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Simpify startup of dynamically linked binaries

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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
This commit is contained in:
Norman Feske
2016-12-22 15:01:19 +01:00
parent 8d521036fb
commit 4da52517c1
112 changed files with 366 additions and 369 deletions
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17
repos/base-linux/src/lib/lx_hybrid/lx_hybrid.cc
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@ -78,16 +78,6 @@ namespace Genode {
extern void bootstrap_component();
extern void call_global_static_constructors();
/*
* Hook for intercepting the call of the 'Component::construct' method. By
* hooking this function pointer in a library constructor, the libc is able
* to create a task context for the component code. This context is
* scheduled by the libc in a cooperative fashion, i.e. when the
* component's entrypoint is activated.
*/
extern void (*call_component_construct)(Genode::Env &) __attribute__((weak));
/*
* This function is normally provided by the cxx library, which is not
* used for lx_hybrid programs. For lx_hybrid programs, the exception
@ -96,13 +86,6 @@ namespace Genode {
void init_exception_handling(Env &) { }
}
static void lx_hybrid_component_construct(Genode::Env &env)
{
Component::construct(env);
}
void (*Genode::call_component_construct)(Genode::Env &) = &lx_hybrid_component_construct;
/*
* Static constructors are handled by the Linux startup code - so implement
* this as empty function.