HP-UX Reference (11i v2 03/08) - 2 System Calls (vol 5)

t
ttrace(2) ttrace(2)
system call number, its number of arguments and all its arguments, its return value
and its error return in the ttstate_t
structure. If the system call is a fork(),
vfork() or exec() and if, respectively, the
TTEVT_FORK, TTEVT_VFORK or
TTEVT_EXEC event is set, only the notification associated with these events is per-
formed. See the TT_PROC_SET_SCBM
request.
TTEVT_SYSCALL_ENTRY
This event flag requests notification of system call entry points. By default, all system
calls stop at this event if it is selected. The information provided is the same as for
TTEVT_SYSCALL_RETURN
events but the return value and error are always zero.
TTEVT_SYSCALL_RESTART
Identical to TTEVT_SYSCALL_ENTRY
but for system call restarts.
TTEVT_EXIT This event flag indicates that the traced process needs to notify the debugger action
when it invokes exit(). When set, the traced thread stops while still potentially
multithreaded.
TTEVT_LWP_CREATE
This event flag indicates that the debugger wants to be notified when the
lwp_create() system call is invoked to create a thread. When set, the calling
thread stops and provides the debugger with the lwpid of the newly created thread.
TTEVT_LWP_EXIT
This event flag indicates that the debugger wants to be notified when a thread is exit-
ing via the lwp_exit() system call. The thread stops upon entry to the system call.
TTEVT_LWP_TERMINATE
This event flag indicates that the debugger wants to be notified when a caller thread
invokes the lwp_terminate()
call on a target thread. When set, the calling
thread stops upon entering the system call and provides the lwpid of the thread to be
terminated in the
ttstate_t structure.
TTEVT_LWP_ABORT_SYSCALL
This event flag indicates that the debugger is to be notified when the
lwp_abort_syscall()
system call is invoked. The lwpid of the target thread is
provided in the
ttstate_t structure.
TTEVT_BPT_SSTEP
This event flag tells the kernel to perform event-based single-stepping and breakpoint
notification. If this event is requested, SIGTRAP loses all special meaning. It is highly
recommended that debuggers use this event instead of the old signal-based method as
it will allow breakpoints and single-steps to take place regardless of the signals the
thread is blocking. Unlike the signal-based method, it also guarantees that single-
steps and breakpoints events are generated in the context of the thread even if other
threads are active in the process.
Note that mixing signal-based and event-based breakpoint/single-stepping may result
in unexpected SIGTRAPs being posted to the process being debugged.
Additional Requests
Additional requests are available:
TT_LWP_RUREGS
TT_LWP_RUREGS_NOATTACH
With these requests, on Itanium-based system: the register specified by addr is
returned to the calling process making the request. The data argument is the size
of the read. The addr2 argument points to the location in the calling process’s
address space where the data will be written. The addr argument must be a value
defined by __uregs_t in <machine/sys/uregs.h>.
The registers that may be read or written vary depending on whether the target
thread is stopped in a syscall or interruption context. Retreive the __reason value
first to determine which applies. The following registers may be read/written in
each context:
Section 2−−448 Hewlett-Packard Company − 11 − HP-UX 11i Version 2: August 2003