[PATCH v2 3/3] vstatus: Display an informational message when the VSTATUS character is pressed or TIOCSTAT ioctl is called.
Walt Drummond
walt at drummond.us
Mon Feb 7 02:48:54 AEDT 2022
When triggered by pressing the VSTATUS key or calling the TIOCSTAT
ioctl, the n_tty line discipline will display a message on the user's
tty that provides basic information about the system and an
'interesting' process in the current foreground process group, eg:
load: 0.58 cmd: sleep 744474 [sleeping] 0.36r 0.00u 0.00s 0% 772k
The status message provides:
- System load average
- Command name and process id (from the perspective of the session)
- Scheduler state
- Total wall-clock run time
- User space run time
- System space run time
- Percentage of on-cpu time
- Resident set size
The message is only displayed when the tty has the VSTATUS character
set, the local flags ICANON and IEXTEN are enabled and NOKERNINFO is
disabled; it is always displayed when TIOCSTAT is called regardless of
tty settings.
Signed-off-by: Walt Drummond <walt at drummond.us>
---
drivers/tty/Makefile | 2 +-
drivers/tty/n_tty.c | 34 +++++++
drivers/tty/n_tty_status.c | 181 +++++++++++++++++++++++++++++++++++++
drivers/tty/tty_io.c | 2 +-
include/linux/tty.h | 5 +
5 files changed, 222 insertions(+), 2 deletions(-)
create mode 100644 drivers/tty/n_tty_status.c
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index a2bd75fbaaa4..3539d7ab77e5 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -2,7 +2,7 @@
obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \
tty_buffer.o tty_port.o tty_mutex.o \
tty_ldsem.o tty_baudrate.o tty_jobctrl.o \
- n_null.o
+ n_null.o n_tty_status.o
obj-$(CONFIG_LEGACY_PTYS) += pty.o
obj-$(CONFIG_UNIX98_PTYS) += pty.o
obj-$(CONFIG_AUDIT) += tty_audit.o
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 64a058a4c63b..fd70efc333d7 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -80,6 +80,7 @@
#define ECHO_BLOCK 256
#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
+#define STATUS_LINE_LEN 160 /* tty status line will truncate at this length */
#undef N_TTY_TRACE
#ifdef N_TTY_TRACE
@@ -127,6 +128,8 @@ struct n_tty_data {
struct mutex output_lock;
};
+static void n_tty_status(struct tty_struct *tty);
+
#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
static inline size_t read_cnt(struct n_tty_data *ldata)
@@ -1334,6 +1337,11 @@ static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
commit_echoes(tty);
return;
}
+ if (c == STATUS_CHAR(tty) && L_IEXTEN(tty)) {
+ if (!L_NOKERNINFO(tty))
+ n_tty_status(tty);
+ return;
+ }
if (c == '\n') {
if (L_ECHO(tty) || L_ECHONL(tty)) {
echo_char_raw('\n', ldata);
@@ -1763,6 +1771,7 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
set_bit(EOF_CHAR(tty), ldata->char_map);
set_bit('\n', ldata->char_map);
set_bit(EOL_CHAR(tty), ldata->char_map);
+ set_bit(STATUS_CHAR(tty), ldata->char_map);
if (L_IEXTEN(tty)) {
set_bit(WERASE_CHAR(tty), ldata->char_map);
set_bit(LNEXT_CHAR(tty), ldata->char_map);
@@ -2413,6 +2422,26 @@ static unsigned long inq_canon(struct n_tty_data *ldata)
return nr;
}
+static void n_tty_status(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ char *msg;
+ size_t len;
+
+ msg = kzalloc(STATUS_LINE_LEN, GFP_KERNEL);
+
+ if (ldata->column != 0) {
+ *msg = '\n';
+ len = n_tty_get_status(tty, msg + 1, STATUS_LINE_LEN - 1);
+ } else {
+ len = n_tty_get_status(tty, msg, STATUS_LINE_LEN);
+ }
+
+ do_n_tty_write(tty, NULL, msg, len);
+
+ kfree(msg);
+}
+
static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg)
{
@@ -2430,6 +2459,11 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
retval = read_cnt(ldata);
up_write(&tty->termios_rwsem);
return put_user(retval, (unsigned int __user *) arg);
+ case TIOCSTAT:
+ down_read(&tty->termios_rwsem);
+ n_tty_status(tty);
+ up_read(&tty->termios_rwsem);
+ return 0;
default:
return n_tty_ioctl_helper(tty, file, cmd, arg);
}
diff --git a/drivers/tty/n_tty_status.c b/drivers/tty/n_tty_status.c
new file mode 100644
index 000000000000..f0e053651368
--- /dev/null
+++ b/drivers/tty/n_tty_status.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-1.0+
+/*
+ * n_tty_status.c --- implements VSTATUS and TIOCSTAT from BSD
+ *
+ * Display a basic status message containing information about the
+ * foreground process and system load on the users tty, triggered by
+ * the VSTATUS character or TIOCSTAT. Ex,
+ *
+ * load: 14.11 cmd: tcsh 19623 [running] 185756.62r 88.00u 17.50s 0% 4260k
+ *
+ */
+
+#include <linux/tty.h>
+#include <linux/mm.h>
+#include <linux/sched/loadavg.h>
+#include <linux/sched/mm.h>
+
+/* Convert nanoseconds into centiseconds */
+static inline long ns_to_cs(long l)
+{
+ return l / (NSEC_PER_MSEC * 10);
+
+}
+
+/* We want the pid from the context of session */
+static inline pid_t __get_pid(struct task_struct *tsk, struct tty_struct *tty)
+{
+ struct pid_namespace *ns;
+
+ spin_lock_irq(&tty->ctrl.lock);
+ ns = ns_of_pid(tty->ctrl.session);
+ spin_unlock_irq(&tty->ctrl.lock);
+
+ return __task_pid_nr_ns(tsk, PIDTYPE_PID, ns);
+}
+
+/* This is the same odd "bitmap" described in
+ * fs/proc/array.c:get_task_state(). Consistency with standard
+ * implementations of VSTATUS requires a different set of state
+ * names.
+ */
+static const char * const task_state_name_array[] = {
+ "running",
+ "sleeping",
+ "disk sleep",
+ "stopped",
+ "tracing stop",
+ "dead",
+ "zombie",
+ "parked",
+ "idle",
+};
+
+static inline const char *get_task_state_name(struct task_struct *tsk)
+{
+ BUILD_BUG_ON(1 + ilog2(TASK_REPORT_MAX) != ARRAY_SIZE(task_state_name_array));
+ return task_state_name_array[task_state_index(tsk)];
+}
+
+static inline struct task_struct *compare(struct task_struct *new,
+ struct task_struct *old)
+{
+ unsigned int ostate, nstate;
+
+ if (old == NULL)
+ return new;
+
+ ostate = task_state_index(old);
+ nstate = task_state_index(new);
+
+ if (ostate == nstate) {
+ if (old->start_time > new->start_time)
+ return old;
+ return new;
+ }
+
+ if (ostate < nstate)
+ return old;
+
+ return new;
+}
+
+static struct task_struct *pick_process(struct tty_struct *tty)
+{
+ struct task_struct *new, *winner = NULL;
+
+ read_lock(&tasklist_lock);
+ spin_lock_irq(&tty->ctrl.lock);
+
+ do_each_pid_task(tty->ctrl.pgrp, PIDTYPE_PGID, new) {
+ winner = compare(new, winner);
+ } while_each_pid_task(tty->ctrl.pgrp, PIDTYPE_PGID, new);
+
+ spin_unlock_irq(&tty->ctrl.lock);
+
+ if (winner)
+ winner = get_task_struct(winner);
+
+ read_unlock(&tasklist_lock);
+
+ return winner;
+}
+
+size_t n_tty_get_status(struct tty_struct *tty, char *msg, size_t msglen)
+{
+ struct task_struct *p;
+ struct mm_struct *mm;
+ struct rusage rusage;
+ unsigned long loadavg[3];
+ uint64_t pcpu, cputime, wallclock;
+ struct timespec64 utime, stime, rtime;
+ char tname[TASK_COMM_LEN];
+ unsigned int pid;
+ char *state;
+ unsigned long rss = 0;
+ size_t len = 0;
+
+ get_avenrun(loadavg, FIXED_1/200, 0);
+ len = scnprintf(msg + len, msglen - len, "load: %lu.%02lu ",
+ LOAD_INT(loadavg[0]), LOAD_FRAC(loadavg[0]));
+
+ if (tty->ctrl.session == NULL) {
+ len += scnprintf(msg + len, msglen - len,
+ "not a controlling terminal\n");
+ goto out;
+ }
+
+ if (tty->ctrl.pgrp == NULL) {
+ len += scnprintf(msg + len, msglen - len,
+ "no foreground process group\n");
+ goto out;
+ }
+
+ /* Note that if p is refcounted */
+ p = pick_process(tty);
+ if (p == NULL) {
+ len += scnprintf(msg + len, msglen - len,
+ "empty foreground process group\n");
+ goto out;
+ }
+
+ mm = get_task_mm(p);
+ if (mm) {
+ rss = get_mm_rss(mm) * PAGE_SIZE / 1024;
+ mmput(mm);
+ }
+ get_task_comm(tname, p);
+ getrusage(p, RUSAGE_BOTH, &rusage);
+ pid = __get_pid(p, tty);
+ state = (char *) get_task_state_name(p);
+ wallclock = ktime_get_ns() - p->start_time;
+ put_task_struct(p);
+
+ /* After this point, any of the information we have on p might
+ * become stale. It's OK if the status message is a little bit
+ * lossy.
+ */
+
+ utime.tv_sec = rusage.ru_utime.tv_sec;
+ utime.tv_nsec = rusage.ru_utime.tv_usec * NSEC_PER_USEC;
+ stime.tv_sec = rusage.ru_stime.tv_sec;
+ stime.tv_nsec = rusage.ru_stime.tv_usec * NSEC_PER_USEC;
+ rtime = ns_to_timespec64(wallclock);
+
+ cputime = timespec64_to_ns(&utime) + timespec64_to_ns(&stime);
+ pcpu = div64_u64(cputime * 100, wallclock);
+
+ len += scnprintf(msg + len, msglen - len,
+ /* task, PID, task state */
+ "cmd: %s %d [%s] "
+ /* rtime, utime, stime, %cpu rss */
+ "%llu.%02lur %llu.%02luu %llu.%02lus %llu%% %luk\n",
+ tname, pid, state,
+ rtime.tv_sec, ns_to_cs(rtime.tv_nsec),
+ utime.tv_sec, ns_to_cs(utime.tv_nsec),
+ stime.tv_sec, ns_to_cs(stime.tv_nsec),
+ pcpu, rss);
+
+out:
+ return len;
+}
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 6616d4a0d41d..f2f4f48ea502 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -125,7 +125,7 @@ struct ktermios tty_std_termios = { /* for the benefit of tty drivers */
.c_oflag = OPOST | ONLCR,
.c_cflag = B38400 | CS8 | CREAD | HUPCL,
.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
- ECHOCTL | ECHOKE | IEXTEN,
+ ECHOCTL | ECHOKE | IEXTEN | NOKERNINFO,
.c_cc = INIT_C_CC,
.c_ispeed = 38400,
.c_ospeed = 38400,
diff --git a/include/linux/tty.h b/include/linux/tty.h
index cbe5d535a69d..2e483708608c 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -49,6 +49,7 @@
#define WERASE_CHAR(tty) ((tty)->termios.c_cc[VWERASE])
#define LNEXT_CHAR(tty) ((tty)->termios.c_cc[VLNEXT])
#define EOL2_CHAR(tty) ((tty)->termios.c_cc[VEOL2])
+#define STATUS_CHAR(tty) ((tty)->termios.c_cc[VSTATUS])
#define _I_FLAG(tty, f) ((tty)->termios.c_iflag & (f))
#define _O_FLAG(tty, f) ((tty)->termios.c_oflag & (f))
@@ -114,6 +115,7 @@
#define L_PENDIN(tty) _L_FLAG((tty), PENDIN)
#define L_IEXTEN(tty) _L_FLAG((tty), IEXTEN)
#define L_EXTPROC(tty) _L_FLAG((tty), EXTPROC)
+#define L_NOKERNINFO(tty) _L_FLAG((tty), NOKERNINFO)
struct device;
struct signal_struct;
@@ -389,6 +391,9 @@ extern void __init n_tty_init(void);
static inline void n_tty_init(void) { }
#endif
+/* n_tty_status.c */
+size_t n_tty_get_status(struct tty_struct *tty, char *msg, size_t msglen);
+
/* tty_audit.c */
#ifdef CONFIG_AUDIT
extern void tty_audit_exit(void);
--
2.30.2
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