Refactor fork1() to make it easier to follow. No functional changes.
Reviewed by: kib (earlier version) Tested by: pho
This commit is contained in:
Edward Tomasz Napierala
parent
fd45cfd6aa
commit
afd01097a0
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=216350
@ -193,6 +193,93 @@ sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
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SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
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0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
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static int
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fork_findpid(int flags)
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{
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struct proc *p;
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int trypid;
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static int pidchecked = 0;
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sx_assert(&allproc_lock, SX_XLOCKED);
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/*
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* Find an unused process ID. We remember a range of unused IDs
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* ready to use (from lastpid+1 through pidchecked-1).
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*
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* If RFHIGHPID is set (used during system boot), do not allocate
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* low-numbered pids.
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*/
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trypid = lastpid + 1;
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if (flags & RFHIGHPID) {
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if (trypid < 10)
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trypid = 10;
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} else {
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if (randompid)
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trypid += arc4random() % randompid;
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}
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retry:
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/*
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* If the process ID prototype has wrapped around,
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* restart somewhat above 0, as the low-numbered procs
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* tend to include daemons that don't exit.
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*/
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if (trypid >= PID_MAX) {
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trypid = trypid % PID_MAX;
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if (trypid < 100)
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trypid += 100;
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pidchecked = 0;
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}
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if (trypid >= pidchecked) {
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int doingzomb = 0;
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pidchecked = PID_MAX;
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/*
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* Scan the active and zombie procs to check whether this pid
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* is in use. Remember the lowest pid that's greater
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* than trypid, so we can avoid checking for a while.
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*/
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p = LIST_FIRST(&allproc);
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again:
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for (; p != NULL; p = LIST_NEXT(p, p_list)) {
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while (p->p_pid == trypid ||
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(p->p_pgrp != NULL &&
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(p->p_pgrp->pg_id == trypid ||
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(p->p_session != NULL &&
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p->p_session->s_sid == trypid)))) {
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trypid++;
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if (trypid >= pidchecked)
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goto retry;
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}
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if (p->p_pid > trypid && pidchecked > p->p_pid)
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pidchecked = p->p_pid;
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if (p->p_pgrp != NULL) {
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if (p->p_pgrp->pg_id > trypid &&
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pidchecked > p->p_pgrp->pg_id)
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pidchecked = p->p_pgrp->pg_id;
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if (p->p_session != NULL &&
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p->p_session->s_sid > trypid &&
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pidchecked > p->p_session->s_sid)
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pidchecked = p->p_session->s_sid;
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}
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}
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if (!doingzomb) {
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doingzomb = 1;
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p = LIST_FIRST(&zombproc);
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goto again;
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}
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}
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/*
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* RFHIGHPID does not mess with the lastpid counter during boot.
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*/
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if (flags & RFHIGHPID)
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pidchecked = 0;
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else
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lastpid = trypid;
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return (trypid);
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}
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static int
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fork_norfproc(struct thread *td, int flags, struct proc **procp)
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{
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@ -244,211 +331,31 @@ fork_norfproc(struct thread *td, int flags, struct proc **procp)
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return (error);
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}
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int
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fork1(struct thread *td, int flags, int pages, struct proc **procp)
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static void
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do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
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struct vmspace *vm2)
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{
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struct proc *p1, *p2, *pptr;
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struct proc *newproc;
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int ok, trypid;
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static int curfail, pidchecked = 0;
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static struct timeval lastfail;
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struct proc *p1, *pptr;
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int trypid;
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struct filedesc *fd;
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struct filedesc_to_leader *fdtol;
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struct thread *td2;
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struct sigacts *newsigacts;
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struct vmspace *vm2;
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vm_ooffset_t mem_charged;
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int error;
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/* Can't copy and clear. */
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if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
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return (EINVAL);
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sx_assert(&proctree_lock, SX_SLOCKED);
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sx_assert(&allproc_lock, SX_XLOCKED);
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p1 = td->td_proc;
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/*
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* Here we don't create a new process, but we divorce
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* certain parts of a process from itself.
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*/
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if ((flags & RFPROC) == 0)
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return (fork_norfproc(td, flags, procp));
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/*
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* XXX
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* We did have single-threading code here
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* however it proved un-needed and caused problems
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*/
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mem_charged = 0;
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vm2 = NULL;
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if (pages == 0)
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pages = KSTACK_PAGES;
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/* Allocate new proc. */
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newproc = uma_zalloc(proc_zone, M_WAITOK);
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td2 = FIRST_THREAD_IN_PROC(newproc);
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if (td2 == NULL) {
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td2 = thread_alloc(pages);
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if (td2 == NULL) {
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error = ENOMEM;
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goto fail1;
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}
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proc_linkup(newproc, td2);
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} else {
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if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
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if (td2->td_kstack != 0)
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vm_thread_dispose(td2);
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if (!thread_alloc_stack(td2, pages)) {
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error = ENOMEM;
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goto fail1;
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}
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}
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}
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if ((flags & RFMEM) == 0) {
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vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
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if (vm2 == NULL) {
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error = ENOMEM;
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goto fail1;
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}
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if (!swap_reserve(mem_charged)) {
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/*
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* The swap reservation failed. The accounting
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* from the entries of the copied vm2 will be
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* substracted in vmspace_free(), so force the
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* reservation there.
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*/
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swap_reserve_force(mem_charged);
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error = ENOMEM;
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goto fail1;
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}
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} else
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vm2 = NULL;
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#ifdef MAC
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mac_proc_init(newproc);
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#endif
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knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
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STAILQ_INIT(&newproc->p_ktr);
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/* We have to lock the process tree while we look for a pid. */
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sx_slock(&proctree_lock);
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/*
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* Although process entries are dynamically created, we still keep
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* a global limit on the maximum number we will create. Don't allow
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* a nonprivileged user to use the last ten processes; don't let root
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* exceed the limit. The variable nprocs is the current number of
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* processes, maxproc is the limit.
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*/
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sx_xlock(&allproc_lock);
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if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
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PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
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error = EAGAIN;
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goto fail;
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}
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/*
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* Increment the count of procs running with this uid. Don't allow
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* a nonprivileged user to exceed their current limit.
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*
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* XXXRW: Can we avoid privilege here if it's not needed?
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*/
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error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
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if (error == 0)
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ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
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else {
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PROC_LOCK(p1);
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ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
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lim_cur(p1, RLIMIT_NPROC));
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PROC_UNLOCK(p1);
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}
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if (!ok) {
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error = EAGAIN;
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goto fail;
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}
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/*
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* Increment the nprocs resource before blocking can occur. There
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* are hard-limits as to the number of processes that can run.
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*/
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nprocs++;
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/*
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* Find an unused process ID. We remember a range of unused IDs
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* ready to use (from lastpid+1 through pidchecked-1).
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*
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* If RFHIGHPID is set (used during system boot), do not allocate
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* low-numbered pids.
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*/
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trypid = lastpid + 1;
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if (flags & RFHIGHPID) {
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if (trypid < 10)
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trypid = 10;
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} else {
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if (randompid)
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trypid += arc4random() % randompid;
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}
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retry:
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/*
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* If the process ID prototype has wrapped around,
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* restart somewhat above 0, as the low-numbered procs
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* tend to include daemons that don't exit.
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*/
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if (trypid >= PID_MAX) {
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trypid = trypid % PID_MAX;
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if (trypid < 100)
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trypid += 100;
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pidchecked = 0;
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}
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if (trypid >= pidchecked) {
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int doingzomb = 0;
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trypid = fork_findpid(flags);
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pidchecked = PID_MAX;
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/*
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* Scan the active and zombie procs to check whether this pid
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* is in use. Remember the lowest pid that's greater
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* than trypid, so we can avoid checking for a while.
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*/
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p2 = LIST_FIRST(&allproc);
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again:
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for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
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while (p2->p_pid == trypid ||
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(p2->p_pgrp != NULL &&
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(p2->p_pgrp->pg_id == trypid ||
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(p2->p_session != NULL &&
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p2->p_session->s_sid == trypid)))) {
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trypid++;
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if (trypid >= pidchecked)
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goto retry;
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}
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if (p2->p_pid > trypid && pidchecked > p2->p_pid)
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pidchecked = p2->p_pid;
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if (p2->p_pgrp != NULL) {
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if (p2->p_pgrp->pg_id > trypid &&
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pidchecked > p2->p_pgrp->pg_id)
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pidchecked = p2->p_pgrp->pg_id;
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if (p2->p_session != NULL &&
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p2->p_session->s_sid > trypid &&
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pidchecked > p2->p_session->s_sid)
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pidchecked = p2->p_session->s_sid;
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}
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}
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if (!doingzomb) {
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doingzomb = 1;
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p2 = LIST_FIRST(&zombproc);
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goto again;
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}
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}
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sx_sunlock(&proctree_lock);
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/*
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* RFHIGHPID does not mess with the lastpid counter during boot.
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*/
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if (flags & RFHIGHPID)
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pidchecked = 0;
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else
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lastpid = trypid;
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p2 = newproc;
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p2->p_state = PRS_NEW; /* protect against others */
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p2->p_pid = trypid;
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/*
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@ -776,11 +683,133 @@ fork1(struct thread *td, int flags, int pages, struct proc **procp)
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cv_wait(&p2->p_pwait, &p2->p_mtx);
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PROC_UNLOCK(p2);
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}
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int
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fork1(struct thread *td, int flags, int pages, struct proc **procp)
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{
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struct proc *p1;
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struct proc *newproc;
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int ok;
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struct thread *td2;
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struct vmspace *vm2;
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vm_ooffset_t mem_charged;
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int error;
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static int curfail;
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static struct timeval lastfail;
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/* Can't copy and clear. */
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if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
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return (EINVAL);
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p1 = td->td_proc;
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/*
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* Return child proc pointer to parent.
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* Here we don't create a new process, but we divorce
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* certain parts of a process from itself.
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*/
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*procp = p2;
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return (0);
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if ((flags & RFPROC) == 0)
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return (fork_norfproc(td, flags, procp));
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/*
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* XXX
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* We did have single-threading code here
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* however it proved un-needed and caused problems
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*/
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mem_charged = 0;
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vm2 = NULL;
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if (pages == 0)
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pages = KSTACK_PAGES;
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/* Allocate new proc. */
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newproc = uma_zalloc(proc_zone, M_WAITOK);
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td2 = FIRST_THREAD_IN_PROC(newproc);
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if (td2 == NULL) {
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td2 = thread_alloc(pages);
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if (td2 == NULL) {
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error = ENOMEM;
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goto fail1;
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}
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proc_linkup(newproc, td2);
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} else {
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if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
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if (td2->td_kstack != 0)
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vm_thread_dispose(td2);
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if (!thread_alloc_stack(td2, pages)) {
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error = ENOMEM;
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goto fail1;
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}
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}
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}
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if ((flags & RFMEM) == 0) {
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vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
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if (vm2 == NULL) {
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error = ENOMEM;
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goto fail1;
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}
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if (!swap_reserve(mem_charged)) {
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/*
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* The swap reservation failed. The accounting
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* from the entries of the copied vm2 will be
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* substracted in vmspace_free(), so force the
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* reservation there.
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*/
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swap_reserve_force(mem_charged);
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error = ENOMEM;
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goto fail1;
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}
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} else
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vm2 = NULL;
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#ifdef MAC
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mac_proc_init(newproc);
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#endif
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knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
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STAILQ_INIT(&newproc->p_ktr);
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/* We have to lock the process tree while we look for a pid. */
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sx_slock(&proctree_lock);
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/*
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* Although process entries are dynamically created, we still keep
|
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* a global limit on the maximum number we will create. Don't allow
|
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* a nonprivileged user to use the last ten processes; don't let root
|
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* exceed the limit. The variable nprocs is the current number of
|
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* processes, maxproc is the limit.
|
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*/
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sx_xlock(&allproc_lock);
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if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
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PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
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error = EAGAIN;
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goto fail;
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}
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/*
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* Increment the count of procs running with this uid. Don't allow
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* a nonprivileged user to exceed their current limit.
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*
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* XXXRW: Can we avoid privilege here if it's not needed?
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*/
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error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
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if (error == 0)
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ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
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else {
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PROC_LOCK(p1);
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ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
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lim_cur(p1, RLIMIT_NPROC));
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PROC_UNLOCK(p1);
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}
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if (ok) {
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do_fork(td, flags, newproc, td2, vm2);
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/*
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* Return child proc pointer to parent.
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*/
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*procp = newproc;
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return (0);
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}
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error = EAGAIN;
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fail:
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sx_sunlock(&proctree_lock);
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if (ppsratecheck(&lastfail, &curfail, 1))
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