ttrace(2)

This request must be issued by a child process if it is to be traced by its parent.

The addr2 argument specifies the action to be taken by the loader when the child process does an exec(). If the value is TT_GEN_SHLIB_BPT, the loader will communicate certain events to the debugger through an architected break instruction. The information obtained through these events can be used by the debugger to identify all the load modules in the program and their unwind information. If the debugger is not interested in these events the value must be set to 0 (zero).

The pid, lwpid, and addr arguments must be set to 0 (zero) and data must be set to TT_VERSION. Peculiar results occur if the parent does not expect to trace the child.

Note: It is critical for future backward compatibility that the TT_VERSION macro itself be used and not its value.

This request allows the calling process to trace the process identified by pid. The process pid does not have to be a child of the calling process, but the effective user ID of the calling process must match the real and saved uid of the process pid unless the tracing process has the OWNER privilege.

When this call returns, the target process (all its threads) is stopped.

The addr argument specifies the action to be taken if the debugger exits without having detached the target process. If the value is TT_KILL_ON_EXIT, the attached process(es) will be killed. If the value is TT_DETACH_ON_EXIT, the attached process(es) will be resumed and detached as if the debugger had performed a TT_PROC_DETACH request.

The addr2 argument specifies the action to be taken by the loader when the target process does an exec(). If the value is TT_GEN_SHLIB_BPT, the loader will communicate certain events to the debugger through an architected break instruction. The information obtained through these events can be used by the debugger to identify all the load modules in the program and their unwind information. If the debugger is not interested in these events the value must be set to 0 (zero).

The lwpid argument must be set to zero and data must be TT_VERSION (see TT_PROC_SETTRC above).

This request detaches the traced process and allows it to continue executing. It behaves identically to TT_PROC_CONTINUE except that the process is no longer being traced after the call returns.

For this request, the lwpid, addr, data, and addr2 arguments must be set to zero.

These requests allow reading from the target process text.

The addr argument specifies the offset to be read from. The data argument specifies the number of bytes to read and the addr2 argument specifies where to store that data in the tracing process.

The lwpid argument must be set to zero.

These requests allow reading from the data space.

The addr argument specifies the offset to be read from. The data argument specifies the number of bytes to read and the addr2 argument specifies where to store that data in the tracing process.

The lwpid argument must be set to zero.

These requests allow writing into the target process text (TT_PROC_WRTEXT) and data spaces (TT_PROC_WRDATA).

The addr argument specifies the offset to be written to. The data argument specifies the number of bytes to write.a The addr2 argument specifies where to get the data in the tracing process.

The lwpid argument must be set to zero.

This request causes the traced process (all its threads) to stop. If a thread was already stopped by the debugger prior to this call, its state is not modified.

The lwpid, addr, data, and addr2 arguments must be set to zero.

This request causes the entire traced process to resume execution. All threads that had been stopped directly (request) or indirectly (event) by the debugger are resumed with all their pending signals intact.

The data, addr, and addr2 arguments must be set to zero.

This request is used by the calling process to access the path name of the executable file provided as a path or file argument to exec(). The request reads data bytes of data of the pathname string from the traced process' context into the data buffer in user space pointed to by addr.

In the typical case, data is equal to the value of the ttexec_data_t.tts_len member of the ttstate_t structure returned via the TT_LWP_GET_STATE or other ttrace requests returning a Lightweight Process (LWP or lwp) state. The length of the path does not include a terminating null character. The data is available during the entire life of the process.

The lwpid and addr2 arguments must be set to zero.

This request returns the process-wide event flags and signal mask values.

The data argument specifies the number of bytes to be read from the context of the traced process into the ttevent_t data structure in user space pointed to by addr.

The lwpid and addr2 arguments must be set to zero.

The ttevent_t data structure is as follows:

The options provided in tte_opts control the behavior of child processes produced by fork() and are as follows:

If TTEO_NOSTRCCHLD is set, the child process resulting from a fork() will not be traced. This makes it possible for a debugger to debug another debugger. The TTEO_PROC_INHERIT and TTEO_LWP_INHERIT options allow events to be inherited by child processes and threads respectively. Refer to the EVENTS section below.

If TTEO_NORM_SIGTRAP is set, the SIGTRAP signal behaves normally. That is, it is getting delivered (the default behavior is to drop these signals).

This request allows the tracing process to establish events and signals the traced process will respond to. Refer to the EVENTS section for a description of these events.

The addr argument is a pointer to a ttevent_t structure to be copied into the target process. The data argument specifies the number of bytes to be transferred.

The lwpid and addr2 arguments must be set to zero.

This request returns the process-wide signal mask value for the target process that was set using TT_PROC_SET_SIGMASK.

The data argument specifies the number of bytes to be read from the context of the traced process into the ttmask_t data structure in user space pointed by addr.

The lwpid and addr2 arguments must be set to zero.

The ttmask_t data structure is as follows:

The options provided in ttm_opts control the behavior of signal masks on child processes produced by fork() and are as follows:

The TTMO_PROC_INHERIT and TT_LWP_INHERIT option allow signal masks to be inherited by child processes and threads respectively.

This request allows the tracing process to change the signal mask on the target process.

The addr argument is a pointer to a ttmask_t structure to be copied into the target process. The data argument specifies the number of bytes to be transferred.

The lwpid and addr2 arguments must be set to zero.

The resulting signal mask on the traced process will be a union of the current signal mask on the target process and the set pointed by the ttm_signals field in the ttmask_t structure. Setting the ttm_signals to an empty set results in clearing the signal mask that was previously set using this request.

This request returns the ttstate_t structure associated with the first thread on the stopped list. It resets the list pointer to the first entry in the list. The TT_PROC_GET_NEXT_LWP_STATE request (see below) provides the means to examine the state of other stopped threads.

The data argument specifies the number bytes to be read from the context of the traced process into the ttstate_t data structure in the user space pointed to by addr. The lwpid and addr2 arguments must be zero.

The ttstate_t structure provides the debugger with the means to query the system for the state of a thread. It is established when a thread enters the debugger stopped state and, except for the TTS_WAITEDFOR bit, is invariant until the thread is resumed. Its layout is as follows:

tts_pid is the process ID.

tts_lwpid is the lwpid of the stopped thread.

tts_user_tid is the thread's user ID.

tts_event is the event that caused the stop (TTEVT_NONE if the thread stopped because of a ttrace command).

The tts_flags provide information about the state of the thread before it was stopped. The information specifies whether or not the thread has been waited for by ttrace_wait(), whether or not it is processing a system call, whether it is a 32-bit or a 64-bit process and whether the thread is in the exit() system call. The values are as follows:

The following three arguments provide information regarding the system call being executed when the thread was stopped. This information is valid only if the TTS_INSYSCALL bit is set in tts_flags.

tts_scno is the system call number.

tts_scnargs is the number of arguments of the system call.

tts_scarg is the argument list of the system call.

The data associated with a TTEVT_EXEC event is as follows:

tts_pathlen is the length of the pathname of the exec() system call.

The data associated with a TTEVT_FORK, TTEVT_VFORK or TTEVT_FORK_FAIL event is as follows:

tts_fpid is the process ID of the other side of the fork. This field is set to zero for the TTEVT_FORK_FAIL event.

tts_flwpid is the thread ID of the other side of the fork. This field is set to zero for the TTEVT_FORK_FAIL event.

tts_isparent is zero for the child event and one for the parent.

tts_errno is set to error code indicating the reason for error in TTEVT_FORK_FAIL event. This field is set to zero for the TTEVT_FORK and TTEVT_VFORK events.

The data associated with a TTEVT_PREFORK event is as follows:

tts_fpid is the process ID of the other side of the fork.

tts_flwpid is the thread ID of the other side of the fork.

tts_type is the type of fork.

The data associated with a TTEVT_SIGNAL event is as follows:

tts_signal is the signal number.

tts_sigflags is TTSF_USERSIGINFO if a siginfo was delivered with the signal, 0 otherwise.

tts_sigaction is the disposition of the signal.

tts_siginfo is the siginfo, if applicable.

The data associated with a TTEVT_LWP_CREATE, TTEVT_LWP_TERMINATE or TTEVT_LWP_ABORT_SYSCALL event is as follows:

tts_target_lwpid is the lwpid of the targeted lwp.

The data associated with a TTEVT_SYSCALL event is as follows:

The tts_rval fields are the return value(s) of the system call.

tts_errno is the error status if the system call failed.

The data associated with a TTEVT_LWP_EXIT event is as follows:

tts_exitcode is the exit code of the process.

The data associated with a TTEVT_BPT_SSTEP event is as follows:

On PA-RISC systems:

tts_isbpt is set to zero if it is a single-step and to one if the event is a breakpoint (including single-stepping into a breakpoint).

On Itanium(\rg-based systems:

This request is identical to TT_PROC_GET_FIRST_LWP_STATE except that it returns the state for the next thread on the stopped list. As events cause threads to stop, they are added to this list. This provides a way for the tracing process to examine the state of all the stopped threads in the target process. Both these requests return either a 1 (one) if valid data is returned or 0 (zero) otherwise. Valid data is returned if the status is that there was a stopped thread for which to return.

This request allows the debugger to obtain protection information for a page in the address space of the code being debugged. The addr argument specifies the address for which the protection is to be obtained. The addr2 argument specifies the address of an integer in which the protection data will be copied.

For this request, the lwpid and data arguments must be set to zero.

This requests allows the debugger to modify the protection of the address space of the code being debugged. The addr argument specifies the start address. The data argument specifies the extent (in bytes) of the space to be modified. The addr2 argument contains the new protection. Note that protection changes affect whole pages (see mprotect(2) for more information).

For this request, the lwpid argument must be set to zero.

This request allows the debugger to pass a bitmap to the kernel indicating which system calls should cause a debugger stop.

The addr argument must be set to TTSCBM_SELECT or TTSCBM_UNSELECT to indicate whether the bitmap represents a positive (meaning that the calls in the bitmap will result in a stop) or a negative (meaning that all calls except those in the bit map will result in a stop) list.

The data argument is the size of the bitmap, in bytes. A size of zero indicates that the current bitmap, if any, should be cleared.

The addr2 argument is the user address where the bitmap is located. If data is zero, this value must be zero too.

The lwpid argument must be zero.

This request causes the traced process to terminate. It has the same consequence as exit() being invoked by one of the process threads. The lwpid, addr, data, and addr2 arguments must be zero.

This request causes the traced process to generate a core file without modifying the process's state. If addr is zero, the core file is created in the target process's current working directory and is named core.pid; where, pid is the process ID of the target process. If addr is non-zero, it is the address of a buffer containing the path of the core file to be created. Up to MAXPATHLEN bytes will be read from the buffer. If the path is not absolute (not starting with a slash), it is relative to the target process's current working directory. In both cases, the directory must exist and, if present, the file must be a regular file. In all cases, the debugger's credentials are used and standard permission checking applies. The lwpid, data, and addr2 arguments must be zero.

Interaction with coreadm() and coreadm: If a process has a non-default core file setting and addr is zero, then the core file will be will be generated with the core file setting in effect. If addr is a non-NULL value, then the core file will be generated in the target path, as specified by addr, and will be created as core.pid.

These requests return the number of physical hardware instruction or data breakpoint registers that are available for use.

These requests write process-wide breakpoint values into breakpoint registers. data bytes from addr2 will be written to the instruction or data breakpoint register(s) named by addr. For Itanium-based systems, addr must be an even number less than the value returned by TT_PROC_GET_NUM_IBPT_REGS or TT_PROC_GET_NUM_DBPT_REGS respectively. data must be 16 bytes. The request will set a value into the pair of instruction or data breakpoint registers addr and addr+1.

Note: The available breakpoint registers must be shared between process-wide breakpoints and per-thread breakpoints. If a breakpoint register is currently being used as a per-thread breakpoint in any thread within the target process, it may not be used for a process-wide breakpoint.

Note: This does not limit the number of break instructions that may be present in the program text.

Note: These requests are not supported on PA-RISC versions of HP-UX.

These requests read process-wide breakpoint values from breakpoint registers. data bytes are copied from the instruction or data breakpoint register(s) specified by addr to addr2 in debugger memory. data must be 16 bytes. The request will get the value of the pair of instruction or data breakpoint registers addr and addr+1.

Note: These requests are not supported on PA-RISC versions of HP-UX.

These requests return a pointer to the argument list passed to the initial thread of the process at execve() time (that is, argc, argv, envp). If the target process has not overwritten these arguments, this address can be used to retrieve the full argument and environment list.

Note: These requests are not supported on PA-RISC versions of HP-UX.

This request causes the thread identified by lwpid to stop executing. If the thread is already stopped by the debugger, or by an event, an error is returned.

The addr, data, and addr2 arguments must be zero.

This request causes the thread identified by lwpid to resume execution or, rather, to return to the state it was in prior to being stopped by the debugger. If the thread had not previously been stopped by the debugger, an error is returned.

If addr is not TT_NOPC, that value is loaded in the program counter before execution is resumed. Unexpected behavior will result if this value is not within the same function since only the PC, not the context, is being modified.

If data is non-zero, it is expected to be a valid signal number and the thread will continue as if it had received this signal.

The addr2 argument must be zero.

This request causes the stopped thread identified by lwpid to resume execution for one machine instruction. It causes a flag to be set so that an interrupt occurs upon the completion of one machine instruction, and then executes the same steps as listed above for the TT_LWP_CONTINUE request.

This request causes the stopped thread identified by lwpid to resume execution until a taken branch instruction is executed. It causes a flag to be set so that an interrupt occurs upon completion of the next taken branch instruction, and then executes the same steps as listed above for the TT_LWP_CONTINUE request.

Note: This request is not supported on PA-RISC versions of HP-UX.

This request is the same as TT_PROC_GET_EVENT_MASK except for the thread identified by lwpid.

This request is the same as TT_PROC_SET_EVENT_MASK except for the thread identified by lwpid.

This request is the same as TT_PROC_GET_SIGMASK except for the thread identified by lwpid.

This request is the same as TT_PROC_SET_SIGMASK except for the thread identified by lwpid.

This calls returns the state of the thread identified by lwpid. If the thread was not previously stopped by the debugger or waiting to be continued after an event, an error is returned.

These requests write per-thread breakpoint values into breakpoint registers. data bytes from addr2 will be written to the instruction or data breakpoint register(s) named by addr. For Itanium-based systems, addr must be an even number less than the value returned by TT_PROC_GET_NUM_IBPT_REGS or TT_PROC_GET_NUM_DBPT_REGS respectively. data must be 16 bytes. The request will set a value into the pair of instruction or data breakpoint registers addr and addr+1. These values will be enabled only when the specified thread is running. They are identical to TT_PROC_SET_IBPT_REGS and TT_PROC_SET_DBPT_REGS respectively in other respects.

Note: The available breakpoint registers must be shared between process-wide breakpoints and per-thread breakpoints. If a breakpoint register is currently being used as a process-wide breakpoint within the target process, it may not be used for a per-thread breakpoint in any thread of the target process.

Note: These requests are not supported on PA-RISC versions of HP-UX.

These requests read per-thread breakpoint values from breakpoint registers. They are identical to TT_PROC_GET_IBPT_REGS and TT_PROC_GET_DBPT_REGS respectively in other respects.

Note: These requests are not supported on PA-RISC versions of HP-UX.

These requests allow the calling process to access stacked general register values that have not yet been written to the RSE backing store. data bytes that would have been spilled at addr on the user's RSE backing store, had the RSE been flushed, are copied to or from addr2 in the calling process. The addr argument must be 8-byte-aligned and conform to ar.bspstore ≤ addr < ar.bsp. data must be a multiple of 8 bytes, and addr+data must also conform to ar.bspstore ≤ addr+data < ar.bsp. As a special case, to retrieve the final NaT collection, addr == ar.bsp | 0x1f8 and data == 8 is also accepted.

Note: This facility should be used only to modify values of registers that were dirty when the thread was stopped. Do not use this facility if the values of ar.bsp or ar.bspstore have been modified.

Note: These requests are not supported on PA-RISC versions of HP-UX.

With these requests, on Itanium-based systems 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. Retrieve the __reason value first to determine which applies. The following registers may be read or written in each context:

On PA-RISC systems, the words at offset addr in the save_state structure are returned to the calling process. 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 word-aligned and addr+data must be less than or equal to sizeof (save_state_t) (see the file <machine/save_state.h>).

Note: On Itanium-based systems, 8, 9 and 16 byte reads are supported. Static general registers may be read with 8 or 9 byte requests. The NaT bit corresponding to the general register is returned in bit 0 of the 9th byte if requested. Floating point register reads must be 16 byte requests. All other register reads must be 8 byte requests. Individual bits, such as __p1...__p63, will be returned in bit 0 of an 8 byte word.

On PA-RISC systems, only 4 and 8 byte reads and writes are currently supported.

With this request, on Itanium-based systems: data bytes of data pointed to by addr2 are written to the register specified by addr which must be a __uregs_t value as noted above. On PA-RISC systems: data bytes of data pointed to by addr2 are written at offset addr in the save_state structure. Only these locations can be written in this way: the general registers, most floating-point registers, a few control registers, and certain bits of the interruption processor status word.

Note: On Itanium-based systems, 8, 9 and 16 byte writes are supported. Static general registers may be written as 8 or 9 byte requests. Bit 0 of the 9th byte is written to the NaT bit corresponding to the general register if requested. An 8 byte write to a static general register will clear the corresponding NaT bit. Floating point register writes must be 16 byte requests. All other register writes must be 8 byte requests.

On PA-RISC systems, only 4 and 8 bytes reads and writes are currently supported.

This request performs a series of requests on arbitrary threads within a single target process specified by pid. The lwpid argument must be 0 (zero).

The addr argument points to an array of up to TT_VEC_MAX tt_vec_ts, in the calling process's address space. Each contains a request to be performed and the corresponding arguments. The tt_vec_t contains at least the following fields:

The array of tt_vec_ts must be cleared (for example, with bzero()) prior to filling in the fields listed above. (The names of fields in this structure, other than those listed above, (if any) are subject to change without notice.)

See the descriptions of the individual requests for details of the addr, data and addr2 arguments required for each.

The data argument specifies the number of request elements in the array pointed to by addr.

The addr2 argument points to a location in the calling process's address space containing a single tt_vec_res_t. The tt_vec_res_t contains at least the following fields:

The tt_vec_res_t must be cleared (for example, with bzero()) prior to filling in the fields listed above.

On return, ttvr_count will contain the number of requests from the array pointed to by addr which succeeded. TT_VEC_GENERIC stops processing requests from the array upon encountering an error.

The first ttvr_count elements of the array pointed to by ttvr_ret1 will be filled in with the return values of the corresponding requests. Although none of the requests supported by TT_VEC_GENERIC at this time produce return values, additional requests which produce return values may be supported in the future.

This request performs a series of TT_LWP_RUREGS requests on a single thread within the target process in a single call. The lwpid argument must specify a valid thread within the target process.

The addr argument points to a location in the calling process's address space containing an array of up to TT_VEC_MAX tt_reg_vecs, each containing the arguments for the request(s) to be performed. The tt_reg_vec_t structure contains the following fields:

The ttrv_reg, ttrv_size, and ttrv_addr arguments correspond to the addr, data, and addr2 arguments (respectively) of the TT_LWP_RUREGS request. See the description of the TT_LWP_RUREGS request for details.

The data argument specifies the number of request elements in the array pointed to by addr.

The addr2 argument points to an 8-byte location in the calling process's address space into which the number of successful requests will be written. The TT_VEC_LWP_RUREGS request stops processing requests upon encountering an error.

This call returns the feature level of the operating system and has been introduced to help debugger developers make their tools more portable from one version to another. The pid, lwpid, addr, data, and addr2 arguments must be 0 (zero).

11.0 systems can be identified by the fact that this call will return an error. Later releases will return the TT_FEATURE_LEVEL value the operating system was compiled with (see ttrace.h). The release levels for systems newer than 11.0 are:

This event flag indicates that the traced thread needs to examine signal mask bits when processing signals. This means that, by default, threads stop when receiving a signal. If the signal being processed has its mask bit set, signal processing continues as though the process were not traced: the traced thread is not stopped, and the tracing process is not notified of the signal. On the other hand, if the signal mask bit is not set for the signal being processed, the traced thread is stopped and the tracing process is notified via ttrace_wait().

Note that the SIGKILL signal can never be unmasked. It behaves as though its mask bit were always set. This means that a SIGKILL signal cannot be used to stop a traced thread. The SIGTRAP signal is also special in that it is used to stop traced threads when they respond to a trap, such as a breakpoint or a single step. Consequently, masking SIGTRAP, even though allowed, will result in unexpected behavior in these conditions.

This event flag indicates that the traced thread needs to take special action when it invokes fork(). When set, both the parent thread and the initial thread in the child process stop (after the child process is marked as a traced process and adopts its parent's debugger). Both threads log the fact that they stopped in response to a TTEVT_FORK event. The parent thread provides the pid of the child process in the appropriate portion of the ttstate_t structure. The initial thread of the child process provides the pid of the parent in the same location. See the ttstate_t structure description for further details.

This event flag indicates that the traced thread needs to take special action when it invokes vfork(). The behavior is identical to that of TTEVT_FORK but it is important to note that the caveats with respect to vfork(), continue to apply here. In particular, it needs to be remembered that when the child process stops, its parent is asleep, and that the child borrows the parent's address space until a call to exec() or an exit (either by a call to exit() or abnormally) takes place. Continuing the parent process before the above steps take place results in an error.

This event flag indicates that the traced thread needs to notify the debugger, during a fork() or vfork() operation, just after the child process ID and thread ID is known and before the child process is created and set to run. The parent thread is stopped and it provides the pid of the child process and lwpid of the child's initial thread.

Note: Upon continuation from this event, the traced thread does not guarantee that the child process with an earlier returned pid and lwpid can be created since the fork() or vfork() operation might fail.

This event flag indicates that the traced thread needs to notify the debugger upon the failure of a fork() or vfork() operation. The traced parent thread is stopped and returns the error code for fork failure.

This event flag indicates that a traced thread needs to notify the debugger upon completion of loading the new executable file, in the exec() system call. The length of the pathname string (not including a null terminating character) is returned in the ttstate_t structure. The path may subsequently be obtained using the TT_PROC_GET_PATHNAME request.

This event flag indicates that the traced process will notify the debugger upon return of all system calls. The traced process will also provide the following information: the 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 performed. See the TT_PROC_SET_SCBM request.

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.

Identical to TTEVT_SYSCALL_ENTRY but for system call restarts.

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.

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.

This event flag indicates that the debugger wants to be notified when a thread is exiting via the lwp_exit() system call. The thread stops upon entry to the system call.

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.

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.

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 breakpoint 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.