Add a minimal dlcall plugin that lets the guest invoke host functions
through magic system calls. The plugin registers a vCPU syscall filter
callback that intercepts a reserved syscall number and dispatches a set
of pass-through operations: querying host attributes, loading and freeing
shared libraries, resolving symbols, retrieving the last library error,
and invoking a host function through a common interface.
The magic syscall number defaults to 4096 and can be overridden at load
time with the "syscall_num=N" argument; values low enough to clash with a
real syscall are rejected.
Co-authored-by: Kailiang Xu <xukl2019@sjtu.edu.cn>
Co-authored-by: Mingyuan Xia <xiamy@ultrarisc.com>
Signed-off-by: Ziyang Zhang <functioner@sjtu.edu.cn>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
Link: https://lore.kernel.org/qemu-devel/20260711094523.622997-2-functioner@sjtu.edu.cn
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
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