https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219153
--- Comment #9 from Mark Millard <mar...@dsl-only.net> ---
(In reply to John Baldwin from comment #5)
As for ps -M /var/crash/vmcore.7 listing no
processes:
main uses kvm_getprocs, which in turn eventually
does:
if (KREAD(kd, nl[0].n_value, &nprocs)) {
_kvm_err(kd, kd->program, "can't read nprocs");
return (0);
}
but that ends up with:
(gdb) print nprocs
$2 = 12873340
(I checked the code and "info reg" and the value
matched.)
So things are already well messed up here.
That in turn ends up used in:
size = nprocs * sizeof(struct kinfo_proc);
kd->procbase = (struct kinfo_proc *)_kvm_malloc(kd,
size);
if (kd->procbase == NULL)
return (0);
which succeeds but later there is:
nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value,
nl[2].n_value, nprocs);
if (nprocs <= 0) {
_kvm_freeprocs(kd);
nprocs = 0;
}
which in kvm_deadprocs gets to:
if (KREAD(kd, a_allproc, &p)) {
_kvm_err(kd, kd->program, "cannot read allproc");
return (-1);
}
acnt = kvm_proclist(kd, what, arg, p, bp, maxcnt);
if (acnt < 0)
return (acnt);
where:
static int
kvm_proclist(kvm_t *kd, int what, int arg, struct proc *p,
struct kinfo_proc *bp, int maxcnt)
{
int cnt = 0;
. . .
is used via:
kvm_proclist (kd=0x41e14000, what=5, arg=0, p=0x0, bp=0x42000000,
maxcnt=12873340)
and the internal kvm_proclist loop no-ops because of p:
for (; cnt < maxcnt && p != NULL; p = LIST_NEXT(&proc, p_list))
{
So no process is listed. After the loop is:
return (cnt);
}
And that means:
nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value,
nl[2].n_value, nprocs);
if (nprocs <= 0) {
_kvm_freeprocs(kd);
nprocs = 0;
}
ends up with nprocs==0 and kd is freed, hopefully including
kd->procbase being freed (I did not look).
But overall: at least one KREAD gets back a junk figure.
And with that I think I will stop for this note.
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