The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/sys_process.c

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    1 /*
    2  * Copyright (c) 1994, Sean Eric Fagan
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by Sean Eric Fagan.
   16  * 4. The name of the author may not be used to endorse or promote products
   17  *    derived from this software without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/5.3/sys/kern/sys_process.c 136588 2004-10-16 08:43:07Z cvs2svn $");
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/lock.h>
   38 #include <sys/mutex.h>
   39 #include <sys/syscallsubr.h>
   40 #include <sys/sysproto.h>
   41 #include <sys/proc.h>
   42 #include <sys/vnode.h>
   43 #include <sys/ptrace.h>
   44 #include <sys/sx.h>
   45 #include <sys/user.h>
   46 #include <sys/malloc.h>
   47 
   48 #include <machine/reg.h>
   49 
   50 #include <vm/vm.h>
   51 #include <vm/pmap.h>
   52 #include <vm/vm_extern.h>
   53 #include <vm/vm_map.h>
   54 #include <vm/vm_kern.h>
   55 #include <vm/vm_object.h>
   56 #include <vm/vm_page.h>
   57 
   58 /*
   59  * Functions implemented using PROC_ACTION():
   60  *
   61  * proc_read_regs(proc, regs)
   62  *      Get the current user-visible register set from the process
   63  *      and copy it into the regs structure (<machine/reg.h>).
   64  *      The process is stopped at the time read_regs is called.
   65  *
   66  * proc_write_regs(proc, regs)
   67  *      Update the current register set from the passed in regs
   68  *      structure.  Take care to avoid clobbering special CPU
   69  *      registers or privileged bits in the PSL.
   70  *      Depending on the architecture this may have fix-up work to do,
   71  *      especially if the IAR or PCW are modified.
   72  *      The process is stopped at the time write_regs is called.
   73  *
   74  * proc_read_fpregs, proc_write_fpregs
   75  *      deal with the floating point register set, otherwise as above.
   76  *
   77  * proc_read_dbregs, proc_write_dbregs
   78  *      deal with the processor debug register set, otherwise as above.
   79  *
   80  * proc_sstep(proc)
   81  *      Arrange for the process to trap after executing a single instruction.
   82  */
   83 
   84 #define PROC_ACTION(action) do {                                        \
   85         int error;                                                      \
   86                                                                         \
   87         PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);                        \
   88         if ((td->td_proc->p_sflag & PS_INMEM) == 0)                     \
   89                 error = EIO;                                            \
   90         else                                                            \
   91                 error = (action);                                       \
   92         return (error);                                                 \
   93 } while(0)
   94 
   95 int
   96 proc_read_regs(struct thread *td, struct reg *regs)
   97 {
   98 
   99         PROC_ACTION(fill_regs(td, regs));
  100 }
  101 
  102 int
  103 proc_write_regs(struct thread *td, struct reg *regs)
  104 {
  105 
  106         PROC_ACTION(set_regs(td, regs));
  107 }
  108 
  109 int
  110 proc_read_dbregs(struct thread *td, struct dbreg *dbregs)
  111 {
  112 
  113         PROC_ACTION(fill_dbregs(td, dbregs));
  114 }
  115 
  116 int
  117 proc_write_dbregs(struct thread *td, struct dbreg *dbregs)
  118 {
  119 
  120         PROC_ACTION(set_dbregs(td, dbregs));
  121 }
  122 
  123 /*
  124  * Ptrace doesn't support fpregs at all, and there are no security holes
  125  * or translations for fpregs, so we can just copy them.
  126  */
  127 int
  128 proc_read_fpregs(struct thread *td, struct fpreg *fpregs)
  129 {
  130 
  131         PROC_ACTION(fill_fpregs(td, fpregs));
  132 }
  133 
  134 int
  135 proc_write_fpregs(struct thread *td, struct fpreg *fpregs)
  136 {
  137 
  138         PROC_ACTION(set_fpregs(td, fpregs));
  139 }
  140 
  141 int
  142 proc_sstep(struct thread *td)
  143 {
  144 
  145         PROC_ACTION(ptrace_single_step(td));
  146 }
  147 
  148 int
  149 proc_rwmem(struct proc *p, struct uio *uio)
  150 {
  151         struct vmspace *vm;
  152         vm_map_t map;
  153         vm_object_t backing_object, object = NULL;
  154         vm_offset_t pageno = 0;         /* page number */
  155         vm_prot_t reqprot;
  156         int error, refcnt, writing;
  157 
  158         /*
  159          * if the vmspace is in the midst of being deallocated or the
  160          * process is exiting, don't try to grab anything.  The page table
  161          * usage in that process can be messed up.
  162          */
  163         vm = p->p_vmspace;
  164         if ((p->p_flag & P_WEXIT))
  165                 return (EFAULT);
  166         do {
  167                 if ((refcnt = vm->vm_refcnt) < 1)
  168                         return (EFAULT);
  169         } while (!atomic_cmpset_int(&vm->vm_refcnt, refcnt, refcnt + 1));
  170 
  171         /*
  172          * The map we want...
  173          */
  174         map = &vm->vm_map;
  175 
  176         writing = uio->uio_rw == UIO_WRITE;
  177         reqprot = writing ? (VM_PROT_WRITE | VM_PROT_OVERRIDE_WRITE) :
  178             VM_PROT_READ;
  179 
  180         /*
  181          * Only map in one page at a time.  We don't have to, but it
  182          * makes things easier.  This way is trivial - right?
  183          */
  184         do {
  185                 vm_map_t tmap;
  186                 vm_offset_t uva;
  187                 int page_offset;                /* offset into page */
  188                 vm_map_entry_t out_entry;
  189                 vm_prot_t out_prot;
  190                 boolean_t wired;
  191                 vm_pindex_t pindex;
  192                 u_int len;
  193                 vm_page_t m;
  194 
  195                 object = NULL;
  196 
  197                 uva = (vm_offset_t)uio->uio_offset;
  198 
  199                 /*
  200                  * Get the page number of this segment.
  201                  */
  202                 pageno = trunc_page(uva);
  203                 page_offset = uva - pageno;
  204 
  205                 /*
  206                  * How many bytes to copy
  207                  */
  208                 len = min(PAGE_SIZE - page_offset, uio->uio_resid);
  209 
  210                 /*
  211                  * Fault the page on behalf of the process
  212                  */
  213                 error = vm_fault(map, pageno, reqprot, VM_FAULT_NORMAL);
  214                 if (error) {
  215                         error = EFAULT;
  216                         break;
  217                 }
  218 
  219                 /*
  220                  * Now we need to get the page.  out_entry, out_prot, wired,
  221                  * and single_use aren't used.  One would think the vm code
  222                  * would be a *bit* nicer...  We use tmap because
  223                  * vm_map_lookup() can change the map argument.
  224                  */
  225                 tmap = map;
  226                 error = vm_map_lookup(&tmap, pageno, reqprot, &out_entry,
  227                     &object, &pindex, &out_prot, &wired);
  228                 if (error) {
  229                         error = EFAULT;
  230                         break;
  231                 }
  232                 VM_OBJECT_LOCK(object);
  233                 while ((m = vm_page_lookup(object, pindex)) == NULL &&
  234                     !writing &&
  235                     (backing_object = object->backing_object) != NULL) {
  236                         /*
  237                          * Allow fallback to backing objects if we are reading.
  238                          */
  239                         VM_OBJECT_LOCK(backing_object);
  240                         pindex += OFF_TO_IDX(object->backing_object_offset);
  241                         VM_OBJECT_UNLOCK(object);
  242                         object = backing_object;
  243                 }
  244                 VM_OBJECT_UNLOCK(object);
  245                 if (m == NULL) {
  246                         vm_map_lookup_done(tmap, out_entry);
  247                         error = EFAULT;
  248                         break;
  249                 }
  250 
  251                 /*
  252                  * Hold the page in memory.
  253                  */
  254                 vm_page_lock_queues();
  255                 vm_page_hold(m);
  256                 vm_page_unlock_queues();
  257 
  258                 /*
  259                  * We're done with tmap now.
  260                  */
  261                 vm_map_lookup_done(tmap, out_entry);
  262 
  263                 /*
  264                  * Now do the i/o move.
  265                  */
  266                 error = uiomove_fromphys(&m, page_offset, len, uio);
  267 
  268                 /*
  269                  * Release the page.
  270                  */
  271                 vm_page_lock_queues();
  272                 vm_page_unhold(m);
  273                 vm_page_unlock_queues();
  274 
  275         } while (error == 0 && uio->uio_resid > 0);
  276 
  277         vmspace_free(vm);
  278         return (error);
  279 }
  280 
  281 /*
  282  * Process debugging system call.
  283  */
  284 #ifndef _SYS_SYSPROTO_H_
  285 struct ptrace_args {
  286         int     req;
  287         pid_t   pid;
  288         caddr_t addr;
  289         int     data;
  290 };
  291 #endif
  292 
  293 /*
  294  * MPSAFE
  295  */
  296 int
  297 ptrace(struct thread *td, struct ptrace_args *uap)
  298 {
  299         /*
  300          * XXX this obfuscation is to reduce stack usage, but the register
  301          * structs may be too large to put on the stack anyway.
  302          */
  303         union {
  304                 struct ptrace_io_desc piod;
  305                 struct ptrace_lwpinfo pl;
  306                 struct dbreg dbreg;
  307                 struct fpreg fpreg;
  308                 struct reg reg;
  309         } r;
  310         void *addr;
  311         int error = 0;
  312 
  313         addr = &r;
  314         switch (uap->req) {
  315         case PT_GETREGS:
  316         case PT_GETFPREGS:
  317         case PT_GETDBREGS:
  318         case PT_LWPINFO:
  319                 break;
  320         case PT_SETREGS:
  321                 error = copyin(uap->addr, &r.reg, sizeof r.reg);
  322                 break;
  323         case PT_SETFPREGS:
  324                 error = copyin(uap->addr, &r.fpreg, sizeof r.fpreg);
  325                 break;
  326         case PT_SETDBREGS:
  327                 error = copyin(uap->addr, &r.dbreg, sizeof r.dbreg);
  328                 break;
  329         case PT_IO:
  330                 error = copyin(uap->addr, &r.piod, sizeof r.piod);
  331                 break;
  332         default:
  333                 addr = uap->addr;
  334                 break;
  335         }
  336         if (error)
  337                 return (error);
  338 
  339         error = kern_ptrace(td, uap->req, uap->pid, addr, uap->data);
  340         if (error)
  341                 return (error);
  342 
  343         switch (uap->req) {
  344         case PT_IO:
  345                 (void)copyout(&r.piod, uap->addr, sizeof r.piod);
  346                 break;
  347         case PT_GETREGS:
  348                 error = copyout(&r.reg, uap->addr, sizeof r.reg);
  349                 break;
  350         case PT_GETFPREGS:
  351                 error = copyout(&r.fpreg, uap->addr, sizeof r.fpreg);
  352                 break;
  353         case PT_GETDBREGS:
  354                 error = copyout(&r.dbreg, uap->addr, sizeof r.dbreg);
  355                 break;
  356         case PT_LWPINFO:
  357                 error = copyout(&r.pl, uap->addr, uap->data);
  358                 break;
  359         }
  360 
  361         return (error);
  362 }
  363 
  364 int
  365 kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
  366 {
  367         struct iovec iov;
  368         struct uio uio;
  369         struct proc *curp, *p, *pp;
  370         struct thread *td2 = NULL;
  371         struct ptrace_io_desc *piod;
  372         struct ptrace_lwpinfo *pl;
  373         int error, write, tmp, num;
  374         int proctree_locked = 0;
  375         lwpid_t tid = 0, *buf;
  376         pid_t saved_pid = pid;
  377 
  378         curp = td->td_proc;
  379 
  380         /* Lock proctree before locking the process. */
  381         switch (req) {
  382         case PT_TRACE_ME:
  383         case PT_ATTACH:
  384         case PT_STEP:
  385         case PT_CONTINUE:
  386         case PT_TO_SCE:
  387         case PT_TO_SCX:
  388         case PT_DETACH:
  389                 sx_xlock(&proctree_lock);
  390                 proctree_locked = 1;
  391                 break;
  392         default:
  393                 break;
  394         }
  395 
  396         write = 0;
  397         if (req == PT_TRACE_ME) {
  398                 p = td->td_proc;
  399                 PROC_LOCK(p);
  400         } else {
  401                 if (pid <= PID_MAX) {
  402                         if ((p = pfind(pid)) == NULL) {
  403                                 if (proctree_locked)
  404                                         sx_xunlock(&proctree_lock);
  405                                 return (ESRCH);
  406                         }
  407                 } else {
  408                         /* this is slow, should be optimized */
  409                         sx_slock(&allproc_lock);
  410                         FOREACH_PROC_IN_SYSTEM(p) {
  411                                 PROC_LOCK(p);
  412                                 mtx_lock_spin(&sched_lock);
  413                                 FOREACH_THREAD_IN_PROC(p, td2) {
  414                                         if (td2->td_tid == pid)
  415                                                 break;
  416                                 }
  417                                 mtx_unlock_spin(&sched_lock);
  418                                 if (td2 != NULL)
  419                                         break; /* proc lock held */
  420                                 PROC_UNLOCK(p);
  421                         }
  422                         sx_sunlock(&allproc_lock);
  423                         if (p == NULL) {
  424                                 if (proctree_locked)
  425                                         sx_xunlock(&proctree_lock);
  426                                 return (ESRCH);
  427                         }
  428                         tid = pid;
  429                         pid = p->p_pid;
  430                 }
  431         }
  432         if ((error = p_cansee(td, p)) != 0)
  433                 goto fail;
  434 
  435         if ((error = p_candebug(td, p)) != 0)
  436                 goto fail;
  437 
  438         /*
  439          * System processes can't be debugged.
  440          */
  441         if ((p->p_flag & P_SYSTEM) != 0) {
  442                 error = EINVAL;
  443                 goto fail;
  444         }
  445 
  446         if (tid == 0) {
  447                 td2 = FIRST_THREAD_IN_PROC(p);
  448                 tid = td2->td_tid;
  449         }
  450 
  451         /*
  452          * Permissions check
  453          */
  454         switch (req) {
  455         case PT_TRACE_ME:
  456                 /* Always legal. */
  457                 break;
  458 
  459         case PT_ATTACH:
  460                 /* Self */
  461                 if (p->p_pid == td->td_proc->p_pid) {
  462                         error = EINVAL;
  463                         goto fail;
  464                 }
  465 
  466                 /* Already traced */
  467                 if (p->p_flag & P_TRACED) {
  468                         error = EBUSY;
  469                         goto fail;
  470                 }
  471 
  472                 /* Can't trace an ancestor if you're being traced. */
  473                 if (curp->p_flag & P_TRACED) {
  474                         for (pp = curp->p_pptr; pp != NULL; pp = pp->p_pptr) {
  475                                 if (pp == p) {
  476                                         error = EINVAL;
  477                                         goto fail;
  478                                 }
  479                         }
  480                 }
  481 
  482 
  483                 /* OK */
  484                 break;
  485 
  486         case PT_CLEARSTEP:
  487                 /* Allow thread to clear single step for itself */
  488                 if (td->td_tid == tid)
  489                         break;
  490 
  491                 /* FALLTHROUGH */
  492         default:
  493                 /* not being traced... */
  494                 if ((p->p_flag & P_TRACED) == 0) {
  495                         error = EPERM;
  496                         goto fail;
  497                 }
  498 
  499                 /* not being traced by YOU */
  500                 if (p->p_pptr != td->td_proc) {
  501                         error = EBUSY;
  502                         goto fail;
  503                 }
  504 
  505                 /* not currently stopped */
  506                 if (!P_SHOULDSTOP(p) || p->p_suspcount != p->p_numthreads ||
  507                     (p->p_flag & P_WAITED) == 0) {
  508                         error = EBUSY;
  509                         goto fail;
  510                 }
  511 
  512                 /* OK */
  513                 break;
  514         }
  515 
  516 #ifdef FIX_SSTEP
  517         /*
  518          * Single step fixup ala procfs
  519          */
  520         FIX_SSTEP(td2);                 /* XXXKSE */
  521 #endif
  522 
  523         /*
  524          * Actually do the requests
  525          */
  526 
  527         td->td_retval[0] = 0;
  528 
  529         switch (req) {
  530         case PT_TRACE_ME:
  531                 /* set my trace flag and "owner" so it can read/write me */
  532                 p->p_flag |= P_TRACED;
  533                 p->p_oppid = p->p_pptr->p_pid;
  534                 PROC_UNLOCK(p);
  535                 sx_xunlock(&proctree_lock);
  536                 return (0);
  537 
  538         case PT_ATTACH:
  539                 /* security check done above */
  540                 p->p_flag |= P_TRACED;
  541                 p->p_oppid = p->p_pptr->p_pid;
  542                 if (p->p_pptr != td->td_proc)
  543                         proc_reparent(p, td->td_proc);
  544                 data = SIGSTOP;
  545                 goto sendsig;   /* in PT_CONTINUE below */
  546 
  547         case PT_CLEARSTEP:
  548                 _PHOLD(p);
  549                 error = ptrace_clear_single_step(td2);
  550                 _PRELE(p);
  551                 if (error)
  552                         goto fail;
  553                 PROC_UNLOCK(p);
  554                 return (0);
  555 
  556         case PT_SETSTEP:
  557                 _PHOLD(p);
  558                 error = ptrace_single_step(td2);
  559                 _PRELE(p);
  560                 if (error)
  561                         goto fail;
  562                 PROC_UNLOCK(p);
  563                 return (0);
  564 
  565         case PT_SUSPEND:
  566                 _PHOLD(p);
  567                 mtx_lock_spin(&sched_lock);
  568                 td2->td_flags |= TDF_DBSUSPEND;
  569                 mtx_unlock_spin(&sched_lock);
  570                 _PRELE(p);
  571                 PROC_UNLOCK(p);
  572                 return (0);
  573 
  574         case PT_RESUME:
  575                 _PHOLD(p);
  576                 mtx_lock_spin(&sched_lock);
  577                 td2->td_flags &= ~TDF_DBSUSPEND;
  578                 mtx_unlock_spin(&sched_lock);
  579                 _PRELE(p);
  580                 PROC_UNLOCK(p);
  581                 return (0);
  582 
  583         case PT_STEP:
  584         case PT_CONTINUE:
  585         case PT_TO_SCE:
  586         case PT_TO_SCX:
  587         case PT_DETACH:
  588                 /* Zero means do not send any signal */
  589                 if (data < 0 || data > _SIG_MAXSIG) {
  590                         error = EINVAL;
  591                         goto fail;
  592                 }
  593 
  594                 _PHOLD(p);
  595 
  596                 switch (req) {
  597                 case PT_STEP:
  598                         PROC_UNLOCK(p);
  599                         error = ptrace_single_step(td2);
  600                         if (error) {
  601                                 PRELE(p);
  602                                 goto fail_noproc;
  603                         }
  604                         PROC_LOCK(p);
  605                         break;
  606                 case PT_TO_SCE:
  607                         p->p_stops |= S_PT_SCE;
  608                         break;
  609                 case PT_TO_SCX:
  610                         p->p_stops |= S_PT_SCX;
  611                         break;
  612                 case PT_SYSCALL:
  613                         p->p_stops |= S_PT_SCE | S_PT_SCX;
  614                         break;
  615                 }
  616 
  617                 if (addr != (void *)1) {
  618                         PROC_UNLOCK(p);
  619                         error = ptrace_set_pc(td2, (u_long)(uintfptr_t)addr);
  620                         if (error) {
  621                                 PRELE(p);
  622                                 goto fail_noproc;
  623                         }
  624                         PROC_LOCK(p);
  625                 }
  626                 _PRELE(p);
  627 
  628                 if (req == PT_DETACH) {
  629                         /* reset process parent */
  630                         if (p->p_oppid != p->p_pptr->p_pid) {
  631                                 struct proc *pp;
  632 
  633                                 PROC_UNLOCK(p);
  634                                 pp = pfind(p->p_oppid);
  635                                 if (pp == NULL)
  636                                         pp = initproc;
  637                                 else
  638                                         PROC_UNLOCK(pp);
  639                                 PROC_LOCK(p);
  640                                 proc_reparent(p, pp);
  641                                 if (pp == initproc)
  642                                         p->p_sigparent = SIGCHLD;
  643                         }
  644                         p->p_flag &= ~(P_TRACED | P_WAITED);
  645                         p->p_oppid = 0;
  646 
  647                         /* should we send SIGCHLD? */
  648                 }
  649 
  650         sendsig:
  651                 if (proctree_locked)
  652                         sx_xunlock(&proctree_lock);
  653                 /* deliver or queue signal */
  654                 if (P_SHOULDSTOP(p)) {
  655                         p->p_xstat = data;
  656                         p->p_flag &= ~(P_STOPPED_TRACE|P_STOPPED_SIG);
  657                         mtx_lock_spin(&sched_lock);
  658                         if (saved_pid <= PID_MAX) {
  659                                 p->p_xthread->td_flags &= ~TDF_XSIG;
  660                                 p->p_xthread->td_xsig = data;
  661                         } else {
  662                                 td2->td_flags &= ~TDF_XSIG;
  663                                 td2->td_xsig = data;
  664                         }
  665                         p->p_xthread = NULL;
  666                         if (req == PT_DETACH) {
  667                                 struct thread *td3;
  668                                 FOREACH_THREAD_IN_PROC(p, td3)
  669                                         td3->td_flags &= ~TDF_DBSUSPEND; 
  670                         }
  671                         /*
  672                          * unsuspend all threads, to not let a thread run,
  673                          * you should use PT_SUSPEND to suspend it before
  674                          * continuing process.
  675                          */
  676                         thread_unsuspend(p);
  677                         thread_continued(p);
  678                         mtx_unlock_spin(&sched_lock);
  679                 } else if (data) {
  680                         psignal(p, data);
  681                 }
  682                 PROC_UNLOCK(p);
  683 
  684                 return (0);
  685 
  686         case PT_WRITE_I:
  687         case PT_WRITE_D:
  688                 write = 1;
  689                 /* FALLTHROUGH */
  690         case PT_READ_I:
  691         case PT_READ_D:
  692                 PROC_UNLOCK(p);
  693                 tmp = 0;
  694                 /* write = 0 set above */
  695                 iov.iov_base = write ? (caddr_t)&data : (caddr_t)&tmp;
  696                 iov.iov_len = sizeof(int);
  697                 uio.uio_iov = &iov;
  698                 uio.uio_iovcnt = 1;
  699                 uio.uio_offset = (off_t)(uintptr_t)addr;
  700                 uio.uio_resid = sizeof(int);
  701                 uio.uio_segflg = UIO_SYSSPACE;  /* i.e.: the uap */
  702                 uio.uio_rw = write ? UIO_WRITE : UIO_READ;
  703                 uio.uio_td = td;
  704                 error = proc_rwmem(p, &uio);
  705                 if (uio.uio_resid != 0) {
  706                         /*
  707                          * XXX proc_rwmem() doesn't currently return ENOSPC,
  708                          * so I think write() can bogusly return 0.
  709                          * XXX what happens for short writes?  We don't want
  710                          * to write partial data.
  711                          * XXX proc_rwmem() returns EPERM for other invalid
  712                          * addresses.  Convert this to EINVAL.  Does this
  713                          * clobber returns of EPERM for other reasons?
  714                          */
  715                         if (error == 0 || error == ENOSPC || error == EPERM)
  716                                 error = EINVAL; /* EOF */
  717                 }
  718                 if (!write)
  719                         td->td_retval[0] = tmp;
  720                 return (error);
  721 
  722         case PT_IO:
  723                 PROC_UNLOCK(p);
  724                 piod = addr;
  725                 iov.iov_base = piod->piod_addr;
  726                 iov.iov_len = piod->piod_len;
  727                 uio.uio_iov = &iov;
  728                 uio.uio_iovcnt = 1;
  729                 uio.uio_offset = (off_t)(uintptr_t)piod->piod_offs;
  730                 uio.uio_resid = piod->piod_len;
  731                 uio.uio_segflg = UIO_USERSPACE;
  732                 uio.uio_td = td;
  733                 switch (piod->piod_op) {
  734                 case PIOD_READ_D:
  735                 case PIOD_READ_I:
  736                         uio.uio_rw = UIO_READ;
  737                         break;
  738                 case PIOD_WRITE_D:
  739                 case PIOD_WRITE_I:
  740                         uio.uio_rw = UIO_WRITE;
  741                         break;
  742                 default:
  743                         return (EINVAL);
  744                 }
  745                 error = proc_rwmem(p, &uio);
  746                 piod->piod_len -= uio.uio_resid;
  747                 return (error);
  748 
  749         case PT_KILL:
  750                 data = SIGKILL;
  751                 goto sendsig;   /* in PT_CONTINUE above */
  752 
  753         case PT_SETREGS:
  754                 _PHOLD(p);
  755                 error = proc_write_regs(td2, addr);
  756                 _PRELE(p);
  757                 PROC_UNLOCK(p);
  758                 return (error);
  759 
  760         case PT_GETREGS:
  761                 _PHOLD(p);
  762                 error = proc_read_regs(td2, addr);
  763                 _PRELE(p);
  764                 PROC_UNLOCK(p);
  765                 return (error);
  766 
  767         case PT_SETFPREGS:
  768                 _PHOLD(p);
  769                 error = proc_write_fpregs(td2, addr);
  770                 _PRELE(p);
  771                 PROC_UNLOCK(p);
  772                 return (error);
  773 
  774         case PT_GETFPREGS:
  775                 _PHOLD(p);
  776                 error = proc_read_fpregs(td2, addr);
  777                 _PRELE(p);
  778                 PROC_UNLOCK(p);
  779                 return (error);
  780 
  781         case PT_SETDBREGS:
  782                 _PHOLD(p);
  783                 error = proc_write_dbregs(td2, addr);
  784                 _PRELE(p);
  785                 PROC_UNLOCK(p);
  786                 return (error);
  787 
  788         case PT_GETDBREGS:
  789                 _PHOLD(p);
  790                 error = proc_read_dbregs(td2, addr);
  791                 _PRELE(p);
  792                 PROC_UNLOCK(p);
  793                 return (error);
  794 
  795         case PT_LWPINFO:
  796                 if (data == 0 || data > sizeof(*pl))
  797                         return (EINVAL);
  798                 pl = addr;
  799                 _PHOLD(p);
  800                 if (saved_pid <= PID_MAX) {
  801                         pl->pl_lwpid = p->p_xthread->td_tid;
  802                         pl->pl_event = PL_EVENT_SIGNAL;
  803                 } else {
  804                         pl->pl_lwpid = td2->td_tid;
  805                         if (td2->td_flags & TDF_XSIG)
  806                                 pl->pl_event = PL_EVENT_SIGNAL;
  807                         else
  808                                 pl->pl_event = 0;
  809                 }
  810                 if (td2->td_pflags & TDP_SA) {
  811                         pl->pl_flags = PL_FLAG_SA;
  812                         if (td2->td_upcall && !TD_CAN_UNBIND(td2))
  813                                 pl->pl_flags |= PL_FLAG_BOUND;
  814                 } else {
  815                         pl->pl_flags = 0;
  816                 }
  817                 _PRELE(p);
  818                 PROC_UNLOCK(p);
  819                 return (0);
  820 
  821         case PT_GETNUMLWPS:
  822                 td->td_retval[0] = p->p_numthreads;
  823                 PROC_UNLOCK(p);
  824                 return (0);
  825 
  826         case PT_GETLWPLIST:
  827                 if (data <= 0) {
  828                         PROC_UNLOCK(p);
  829                         return (EINVAL);
  830                 }
  831                 num = imin(p->p_numthreads, data);
  832                 PROC_UNLOCK(p);
  833                 buf = malloc(num * sizeof(lwpid_t), M_TEMP, M_WAITOK);
  834                 tmp = 0;
  835                 PROC_LOCK(p);
  836                 mtx_lock_spin(&sched_lock);
  837                 FOREACH_THREAD_IN_PROC(p, td2) {
  838                         if (tmp >= num)
  839                                 break;
  840                         buf[tmp++] = td2->td_tid;
  841                 }
  842                 mtx_unlock_spin(&sched_lock);
  843                 PROC_UNLOCK(p);
  844                 error = copyout(buf, addr, tmp * sizeof(lwpid_t));
  845                 free(buf, M_TEMP);
  846                 if (!error)
  847                         td->td_retval[0] = num;
  848                 return (error);
  849 
  850         default:
  851 #ifdef __HAVE_PTRACE_MACHDEP
  852                 if (req >= PT_FIRSTMACH) {
  853                         _PHOLD(p);
  854                         PROC_UNLOCK(p);
  855                         error = cpu_ptrace(td2, req, addr, data);
  856                         PRELE(p);
  857                         return (error);
  858                 }
  859 #endif
  860                 break;
  861         }
  862 
  863         /* Unknown request. */
  864         error = EINVAL;
  865 
  866 fail:
  867         PROC_UNLOCK(p);
  868 fail_noproc:
  869         if (proctree_locked)
  870                 sx_xunlock(&proctree_lock);
  871         return (error);
  872 }
  873 
  874 /*
  875  * Stop a process because of a debugging event;
  876  * stay stopped until p->p_step is cleared
  877  * (cleared by PIOCCONT in procfs).
  878  */
  879 void
  880 stopevent(struct proc *p, unsigned int event, unsigned int val)
  881 {
  882 
  883         PROC_LOCK_ASSERT(p, MA_OWNED);
  884         p->p_step = 1;
  885         do {
  886                 p->p_xstat = val;
  887                 p->p_xthread = NULL;
  888                 p->p_stype = event;     /* Which event caused the stop? */
  889                 wakeup(&p->p_stype);    /* Wake up any PIOCWAIT'ing procs */
  890                 msleep(&p->p_step, &p->p_mtx, PWAIT, "stopevent", 0);
  891         } while (p->p_step);
  892 }

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