Merge pull request #22 from p-x9/feature/relocation-info

Section Relocation Info

Author: p-x9

Sources/MachOKit/LoadCommand/Model/Section.swift

@@ -21,6 +21,15 @@ public protocol SectionProtocol: LayoutWrapper {
 
     /// returns nil except when type is `cstring_literals
     func strings(in machO: MachOFile) -> MachOFile.Strings?
+
+    /// relocation informations.
+    /// (contains only in object file (.o))
+    ///
+    /// It can also be obtained with the following command
+    /// ```sh
+    /// otool -r <path to object file>
+    /// ```
+    func relocations(in machO: MachOFile) -> DataSequence<Relocation>
 }
 
 public struct Section: SectionProtocol {
@@ -170,3 +179,56 @@ extension Section64 {
         _strings(in: machO, sectionOffset: layout.offset, sectionSize: UInt64(layout.size))
     }
 }
+
+extension SectionProtocol {
+    fileprivate func _relocations(
+        in machO: MachOFile,
+        reloff: UInt32,
+        nreloc: UInt32
+    ) -> DataSequence<Relocation> {
+        machO.fileHandle.seek(
+            toFileOffset: numericCast(reloff)
+        )
+        var data = machO.fileHandle.readData(
+            ofLength: numericCast(nreloc) * MemoryLayout<relocation_info>.size
+        )
+
+        if machO.isSwapped {
+            data.withUnsafeMutableBytes {
+                guard let baseAddress = $0.baseAddress else { return }
+                let ptr = baseAddress
+                    .assumingMemoryBound(to: relocation_info.self)
+                swap_relocation_info(ptr, nreloc, NXHostByteOrder())
+            }
+        }
+
+        return DataSequence<Relocation>(
+            data: data,
+            numberOfElements: numericCast(nreloc)
+        )
+    }
+}
+
+extension Section64 {
+    public func relocations(
+        in machO: MachOFile
+    ) -> DataSequence<Relocation> {
+        _relocations(
+            in: machO,
+            reloff: layout.reloff,
+            nreloc: layout.nreloc
+        )
+    }
+}
+
+extension Section {
+    public func relocations(
+        in machO: MachOFile
+    ) -> DataSequence<Relocation> {
+        _relocations(
+            in: machO,
+            reloff: layout.reloff,
+            nreloc: layout.nreloc
+        )
+    }
+}

Sources/MachOKit/Model/Relocation/Relocation.swift

@@ -0,0 +1,45 @@
+//
+//  Relocation.swift
+//
+//
+//  Created by p-x9 on 2024/01/10.
+//
+//
+
+import Foundation
+
+public struct Relocation {
+    public enum Info {
+        case general(RelocationInfo)
+        case scattered(ScatteredRelocationInfo)
+    }
+
+    public let _data: UInt64
+
+    public var isScattered: Bool {
+        _data & UInt64(R_SCATTERED) != 0
+    }
+
+    public var info: Info {
+        var buffer = _data
+        if isScattered {
+            let info: ScatteredRelocationInfo = withUnsafePointer(
+                to: &buffer,
+                {
+                    let ptr = UnsafeRawPointer($0)
+                    return ptr.autoBoundPointee()
+                }
+            )
+            return .scattered(info)
+        } else {
+            let info: RelocationInfo = withUnsafePointer(
+                to: &buffer,
+                {
+                    let ptr = UnsafeRawPointer($0)
+                    return ptr.autoBoundPointee()
+                }
+            )
+            return .general(info)
+        }
+    }
+}

Sources/MachOKit/Model/Relocation/RelocationInfo.swift

@@ -0,0 +1,45 @@
+//
+//  RelocationInfo.swift
+//  
+//
+//  Created by p-x9 on 2024/01/10.
+//  
+//
+
+import Foundation
+
+public struct RelocationInfo: LayoutWrapper {
+    public typealias Layout = relocation_info
+
+    public var layout: Layout
+}
+
+extension RelocationInfo {
+    public var isRelocatedPCRelative: Bool {
+        layout.r_pcrel != 0
+    }
+
+    public var length: RelocationLength? {
+        .init(rawValue: layout.r_length)
+    }
+
+    public var isExternal: Bool {
+        layout.r_extern != 0
+    }
+
+    public var isScattered: Bool {
+        UInt32(bitPattern: layout.r_address) & R_SCATTERED != 0
+    }
+
+    public var symbolIndex: Int? {
+        isExternal ? numericCast(layout.r_symbolnum) : nil
+    }
+
+    public var sectionOrdinal: Int? {
+        isExternal ? nil : numericCast(layout.r_symbolnum)
+    }
+
+    public func type(for cpuType: CPUType) -> RelocationType? {
+        .init(rawValue: layout.r_type, for: cpuType)
+    }
+}

Sources/MachOKit/Model/Relocation/RelocationLength.swift

@@ -0,0 +1,27 @@
+//
+//  RelocationLength.swift
+//
+//
+//  Created by p-x9 on 2024/01/10.
+//
+//
+
+import Foundation
+
+public enum RelocationLength: UInt32 {
+    case byte
+    case word
+    case long
+    case quad
+}
+
+extension RelocationLength: CustomStringConvertible {
+    public var description: String {
+        switch self {
+        case .byte: "byte"
+        case .word: "word"
+        case .long: "long"
+        case .quad: "quad"
+        }
+    }
+}