TNFCTL_INDIRECT_OPEN(3TNF)TNFCTL_INDIRECT_OPEN(3TNF)NAME
tnfctl_indirect_open, tnfctl_check_libs - control probes of another
process where caller provides /proc functionality
SYNOPSIS
cc [ flag ... ] file ... -ltnfctl [ library ... ]
#include <tnf/tnfctl.h>
tnfctl_errcode_t tnfctl_indirect_open(void *prochandle,
tnfctl_ind_config_t *config, tnfctl_handle_t **ret_val);
tnfctl_errcode_t tnfctl_check_libs(tnfctl_handle_t *hndl);
DESCRIPTION
The interfaces tnfctl_indirect_open() and tnfctl_check_libs() are used
to control probes in another process where the libtnfctl(3TNF) client
has already opened proc(4) on the target process. An example of this
is when the client is a debugger. Since these clients already use /proc
on the target, libtnfctl(3TNF) cannot use /proc directly. Therefore,
these clients must provide callback functions that can be used to
inspect and to update the target process. The target process must
load libtnfprobe.so.1 (defined in <tnf/tnfctl.h> as macro TNFCTL_LIBT‐
NFPROBE).
The first argument prochandle is a pointer to an opaque structure that
is used in the callback functions that inspect and update the target
process. This structure should encapsulate the state that the caller
needs to use /proc on the target process (the /proc file descriptor).
The second argument, config, is a pointer to
typedef
struct tnfctl_ind_config {
int (*p_read)(void *prochandle, paddr_t addr, char *buf,
size_t size);
int (*p_write)(void *prochandle, paddr_t addr, char *buf,
size_t size);
pid_t (*p_getpid)(void *prochandle);
int (*p_obj_iter)(void *prochandle, tnfctl_ind_obj_f *func,
void *client_data);
} tnfctl_ind_config_t;
The first field p_read is the address of a function that can read size
bytes at address addr in the target image into the buffer buf. The
function should return 0 upon success.. The second field p_write is
the address of a function that can write size bytes at address addr in
the target image from the buffer buf. The function should return 0 upon
success. The third field p_getpid is the address of a function that
should return the process id of the target process (prochandle). The
fourth field p_obj_iter is the address of a function that iterates
over all load objects and the executable by calling the callback func‐
tion func with client_data. If func returns 0, p_obj_iter should con‐
tinue processing link objects. If func returns any other value,
p_obj_iter should stop calling the callback function and return that
value. p_obj_iter should return 0 if it iterates over all load objects.
If a failure is returned by any of the functions in config, the error
is propagated back as PREX_ERR_INTERNAL by the libtnfctl interface that
called it.
The definition of tnfctl_ind_obj_f is:
typedef int
tnfctl_ind_obj_f(void *prochandle,
const struct tnfctl_ind_obj_info *obj
void *client_data);
typedef struct tnfctl_ind_obj_info {
int objfd; /* -1 indicates fd not available */
paddr_t text_base; /* virtual addr of text segment */
paddr_t data_base; /* virtual addr of data segment */
const char *objname; /* null-term. pathname to loadobj */
} tnfctl_ind_obj_info_t;
objfd should be the file descriptor of the load object or executable.
If it is −1, then objname should be an absolute pathname to the load
object or executable. If objfd is not closed by libtnfctl, it should
be closed by the load object iterator function. text_base and data_base
are the addresses where the text and data segments of the load object
are mapped in the target process.
Whenever the target process opens or closes a dynamic object, the set
of available probes may change. See dlopen(3C) and dlclose(3C). In
indirect mode, call tnfctl_check_libs() when such events occur to make
libtnfctl aware of any changes. In other modes this is unnecessary but
harmless. It is also harmless to call tnfctl_check_libs() when no such
events have occurred.
RETURN VALUEStnfctl_indirect_open() and tnfctl_check_libs() return TNFCTL_ERR_NONE
upon success.
ERRORS
The following error codes apply to tnfctl_indirect_open():
TNFCTL_ERR_ALLOCFAIL
A memory allocation failure occurred.
TNFCTL_ERR_BUSY
Internal tracing is being used.
TNFCTL_ERR_NOLIBTNFPROBE
libtnfprobe.so.1 is not loaded in the tar‐
get process.
TNFCTL_ERR_INTERNAL
An internal error occurred.
The following error codes apply to tnfctl_check_libs():
TNFCTL_ERR_ALLOCFAIL
A memory allocation failure occurred.
TNFCTL_ERR_INTERNAL
An internal error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT Level │ MT-Safe │
└───────────────┴─────────────────┘
SEE ALSOprex(1), TNF_PROBE(3TNF), dlclose(3C), dlopen(3C), libtnfctl(3TNF),
tnfctl_probe_enable(3TNF), tnfctl_probe_trace(3TNF), tracing(3TNF),
proc(4), attributes(5)
Linker and Libraries Guide
NOTEStnfctl_indirect_open() should only be called after the dynamic linker
has mapped in all the libraries (rtld sync point) and called only after
the process is stopped. Indirect process probe control assumes the tar‐
get process is stopped whenever any libtnfctl interface is used on it.
For example, when used for indirect process probe control,
tnfctl_probe_enable(3TNF) and tnfctl_probe_trace(3TNF) should be called
only for a process that is stopped.
Mar 1, 2004 TNFCTL_INDIRECT_OPEN(3TNF)
