genode/repos/libports/include/libc/component.h
Norman Feske 4da52517c1 Simpify startup of dynamically linked binaries
This patch removes the component_entry_point library, which used to
proved a hook for the libc to intercept the call of the
'Component::construct' function. The mechansim has several shortcomings
(see the discussion in the associated issue) and was complex. So we
eventually discarded the approach in favor of the explicit handling of
the startup.

A regular Genode component provides a 'Component::construct' function,
which is determined by the dynamic linker via a symbol lookup.
For the time being, the dynamic linker falls back to looking up a 'main'
function if no 'Component::construct' function could be found.

The libc provides an implementation of 'Component::construct', which
sets up the libc's task handling and finally call the function
'Libc::Component::construct' from the context of the appllication task.
This function is expected to be provided by the libc-using application.
Consequently, Genode components that use the libc have to implement the
'Libc::Component::construct' function.

The new 'posix' library provides an implementation of
'Libc::Component::construct' that calls a main function. Hence, POSIX
programs that merely use the POSIX API merely have to add 'posix' to the
'LIBS' declaration in their 'target.mk' file. Their execution starts at
'main'.

Issue #2199
2017-01-13 13:06:52 +01:00

49 lines
1.3 KiB
C++

/*
* \brief Hook functions for bootstrapping a libc-using Genode component
* \author Norman Feske
* \date 2016-12-23
*
* This interface is implemented by components that use both Genode's API and
* the libc. For such components, the libc provides the 'Component::construct'
* function that takes the precautions needed for letting the application use
* blocking I/O via POSIX functions like 'read' or 'select'. The libc's
* 'Component::construct' function finally passes control to the application by
* calling the application-provided 'Libc::Component::construct' function.
*/
/*
* Copyright (C) 2016 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU General Public License version 2.
*/
#ifndef _INCLUDE__LIBC__COMPONENT_H_
#define _INCLUDE__LIBC__COMPONENT_H_
#include <base/env.h>
#include <base/stdint.h>
namespace Genode { struct Env; }
/**
* Interface to be provided by the component implementation
*/
namespace Libc { namespace Component {
/**
* Return stack size of the component's initial entrypoint
*/
Genode::size_t stack_size();
/**
* Construct component
*
* \param env interface to the component's execution environment
*/
void construct(Genode::Env &env);
} }
#endif /* _INCLUDE__LIBC__COMPONENT_H_ */