Add procstat_getpathname function to retrieve a process executable.

MFC after:	1 month

lib/libprocstat/Symbol.map

@@ -20,6 +20,7 @@ FBSD_1.3 {
 	procstat_freevmmap;
 	procstat_get_shm_info;
 	procstat_getgroups;
+	procstat_getpathname;
 	procstat_getrlimit;
 	procstat_getumask;
 	procstat_getvmmap;

lib/libprocstat/libprocstat.3

@@ -34,6 +34,7 @@
 .Nm procstat_close ,
 .Nm procstat_getfiles ,
 .Nm procstat_getgroups ,
+.Nm procstat_getpathname ,
 .Nm procstat_getprocs ,
 .Nm procstat_getumask ,
 .Nm procstat_getvmmap ,
@@ -128,6 +129,13 @@
 .Fa "unsigned int *count"
 .Fc
 .Ft "int"
+.Fo procstat_getpathname
+.Fa "struct procstat *procstat"
+.Fa "struct kinfo_proc *kp"
+.Fa "char *pathname"
+.Fa "size_t maxlen"
+.Fc
+.Ft "int"
 .Fo procstat_getrlimit
 .Fa "struct procstat *procstat"
 .Fa "struct kinfo_proc *kp"
@@ -268,6 +276,18 @@ The caller is responsible to free the allocated memory with a subsequent
 function call.
 .Pp
 The
+.Fn procstat_getpathname
+function gets a pointer to the
+.Vt procstat
+structure, a pointer to
+.Vt kinfo_proc
+structure, and copies the path of the process executable to
+.Fa pathname
+buffer, limiting to
+.Fa maxlen
+characters.
+.Pp
+The
 .Fn procstat_getrlimit
 function gets a pointer to the
 .Vt procstat

lib/libprocstat/libprocstat.c

@@ -136,6 +136,10 @@ static int	procstat_get_vnode_info_sysctl(struct filestat *fst,
 static gid_t	*procstat_getgroups_core(struct procstat_core *core,
     unsigned int *count);
 static gid_t	*procstat_getgroups_sysctl(pid_t pid, unsigned int *count);
+static int	procstat_getpathname_core(struct procstat_core *core,
+    char *pathname, size_t maxlen);
+static int	procstat_getpathname_sysctl(pid_t pid, char *pathname,
+    size_t maxlen);
 static int	procstat_getrlimit_core(struct procstat_core *core, int which,
     struct rlimit* rlimit);
 static int	procstat_getrlimit_sysctl(pid_t pid, int which,
@@ -1780,3 +1784,64 @@ procstat_getrlimit(struct procstat *procstat, struct kinfo_proc *kp, int which,
 		return (-1);
 	}
 }
+
+static int
+procstat_getpathname_sysctl(pid_t pid, char *pathname, size_t maxlen)
+{
+	int error, name[4];
+	size_t len;
+
+	name[0] = CTL_KERN;
+	name[1] = KERN_PROC;
+	name[2] = KERN_PROC_PATHNAME;
+	name[3] = pid;
+	len = maxlen;
+	error = sysctl(name, 4, pathname, &len, NULL, 0);
+	if (error != 0 && errno != ESRCH)
+		warn("sysctl: kern.proc.pathname: %d", pid);
+	if (len == 0)
+		pathname[0] = '\0';
+	return (error);
+}
+
+static int
+procstat_getpathname_core(struct procstat_core *core, char *pathname,
+    size_t maxlen)
+{
+	struct kinfo_file *files;
+	int cnt, i, result;
+
+	files = kinfo_getfile_core(core, &cnt);
+	if (files == NULL)
+		return (-1);
+	result = -1;
+	for (i = 0; i < cnt; i++) {
+		if (files[i].kf_fd != KF_FD_TYPE_TEXT)
+			continue;
+		strncpy(pathname, files[i].kf_path, maxlen);
+		result = 0;
+		break;
+	}
+	free(files);
+	return (result);
+}
+
+int
+procstat_getpathname(struct procstat *procstat, struct kinfo_proc *kp,
+    char *pathname, size_t maxlen)
+{
+	switch(procstat->type) {
+	case PROCSTAT_KVM:
+		warnx("kvm method is not supported");
+		return (-1);
+	case PROCSTAT_SYSCTL:
+		return (procstat_getpathname_sysctl(kp->ki_pid, pathname,
+		    maxlen));
+	case PROCSTAT_CORE:
+		return (procstat_getpathname_core(procstat->core, pathname,
+		    maxlen));
+	default:
+		warnx("unknown access method: %d", procstat->type);
+		return (-1);
+	}
+}

lib/libprocstat/libprocstat.h

@@ -169,10 +169,12 @@ int	procstat_get_vnode_info(struct procstat *procstat, struct filestat *fst,
     struct vnstat *vn, char *errbuf);
 gid_t	*procstat_getgroups(struct procstat *procstat, struct kinfo_proc *kp,
     unsigned int *count);
-int	procstat_getumask(struct procstat *procstat, struct kinfo_proc *kp,
-    unsigned short* umask);
+int	procstat_getpathname(struct procstat *procstat, struct kinfo_proc *kp,
+    char *pathname, size_t maxlen);
 int	procstat_getrlimit(struct procstat *procstat, struct kinfo_proc *kp,
     int which, struct rlimit* rlimit);
+int	procstat_getumask(struct procstat *procstat, struct kinfo_proc *kp,
+    unsigned short* umask);
 struct kinfo_vmentry	*procstat_getvmmap(struct procstat *procstat,
     struct kinfo_proc *kp, unsigned int *count);
 struct procstat	*procstat_open_core(const char *filename);