8000 Missing capability fault generated for receive on bound notifications · Issue #1424 · seL4/seL4 · GitHub
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Missing capability fault generated for receive on bound notifications #1424

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talsewell opened this issue Mar 12, 2025 · 0 comments
Open

Missing capability fault generated for receive on bound notifications #1424

talsewell opened this issue Mar 12, 2025 · 0 comments

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@talsewell
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Spotted while poking around in the l4v repository.

If a thread attempts to receive on a notification object, and the notification object is bound to a different thread, this fails. That's not unreasonable. The failure is processed as a fault, probably for simplicity, as the receive paths do not generate errors.

The fault created is a "missing capability" fault, which I think is misleading.

seL4/src/api/syscall.c

Lines 456 to 460 in d047ce8

boundTCB = (tcb_t *)notification_ptr_get_ntfnBoundTCB(ntfnPtr);
if (unlikely(!cap_notification_cap_get_capNtfnCanReceive(lu_ret.cap)
|| (boundTCB && boundTCB != NODE_STATE(ksCurThread)))) {
current_lookup_fault = lookup_fault_missing_capability_new(0);
current_fault = seL4_Fault_CapFault_new(epCPtr, true);

In the fullness of time, this should probably be turned into its own kind of fault, to avoid misreporting to a fault handler.
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