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- Push down Giant around vnode operations in ktrace().

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- Mark the ktrace() and utrace() syscalls as being MP safe.
- Validate the facs argument to ktrace() prior to doing any vnode
  operations or acquiring any locks.
- Share lock the proctree lock over the entire section that calls
  ktrsetchildren() and ktrops().  We already did this for process groups.
  Doing it for the process case closes a small race where a process might
  go away after we look it up.  As a result of this, ktrstchildren() now
  just asserts that the proctree lock is locked rather than acquiring the
  lock itself.
- Add some missing comments to #else and #endif.
This commit is contained in:
John Baldwin 2003-04-25 19:59:35 +00:00
parent fdbaa60278
commit 64cc6a13e7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=114026
1 changed files with 39 additions and 22 deletions
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61
sys/kern/kern_ktrace.c
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@ -473,12 +473,14 @@ ktrcsw(out, user)
kc->user = user;
ktr_submitrequest(req);
}
#endif
#endif /* KTRACE */
/* Interface and common routines */
/*
* ktrace system call
*
* MPSAFE
*/
#ifndef _SYS_SYSPROTO_H_
struct ktrace_args {
@ -506,6 +508,12 @@ ktrace(td, uap)
struct nameidata nd;
struct ucred *cred;
/*
* Need something to (un)trace.
*/
if (ops != KTROP_CLEARFILE && facs == 0)
return (EINVAL);
td->td_inktrace = 1;
if (ops != KTROP_CLEAR) {
/*
@ -513,8 +521,10 @@ ktrace(td, uap)
*/
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->fname, td);
flags = FREAD | FWRITE | O_NOFOLLOW;
mtx_lock(&Giant);
error = vn_open(&nd, &flags, 0);
if (error) {
mtx_unlock(&Giant);
td->td_inktrace = 0;
return (error);
}
@ -523,9 +533,11 @@ ktrace(td, uap)
VOP_UNLOCK(vp, 0, td);
if (vp->v_type != VREG) {
(void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
mtx_unlock(&Giant);
td->td_inktrace = 0;
return (EACCES);
}
mtx_unlock(&Giant);
}
/*
* Clear all uses of the tracefile.
@ -543,8 +555,10 @@ ktrace(td, uap)
p->p_traceflag = 0;
mtx_unlock(&ktrace_mtx);
PROC_UNLOCK(p);
mtx_lock(&Giant);
(void) vn_close(vp, FREAD|FWRITE,
cred, td);
mtx_unlock(&Giant);
crfree(cred);
} else {
PROC_UNLOCK(p);
@ -556,21 +570,14 @@ ktrace(td, uap)
sx_sunlock(&allproc_lock);
goto done;
}
/*
* need something to (un)trace (XXX - why is this here?)
*/
if (!facs) {
error = EINVAL;
goto done;
}
/*
* do it
*/
sx_slock(&proctree_lock);
if (uap->pid < 0) {
/*
* by process group
*/
sx_slock(&proctree_lock);
pg = pgfind(-uap->pid);
if (pg == NULL) {
sx_sunlock(&proctree_lock);
@ -587,37 +594,46 @@ ktrace(td, uap)
ret |= ktrsetchildren(td, p, ops, facs, vp);
else
ret |= ktrops(td, p, ops, facs, vp);
sx_sunlock(&proctree_lock);
} else {
/*
* by pid
*/
p = pfind(uap->pid);
if (p == NULL) {
sx_sunlock(&proctree_lock);
error = ESRCH;
goto done;
}
/*
* The slock of the proctree lock will keep this process
* from going away, so unlocking the proc here is ok.
*/
PROC_UNLOCK(p);
/* XXX: UNLOCK above has a race */
if (descend)
ret |= ktrsetchildren(td, p, ops, facs, vp);
else
ret |= ktrops(td, p, ops, facs, vp);
}
sx_sunlock(&proctree_lock);
if (!ret)
error = EPERM;
done:
if (vp != NULL)
if (vp != NULL) {
mtx_lock(&Giant);
(void) vn_close(vp, FWRITE, td->td_ucred, td);
mtx_unlock(&Giant);
}
td->td_inktrace = 0;
return (error);
#else
return ENOSYS;
#endif
#else /* !KTRACE */
return (ENOSYS);
#endif /* KTRACE */
}
/*
* utrace system call
*
* MPSAFE
*/
/* ARGSUSED */
int
@ -650,9 +666,9 @@ utrace(td, uap)
req->ktr_header.ktr_len = uap->len;
ktr_submitrequest(req);
return (0);
#else
#else /* !KTRACE */
return (ENOSYS);
#endif
#endif /* KTRACE */
}
#ifdef KTRACE
@ -701,8 +717,11 @@ ktrops(td, p, ops, facs, vp)
}
mtx_unlock(&ktrace_mtx);
PROC_UNLOCK(p);
if (tracevp != NULL)
if (tracevp != NULL) {
mtx_lock(&Giant);
vrele(tracevp);
mtx_unlock(&Giant);
}
if (tracecred != NULL)
crfree(tracecred);
@ -720,7 +739,7 @@ ktrsetchildren(td, top, ops, facs, vp)
register int ret = 0;
p = top;
sx_slock(&proctree_lock);
sx_assert(&proctree_lock, SX_LOCKED);
for (;;) {
ret |= ktrops(td, p, ops, facs, vp);
/*
@ -731,10 +750,8 @@ ktrsetchildren(td, top, ops, facs, vp)
if (!LIST_EMPTY(&p->p_children))
p = LIST_FIRST(&p->p_children);
else for (;;) {
if (p == top) {
sx_sunlock(&proctree_lock);
if (p == top)
return (ret);
}
if (LIST_NEXT(p, p_sibling)) {
p = LIST_NEXT(p, p_sibling);
break;