ca4f574f4c
This patch adds prinicipal support for transmitting socket descriptors as RPC payload. Socket descriptors are handled by the linux-specific implementation of the capability marshalling and unmarshalling functions in 'ipc.h'. The 'Message' type in 'src/platform/linux_socket.h' has been extended to carry multiple descriptors in a single message. Unfortuately, we hit a problem (and potential show stopper) here: lx_sendmsg failed with -109 in lx_call() The error code corresponds to ETOOMANYREFS. There is only one place in the Linux kernel where this error code is used (net/unix/af_unix.c). The code for 'unix_attach_fds()' suggests that there is a limit with regard to the maximum number of references for a given Unix domain socket. When the error occurs, core and init are running. The socket of core's server entrypoint is present in the '/proc/pid/fd' of those processes 8 times. The error occurs when core tries to perform an RPC to the entrypoint to perform 'Ram_session::transfer_quota()' (base/include/base/child.h at line 248).
117 lines
2.1 KiB
C++
117 lines
2.1 KiB
C++
/*
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* \brief Linux-specific layout of IPC message buffer
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* \author Norman Feske
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* \date 2006-06-14
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*/
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/*
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* Copyright (C) 2006-2012 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BASE__IPC_MSGBUF_H_
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#define _INCLUDE__BASE__IPC_MSGBUF_H_
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namespace Genode {
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/**
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* IPC message buffer layout
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*/
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class Msgbuf_base
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{
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public:
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enum { MAX_CAPS_PER_MSG = 8 };
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protected:
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/*
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* Capabilities (file descriptors) to be transferred
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*/
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int _caps[MAX_CAPS_PER_MSG];
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Genode::size_t _used_caps;
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Genode::size_t _read_cap_index;
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/**
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* Maximum size of plain-data message payload
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*/
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Genode::size_t _size;
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/**
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* Actual size of plain-data message payload
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*/
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Genode::size_t _used_size;
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char _msg_start[]; /* symbol marks start of message buffer data */
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/*
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* No member variables are allowed beyond this point!
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*/
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public:
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char buf[];
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Msgbuf_base() { reset_caps(); }
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/**
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* Return size of message buffer
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*/
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inline Genode::size_t size() const { return _size; };
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/**
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* Return address of message buffer
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*/
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inline void *addr() { return &_msg_start[0]; };
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void reset_caps() { _used_caps = 0; _read_cap_index = 0; }
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bool append_cap(int cap)
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{
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if (_used_caps == MAX_CAPS_PER_MSG)
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return false;
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_caps[_used_caps++] = cap;
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return true;
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}
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int read_cap()
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{
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if (_read_cap_index == _used_caps)
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return -1;
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return _caps[_read_cap_index++];
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}
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size_t used_caps() const { return _used_caps; }
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int cap(unsigned index) const
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{
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return index < _used_caps ? _caps[index] : -1;
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}
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size_t used_size() const { return _used_size; }
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void used_size(size_t used_size) { _used_size = used_size; }
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};
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/**
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* Pump up IPC message buffer to specified buffer size
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*/
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template <unsigned BUF_SIZE>
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class Msgbuf : public Msgbuf_base
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{
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public:
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char buf[BUF_SIZE];
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Msgbuf() { _size = BUF_SIZE; }
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};
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}
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#endif /* _INCLUDE__BASE__IPC_MSGBUF_H_ */
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