fix(syscall): honor per-handle FD_CLOEXEC in fcntl

Author: FlareCoding

kernel/fs/fstypes.h

@@ -26,6 +26,7 @@ constexpr uint32_t O_EXCL   = 0x80;
 constexpr uint32_t O_TRUNC  = 0x200;
 constexpr uint32_t O_APPEND   = 0x400;
 constexpr uint32_t O_NONBLOCK = 0x800;
+constexpr uint32_t O_CLOEXEC  = 0x80000;
 
 constexpr uint32_t ACCESS_MODE_MASK = 0x3;
 

kernel/resource/handle_table.h

@@ -10,6 +10,9 @@ struct resource_object;
 
 constexpr uint32_t MAX_TASK_HANDLES = 128;
 
+// Private high bit in handle_entry::flags reserved for FD_CLOEXEC state
+constexpr uint32_t RESOURCE_HANDLE_CLOEXEC = 0x80000000;
+
 struct handle_entry {
     bool used;
     uint16_t generation;

kernel/resource/resource.cpp

@@ -113,6 +113,13 @@ __PRIVILEGED_CODE int32_t open(
         return (rc == HANDLE_ERR_NOSPC) ? ERR_TABLEFULL : ERR_IO;
     }
 
+    if (flags & fs::O_CLOEXEC) {
+        uint32_t handle_flags = 0;
+        get_handle_flags(&owner->handles, *out_handle, &handle_flags);
+        set_handle_flags(&owner->handles, *out_handle,
+                         handle_flags | RESOURCE_HANDLE_CLOEXEC);
+    }
+
     // Table now owns one reference.
     resource_release(obj);
     return OK;

kernel/syscall/handlers/sys_fd.cpp

@@ -1184,7 +1184,7 @@ DEFINE_SYSCALL3(fcntl, fd, cmd, arg) {
         if (rc != resource::HANDLE_OK) {
             return syscall::EBADF;
         }
-        return FD_CLOEXEC;
+        return (flags & resource::RESOURCE_HANDLE_CLOEXEC) ? FD_CLOEXEC : 0;
     }
 
     if (cmd == F_SETFD) {
@@ -1194,24 +1194,46 @@ DEFINE_SYSCALL3(fcntl, fd, cmd, arg) {
         if (rc != resource::HANDLE_OK) {
             return syscall::EBADF;
         }
-        (void)arg;
+
+        flags &= ~resource::RESOURCE_HANDLE_CLOEXEC;
+        if (arg & FD_CLOEXEC) {
+            flags |= resource::RESOURCE_HANDLE_CLOEXEC;
+        }
+        
+        rc = resource::set_handle_flags(
+            &task->handles, static_cast<resource::handle_t>(fd), flags);
+        
+        if (rc != resource::HANDLE_OK) {
+            return syscall::EBADF;
+        }
         return 0;
     }
 
     if (cmd == F_GETFL) {
         uint32_t flags = 0;
         int32_t rc = resource::get_handle_flags(
             &task->handles, static_cast<resource::handle_t>(fd), &flags);
+        
         if (rc != resource::HANDLE_OK) {
             return syscall::EBADF;
         }
-        return static_cast<int64_t>(flags);
+        
+        return static_cast<int64_t>(flags & ~resource::RESOURCE_HANDLE_CLOEXEC);
     }
 
     if (cmd == F_SETFL) {
-        uint32_t flags = static_cast<uint32_t>(arg) & SETFL_MASK;
-        int32_t rc = resource::set_handle_flags(
+        uint32_t flags = 0;
+        int32_t rc = resource::get_handle_flags(
+            &task->handles, static_cast<resource::handle_t>(fd), &flags);
+        
+        if (rc != resource::HANDLE_OK) {
+            return syscall::EBADF;
+        }
+        
+        flags = (flags & ~SETFL_MASK) | (static_cast<uint32_t>(arg) & SETFL_MASK);
+        rc = resource::set_handle_flags(
             &task->handles, static_cast<resource::handle_t>(fd), flags);
+        
         if (rc != resource::HANDLE_OK) {
             return syscall::EBADF;
         }