Enable creation of host tasks with new tgid in LKL. #553
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Introduce a new LKL-specific syscall `new_thread_group_leader` which creates a new task_struct for the host thread with new tgid. This should be the very first LKL syscall invoked by a newly spawned thread which wants to be threat group leader. Upon return from the syscall LKL creates a new tast_struct with a new tgid for the calling thread. The parent of the thread invoking the syscall (as returned via `lkl_sys_getppid`) is equal to pid of the thread which spawned the child thread. The child thread is cloned from the parent using CLONE_VM, CLONE_FS, CLONE_FILES and CLONE_SIGHAND flags. Signed-off-by: Zi Fan Tan <[email protected]> Signed-off-by: Eugene Rodionov <[email protected]>
tavip
approved these changes
Jan 10, 2025
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Hi @tavip, @thehajime,
Here is a change by @abcSup which enables creation of new processes in LKL (tasks with new thread group leader id). At the moment in LKL all the host tasks share the same tgid field and, thus, are considered to be part of the same process. With this change it will be possible to "emulate" multiple processes running on top of LKL. These processes would still share the same virtual address space and file descriptor table but would have different thread group leaders.
This functionality is needed to enable Android Binder fuzzing which restricts threads to sending transactions to each other when they belong to the same process (i.e. share the same tgid).
The approach taken here is very similar to okuoku@3847b0a by @okuoku (context in #551 (comment))
Let us know what you think.
Thanks,
Eugene