Dynamic linker subsystem

Interface to libdl-style dynamic linker. More...

Files
file	dlfcn.c
	Dynamic linker subsystem.
file	dlfcn.h
	Dynamic linker subsystem.

Macros
#define	PTR_ROUND_UP(ptr, d)   ((void *)ROUND_UP((uintptr_t)(ptr), (d)))
	Macro to round up pointer.
#define	PTR_DECODE(base, ptr)   ((void*)(((uint8_t*)(base)) + (uintptr_t)(ptr)))
	Macro to add base to pointer.

Functions
void	__register_frame_info (void *ptr, void *object)
	Function to register exception frames.
void	__deregister_frame_info (void *ptr)
	Function to unregister exception frames.
void	__cxa_finalize (void *dso)
	Function to run atexit destructors for a module.
void	__dl_insert_module (dl_module_t *module)
	Insert module into module list.
void	__dl_remove_module (dl_module_t *module)
	Remove module from module list.
void *	dlopen (const char *filename, int mode)
	Open dynamic library.
void *	dlsym (void *handle, const char *symbol)
	Grab symbol from loaded dynamic library.
int	dlclose (void *handle)
	Close loaded dynamic library.
int	dladdr (const void *addr, Dl_info *info)
	Convert address to symbol.
char *	dlerror (void)
	Return last error that occurred in dynamic linker.

Variables
demangle_func	__dl_demangle_func
	Demangler function.
module_lookup_func	__dl_lookup_module
	Module resolver.
dl_module_t *	__dl_list_head
	Module list head.
dl_module_t *	__dl_list_tail
	Module list tail.
size_t	__dl_num_loaded_modules
	Number of loaded modules.

Detailed Description

Interface to libdl-style dynamic linker.

The dynamic linker subsystem allows users to load code from the program's DragonFS filesystem (see dfs.h). Code is stored in a custom dynamically linked format (extension of .dso) to allow for loading and running code placed at arbitrary memory addresses and resolving external references to the main executable and other dynamically linked modules. External references are resolved by name with symbol tables provided by each dynamically linked module and are also provided by a file in the rompak (MSYM) (see rompak_internal.h) for the main executable.

To access this system, one must first call dlopen to load a dynamically linked module and return a handle to the module. Then, one can all dlsym to access functions and variables exported from this module with the returned handle. This function can also access symbols that are in the global symbol table with the special handle RTLD_DEFAULT. Once one is done with the module, one can call dlclose to close the module.

Function Documentation

__dl_insert_module()

void __dl_insert_module

(

dl_module_t *

module

)

Insert module into module list.

This function is non-static to help debuggers support overlays.

Parameters

module

Pointer to module

__dl_remove_module()

void __dl_remove_module

(

dl_module_t *

module

)

Remove module from module list.

This function is non-static to help debuggers support overlays.

Parameters

module

Pointer to module

dlopen()

void * dlopen	(	const char *	filename,
		int	mode
	)

Open dynamic library.

Parameters

filename	Path to dynamic library
mode	Flags for loading dynamic library

Returns

Handle for loaded dynamic library

dlsym()

void * dlsym	(	void *	handle,
		const char *	symbol
	)

Grab symbol from loaded dynamic library.

Parameters

handle	Dynamic library handle to search symbol from
symbol	Name of symbol to search for

Returns

Pointer to symbol

dlclose()

int dlclose

(

void *

handle

)

Close loaded dynamic library.

Parameters

handle

Dynamic library handle to close

Returns

Whether an error occurred

dladdr()

int dladdr	(	const void *	addr,
		Dl_info *	info
	)

Convert address to symbol.

Parameters

addr	Address to search
info	Info of symbol found

Returns

Zero on success and non-zero on failure

dlerror()

char * dlerror

(

void

)

Return last error that occurred in dynamic linker.

Returns

String describing last error occurring in dynamic linker

Variable Documentation

__dl_lookup_module

module_lookup_func __dl_lookup_module

Module resolver.

Module lookup function.