DYLD_DEBUG(3)DYLD_DEBUG(3)NAME
dyld debug - programmatic interface for debugging a task using the
dynamic link editor
SYNOPSIS
#include <mach-o/dyld_debug.h>
extern enum dyld_debug_return _dyld_debug_defining_module(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
char *name,
struct dyld_debug_module *module);
extern enum dyld_debug_return _dyld_debug_is_module_bound(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
struct dyld_debug_module module,
boolean_t *bound);
extern enum dyld_debug_return _dyld_debug_bind_module(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
struct dyld_debug_module module);
extern enum dyld_debug_return _dyld_debug_module_name(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
struct dyld_debug_module module,
char **image_name,
unsigned long *image_nameCnt,
char **module_name,
unsigned long *module_nameCnt);
extern enum dyld_debug_return _dyld_debug_subscribe_to_events(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
void (*dyld_event_routine)(struct dyld_event event));
extern enum dyld_debug_return _dyld_debug_add_event_subscriber(
task_t target_task,
unsigned long send_timeout,
unsigned long rcv_timeout,
boolean_t inconsistent_data_ok,
port_t subscriber);
extern boolean_t _dyld_event_server(
struct _dyld_event_message_request *request,
struct _dyld_event_message_reply *reply);
extern void _dyld_event_server_callback(
port_t subscriber,
struct dyld_event event);
DESCRIPTION
These routines are the programmatic interface for debugging or
examining a task that is using the dynamic link editor. Using these
routines allows one to get accurate information on which symbols (and
from which library or image they come from) are being used by a target
task.
These routines communicate with the target_task being debugged with
mach messages. The parameters target_task, send_timeout, rcv_timeout
and inconsistent_data_ok have the same meaning for all the routines.
All the routines return the same return code type which is interpreted
the same for all routines.
target_task is the task port for the task which is being debugged.
send_timeout and rcv_timeout are the mach message send and receive time
out values in milliseconds to be used with msg_rpc(2).
inconsistent_data_ok indicates if it is ok to attempt to the operation
even though the state of the dynamic linker in the target task is
inconsistent. All of these calls suspend all threads in the target
task during the duration of the calls. Then they first attempt to
finish any current dynamic linking operation in process, there by
getting the dynamic linker into a consistent state. If the operation
is done successfully and inconsistent_data_ok was FALSE it is assured
the results are consistent. If the operation fails with
inconsistent_data_ok FALSE it can be retried with inconsistent_data_ok
TRUE to possibly get the information. Even if inconsistent_data_ok is
TRUE the operation may still fail with the return code
DYLD_INCONSISTENT_DATA depending on the state of the dynamic linker in
the target task and the operation to be performed.
_dyld_debug_defining_module is passed a symbol name and returns which
module the symbol name is being or would be used from. If the symbol
does not exist in the target_task this returns DYLD_INVALID_ARGUMENTS.
_dyld_debug_is_module_bound is passed a dyld_debug_module struct and
sets bound to TRUE if the module is bound and FALSE otherwise. If the
module does not refer to a valid module DYLD_INVALID_ARGUMENTS is
returned.
_dyld_debug_bind_module binds the modules specified by
dyld_debug_module into the target task. If the module does not refer
to a valid module DYLD_INVALID_ARGUMENTS is returned. This will return
DYLD_FAILURE if there is a dynamic linking operation in progress that
could not be first completed without error. This routine can cause the
task to exit if when binding the specified module it results in an
undefined symbol, a multiply defined symbol or other link edit error
and the target task does not handle the error. _dyld_debug_bind_module
should be used with this in mind.
_dyld_debug_module_name returns the image name and module name for the
specified dyld_debug_module in the target task. If the module does not
refer to a valid module DYLD_INVALID_ARGUMENTS is returned. This will
return DYLD_FAILURE if there is a dynamic linking operation in progress
that could not be first completed without error. The names are
returned as pointers to vm_allocated memory. Their sizes are also
returned so the memory can be vm_deallocated when no longer needed.
Tempting as it might be, this can not be called from the function
passed to _dyld_debug_subscribe_to_events as the mach message queues
will fill and the calls will time out.
_dyld_debug_subscribe_to_events creates a new thread that is will call
the specified dyld_event_routine when dynamic link events occur in the
target task. These events are described below.
_dyld_debug_add_event_subscriber adds the subscriber port to the list
of event ports that dyld event messages are sent to. This is just a
different interface to get dynamic link events on a mach port rather
than using _dyld_debug_subscribe_to_events which creates a new thread.
_dyld_event_server is the mig generated routine to dispatch dyld event
messages that can be used if the _dyld_debug_add_event_subscriber
interface is used. This routine will call the routine
_dyld_event_server_callback which must be provided if
_dyld_event_server is used.
DYLD EVENTS
If _dyld_debug_subscribe_to_events or _dyld_debug_add_event_subscriber
is used dynamic link events will be sent to the dyld_event_routine or
_dyld_event_server_callback respectfully. The dyld_event structure
parameter describes the dynamic link event that happened in the target
task. The event field of the dyld_event structure specified the type
of the event and the arg field describes the module(s) or image for the
event. The dyld_debug_module of the arg's for non-library modules
always have module_index field of 0. The possible event types are as
follows:
The DYLD_IMAGE_ADDED event is sent when a new images is brought into
the target task. These images include the dynamic linker itself, the
executable image, dynamic shared libraries that get loaded and objects
loaded by NXLoadModule. For this event only the arg[0] field of the
dyld_event structure is used for the image and the module_index is has
no meaning since this event is for the entire image.
A DYLD_MODULE_BOUND event is sent for each module that is bound into
the target task. For this event only the arg[0] field of the
dyld_event structure is used to identify the module being bound.
A DYLD_MODULE_REMOVED event is sent for each module that is removed in
the target task via an NXUnloadModule call done by the target task.
For this event only the arg[0] field of the dyld_event structure is
used to identify the module being unloaded.
A DYLD_MODULE_REPLACED event is sent for each module that is replaced
in the target task via an NXReplaceModule call done by the target task.
For this event the arg[0] field of the dyld_event structure is used to
identify the module that was replaced and the arg[1] field identifies
the new moduled that replaced it.
RETURN CODES
DYLD_SUCCESS
Indicates the operation and the communication with the target
task was successful.
DYLD_INCONSISTENT_DATA
Indicates the operation was not attempted because the state of
the dynamic linker was able to be brought into a consistent
state.
DYLD_INVALID_ARGUMENTS
Indicates the operation failed because the arguments to the
operation were invalid.
DYLD_FAILURE
Indicates the operation or the communication with the target
task was unsuccessful.
NeXT Computer, Inc. May 10, 1995 DYLD_DEBUG(3)