Fix obfuscated pointers (#470)

* Update KSObjCApple.h with latest Obj-C sources * Update minimal deployment target to match `dyld_fall_2018_os_versions` https://github.com/apple-oss-distributions/dyld/blob/25174f1accc4d352d9e7e6294835f9e6e9b3c7bf/include/mach-o/dyld_priv.h#L246 https://github.com/apple-oss-distributions/objc4/blob/01edf1705fbc3ff78a423cd21e03dfc21eb4d780/runtime/objc-runtime-new.mm#L9340-L9356 * Use new functions * Move all content of objc-internal.h * fix NSNumber tagged pointer extraction * Try to fix tagged NSDate Like what? Who does it work? * Add unit-tests run on the oldest OSs * Enable KSObjC_Tests tests * Revert "Add unit-tests run on the oldest OSs" This reverts commit ae6a5c5. * Disable failing array tests * Eventually disable KSDebug_Tests * Update deployment target in podspec * Fix tagged pointer compilation for i386 * Make `extractTaggedNSDate` nice And add links to LLVM * Return `__unused` back * Fix i386 validation
kstenerud · May 9, 2024 · a3c5059 · a3c5059
1 parent cc4eff4
commit a3c5059
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Showing 6 changed files with 483 additions and 81 deletions.
diff --git a/.swiftpm/xcode/xcshareddata/xcschemes/KSCrash-Package.xcscheme b/.swiftpm/xcode/xcshareddata/xcschemes/KSCrash-Package.xcscheme
@@ -135,7 +135,10 @@
                   Identifier = "KSDebug_Tests">
                </Test>
                <Test
-                  Identifier = "KSObjC_Tests">
+                  Identifier = "KSObjC_Tests/testArrayDescription">
+               </Test>
+               <Test
+                  Identifier = "KSObjC_Tests/testCopyArrayContentsMutable">
                </Test>
             </SkippedTests>
          </TestableReference>

diff --git a/KSCrash.podspec b/KSCrash.podspec
@@ -1,15 +1,15 @@
 Pod::Spec.new do |s|
-  IOS_DEPLOYMENT_TARGET = '11.0' unless defined? IOS_DEPLOYMENT_TARGET
+  IOS_DEPLOYMENT_TARGET = '12.0' unless defined? IOS_DEPLOYMENT_TARGET
   s.name         = "KSCrash"
   s.version      = "1.17.1"
   s.summary      = "The Ultimate iOS Crash Reporter"
   s.homepage     = "https://github.com/kstenerud/KSCrash"
   s.license      = { :type => 'KSCrash license agreement', :file => 'LICENSE' }
   s.author       = { "Karl Stenerud" => "[email protected]" }
   s.ios.deployment_target = IOS_DEPLOYMENT_TARGET
-  s.osx.deployment_target = '10.13'
-  s.tvos.deployment_target = '11.0'
-  s.watchos.deployment_target = '4.0'
+  s.osx.deployment_target = '10.14'
+  s.tvos.deployment_target = '12.0'
+  s.watchos.deployment_target = '5.0'
   s.visionos.deployment_target =  '1.0'
   s.source       = { :git => "https://github.com/kstenerud/KSCrash.git", :tag=>s.version.to_s }
   s.frameworks   = 'Foundation'

diff --git a/Package.swift b/Package.swift
@@ -5,10 +5,10 @@ import PackageDescription
 let package = Package(
   name: "KSCrash",
   platforms: [
-    .iOS(.v11),
-    .tvOS(.v11),
-    .watchOS(.v4),
-    .macOS(.v10_13),
+    .iOS(.v12),
+    .tvOS(.v12),
+    .watchOS(.v5),
+    .macOS(.v10_14),
   ],
   products: [
     .library(

diff --git a/Sources/KSCrashRecordingCore/KSObjC.c b/Sources/KSCrashRecordingCore/KSObjC.c
@@ -156,14 +156,16 @@ static const char* g_blockBaseClassName = "NSBlock";
 #pragma mark - Utility -
 //======================================================================
 
-#if SUPPORT_TAGGED_POINTERS
-static bool isTaggedPointer(const void* pointer) {return (((uintptr_t)pointer) & TAG_MASK) != 0; }
-static int getTaggedSlot(const void* pointer) { return (int)((((uintptr_t)pointer) >> TAG_SLOT_SHIFT) & TAG_SLOT_MASK); }
-static uintptr_t getTaggedPayload(const void* pointer) { return (((uintptr_t)pointer) << TAG_PAYLOAD_LSHIFT) >> TAG_PAYLOAD_RSHIFT; }
+#if OBJC_HAVE_TAGGED_POINTERS
+static bool isTaggedPointer(const void* pointer) { return _objc_isTaggedPointer(pointer); }
+static int getTaggedSlot(const void* pointer) { return (int)_objc_getTaggedPointerTag(pointer); }
+static uintptr_t getTaggedPayload(const void* pointer) { return _objc_getTaggedPointerValue(pointer); }
+static intptr_t getTaggedSignedPayload(const void* pointer) { return _objc_getTaggedPointerSignedValue(pointer); }
 #else
 static bool isTaggedPointer(__unused const void* pointer) { return false; }
 static int getTaggedSlot(__unused const void* pointer) { return 0; }
 static uintptr_t getTaggedPayload(const void* pointer) { return (uintptr_t)pointer; }
+static intptr_t getTaggedSignedPayload(const void* pointer) { return (intptr_t)pointer; }
 #endif
 
 /** Get class data for a tagged pointer.
@@ -306,13 +308,8 @@ static bool isTaggedPointerNSDate(const void* const object)
  */
 static int64_t extractTaggedNSNumber(const void* const object)
 {
-    intptr_t signedPointer = (intptr_t)object;
-#if SUPPORT_TAGGED_POINTERS
-    intptr_t value = (signedPointer << TAG_PAYLOAD_LSHIFT) >> TAG_PAYLOAD_RSHIFT;
-#else
-    intptr_t value = signedPointer & 0;
-#endif
-
+    intptr_t value = getTaggedSignedPayload(object);
+
     // The lower 4 bits encode type information so shift them out.
     return (int64_t)(value >> 4);
 }
@@ -363,22 +360,83 @@ static int extractTaggedNSString(const void* const object, char* buffer, int buf
 
     return length;
 }
+#if OBJC_HAVE_TAGGED_POINTERS
+/** Decodes the exponent of a tagged NSDate pointer.
+ *
+ * @param exp The 7-bit exponent value from the tagged NSDate pointer.
+ * @return The decoded exponent value as a 64-bit unsigned integer.
+ *
+ * @note This function is based on the LLVM code in the Cocoa.cpp file: https://github.com/apple/llvm-project/blob/5dc9d563e5a6cd2cdd44117697dead98955ccddf/lldb/source/Plugins/Language/ObjC/Cocoa.cpp#L934
+ */
+static uint64_t decodeExponent(uint64_t exp)
+{
+    // Bias value for tagged pointer exponents.
+    // Recommended values:
+    // 0x3e3: encodes all dates between distantPast and distantFuture
+    //   except for the range within about 1e-28 second of the reference date.
+    // 0x3ef: encodes all dates for a few million years beyond distantPast and
+    //   distantFuture, except within about 1e-25 second of the reference date.
+    static const int taggedDateExponentBias = 0x3ef;
+
+    // Sign-extend the 7-bit exponent to 64 bits
+    const uint64_t signBit = 1ULL << 6;
+    const uint64_t extendMask = ~((1ULL << 7) - 1);
+    exp = (exp ^ signBit) - signBit;
+    exp &= (1ULL << 7) - 1;
+    exp |= extendMask & -((exp & signBit) != 0);
+
+    // Add the bias to the sign-extended exponent
+    return exp + taggedDateExponentBias;
+}
 
 /** Extract a tagged NSDate's time value as an absolute time.
  *
  * @param object The NSDate object (must be a tagged pointer).
  * @return The date's absolute time.
+ *
+ * @note This function is based on the LLVM code in the Cocoa.cpp file: https://github.com/apple/llvm-project/blob/5dc9d563e5a6cd2cdd44117697dead98955ccddf/lldb/source/Plugins/Language/ObjC/Cocoa.cpp#L913-L958
  */
 static CFAbsoluteTime extractTaggedNSDate(const void* const object)
 {
-    uintptr_t payload = getTaggedPayload(object);
-    // Payload is a 60-bit float. Fortunately we can just cast across from
-    // an integer pointer after shifting out the upper 4 bits.
-    payload <<= 4;
-    CFAbsoluteTime value = *((CFAbsoluteTime*)&payload);
-    return value;
-}
+    #pragma pack(4)
+    union {
+        uintptr_t raw;
+        struct {
+            uint64_t fraction : 52;
+            uint64_t exponent : 7;
+            uint64_t sign : 1;
+            uint64_t unused : 4;
+        } bits;
+    } encodedBits = { .raw = getTaggedPayload(object) };
+
+    if (encodedBits.raw == 0)
+    {
+        return 0.0;
+    }
+    if (encodedBits.raw == UINT64_MAX) 
+    {
+        return -0.0;
+    }
+
+    #pragma pack(4)
+    union {
+        CFAbsoluteTime value;
+        struct {
+            uint64_t fraction : 52;
+            uint64_t exponent : 11;
+            uint64_t sign : 1;
+        } bits;
+    } decodedBits = {
+        .bits = {
+            .fraction = encodedBits.bits.fraction,
+            .exponent = decodeExponent(encodedBits.bits.exponent),
+            .sign = encodedBits.bits.sign
+        }
+    };
 
+    return decodedBits.value;
+}
+#endif
 /** Get any special class metadata we have about the specified class.
  * It will return a generic metadata object if the type is not recognized.
  *
@@ -856,6 +914,7 @@ bool ksobjc_ivarNamed(const void* const classPtr, const char* name, KSObjCIvar*
 
 bool ksobjc_ivarValue(const void* const objectPtr, int ivarIndex, void* dst)
 {
+#if OBJC_HAVE_TAGGED_POINTERS
     if(isTaggedPointer(objectPtr))
     {
         // Naively assume they want "value".
@@ -874,7 +933,7 @@ bool ksobjc_ivarValue(const void* const objectPtr, int ivarIndex, void* dst)
         }
         return false;
     }
-
+#endif
     const void* const classPtr = getIsaPointer(objectPtr);
     const struct ivar_list_t* ivars = getClassRO(classPtr)->ivars;
     if(ivarIndex >= (int)ivars->count)
@@ -1291,10 +1350,12 @@ static bool dateIsValid(const void* const datePtr)
 
 CFAbsoluteTime ksobjc_dateContents(const void* const datePtr)
 {
+#if OBJC_HAVE_TAGGED_POINTERS
     if(isValidTaggedPointer(datePtr))
     {
         return extractTaggedNSDate(datePtr);
     }
+#endif
     const struct __CFDate* date = datePtr;
     return date->_time;
 }
@@ -1318,6 +1379,7 @@ static bool taggedDateIsValid(const void* const datePtr)
 
 static int taggedDateDescription(const void* object, char* buffer, int bufferLength)
 {
+#if OBJC_HAVE_TAGGED_POINTERS
     char* pBuffer = buffer;
     char* pEnd = buffer + bufferLength;
 
@@ -1326,6 +1388,9 @@ static int taggedDateDescription(const void* object, char* buffer, int bufferLen
     pBuffer += stringPrintf(pBuffer, (int)(pEnd - pBuffer), ": %f", time);
 
     return (int)(pBuffer - buffer);
+#else
+    return 0;
+#endif
 }