Merge pull request #77165 from mikeash/swift-inspect-force-fork-corpse

[swift-inspect] Force forkCorpse if VMUProcInfo advises it.

Author: mikeash

tools/swift-inspect/Sources/swift-inspect/DarwinRemoteProcess.swift

@@ -125,7 +125,17 @@ internal final class DarwinRemoteProcess: RemoteProcess {
       return nil
     }
 
-    if forkCorpse {
+    // Consult with VMUProcInfo to determine if we should force forkCorpse.
+    let forceForkCorpse: Bool
+    if let procInfoClass = getVMUProcInfoClass() {
+      let procInfo = procInfoClass.init(task: task)
+      forceForkCorpse = procInfo.shouldAnalyzeWithCorpse
+    } else {
+      // Default to not forcing forkCorpse.
+      forceForkCorpse = false
+    }
+
+    if forkCorpse || forceForkCorpse {
       var corpse = task_t()
       let maxRetry = 6
       for retry in 0..<maxRetry {

tools/swift-inspect/Sources/swift-inspect/Symbolication+Extensions.swift

@@ -30,6 +30,13 @@ private func symbol<T>(_ handle: UnsafeMutableRawPointer, _ name: String) -> T {
   return unsafeBitCast(result, to: T.self)
 }
 
+private func objcClass<T>(_ name: String) -> T? {
+  guard let result = objc_getClass(name) as? AnyClass else {
+    return nil
+  }
+  return unsafeBitCast(result, to: T.self)
+}
+
 enum Sym {
   static let pidFromHint: @convention(c) (AnyObject) -> pid_t =
     symbol(symbolicationHandle, "pidFromHint")
@@ -97,6 +104,16 @@ typealias CSSymbolicatorRef = CSTypeRef
 typealias CSSymbolRef = CSTypeRef
 typealias CSSymbolOwnerRef = CSTypeRef
 
+// Declare just enough of VMUProcInfo for our purposes. It does not actually
+// conform to this protocol, but ObjC protocol method dispatch is based entirely
+// around msgSend and the presence of the method on the class, not conformance.
+@objc protocol VMUProcInfo {
+  @objc(initWithTask:)
+  init(task: task_read_t)
+
+  var shouldAnalyzeWithCorpse: Bool { get }
+}
+
 func pidFromHint(_ hint: String) -> pid_t? {
   let result = Sym.pidFromHint(hint as NSString)
   return result == 0 ? nil : result
@@ -231,4 +248,8 @@ func machErrStr(_ kr: kern_return_t) -> String {
   return "\(errStr) (0x\(errHex))"
 }
 
+func getVMUProcInfoClass() -> VMUProcInfo.Type? {
+  return objcClass("VMUProcInfo")
+}
+
 #endif