dtrace_proc4

Usage

Overview

The DTrace proc provider provides insight into events related to user processes: process and thread creation and termination events, and process signalling.

The proc:::create() probe fires when a user process is created via the fork(2), vfork(2), pdfork(2), or rfork(2) system calls. In particular, kernel processes created with the kproc(9) KPI will not trigger this probe. The proc:::create() probe's first two arguments are the new child process and its parent, respectively. The third argument is a mask of rfork(2) flags indicating which process resources are to be shared between the parent and child processes.

The proc:::exec() probe fires when a process attempts to execute a file. Its argument is the specified filename for the file. If the attempt fails because of an error, the proc:::exec-failure() probe will subsequently fire, providing the corresponding errno(2) value in its first argument. Otherwise, the proc:::exec-success() probe will fire.

The proc:::exit() probe fires when a process exits or is terminated. Its argument is the corresponding SIGCHLD signal code; valid values are documented in the siginfo(3) manual page and defined in signal.h. For example, when a process exits normally, the value of args[0] will be CLD_EXITED.

The proc:::signal-send() probe fires when a signal is about to be sent to a process. The proc:::signal-discard() probe fires when a signal is sent to a process that ignores it. This probe will fire after the proc:::signal-send() probe for the signal in question. The arguments to these probes are the thread and process to which the signal will be sent, and the signal number of the signal. Valid signal numbers are defined in the signal(3) manual page. The proc:::signal-clear() probe fires when a pending signal has been cleared by one of the sigwait(2), sigtimedwait(2), or sigwaitinfo(2) system calls. Its arguments are the signal number of the cleared signal, and a pointer to the corresponding signal information. The siginfo_t for the signal can be obtained from args[1]->ksi_info.

Arguments

Though the proc provider probes use native FreeBSD arguments types, standard D types for processes and threads are available. These are psinfo_t and lwpsinfo_t respectively, and are defined in /usr/lib/dtrace/psinfo.d. This file also defines two global variables, curpsinfo and curlwpsinfo, which provide representations of the current process and thread using these types.

The fields of psinfo_t are:

int pr_nlwp

Number of threads in the process.

pid_t pr_pid

Process ID.

pid_t pr_ppid

Process ID of the parent process, or 0 if the process does not have a parent.

pid_t pr_pgid

Process ID of the process group leader.

pid_t pr_sid

Session ID, or 0 if the process does not belong to a session.

pid_t pr_uid

Real user ID.

pid_t pr_euid

Effective user ID.

pid_t pr_gid

Real group ID.

pid_t pr_egid

Effective group ID.

uintptr_t pr_addr

Pointer to the struct proc for the process.

string pr_psargs

Process arguments.

u_int pr_arglen

Length of the process argument string.

u_int pr_jailid

Jail ID of the process.

The fields of lwpsinfo_t are:

id_t pr_lwpid

Thread ID.

int pr_flag

Thread flags.

int pr_pri

Real scheduling priority of the thread.

char pr_state

Currently always 0.

char pr_sname

Currently always ‘?’.

short pr_syscall

Currently always 0.

uintptr_t pr_addr

Pointer to the struct thread for the thread.

uintptr_t pr_wchan

Current wait address on which the thread is sleeping.

Files

/usr/lib/dtrace/psinfo.d

DTrace type and translator definitions for the proc provider.

Examples

The following script logs process execution events as they occur:

#pragma D option quiet
proc:::exec-success
{
        printf("%s", curpsinfo->pr_psargs);
}

Note that the pr_psargs field is subject to the limit defined by the kern.ps_arg_cache_limit sysctl. In particular, processes with an argument list longer than the value defined by this sysctl cannot be logged in this way.

Compatibility

The proc provider in FreeBSD is not compatible with the proc provider in Solaris. In particular, FreeBSD uses the native struct proc and struct thread types for probe arguments rather than translated types. Additionally, a number of proc provider probes found in Solaris are not currently available on FreeBSD.