From 1cce5759c7d202625d2716df4c1993b7f1d0114b Mon Sep 17 00:00:00 2001
From: Artemis Tosini <me@artem.ist>
Date: Sat, 30 Mar 2024 21:47:59 -0400
Subject: [PATCH] gc: Read per-thread cwds on Darwin

---
 src/libstore/gc.cc | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 02502b945..0342965b3 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -431,12 +431,12 @@ static void readLibprocRoots(const Path & storeDir, UncheckedRoots & unchecked)
     auto storePathRegex = std::regex(quoteRegexChars(storeDir) + R"(/[0-9a-z]+[0-9a-zA-Z\+\-\._\?=]*)");
 
     int pidBufSize = proc_listpids(PROC_ALL_PIDS, 0, nullptr, 0);
-    if (pidBufSize <= 0 || pidBufSize % sizeof(int) != 0)
+    if (pidBufSize <= 0)
         throw SysError("Listing PIDs");
 
     std::vector<int> pids(pidBufSize / sizeof(int));
-    pidBufSize = proc_listpids(PROC_ALL_PIDS, 0, pids.data(), pidBufSize);
-    if (pidBufSize <= 0 || pidBufSize % sizeof(int) != 0)
+    pidBufSize = proc_listpids(PROC_ALL_PIDS, 0, pids.data(), pids.size() * sizeof(int));
+    if (pidBufSize <= 0)
         throw SysError("Listing PIDs");
     pids.resize(pidBufSize / sizeof(int));
 
@@ -456,12 +456,12 @@ static void readLibprocRoots(const Path & storeDir, UncheckedRoots & unchecked)
 
         // File descriptors
         int fdBufSize = proc_pidinfo(pid, PROC_PIDLISTFDS, 0, nullptr, 0);
-        if (fdBufSize <= 0 || fdBufSize % sizeof(struct proc_fdinfo) != 0) {
+        if (fdBufSize <= 0) {
             if ((errno == ESRCH) || (errno == EPERM)) continue;
             throw SysError("Listing pid %1% file descriptors", pid);
         }
         std::vector<struct proc_fdinfo> fds(fdBufSize / sizeof(struct proc_fdinfo));
-        fdBufSize = proc_pidinfo(pid, PROC_PIDLISTFDS, 0, fds.data(), fdBufSize);
+        fdBufSize = proc_pidinfo(pid, PROC_PIDLISTFDS, 0, fds.data(), fds.size() * sizeof(struct proc_fdinfo));
         if (fdBufSize <= 0) {
             if ((errno == ESRCH) || (errno == EPERM)) continue;
             throw SysError("Listing pid %1% file descriptors", pid);
@@ -517,13 +517,13 @@ static void readLibprocRoots(const Path & storeDir, UncheckedRoots & unchecked)
         int sysctlName[3] = {CTL_KERN, KERN_PROCARGS2, pid};
         size_t argsSize = 0;
         if (sysctl(sysctlName, 3, nullptr, &argsSize, nullptr, 0) < 0) {
-            throw SysError("Reading pid %1% arguments");
+            throw SysError("Reading pid %1% arguments", pid);
         }
 
         std::vector<char> args(argsSize);
 
         if (sysctl(sysctlName, 3, args.data(), &argsSize, nullptr, 0) < 0) {
-            throw SysError("Reading pid %1% arguments");
+            throw SysError("Reading pid %1% arguments", pid);
         }
 
         if (argsSize < args.size())
@@ -534,8 +534,32 @@ static void readLibprocRoots(const Path & storeDir, UncheckedRoots & unchecked)
             unchecked[i->str()].emplace("{libproc/args}");
 
 
-        // TODO: per-thread cwds (apparently exist but I don't see them much)
+        // Per-thread working directories
+        struct proc_taskallinfo taskAllInfo;
+        if (proc_pidinfo(pid, PROC_PIDTASKALLINFO, 0, &taskAllInfo, sizeof(taskAllInfo)) <= 0) {
+            if ((errno == ESRCH) || (errno == EPERM)) continue;
+            throw SysError("Reading pid %1% tasks", pid);
+        }
 
+        // If the process doesn't have the per-thread cwd flag then we already have the
+        // process-wide cwd from PROC_PIDVNODEPATHINFO
+        if (taskAllInfo.pbsd.pbi_flags & PROC_FLAG_THCWD) {
+            std::vector<uint64_t> tids(taskAllInfo.ptinfo.pti_threadnum);
+            int tidBufSize = proc_pidinfo(pid, PROC_PIDLISTTHREADS, 0, tids.data(), tids.size() * sizeof(uint64_t));
+            if (tidBufSize <= 0) {
+                if ((errno == ESRCH) || (errno == EPERM)) continue;
+                throw SysError("Listing pid %1% threads", pid);
+            }
+
+            for (auto tid: tids) {
+                struct proc_threadwithpathinfo threadPathInfo;
+                if (proc_pidinfo(pid, PROC_PIDTHREADPATHINFO, tid, &threadPathInfo, sizeof(threadPathInfo)) <= 0) {
+                    if ((errno == ESRCH) || (errno == EPERM)) continue;
+                    throw SysError("Reading pid %1% thread %2% cwd", pid, tid);
+                }
+                unchecked[std::string(threadPathInfo.pvip.vip_path)].emplace("{libproc/threadcwd}");
+            }
+        }
     }
 }
 #endif