ircd::mods: Add platform-dependent ldso interface.

configure.ac

@@ -763,6 +763,7 @@ RB_CHK_SYSHEADER(signal.h, [SIGNAL_H])
 RB_CHK_SYSHEADER(ifaddrs.h, [IFADDRS_H])
 RB_CHK_SYSHEADER(fcntl.h, [FCNTL_H])
 RB_CHK_SYSHEADER(link.h, [LINK_H])
+RB_CHK_SYSHEADER(dlfcn.h, [DLFCN_H])
 RB_CHK_SYSHEADER(sys/types.h, [SYS_TYPES_H])
 RB_CHK_SYSHEADER(sys/time.h, [SYS_TIME_H])
 RB_CHK_SYSHEADER(sys/stat.h, [SYS_STAT_H])

include/ircd/mods/ldso.h

@@ -0,0 +1,32 @@
+// 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.
+
+#pragma once
+#define HAVE_IRCD_MODS_LDSO_H
+
+// This is a platform dependent interface. While this header and these decls
+// are unconditionally included in the standard include stack, the defs
+// behind them may not be compiled and linked on all platforms.
+
+// Forward declarations for <link.h> because it is not included here.
+extern "C"
+{
+	struct link_map;
+}
+
+/// Platform-dependent interface on ELF+ld.so supporting compilations.
+namespace ircd::mods::ldso
+{
+	using link_map_closure = std::function<bool (struct link_map &)>;
+	using link_name_closure = std::function<bool (const string_view &)>;
+
+	bool for_each(const link_map_closure &);
+	bool for_each(const link_name_closure &);
+}

include/ircd/mods/mods.h

@@ -67,6 +67,7 @@ namespace ircd::mods
 #include "sym_ptr.h"
 #include "import.h"
 #include "import_shared.h"
+#include "ldso.h"
 
 // Exports down into ircd::
 namespace ircd

ircd/mods_ldso.cc

@@ -12,8 +12,45 @@
 // 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
+//
+
+bool
+ircd::mods::ldso::for_each(const link_name_closure &closure)
+{
+	return !for_each(link_map_closure{[&closure]
+	(struct link_map &map)
+	{
+		return closure(map.l_name);
+	}});
+}
+
+bool
+ircd::mods::ldso::for_each(const link_map_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;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // Symbolic dl-error redefinition to throw our C++ exception for the symbol

modules/console.cc

@@ -1602,6 +1602,23 @@ console_cmd__mod__unload(opt &out, const string_view &line)
 	return true;
 }
 
+bool
+console_cmd__mod__link_map(opt &out, const string_view &line)
+{
+	size_t i(0);
+	mods::ldso::for_each([&out, &i]
+	(const string_view &name)
+	{
+		out << std::setw(2) << (i++)
+		    << " " << name
+		    << std::endl;
+
+		return true;
+	});
+
+	return true;
+}
+
 //
 // ctx
 //