FileManagement: Gate new openat2() codepaths on recent enough kernel

FEX-Emu · Dec 19, 2024 · 01d56e0 · 01d56e0
1 parent 6862e72
commit 01d56e0
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Showing 2 changed files with 13 additions and 6 deletions.
diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/FileManagement.cpp b/Source/Tools/LinuxEmulation/LinuxSyscalls/FileManagement.cpp
@@ -333,6 +333,8 @@ FileManager::FileManager(FEXCore::Context::Context* ctx)
     ProcFSDev = Buffer.st_dev;
   }
 
+  uint32_t KernelVersion = FEX::HLE::SyscallHandler::CalculateHostKernelVersion();
+  HasOpenat2 = KernelVersion >= FEX::HLE::SyscallHandler::KernelVersion(5, 8, 0);
   UpdatePID(::getpid());
 }
 
@@ -646,15 +648,17 @@ uint64_t FileManager::Open(const char* pathname, int flags, uint32_t mode) {
 
   if (!ShouldSkipOpenInEmu(flags)) {
     FDPathTmpData TmpFilename;
-    auto Path = GetEmulatedFDPath(AT_FDCWD, SelfPath, false, TmpFilename);
+    auto Path = GetEmulatedFDPath(AT_FDCWD, SelfPath, !HasOpenat2, TmpFilename);
     if (Path.first != -1) {
       FEX::HLE::open_how how = {
         .flags = (uint64_t)flags,
         .mode = (flags & (O_CREAT | O_TMPFILE)) ? mode & 07777 : 0, // openat2() is stricter about this
         .resolve = RESOLVE_IN_ROOT,
       };
-      fd = ::syscall(SYSCALL_DEF(openat2), Path.first, Path.second, &how, sizeof(how));
-      if (fd == -1 && errno == EXDEV) {
+      if (HasOpenat2) {
+        fd = ::syscall(SYSCALL_DEF(openat2), Path.first, Path.second, &how, sizeof(how));
+      }
+      if (fd == -1 && (!HasOpenat2 || errno == EXDEV)) {
         // This means a magic symlink (/proc/foo) was involved. In this case we
         // just punt and do the access without RESOLVE_IN_ROOT.
         fd = ::syscall(SYSCALL_DEF(openat), Path.first, Path.second, flags, mode);
@@ -899,15 +903,17 @@ uint64_t FileManager::Openat([[maybe_unused]] int dirfs, const char* pathname, i
 
   if (!ShouldSkipOpenInEmu(flags)) {
     FDPathTmpData TmpFilename;
-    auto Path = GetEmulatedFDPath(dirfs, SelfPath, false, TmpFilename);
+    auto Path = GetEmulatedFDPath(dirfs, SelfPath, !HasOpenat2, TmpFilename);
     if (Path.first != -1) {
       FEX::HLE::open_how how = {
         .flags = (uint64_t)flags,
         .mode = (flags & (O_CREAT | O_TMPFILE)) ? mode & 07777 : 0, // openat2() is stricter about this,
         .resolve = RESOLVE_IN_ROOT,
       };
-      fd = ::syscall(SYSCALL_DEF(openat2), Path.first, Path.second, &how, sizeof(how));
-      if (fd == -1 && errno == EXDEV) {
+      if (HasOpenat2) {
+        fd = ::syscall(SYSCALL_DEF(openat2), Path.first, Path.second, &how, sizeof(how));
+      }
+      if (fd == -1 && (!HasOpenat2 || errno == EXDEV)) {
         // This means a magic symlink (/proc/foo) was involved. In this case we
         // just punt and do the access without RESOLVE_IN_ROOT.
         fd = ::syscall(SYSCALL_DEF(openat), Path.first, Path.second, flags, mode);

diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/FileManagement.h b/Source/Tools/LinuxEmulation/LinuxSyscalls/FileManagement.h
@@ -170,5 +170,6 @@ class FileManager final {
   int64_t RootFSFDInode = 0;
   int64_t ProcFDInode = 0;
   dev_t ProcFSDev;
+  bool HasOpenat2;
 };
 } // namespace FEX::HLE