Sinan KARAKAYA becb2be5bd Let a thread resume at the instruction after a syscall ...

A syscall can hand control back to the scheduler before the instruction
after it runs. SetSyscall lets the guest install its own handler for a
syscall number; dispatchSyscallOverride then suspends the calling
thread and queues that handler as a GuestInvocation. When the
invocation finishes, EeScheduler resumes the parent thread at the
address the generated code stored just before calling handleSyscall --
the instruction right after the syscall.

The analyzer never marked that address as an entry point. It queues
resume entries for JAL and JALR only, so no generated function could be
re-entered there, EeScheduler's hasFunction() check failed, and the
thread was made dormant instead of resumed. The thread simply stops;
because the scheduler then drains normally and run() returns, it looks
like a clean shutdown rather than a fault, which makes it awkward to
recognise.

This is reachable during early boot on a real title. Dragon Quest VIII
hits it in crt0: the Metrowerks startup code installs a handler for
syscall 0x83 and immediately issues it, and execution ends there,
roughly ten functions into the binary.

Note the offset is +4, not the +8 used for JAL and JALR -- syscall has
no delay slot.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

2026-08-17 22:57:02 +02:00

..

lib

Let a thread resume at the instruction after a syscall

2026-08-17 22:57:02 +02:00

runner

Refactor runtime for move speed and better code style (#140)

2026-07-04 00:43:22 -03:00