NOVA: Capability selectors cause call of invalid portal

[Markus Partheymueller]

Hi,

I am quite stuck with a problem I encountered when using a timer
connection in Vancouver. As soon as the unique IDs of the capabilities
for RPC reach numbers >= 0x100000, RPC calls fail because of calls to
invalid portal numbers. In my particular case, there are 4 portals
created:

[ 0] EC:0xc0019f00 SYS_CREATE PT:0x1a06 EC:0xa7 EIP:0x139950
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x1a07 EC:0xa7 EIP:0x1398d0
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x1a08 EC:0xa7 EIP:0x139950
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x1a09 EC:0xa7 EIP:0x1398d0

In base/include/base/rpc_client.h, I inserted a debug statement
showing that the "internal" portal being called is 0x82260. I think
this is due to the translation between global capability selectors and
NOVA portals, is that correct?

When the internal IDs hit 0x100000, what happens is this:

[ 0] EC:0xc0019f00 SYS_CREATE PT:0x30e6 EC:0xa7 EIP:0x139950
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x30e7 EC:0xa7 EIP:0x1398d0
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x30e8 EC:0xa7 EIP:0x139950
[ 0] EC:0xc0019f00 SYS_CREATE PT:0x30e9 EC:0xa7 EIP:0x1398d0

But the next event in NOVA is a call to portal number 0x100018, which
doesn't exist because it was not created beforehand. It seems to me
that from this point in time, the internal IDs are being used as NOVA
portals somehow. But all I found was this unmarshalling method in
base-nova/include/base/ipc.h:

inline void Genode::Ipc_istream::_unmarshal_capability(Genode::Native_capability
&cap)
{
        long unique_id = 0;
        _read_from_buf(unique_id);
        int pt_sel = unique_id != ~0L ? _rcv_msg->rcv_pt_sel() : 0;

        cap = Native_capability(pt_sel, unique_id);
}

I put another debug instruction there and found out that rcv_pt_base
was 0x100018, when the call failed.

Right now I'm quite lost in all that RPC and Capability wrangling.
Maybe someone can shed some light on this? How is that translation
between internal IDs and NOVA portals done, anyway?

Cheers

Markus