageStartsOffset;
 
 			for (size_t i = 0; i < pageStartCount; i++)
 			{
 				try
 				{
-					uint64_t pageStart = mapping.file->ReadUShort(cursor) * 4;
-					cursor += 2;
-					if (pageStart & 0x4000)
+					uint16_t start = mapping.file->ReadUShort(cursor);
+					cursor += sizeof(uint16_t);
+					if (start == DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE)
 						continue;
-					pageStartFileOffsets.push_back(mapping.mappingInfo.fileOffset + (pageSize * i) + pageStart);
+
+					auto rebaseChain = [&](const dyld_cache_slide_info_v2& slideInfo, uint64_t pageContent, uint16_t startOffset)
+					{
+						uintptr_t slideAmount = 0;
+
+						auto deltaMask = slideInfo.delta_mask;
+						auto valueMask = ~deltaMask;
+						auto valueAdd = slideInfo.value_add;
+
+						auto deltaShift = count_trailing_zeros(deltaMask) - 2;
+
+						uint32_t pageOffset = startOffset;
+						uint32_t delta = 1;
+						while ( delta != 0 )
+						{
+							uint64_t loc = pageContent + pageOffset;
+							try
+							{
+								uintptr_t rawValue = file->ReadULong(loc);
+								delta = (uint32_t)((rawValue & deltaMask) >> deltaShift);
+								uintptr_t value = (rawValue & valueMask);
+								if (value != 0)
+								{
+									value += valueAdd;
+									value += slideAmount;
+								}
+								pageOffset += delta;
+								rewrites.emplace_back(loc, value);
+							}
+							catch (MappingReadException& ex)
+							{
+								m_logger->LogError("Failed to read v2 slide pointer at 0x%llx\n", loc);
+								break;
+							}
+						}
+					};
+
+					if (start & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA)
+					{
+						int j=(start & 0x3FFF);
+						bool done = false;
+						do
+						{
+							uint64_t extraCursor = extrasOffset + (j * sizeof(uint16_t));
+							try
+							{
+								auto extra = mapping.file->ReadUShort(extraCursor);
+								uint16_t aStart = extra;
+								uint64_t page = mapping.mappingInfo.fileOffset + (pageSize * i);
+								uint16_t pageStartOffset = (aStart & 0x3FFF)*4;
+								rebaseChain(mapping.slideInfoV2, page, pageStartOffset);
+								done = (extra & DYLD_CACHE_SLIDE_PAGE_ATTR_END);
+								++j;
+							}
+							catch (MappingReadException& ex)
+							{
+								m_logger->LogError("Failed to read v2 slide extra at 0x%llx\n", cursor);
+								break;
+							}
+						} while (!done);
+					}
+					else
+					{
+						uint64_t page = mapping.mappingInfo.fileOffset + (pageSize * i);
+						uint16_t pageStartOffset = start*4;
+						rebaseChain(mapping.slideInfoV2, page, pageStartOffset);
+					}
 				}
 				catch (MappingReadException& ex)
 				{
-
+					m_logger->LogError("Failed to read v2 slide info at 0x%llx\n", cursor);
 				}
 			}
 		}
@@ -1170,23 +1235,53 @@ void SharedCache::ParseAndApplySlideInfoForFile(std::shared_ptr<MMappedFileAcces
 			pageStartsOffset += sizeof(dyld_cache_slide_info_v3);
 			pageStartCount = mapping.slideInfoV3.page_starts_count;
 			pageSize = mapping.slideInfoV3.page_size;
-
-			pageStartFileOffsets.reserve(pageStartCount);
-			size_t cursor = pageStartsOffset;
+			auto cursor = pageStartsOffset;
 
 			for (size_t i = 0; i < pageStartCount; i++)
 			{
 				try
 				{
-					uint64_t pageStart = mapping.file->ReadUShort(cursor);
-					cursor += 2;
-					if (pageStart & 0x4000)
+					uint16_t delta = mapping.file->ReadUShort(cursor);
+					cursor += sizeof(uint16_t);
+					if (delta == DYLD_CACHE_SLIDE_V3_PAGE_ATTR_NO_REBASE)
 						continue;
-					pageStartFileOffsets.push_back(mapping.mappingInfo.fileOffset + (pageSize * i) + pageStart);
+					
+					delta = delta/sizeof(uint64_t); // initial offset is byte based
+					uint64_t loc = mapping.mappingInfo.fileOffset + (pageSize * i);
+					do
+					{
+						loc += delta * sizeof(dyld_cache_slide_pointer3);
+						try
+						{
+							dyld_cache_slide_pointer3 slideInfo;
+							file->Read(&slideInfo, loc, sizeof(slideInfo));
+							delta = slideInfo.plain.offsetToNextPointer;
+
+							if (slideInfo.auth.authenticated)
+							{
+								uint64_t value = slideInfo.auth.offsetFromSharedCacheBase;
+								value += mapping.slideInfoV3.auth_value_add;
+								rewrites.emplace_back(loc, value);
+							}
+							else
+							{
+								uint64_t value51 = slideInfo.plain.pointerValue;
+								uint64_t top8Bits = value51 & 0x0007F80000000000;
+								uint64_t bottom43Bits = value51 & 0x000007FFFFFFFFFF;
+								uint64_t value = (uint64_t)top8Bits << 13 | bottom43Bits;
+								rewrites.emplace_back(loc, value);
+							}
+						}
+						catch (MappingReadException& ex)
+						{
+							m_logger->LogError("Failed to read v3 slide pointer at 0x%llx\n", loc);
+							break;
+						}
+					} while (delta != 0);
 				}
 				catch (MappingReadException& ex)
 				{
-					m_logger->LogError("Failed to read slide info at 0x%llx\n", cursor);
+					m_logger->LogError("Failed to read v3 slide info at 0x%llx\n", cursor);
 				}
 			}
 		}
@@ -1194,124 +1289,49 @@ void SharedCache::ParseAndApplySlideInfoForFile(std::shared_ptr<MMappedFileAcces
 		{
 			pageStartsOffset += sizeof(dyld_cache_slide_info5);
 			pageStartCount = mapping.slideInfoV5.page_starts_count;
-			m_logger->LogDebug("Page Start Count: %d", pageStartCount);
 			pageSize = mapping.slideInfoV5.page_size;
 			auto cursor = pageStartsOffset;
+
 			for (size_t i = 0; i < pageStartCount; i++)
 			{
 				try
 				{
-					uint64_t pageStart = mapping.file->ReadUShort(cursor);
-					cursor += 2;
-					if (pageStart == DYLD_CACHE_SLIDE_V5_PAGE_ATTR_NO_REBASE)
+					uint16_t delta = mapping.file->ReadUShort(cursor);
+					cursor += sizeof(uint16_t);
+					if (delta == DYLD_CACHE_SLIDE_V5_PAGE_ATTR_NO_REBASE)
 						continue;
-					pageStartFileOffsets.push_back(mapping.mappingInfo.fileOffset + (pageSize * i) + pageStart);
-				}
-				catch (MappingReadException& ex)
-				{
-					m_logger->LogError("Failed to read slide info at 0x%llx\n", cursor);
-				}
-			}
-		}
-		if (pageStartFileOffsets.empty())
-		{
-			m_logger->LogDebug("No page start file offsets found");
-		}
-		for (auto pageStart : pageStartFileOffsets)
-		{
-			if (mapping.slideInfoVersion == 2)
-			{
-				auto deltaMask = mapping.slideInfoV2.delta_mask;
-				auto valueMask = ~deltaMask;
-				auto valueAdd = mapping.slideInfoV2.value_add;
-
-				auto deltaShift = count_trailing_zeros(deltaMask) - 2;
-
-				uint64_t delta = 1;
-				uint64_t loc = pageStart;
-				while (delta != 0)
-				{
-					try {
-						uint64_t rawValue = file->ReadULong(loc);
-						delta = (rawValue & deltaMask) >> deltaShift;
-						uint64_t value = (rawValue & valueMask);
-						if (valueMask != 0)
-						{
-							value += valueAdd;
-						}
-						rewrites.emplace_back(loc, value);
-					}
-					catch (MappingReadException& ex)
-					{
-						m_logger->LogError("Failed to read slide info at 0x%llx\n", loc);
-						delta = 0;
-					}
-					loc += delta;
-				}
-			}
-			else if (mapping.slideInfoVersion == 3)
-			{
-				uint64_t loc = pageStart;
-				uint64_t delta = 1;
-				while (delta != 0)
-				{
-					dyld_cache_slide_pointer3 slideInfo;
-					try
+					
+					delta = delta/sizeof(uint64_t); // initial offset is byte based
+					uint64_t loc = mapping.mappingInfo.fileOffset + (pageSize * i);
+					do
 					{
-						file->Read(&slideInfo, loc, 8);
-						delta = slideInfo.plain.offsetToNextPointer * 8;
-
-						if (slideInfo.auth.authenticated)
+						loc += delta * sizeof(dyld_cache_slide_pointer5);
+						try
 						{
-							uint64_t value = slideInfo.auth.offsetFromSharedCacheBase;
-							value += mapping.slideInfoV3.auth_value_add;
-							rewrites.emplace_back(loc, value);
+							dyld_cache_slide_pointer5 slideInfo;
+							file->Read(&slideInfo, loc, sizeof(slideInfo));
+							delta = slideInfo.regular.next;
+							if (slideInfo.auth.auth)
+							{
+								uint64_t value = mapping.slideInfoV5.value_add + slideInfo.auth.runtimeOffset;
+								rewrites.emplace_back(loc, value);
+							}
+							else
+							{
+								uint64_t value = mapping.slideInfoV5.value_add + slideInfo.regular.runtimeOffset;
+								rewrites.emplace_back(loc, value);
+							}
 						}
-						else
+						catch (MappingReadException& ex)
 						{
-							uint64_t value51 = slideInfo.plain.pointerValue;
-							uint64_t top8Bits = value51 & 0x0007F80000000000;
-							uint64_t bottom43Bits = value51 & 0x000007FFFFFFFFFF;
-							uint64_t value = (uint64_t)top8Bits << 13 | bottom43Bits;
-							rewrites.emplace_back(loc, value);
+							m_logger->LogError("Failed to read v5 slide pointer at 0x%llx\n", loc);
+							break;
 						}
-						loc += delta;
-					}
-					catch (MappingReadException& ex)
-					{
-						m_logger->LogError("Failed to read slide info at 0x%llx\n", loc);
-						delta = 0;
-					}
+					} while (delta != 0);
 				}
-			}
-			else if (mapping.slideInfoVersion == 5)
-			{
-				uint64_t loc = pageStart;
-				uint64_t delta = 1;
-				while (delta != 0)
+				catch (MappingReadException& ex)
 				{
-					dyld_cache_slide_pointer5 slideInfo;
-					try
-					{
-						file->Read(&slideInfo, loc, 8);
-						delta = slideInfo.regular.next * 8;
-						if (slideInfo.auth.auth)
-						{
-							uint64_t value = slideInfo.auth.runtimeOffset + mapping.slideInfoV5.value_add;
-							rewrites.emplace_back(loc, value);
-						}
-						else
-						{
-							uint64_t value = base + slideInfo.regular.runtimeOffset;
-							rewrites.emplace_back(loc, value);
-						}
-						loc += delta;
-					}
-					catch (MappingReadException& ex)
-					{
-						m_logger->LogError("Failed to read slide info at 0x%llx\n", loc);
-						delta = 0;
-					}
+					m_logger->LogError("Failed to read v5 slide info at 0x%llx\n", cursor);
 				}
 			}
 		}