Date: Sun, 18 Jun 2023 21:23:06 -0700 From: Mark Millard <marklmi@yahoo.com> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: top vs. array sorted_state's out of bounds indexing (and related issues) Message-ID: <DA51FDC7-EAF0-486E-9A85-22044D621E7D@yahoo.com> References: <DA51FDC7-EAF0-486E-9A85-22044D621E7D.ref@yahoo.com>
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usr.bin/top/machine.c (from main) has:
/*
. . . The process states are ordered as follows (from least
* to most important): WAIT, zombie, sleep, stop, start, run. The
* array declaration below maps a process state index into a number
* that reflects this ordering.
*/
static int sorted_state[] = {
0, /* not used */
3, /* sleep */
1, /* ABANDONED (WAIT) */
6, /* run */
5, /* start */
2, /* zombie */
4 /* stop */
};
Note the elements are 0..6, so 7 elements.
It is accessed via code like:
sorted_state[(unsigned char)(b)->ki_stat]
But ->ki_stat has the values listed in
sys/sys/proc.h :
/*
* These were process status values (p_stat), now they are only used in
* legacy conversion code.
*/
#define SIDL 1 /* Process being created by fork. */
#define SRUN 2 /* Currently runnable. */
#define SSLEEP 3 /* Sleeping on an address. */
#define SSTOP 4 /* Process debugging or suspension. */
#define SZOMB 5 /* Awaiting collection by parent. */
#define SWAIT 6 /* Waiting for interrupt. */
#define SLOCK 7 /* Blocked on a lock. */
This leads to element indexes (including the
"unused" 0) of 0..7 so spanning 8 elements.
Thus there is a out of bounds error involved when
->ki_stat == SLOCK .
(I later show the ki_stat assignments.)
There is also the issue that:
SIDL is misidentified as: sleep
SRUN is misidentified as: ABANDONED (WAIT)
SSLEEP is misidentified as: run
SZOMB is misidentified as: start
SWAIT is misidentified as: zombie
SLOCK is out of bounds (as indicated above).
So the sort order in top is not as documented.
For reference, from sys/kern/kern_proc.c :
if (p->p_state == PRS_NORMAL) { /* approximate. */
if (TD_ON_RUNQ(td) ||
TD_CAN_RUN(td) ||
TD_IS_RUNNING(td)) {
kp->ki_stat = SRUN;
} else if (P_SHOULDSTOP(p)) {
kp->ki_stat = SSTOP;
} else if (TD_IS_SLEEPING(td)) {
kp->ki_stat = SSLEEP;
} else if (TD_ON_LOCK(td)) {
kp->ki_stat = SLOCK;
} else {
kp->ki_stat = SWAIT;
}
} else if (p->p_state == PRS_ZOMBIE) {
kp->ki_stat = SZOMB;
} else {
kp->ki_stat = SIDL;
}
===
Mark Millard
marklmi at yahoo.com
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