// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.

// This file is platform specific. It is conditionally compiled and included
// in libircd glibc+ELF supporting environments. Do not rely on these
// definitions being available on all platforms.

#include <RB_INC_DLFCN_H
#include <RB_INC_LINK_H

///////////////////////////////////////////////////////////////////////////////
//
// mods/ldso.h
//

size_t
ircd::mods::ldso::count()
{
	size_t ret(0);
	for_each([&ret](const struct link_map &)
	{
		++ret;
		return true;
	});

	return ret;
}

bool
ircd::mods::ldso::has(const string_view &name)
{
	return !for_each([&name]
	(const auto &link)
	{
		// false to break
		return name == ldso::name(link)? false : true;
	});
}

bool
ircd::mods::ldso::for_each(const link_closure &closure)
{
	auto *map
	{
		reinterpret_cast<struct link_map *>(::dlopen(NULL, RTLD_NOLOAD|RTLD_LAZY))
	};

	if(unlikely(!map))
		throw error
		{
			::dlerror()
		};

	for(; map; map = map->l_next)
		if(!closure(*map))
			return false;

	return true;
}

ircd::string_view
ircd::mods::ldso::name(const struct link_map &map)
{
	return map.l_name;
}

///////////////////////////////////////////////////////////////////////////////
//
// Symbolic dl-error redefinition to throw our C++ exception for the symbol
// lookup failure, during the lazy binding, directly from the callsite. THIS IS
// BETTER than the default glibc/elf/dl behavior of terminating the program.
//
// We probably need asynchronous-unwind-tables for an exception to safely
// transit from here through libdl and out of a random PLT slot. non-call-
// exceptions does not appear to be necessary, at least for FUNC symbols.
//

// glibc/sysdeps/generic/ldsodefs.h
struct dl_exception
{
	const char *objname;
	const char *errstring;
	char *message_buffer;
};

extern "C" void
_dl_exception_free(struct dl_exception *)
__attribute__ ((nonnull(1)));

extern "C" void
__attribute__((noreturn))
_dl_signal_exception(int errcode,
                     struct dl_exception *e,
                     const char *occasion)
{
	const ircd::unwind free
	{
		std::bind(_dl_exception_free, e)
	};

	ircd::log::derror
	{
		ircd::mods::log, "dynamic linker (%d) %s in `%s' :%s",
		errcode,
		occasion,
		e->objname,
		e->errstring
	};

	throw ircd::mods::error
	{
		"%s in %s (%d) %s",
		occasion,
		e->objname,
		errcode,
		e->errstring,
	};
}

///////////////////////////////////////////////////////////////////////////////
//
// symbolic dlsym hook
//
#ifdef IRCD_MODS_HOOK_DLSYM

extern "C" void *
__libc_dlsym(void *, const char *);

extern "C" void *
dlsym(void *const handle,
      const char *const symbol)
{
	#ifdef RB_DEBUG_MODS_HOOK_DLSYM
	ircd::log::debug
	{
		ircd::mods::log, "handle:%p symbol lookup '%s'",
		handle,
		symbol
	};
	#endif

	return __libc_dlsym(handle, symbol);
}

#endif IRCD_MODS_HOOK_DLSYM