/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1994, Sean Eric Fagan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Sean Eric Fagan.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ktr.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/reg.h>
#include <sys/sleepqueue.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/ptrace.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/malloc.h>
#include <sys/signalvar.h>
#include <sys/caprights.h>
#include <sys/filedesc.h>

#include <security/audit/audit.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_param.h>

#ifdef COMPAT_FREEBSD32
#include <sys/procfs.h>
#endif

/* Assert it's safe to unlock a process, e.g. to allocate working memory */
#define PROC_ASSERT_TRACEREQ(p) MPASS(((p)->p_flag2 & P2_PTRACEREQ) != 0)

/*
 * Functions implemented below:
 *
 * proc_read_regs(proc, regs)
 *      Get the current user-visible register set from the process
 *      and copy it into the regs structure (<machine/reg.h>).
 *      The process is stopped at the time read_regs is called.
 *
 * proc_write_regs(proc, regs)
 *      Update the current register set from the passed in regs
 *      structure.  Take care to avoid clobbering special CPU
 *      registers or privileged bits in the PSL.
 *      Depending on the architecture this may have fix-up work to do,
 *      especially if the IAR or PCW are modified.
 *      The process is stopped at the time write_regs is called.
 *
 * proc_read_fpregs, proc_write_fpregs
 *      deal with the floating point register set, otherwise as above.
 *
 * proc_read_dbregs, proc_write_dbregs
 *      deal with the processor debug register set, otherwise as above.
 *
 * proc_sstep(proc)
 *      Arrange for the process to trap after executing a single instruction.
 */

int
proc_read_regs(struct thread *td, struct reg *regs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_regs(td, regs));
}

int
proc_write_regs(struct thread *td, struct reg *regs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_regs(td, regs));
}

int
proc_read_dbregs(struct thread *td, struct dbreg *dbregs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_dbregs(td, dbregs));
}

int
proc_write_dbregs(struct thread *td, struct dbreg *dbregs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_dbregs(td, dbregs));
}

/*
 * Ptrace doesn't support fpregs at all, and there are no security holes
 * or translations for fpregs, so we can just copy them.
 */
int
proc_read_fpregs(struct thread *td, struct fpreg *fpregs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_fpregs(td, fpregs));
}

int
proc_write_fpregs(struct thread *td, struct fpreg *fpregs)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_fpregs(td, fpregs));
}

static struct regset *
proc_find_regset(struct thread *td, int note)
{
        struct regset **regsetp, **regset_end, *regset;
        struct sysentvec *sv;

        sv = td->td_proc->p_sysent;
        regsetp = sv->sv_regset_begin;
        if (regsetp == NULL)
                return (NULL);
        regset_end = sv->sv_regset_end;
        MPASS(regset_end != NULL);
        for (; regsetp < regset_end; regsetp++) {
                regset = *regsetp;
                if (regset->note != note)
                        continue;

                return (regset);
        }

        return (NULL);
}

static int
proc_read_regset(struct thread *td, int note, struct iovec *iov)
{
        struct regset *regset;
        struct proc *p;
        void *buf;
        size_t size;
        int error;

        regset = proc_find_regset(td, note);
        if (regset == NULL)
                return (EINVAL);

        if (regset->get == NULL)
                return (EINVAL);

        size = regset->size;
        /*
         * The regset is dynamically sized, e.g. the size could change
         * depending on the hardware, or may have a per-thread size.
         */
        if (size == 0) {
                if (!regset->get(regset, td, NULL, &size))
                        return (EINVAL);
        }

        if (iov->iov_base == NULL) {
                iov->iov_len = size;
                if (iov->iov_len == 0)
                        return (EINVAL);

                return (0);
        }

        /* The length is wrong, return an error */
        if (iov->iov_len != size)
                return (EINVAL);

        error = 0;
        p = td->td_proc;

        /* Drop the proc lock while allocating the temp buffer */
        PROC_ASSERT_TRACEREQ(p);
        PROC_UNLOCK(p);
        buf = malloc(size, M_TEMP, M_WAITOK);
        PROC_LOCK(p);

        if (!regset->get(regset, td, buf, &size)) {
                error = EINVAL;
        } else {
                KASSERT(size == regset->size || regset->size == 0,
                    ("%s: Getter function changed the size", __func__));

                iov->iov_len = size;
                PROC_UNLOCK(p);
                error = copyout(buf, iov->iov_base, size);
                PROC_LOCK(p);
        }

        free(buf, M_TEMP);

        return (error);
}

static int
proc_write_regset(struct thread *td, int note, struct iovec *iov)
{
        struct regset *regset;
        struct proc *p;
        void *buf;
        size_t size;
        int error;

        regset = proc_find_regset(td, note);
        if (regset == NULL)
                return (EINVAL);

        size = regset->size;
        /*
         * The regset is dynamically sized, e.g. the size could change
         * depending on the hardware, or may have a per-thread size.
         */
        if (size == 0) {
                if (!regset->get(regset, td, NULL, &size))
                        return (EINVAL);
        }

        /* The length is wrong, return an error */
        if (iov->iov_len != size)
                return (EINVAL);

        if (regset->set == NULL)
                return (EINVAL);

        p = td->td_proc;

        /* Drop the proc lock while allocating the temp buffer */
        PROC_ASSERT_TRACEREQ(p);
        PROC_UNLOCK(p);
        buf = malloc(size, M_TEMP, M_WAITOK);
        error = copyin(iov->iov_base, buf, size);
        PROC_LOCK(p);

        if (error == 0) {
                if (!regset->set(regset, td, buf, size)) {
                        error = EINVAL;
                }
        }

        free(buf, M_TEMP);

        return (error);
}

#ifdef COMPAT_FREEBSD32
/* For 32 bit binaries, we need to expose the 32 bit regs layouts. */
int
proc_read_regs32(struct thread *td, struct reg32 *regs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_regs32(td, regs32));
}

int
proc_write_regs32(struct thread *td, struct reg32 *regs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_regs32(td, regs32));
}

int
proc_read_dbregs32(struct thread *td, struct dbreg32 *dbregs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_dbregs32(td, dbregs32));
}

int
proc_write_dbregs32(struct thread *td, struct dbreg32 *dbregs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_dbregs32(td, dbregs32));
}

int
proc_read_fpregs32(struct thread *td, struct fpreg32 *fpregs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (fill_fpregs32(td, fpregs32));
}

int
proc_write_fpregs32(struct thread *td, struct fpreg32 *fpregs32)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (set_fpregs32(td, fpregs32));
}
#endif

int
proc_sstep(struct thread *td)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        return (ptrace_single_step(td));
}

int
proc_rwmem(struct proc *p, struct uio *uio)
{
        vm_map_t map;
        vm_offset_t pageno;             /* page number */
        vm_prot_t reqprot;
        int error, fault_flags, page_offset, writing;

        /*
         * Make sure that the process' vmspace remains live.
         */
        if (p != curproc)
                PROC_ASSERT_HELD(p);
        PROC_LOCK_ASSERT(p, MA_NOTOWNED);

        /*
         * The map we want...
         */
        map = &p->p_vmspace->vm_map;

        /*
         * If we are writing, then we request vm_fault() to create a private
         * copy of each page.  Since these copies will not be writeable by the
         * process, we must explicitly request that they be dirtied.
         */
        writing = uio->uio_rw == UIO_WRITE;
        reqprot = writing ? VM_PROT_COPY | VM_PROT_READ : VM_PROT_READ;
        fault_flags = writing ? VM_FAULT_DIRTY : VM_FAULT_NORMAL;

        if (writing) {
                error = priv_check_cred(p->p_ucred, PRIV_PROC_MEM_WRITE);
                if (error)
                        return (error);
        }

        /*
         * Only map in one page at a time.  We don't have to, but it
         * makes things easier.  This way is trivial - right?
         */
        do {
                vm_offset_t uva;
                u_int len;
                vm_page_t m;

                uva = (vm_offset_t)uio->uio_offset;

                /*
                 * Get the page number of this segment.
                 */
                pageno = trunc_page(uva);
                page_offset = uva - pageno;

                /*
                 * How many bytes to copy
                 */
                len = MIN(PAGE_SIZE - page_offset, uio->uio_resid);

                /*
                 * Fault and hold the page on behalf of the process.
                 */
                error = vm_fault(map, pageno, reqprot, fault_flags, &m);
                if (error != KERN_SUCCESS) {
                        if (error == KERN_RESOURCE_SHORTAGE)
                                error = ENOMEM;
                        else
                                error = EFAULT;
                        break;
                }

                /*
                 * Now do the i/o move.
                 */
                error = uiomove_fromphys(&m, page_offset, len, uio);

                /* Make the I-cache coherent for breakpoints. */
                if (writing && error == 0) {
                        vm_map_lock_read(map);
                        if (vm_map_check_protection(map, pageno, pageno +
                            PAGE_SIZE, VM_PROT_EXECUTE))
                                vm_sync_icache(map, uva, len);
                        vm_map_unlock_read(map);
                }

                /*
                 * Release the page.
                 */
                vm_page_unwire(m, PQ_ACTIVE);

        } while (error == 0 && uio->uio_resid > 0);

        return (error);
}

static ssize_t
proc_iop(struct thread *td, struct proc *p, vm_offset_t va, void *buf,
    size_t len, enum uio_rw rw)
{
        struct iovec iov;
        struct uio uio;
        ssize_t slen;

        MPASS(len < SSIZE_MAX);
        slen = (ssize_t)len;

        iov.iov_base = (caddr_t)buf;
        iov.iov_len = len;
        uio.uio_iov = &iov;
        uio.uio_iovcnt = 1;
        uio.uio_offset = va;
        uio.uio_resid = slen;
        uio.uio_segflg = UIO_SYSSPACE;
        uio.uio_rw = rw;
        uio.uio_td = td;
        proc_rwmem(p, &uio);
        if (uio.uio_resid == slen)
                return (-1);
        return (slen - uio.uio_resid);
}

ssize_t
proc_readmem(struct thread *td, struct proc *p, vm_offset_t va, void *buf,
    size_t len)
{

        return (proc_iop(td, p, va, buf, len, UIO_READ));
}

ssize_t
proc_writemem(struct thread *td, struct proc *p, vm_offset_t va, void *buf,
    size_t len)
{

        return (proc_iop(td, p, va, buf, len, UIO_WRITE));
}

static int
ptrace_vm_entry(struct thread *td, struct proc *p, struct ptrace_vm_entry *pve)
{
        struct vattr vattr;
        vm_map_t map;
        vm_map_entry_t entry;
        vm_object_t obj, tobj, lobj;
        struct vmspace *vm;
        struct vnode *vp;
        char *freepath, *fullpath;
        u_int pathlen;
        int error, index;

        error = 0;
        obj = NULL;

        vm = vmspace_acquire_ref(p);
        map = &vm->vm_map;
        vm_map_lock_read(map);

        do {
                KASSERT((map->header.eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
                    ("Submap in map header"));
                index = 0;
                VM_MAP_ENTRY_FOREACH(entry, map) {
                        if (index >= pve->pve_entry &&
                            (entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0)
                                break;
                        index++;
                }
                if (index < pve->pve_entry) {
                        error = EINVAL;
                        break;
                }
                if (entry == &map->header) {
                        error = ENOENT;
                        break;
                }

                /* We got an entry. */
                pve->pve_entry = index + 1;
                pve->pve_timestamp = map->timestamp;
                pve->pve_start = entry->start;
                pve->pve_end = entry->end - 1;
                pve->pve_offset = entry->offset;
                pve->pve_prot = entry->protection |
                    PROT_MAX(entry->max_protection);

                /* Backing object's path needed? */
                if (pve->pve_pathlen == 0)
                        break;

                pathlen = pve->pve_pathlen;
                pve->pve_pathlen = 0;

                obj = entry->object.vm_object;
                if (obj != NULL)
                        VM_OBJECT_RLOCK(obj);
        } while (0);

        vm_map_unlock_read(map);

        pve->pve_fsid = VNOVAL;
        pve->pve_fileid = VNOVAL;

        if (error == 0 && obj != NULL) {
                lobj = obj;
                for (tobj = obj; tobj != NULL; tobj = tobj->backing_object) {
                        if (tobj != obj)
                                VM_OBJECT_RLOCK(tobj);
                        if (lobj != obj)
                                VM_OBJECT_RUNLOCK(lobj);
                        lobj = tobj;
                        pve->pve_offset += tobj->backing_object_offset;
                }
                vp = vm_object_vnode(lobj);
                if (vp != NULL)
                        vref(vp);
                if (lobj != obj)
                        VM_OBJECT_RUNLOCK(lobj);
                VM_OBJECT_RUNLOCK(obj);

                if (vp != NULL) {
                        freepath = NULL;
                        fullpath = NULL;
                        vn_fullpath(vp, &fullpath, &freepath);
                        vn_lock(vp, LK_SHARED | LK_RETRY);
                        if (VOP_GETATTR(vp, &vattr, td->td_ucred) == 0) {
                                pve->pve_fileid = vattr.va_fileid;
                                pve->pve_fsid = vattr.va_fsid;
                        }
                        vput(vp);

                        if (fullpath != NULL) {
                                pve->pve_pathlen = strlen(fullpath) + 1;
                                if (pve->pve_pathlen <= pathlen) {
                                        error = copyout(fullpath, pve->pve_path,
                                            pve->pve_pathlen);
                                } else
                                        error = ENAMETOOLONG;
                        }
                        if (freepath != NULL)
                                free(freepath, M_TEMP);
                }
        }
        vmspace_free(vm);
        if (error == 0)
                CTR3(KTR_PTRACE, "PT_VM_ENTRY: pid %d, entry %d, start %p",
                    p->p_pid, pve->pve_entry, pve->pve_start);

        return (error);
}

/*
 * Process debugging system call.
 */
#ifndef _SYS_SYSPROTO_H_
struct ptrace_args {
        int     req;
        pid_t   pid;
        caddr_t addr;
        int     data;
};
#endif

int
sys_ptrace(struct thread *td, struct ptrace_args *uap)
{
        /*
         * XXX this obfuscation is to reduce stack usage, but the register
         * structs may be too large to put on the stack anyway.
         */
        union {
                struct ptrace_io_desc piod;
                struct ptrace_lwpinfo pl;
                struct ptrace_vm_entry pve;
                struct ptrace_coredump pc;
                struct ptrace_sc_remote sr;
                struct dbreg dbreg;
                struct fpreg fpreg;
                struct reg reg;
                struct iovec vec;
                syscallarg_t args[nitems(td->td_sa.args)];
                struct ptrace_sc_ret psr;
                int ptevents;
        } r;
        syscallarg_t pscr_args[nitems(td->td_sa.args)];
        void *addr;
        int error;

        if (!allow_ptrace)
                return (ENOSYS);
        error = 0;

        AUDIT_ARG_PID(uap->pid);
        AUDIT_ARG_CMD(uap->req);
        AUDIT_ARG_VALUE(uap->data);
        addr = &r;
        switch (uap->req) {
        case PT_GET_EVENT_MASK:
        case PT_LWPINFO:
        case PT_GET_SC_ARGS:
        case PT_GET_SC_RET:
                break;
        case PT_GETREGS:
                bzero(&r.reg, sizeof(r.reg));
                break;
        case PT_GETFPREGS:
                bzero(&r.fpreg, sizeof(r.fpreg));
                break;
        case PT_GETDBREGS:
                bzero(&r.dbreg, sizeof(r.dbreg));
                break;
        case PT_GETREGSET:
        case PT_SETREGSET:
                error = copyin(uap->addr, &r.vec, sizeof(r.vec));
                break;
        case PT_SETREGS:
                error = copyin(uap->addr, &r.reg, sizeof(r.reg));
                break;
        case PT_SETFPREGS:
                error = copyin(uap->addr, &r.fpreg, sizeof(r.fpreg));
                break;
        case PT_SETDBREGS:
                error = copyin(uap->addr, &r.dbreg, sizeof(r.dbreg));
                break;
        case PT_SET_EVENT_MASK:
                if (uap->data != sizeof(r.ptevents))
                        error = EINVAL;
                else
                        error = copyin(uap->addr, &r.ptevents, uap->data);
                break;
        case PT_IO:
                error = copyin(uap->addr, &r.piod, sizeof(r.piod));
                break;
        case PT_VM_ENTRY:
                error = copyin(uap->addr, &r.pve, sizeof(r.pve));
                break;
        case PT_COREDUMP:
                if (uap->data != sizeof(r.pc))
                        error = EINVAL;
                else
                        error = copyin(uap->addr, &r.pc, uap->data);
                break;
        case PT_SC_REMOTE:
                if (uap->data != sizeof(r.sr)) {
                        error = EINVAL;
                        break;
                }
                error = copyin(uap->addr, &r.sr, uap->data);
                if (error != 0)
                        break;
                if (r.sr.pscr_nargs > nitems(td->td_sa.args)) {
                        error = EINVAL;
                        break;
                }
                error = copyin(r.sr.pscr_args, pscr_args,
                    sizeof(u_long) * r.sr.pscr_nargs);
                if (error != 0)
                        break;
                r.sr.pscr_args = pscr_args;
                break;
        case PTINTERNAL_FIRST ... PTINTERNAL_LAST:
                error = EINVAL;
                break;
        default:
                addr = uap->addr;
                break;
        }
        if (error)
                return (error);

        error = kern_ptrace(td, uap->req, uap->pid, addr, uap->data);
        if (error)
                return (error);

        switch (uap->req) {
        case PT_VM_ENTRY:
                error = copyout(&r.pve, uap->addr, sizeof(r.pve));
                break;
        case PT_IO:
                error = copyout(&r.piod, uap->addr, sizeof(r.piod));
                break;
        case PT_GETREGS:
                error = copyout(&r.reg, uap->addr, sizeof(r.reg));
                break;
        case PT_GETFPREGS:
                error = copyout(&r.fpreg, uap->addr, sizeof(r.fpreg));
                break;
        case PT_GETDBREGS:
                error = copyout(&r.dbreg, uap->addr, sizeof(r.dbreg));
                break;
        case PT_GETREGSET:
                error = copyout(&r.vec, uap->addr, sizeof(r.vec));
                break;
        case PT_GET_EVENT_MASK:
                /* NB: The size in uap->data is validated in kern_ptrace(). */
                error = copyout(&r.ptevents, uap->addr, uap->data);
                break;
        case PT_LWPINFO:
                /* NB: The size in uap->data is validated in kern_ptrace(). */
                error = copyout(&r.pl, uap->addr, uap->data);
                break;
        case PT_GET_SC_ARGS:
                error = copyout(r.args, uap->addr, MIN(uap->data,
                    sizeof(r.args)));
                break;
        case PT_GET_SC_RET:
                error = copyout(&r.psr, uap->addr, MIN(uap->data,
                    sizeof(r.psr)));
                break;
        case PT_SC_REMOTE:
                error = copyout(&r.sr.pscr_ret, uap->addr +
                    offsetof(struct ptrace_sc_remote, pscr_ret),
                    sizeof(r.sr.pscr_ret));
                break;
        }

        return (error);
}

#ifdef COMPAT_FREEBSD32
/*
 *   PROC_READ(regs, td2, addr);
 * becomes either:
 *   proc_read_regs(td2, addr);
 * or
 *   proc_read_regs32(td2, addr);
 * .. except this is done at runtime.  There is an additional
 * complication in that PROC_WRITE disallows 32 bit consumers
 * from writing to 64 bit address space targets.
 */
#define PROC_READ(w, t, a)      wrap32 ? \
        proc_read_ ## w ## 32(t, a) : \
        proc_read_ ## w (t, a)
#define PROC_WRITE(w, t, a)     wrap32 ? \
        (safe ? proc_write_ ## w ## 32(t, a) : EINVAL ) : \
        proc_write_ ## w (t, a)
#else
#define PROC_READ(w, t, a)      proc_read_ ## w (t, a)
#define PROC_WRITE(w, t, a)     proc_write_ ## w (t, a)
#endif

void
proc_set_traced(struct proc *p, bool stop)
{

        sx_assert(&proctree_lock, SX_XLOCKED);
        PROC_LOCK_ASSERT(p, MA_OWNED);
        p->p_flag |= P_TRACED;
        if (stop)
                p->p_flag2 |= P2_PTRACE_FSTP;
        p->p_ptevents = PTRACE_DEFAULT;
}

void
ptrace_unsuspend(struct proc *p)
{
        PROC_LOCK_ASSERT(p, MA_OWNED);

        PROC_SLOCK(p);
        p->p_flag &= ~(P_STOPPED_TRACE | P_STOPPED_SIG | P_WAITED);
        thread_unsuspend(p);
        PROC_SUNLOCK(p);
        itimer_proc_continue(p);
        kqtimer_proc_continue(p);
}

static int
proc_can_ptrace(struct thread *td, struct proc *p)
{
        int error;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        if ((p->p_flag & P_WEXIT) != 0)
                return (ESRCH);

        if ((error = p_cansee(td, p)) != 0)
                return (error);
        if ((error = p_candebug(td, p)) != 0)
                return (error);

        /* not being traced... */
        if ((p->p_flag & P_TRACED) == 0)
                return (EPERM);

        /* not being traced by YOU */
        if (p->p_pptr != td->td_proc)
                return (EBUSY);

        /* not currently stopped */
        if ((p->p_flag & P_STOPPED_TRACE) == 0 ||
            p->p_suspcount != p->p_numthreads  ||
            (p->p_flag & P_WAITED) == 0)
                return (EBUSY);

        return (0);
}

static struct thread *
ptrace_sel_coredump_thread(struct proc *p)
{
        struct thread *td2;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        MPASS((p->p_flag & P_STOPPED_TRACE) != 0);

        FOREACH_THREAD_IN_PROC(p, td2) {
                if ((td2->td_dbgflags & TDB_SSWITCH) != 0)
                        return (td2);
        }
        return (NULL);
}

int
kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
{
        struct iovec iov;
        struct uio uio;
        struct proc *curp, *p, *pp;
        struct thread *td2 = NULL, *td3;
        struct ptrace_io_desc *piod = NULL;
        struct ptrace_lwpinfo *pl;
        struct ptrace_sc_ret *psr;
        struct ptrace_sc_remote *pscr;
        struct file *fp;
        struct ptrace_coredump *pc;
        struct thr_coredump_req *tcq;
        struct thr_syscall_req *tsr;
        int error, num, tmp;
        lwpid_t tid = 0, *buf;
#ifdef COMPAT_FREEBSD32
        int wrap32 = 0, safe = 0;
#endif
        bool proctree_locked, p2_req_set;

        curp = td->td_proc;
        proctree_locked = false;
        p2_req_set = false;

        /* Lock proctree before locking the process. */
        switch (req) {
        case PT_TRACE_ME:
        case PT_ATTACH:
        case PT_STEP:
        case PT_CONTINUE:
        case PT_TO_SCE:
        case PT_TO_SCX:
        case PT_SYSCALL:
        case PT_FOLLOW_FORK:
        case PT_LWP_EVENTS:
        case PT_GET_EVENT_MASK:
        case PT_SET_EVENT_MASK:
        case PT_DETACH:
        case PT_GET_SC_ARGS:
                sx_xlock(&proctree_lock);
                proctree_locked = true;
                break;
        default:
                break;
        }

        if (req == PT_TRACE_ME) {
                p = td->td_proc;
                PROC_LOCK(p);
        } else {
                if (pid <= PID_MAX) {
                        if ((p = pfind(pid)) == NULL) {
                                if (proctree_locked)
                                        sx_xunlock(&proctree_lock);
                                return (ESRCH);
                        }
                } else {
                        td2 = tdfind(pid, -1);
                        if (td2 == NULL) {
                                if (proctree_locked)
                                        sx_xunlock(&proctree_lock);
                                return (ESRCH);
                        }
                        p = td2->td_proc;
                        tid = pid;
                        pid = p->p_pid;
                }
        }
        AUDIT_ARG_PROCESS(p);

        if ((p->p_flag & P_WEXIT) != 0) {
                error = ESRCH;
                goto fail;
        }
        if ((error = p_cansee(td, p)) != 0)
                goto fail;

        if ((error = p_candebug(td, p)) != 0)
                goto fail;

        /*
         * System processes can't be debugged.
         */
        if ((p->p_flag & P_SYSTEM) != 0) {
                error = EINVAL;
                goto fail;
        }

        if (tid == 0) {
                if ((p->p_flag & P_STOPPED_TRACE) != 0)
                        td2 = p->p_xthread;
                if (td2 == NULL)
                        td2 = FIRST_THREAD_IN_PROC(p);
                tid = td2->td_tid;
        }

#ifdef COMPAT_FREEBSD32
        /*
         * Test if we're a 32 bit client and what the target is.
         * Set the wrap controls accordingly.
         */
        if (SV_CURPROC_FLAG(SV_ILP32)) {
                if (SV_PROC_FLAG(td2->td_proc, SV_ILP32))
                        safe = 1;
                wrap32 = 1;
        }
#endif
        /*
         * Permissions check
         */
        switch (req) {
        case PT_TRACE_ME:
                /*
                 * Always legal, when there is a parent process which
                 * could trace us.  Otherwise, reject.
                 */
                if ((p->p_flag & P_TRACED) != 0) {
                        error = EBUSY;
                        goto fail;
                }
                if (p->p_pptr == initproc) {
                        error = EPERM;
                        goto fail;
                }
                break;

        case PT_ATTACH:
                /* Self */
                if (p == td->td_proc) {
                        error = EINVAL;
                        goto fail;
                }

                /* Already traced */
                if (p->p_flag & P_TRACED) {
                        error = EBUSY;
                        goto fail;
                }

                /* Can't trace an ancestor if you're being traced. */
                if (curp->p_flag & P_TRACED) {
                        for (pp = curp->p_pptr; pp != NULL; pp = pp->p_pptr) {
                                if (pp == p) {
                                        error = EINVAL;
                                        goto fail;
                                }
                        }
                }

                /* OK */
                break;

        case PT_CLEARSTEP:
                /* Allow thread to clear single step for itself */
                if (td->td_tid == tid)
                        break;

                /* FALLTHROUGH */
        default:
                /*
                 * Check for ptrace eligibility before waiting for
                 * holds to drain.
                 */
                error = proc_can_ptrace(td, p);
                if (error != 0)
                        goto fail;

                /*
                 * Block parallel ptrace requests.  Most important, do
                 * not allow other thread in debugger to continue the
                 * debuggee until coredump finished.
                 */
                while ((p->p_flag2 & P2_PTRACEREQ) != 0) {
                        if (proctree_locked)
                                sx_xunlock(&proctree_lock);
                        error = msleep(&p->p_flag2, &p->p_mtx, PPAUSE | PCATCH |
                            (proctree_locked ? PDROP : 0), "pptrace", 0);
                        if (proctree_locked) {
                                sx_xlock(&proctree_lock);
                                PROC_LOCK(p);
                        }
                        if (error == 0 && td2->td_proc != p)
                                error = ESRCH;
                        if (error == 0)
                                error = proc_can_ptrace(td, p);
                        if (error != 0)
                                goto fail;
                }

                /* Ok */
                break;
        }

        /*
         * Keep this process around and request parallel ptrace()
         * request to wait until we finish this request.
         */
        MPASS((p->p_flag2 & P2_PTRACEREQ) == 0);
        p->p_flag2 |= P2_PTRACEREQ;
        p2_req_set = true;
        _PHOLD(p);

        /*
         * Actually do the requests
         */

        td->td_retval[0] = 0;

        switch (req) {
        case PT_TRACE_ME:
                /* set my trace flag and "owner" so it can read/write me */
                proc_set_traced(p, false);
                if (p->p_flag & P_PPWAIT)
                        p->p_flag |= P_PPTRACE;
                CTR1(KTR_PTRACE, "PT_TRACE_ME: pid %d", p->p_pid);
                break;

        case PT_ATTACH:
                /* security check done above */
                /*
                 * It would be nice if the tracing relationship was separate
                 * from the parent relationship but that would require
                 * another set of links in the proc struct or for "wait"
                 * to scan the entire proc table.  To make life easier,
                 * we just re-parent the process we're trying to trace.
                 * The old parent is remembered so we can put things back
                 * on a "detach".
                 */
                proc_set_traced(p, true);
                proc_reparent(p, td->td_proc, false);
                CTR2(KTR_PTRACE, "PT_ATTACH: pid %d, oppid %d", p->p_pid,
                    p->p_oppid);

                sx_xunlock(&proctree_lock);
                proctree_locked = false;
                MPASS(p->p_xthread == NULL);
                MPASS((p->p_flag & P_STOPPED_TRACE) == 0);

                /*
                 * If already stopped due to a stop signal, clear the
                 * existing stop before triggering a traced SIGSTOP.
                 */
                if ((p->p_flag & P_STOPPED_SIG) != 0) {
                        PROC_SLOCK(p);
                        p->p_flag &= ~(P_STOPPED_SIG | P_WAITED);
                        thread_unsuspend(p);
                        PROC_SUNLOCK(p);
                }

                kern_psignal(p, SIGSTOP);
                break;

        case PT_CLEARSTEP:
                CTR2(KTR_PTRACE, "PT_CLEARSTEP: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = ptrace_clear_single_step(td2);
                break;

        case PT_SETSTEP:
                CTR2(KTR_PTRACE, "PT_SETSTEP: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = ptrace_single_step(td2);
                break;

        case PT_SUSPEND:
                CTR2(KTR_PTRACE, "PT_SUSPEND: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                td2->td_dbgflags |= TDB_SUSPEND;
                ast_sched(td2, TDA_SUSPEND);
                break;

        case PT_RESUME:
                CTR2(KTR_PTRACE, "PT_RESUME: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                td2->td_dbgflags &= ~TDB_SUSPEND;
                break;

        case PT_FOLLOW_FORK:
                CTR3(KTR_PTRACE, "PT_FOLLOW_FORK: pid %d %s -> %s", p->p_pid,
                    p->p_ptevents & PTRACE_FORK ? "enabled" : "disabled",
                    data ? "enabled" : "disabled");
                if (data)
                        p->p_ptevents |= PTRACE_FORK;
                else
                        p->p_ptevents &= ~PTRACE_FORK;
                break;

        case PT_LWP_EVENTS:
                CTR3(KTR_PTRACE, "PT_LWP_EVENTS: pid %d %s -> %s", p->p_pid,
                    p->p_ptevents & PTRACE_LWP ? "enabled" : "disabled",
                    data ? "enabled" : "disabled");
                if (data)
                        p->p_ptevents |= PTRACE_LWP;
                else
                        p->p_ptevents &= ~PTRACE_LWP;
                break;

        case PT_GET_EVENT_MASK:
                if (data != sizeof(p->p_ptevents)) {
                        error = EINVAL;
                        break;
                }
                CTR2(KTR_PTRACE, "PT_GET_EVENT_MASK: pid %d mask %#x", p->p_pid,
                    p->p_ptevents);
                *(int *)addr = p->p_ptevents;
                break;

        case PT_SET_EVENT_MASK:
                if (data != sizeof(p->p_ptevents)) {
                        error = EINVAL;
                        break;
                }
                tmp = *(int *)addr;
                if ((tmp & ~(PTRACE_EXEC | PTRACE_SCE | PTRACE_SCX |
                    PTRACE_FORK | PTRACE_LWP | PTRACE_VFORK)) != 0) {
                        error = EINVAL;
                        break;
                }
                CTR3(KTR_PTRACE, "PT_SET_EVENT_MASK: pid %d mask %#x -> %#x",
                    p->p_pid, p->p_ptevents, tmp);
                p->p_ptevents = tmp;
                break;

        case PT_GET_SC_ARGS:
        case PTLINUX_GET_SC_ARGS:
                CTR2(KTR_PTRACE, "%s: pid %d", req == PT_GET_SC_ARGS ?
                    "PT_GET_SC_ARGS" : "PT_LINUX_GET_SC_ARGS", p->p_pid);
                if (((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) == 0 &&
                     td2->td_sa.code == 0)
#ifdef COMPAT_FREEBSD32
                    || (wrap32 && !safe)
#endif
                    ) {
                        error = EINVAL;
                        break;
                }
                if (req == PT_GET_SC_ARGS) {
                        bzero(addr, sizeof(td2->td_sa.args));
                        bcopy(td2->td_sa.args, addr, td2->td_sa.callp->sy_narg *
                            sizeof(syscallarg_t));
                } else {
                        /*
                         * Emulate a Linux bug which which strace(1) depends on:
                         * at initialization it tests whether ptrace works by
                         * calling close(2), or some other single-argument
                         * syscall, _with six arguments_, and then verifies
                         * whether it can fetch them all using this API;
                         * otherwise it bails out.
                         */
                        bcopy(td2->td_sa.args, addr, 6 * sizeof(syscallarg_t));
                }
                break;

        case PT_GET_SC_RET:
                if ((td2->td_dbgflags & (TDB_SCX)) == 0
#ifdef COMPAT_FREEBSD32
                    || (wrap32 && !safe)
#endif
                    ) {
                        error = EINVAL;
                        break;
                }
                psr = addr;
                bzero(psr, sizeof(*psr));
                psr->sr_error = td2->td_errno;
                if (psr->sr_error == 0) {
                        psr->sr_retval[0] = td2->td_retval[0];
                        psr->sr_retval[1] = td2->td_retval[1];
                }
                CTR4(KTR_PTRACE,
                    "PT_GET_SC_RET: pid %d error %d retval %#lx,%#lx",
                    p->p_pid, psr->sr_error, psr->sr_retval[0],
                    psr->sr_retval[1]);
                break;

        case PT_STEP:
        case PT_CONTINUE:
        case PT_TO_SCE:
        case PT_TO_SCX:
        case PT_SYSCALL:
        case PT_DETACH:
                /* Zero means do not send any signal */
                if (data < 0 || data > _SIG_MAXSIG) {
                        error = EINVAL;
                        break;
                }

                switch (req) {
                case PT_STEP:
                        CTR3(KTR_PTRACE, "PT_STEP: tid %d (pid %d), sig = %d",
                            td2->td_tid, p->p_pid, data);
                        error = ptrace_single_step(td2);
                        if (error)
                                goto out;
                        break;
                case PT_CONTINUE:
                case PT_TO_SCE:
                case PT_TO_SCX:
                case PT_SYSCALL:
                        if (addr != (void *)1) {
                                error = ptrace_set_pc(td2,
                                    (u_long)(uintfptr_t)addr);
                                if (error)
                                        goto out;
                                td2->td_dbgflags |= TDB_USERWR;
                        }
                        switch (req) {
                        case PT_TO_SCE:
                                p->p_ptevents |= PTRACE_SCE;
                                CTR4(KTR_PTRACE,
                    "PT_TO_SCE: pid %d, events = %#x, PC = %#lx, sig = %d",
                                    p->p_pid, p->p_ptevents,
                                    (u_long)(uintfptr_t)addr, data);
                                break;
                        case PT_TO_SCX:
                                p->p_ptevents |= PTRACE_SCX;
                                CTR4(KTR_PTRACE,
                    "PT_TO_SCX: pid %d, events = %#x, PC = %#lx, sig = %d",
                                    p->p_pid, p->p_ptevents,
                                    (u_long)(uintfptr_t)addr, data);
                                break;
                        case PT_SYSCALL:
                                p->p_ptevents |= PTRACE_SYSCALL;
                                CTR4(KTR_PTRACE,
                    "PT_SYSCALL: pid %d, events = %#x, PC = %#lx, sig = %d",
                                    p->p_pid, p->p_ptevents,
                                    (u_long)(uintfptr_t)addr, data);
                                break;
                        case PT_CONTINUE:
                                CTR3(KTR_PTRACE,
                                    "PT_CONTINUE: pid %d, PC = %#lx, sig = %d",
                                    p->p_pid, (u_long)(uintfptr_t)addr, data);
                                break;
                        }
                        break;
                case PT_DETACH:
                        /*
                         * Clear P_TRACED before reparenting
                         * a detached process back to its original
                         * parent.  Otherwise the debugee will be set
                         * as an orphan of the debugger.
                         */
                        p->p_flag &= ~(P_TRACED | P_WAITED);

                        /*
                         * Reset the process parent.
                         */
                        if (p->p_oppid != p->p_pptr->p_pid) {
                                PROC_LOCK(p->p_pptr);
                                sigqueue_take(p->p_ksi);
                                PROC_UNLOCK(p->p_pptr);

                                pp = proc_realparent(p);
                                proc_reparent(p, pp, false);
                                if (pp == initproc)
                                        p->p_sigparent = SIGCHLD;
                                CTR3(KTR_PTRACE,
                            "PT_DETACH: pid %d reparented to pid %d, sig %d",
                                    p->p_pid, pp->p_pid, data);
                        } else {
                                CTR2(KTR_PTRACE, "PT_DETACH: pid %d, sig %d",
                                    p->p_pid, data);
                        }

                        p->p_ptevents = 0;
                        FOREACH_THREAD_IN_PROC(p, td3) {
                                if ((td3->td_dbgflags & TDB_FSTP) != 0) {
                                        sigqueue_delete(&td3->td_sigqueue,
                                            SIGSTOP);
                                }
                                td3->td_dbgflags &= ~(TDB_XSIG | TDB_FSTP |
                                    TDB_SUSPEND | TDB_BORN);
                        }

                        if ((p->p_flag2 & P2_PTRACE_FSTP) != 0) {
                                sigqueue_delete(&p->p_sigqueue, SIGSTOP);
                                p->p_flag2 &= ~P2_PTRACE_FSTP;
                        }

                        /*
                         * Send SIGCHLD and wakeup the parent as needed.  It
                         * may be the case that they had stopped the child
                         * before it got ptraced, and now they're in the middle
                         * of a wait(2) for it to continue.
                         */
                        PROC_LOCK(p->p_pptr);
                        childproc_continued(p);
                        PROC_UNLOCK(p->p_pptr);
                        break;
                }

                sx_xunlock(&proctree_lock);
                proctree_locked = false;

        sendsig:
                MPASS(!proctree_locked);

                /*
                 * Clear the pending event for the thread that just
                 * reported its event (p_xthread), if any.  This may
                 * not be the thread passed to PT_CONTINUE, PT_STEP,
                 * etc. if the debugger is resuming a different
                 * thread.  There might be no reporting thread if
                 * the process was just attached.
                 *
                 * Deliver any pending signal via the reporting thread.
                 */
                if (p->p_xthread != NULL) {
                        p->p_xthread->td_dbgflags &= ~TDB_XSIG;
                        p->p_xthread->td_xsig = data;
                        p->p_xthread = NULL;
                }
                p->p_xsig = data;

                /*
                 * P_WKILLED is insurance that a PT_KILL/SIGKILL
                 * always works immediately, even if another thread is
                 * unsuspended first and attempts to handle a
                 * different signal or if the POSIX.1b style signal
                 * queue cannot accommodate any new signals.
                 */
                if (data == SIGKILL)
                        proc_wkilled(p);

                /*
                 * If the PT_CONTINUE-like operation is attempted on
                 * the thread on sleepq, this is possible only after
                 * the transparent PT_ATTACH.  In this case, if the
                 * caller modified the thread state, e.g. by writing
                 * register file or specifying the pc, make the thread
                 * xstopped by waking it up.
                 */
                if ((td2->td_dbgflags & TDB_USERWR) != 0) {
                        if (pt_attach_transparent) {
                                thread_lock(td2);
                                if (TD_ON_SLEEPQ(td2) &&
                                    (td2->td_flags & TDF_SINTR) != 0) {
                                        sleepq_abort(td2, EINTR);
                                } else {
                                        thread_unlock(td2);
                                }
                        }
                        td2->td_dbgflags &= ~TDB_USERWR;
                }

                /*
                 * Unsuspend all threads.  To leave a thread
                 * suspended, use PT_SUSPEND to suspend it before
                 * continuing the process.
                 */
                ptrace_unsuspend(p);
                break;

        case PT_WRITE_I:
        case PT_WRITE_D:
                td2->td_dbgflags |= TDB_USERWR;
                PROC_UNLOCK(p);
                error = 0;
                if (proc_writemem(td, p, (off_t)(uintptr_t)addr, &data,
                    sizeof(int)) != sizeof(int))
                        error = ENOMEM;
                else
                        CTR3(KTR_PTRACE, "PT_WRITE: pid %d: %p <= %#x",
                            p->p_pid, addr, data);
                PROC_LOCK(p);
                break;

        case PT_READ_I:
        case PT_READ_D:
                PROC_UNLOCK(p);
                error = tmp = 0;
                if (proc_readmem(td, p, (off_t)(uintptr_t)addr, &tmp,
                    sizeof(int)) != sizeof(int))
                        error = ENOMEM;
                else
                        CTR3(KTR_PTRACE, "PT_READ: pid %d: %p >= %#x",
                            p->p_pid, addr, tmp);
                td->td_retval[0] = tmp;
                PROC_LOCK(p);
                break;

        case PT_IO:
                piod = addr;
                if (piod->piod_len > SSIZE_MAX) {
                        error = EINVAL;
                        goto out;
                }
                iov.iov_base = piod->piod_addr;
                iov.iov_len = piod->piod_len;
                uio.uio_offset = (off_t)(uintptr_t)piod->piod_offs;
                uio.uio_resid = piod->piod_len;
                uio.uio_iov = &iov;
                uio.uio_iovcnt = 1;
                uio.uio_segflg = UIO_USERSPACE;
                uio.uio_td = td;
                switch (piod->piod_op) {
                case PIOD_READ_D:
                case PIOD_READ_I:
                        CTR3(KTR_PTRACE, "PT_IO: pid %d: READ (%p, %#x)",
                            p->p_pid, (uintptr_t)uio.uio_offset, uio.uio_resid);
                        uio.uio_rw = UIO_READ;
                        break;
                case PIOD_WRITE_D:
                case PIOD_WRITE_I:
                        CTR3(KTR_PTRACE, "PT_IO: pid %d: WRITE (%p, %#x)",
                            p->p_pid, (uintptr_t)uio.uio_offset, uio.uio_resid);
                        td2->td_dbgflags |= TDB_USERWR;
                        uio.uio_rw = UIO_WRITE;
                        break;
                default:
                        error = EINVAL;
                        goto out;
                }
                PROC_UNLOCK(p);
                error = proc_rwmem(p, &uio);
                piod->piod_len -= uio.uio_resid;
                PROC_LOCK(p);
                break;

        case PT_KILL:
                CTR1(KTR_PTRACE, "PT_KILL: pid %d", p->p_pid);
                data = SIGKILL;
                goto sendsig;   /* in PT_CONTINUE above */

        case PT_SETREGS:
                CTR2(KTR_PTRACE, "PT_SETREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                td2->td_dbgflags |= TDB_USERWR;
                error = PROC_WRITE(regs, td2, addr);
                break;

        case PT_GETREGS:
                CTR2(KTR_PTRACE, "PT_GETREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = PROC_READ(regs, td2, addr);
                break;

        case PT_SETFPREGS:
                CTR2(KTR_PTRACE, "PT_SETFPREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                td2->td_dbgflags |= TDB_USERWR;
                error = PROC_WRITE(fpregs, td2, addr);
                break;

        case PT_GETFPREGS:
                CTR2(KTR_PTRACE, "PT_GETFPREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = PROC_READ(fpregs, td2, addr);
                break;

        case PT_SETDBREGS:
                CTR2(KTR_PTRACE, "PT_SETDBREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                td2->td_dbgflags |= TDB_USERWR;
                error = PROC_WRITE(dbregs, td2, addr);
                break;

        case PT_GETDBREGS:
                CTR2(KTR_PTRACE, "PT_GETDBREGS: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = PROC_READ(dbregs, td2, addr);
                break;

        case PT_SETREGSET:
                CTR2(KTR_PTRACE, "PT_SETREGSET: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = proc_write_regset(td2, data, addr);
                break;

        case PT_GETREGSET:
                CTR2(KTR_PTRACE, "PT_GETREGSET: tid %d (pid %d)", td2->td_tid,
                    p->p_pid);
                error = proc_read_regset(td2, data, addr);
                break;

        case PT_LWPINFO:
                if (data <= 0 || data > sizeof(*pl)) {
                        error = EINVAL;
                        break;
                }
                pl = addr;
                bzero(pl, sizeof(*pl));
                pl->pl_lwpid = td2->td_tid;
                pl->pl_event = PL_EVENT_NONE;
                pl->pl_flags = 0;
                if (td2->td_dbgflags & TDB_XSIG) {
                        pl->pl_event = PL_EVENT_SIGNAL;
                        if (td2->td_si.si_signo != 0 &&
                            data >= offsetof(struct ptrace_lwpinfo, pl_siginfo)
                            + sizeof(pl->pl_siginfo)){
                                pl->pl_flags |= PL_FLAG_SI;
                                pl->pl_siginfo = td2->td_si;
                        }
                }
                if (td2->td_dbgflags & TDB_SCE)
                        pl->pl_flags |= PL_FLAG_SCE;
                else if (td2->td_dbgflags & TDB_SCX)
                        pl->pl_flags |= PL_FLAG_SCX;
                if (td2->td_dbgflags & TDB_EXEC)
                        pl->pl_flags |= PL_FLAG_EXEC;
                if (td2->td_dbgflags & TDB_FORK) {
                        pl->pl_flags |= PL_FLAG_FORKED;
                        pl->pl_child_pid = td2->td_dbg_forked;
                        if (td2->td_dbgflags & TDB_VFORK)
                                pl->pl_flags |= PL_FLAG_VFORKED;
                } else if ((td2->td_dbgflags & (TDB_SCX | TDB_VFORK)) ==
                    TDB_VFORK)
                        pl->pl_flags |= PL_FLAG_VFORK_DONE;
                if (td2->td_dbgflags & TDB_CHILD)
                        pl->pl_flags |= PL_FLAG_CHILD;
                if (td2->td_dbgflags & TDB_BORN)
                        pl->pl_flags |= PL_FLAG_BORN;
                if (td2->td_dbgflags & TDB_EXIT)
                        pl->pl_flags |= PL_FLAG_EXITED;
                pl->pl_sigmask = td2->td_sigmask;
                pl->pl_siglist = td2->td_siglist;
                strcpy(pl->pl_tdname, td2->td_name);
                if (td2->td_sa.code != 0) {
                        pl->pl_syscall_code = td2->td_sa.code;
                        pl->pl_syscall_narg = td2->td_sa.callp->sy_narg;
                }
                CTR6(KTR_PTRACE,
    "PT_LWPINFO: tid %d (pid %d) event %d flags %#x child pid %d syscall %d",
                    td2->td_tid, p->p_pid, pl->pl_event, pl->pl_flags,
                    pl->pl_child_pid, pl->pl_syscall_code);
                break;

        case PT_GETNUMLWPS:
                CTR2(KTR_PTRACE, "PT_GETNUMLWPS: pid %d: %d threads", p->p_pid,
                    p->p_numthreads);
                td->td_retval[0] = p->p_numthreads;
                break;

        case PT_GETLWPLIST:
                CTR3(KTR_PTRACE, "PT_GETLWPLIST: pid %d: data %d, actual %d",
                    p->p_pid, data, p->p_numthreads);
                if (data <= 0) {
                        error = EINVAL;
                        break;
                }
                num = imin(p->p_numthreads, data);
                PROC_UNLOCK(p);
                buf = malloc(num * sizeof(lwpid_t), M_TEMP, M_WAITOK);
                tmp = 0;
                PROC_LOCK(p);
                FOREACH_THREAD_IN_PROC(p, td2) {
                        if (tmp >= num)
                                break;
                        buf[tmp++] = td2->td_tid;
                }
                PROC_UNLOCK(p);
                error = copyout(buf, addr, tmp * sizeof(lwpid_t));
                free(buf, M_TEMP);
                if (!error)
                        td->td_retval[0] = tmp;
                PROC_LOCK(p);
                break;

        case PT_VM_TIMESTAMP:
                CTR2(KTR_PTRACE, "PT_VM_TIMESTAMP: pid %d: timestamp %d",
                    p->p_pid, p->p_vmspace->vm_map.timestamp);
                td->td_retval[0] = p->p_vmspace->vm_map.timestamp;
                break;

        case PT_VM_ENTRY:
                PROC_UNLOCK(p);
                error = ptrace_vm_entry(td, p, addr);
                PROC_LOCK(p);
                break;

        case PT_COREDUMP:
                pc = addr;
                CTR2(KTR_PTRACE, "PT_COREDUMP: pid %d, fd %d",
                    p->p_pid, pc->pc_fd);

                if ((pc->pc_flags & ~(PC_COMPRESS | PC_ALL)) != 0) {
                        error = EINVAL;
                        break;
                }
                PROC_UNLOCK(p);

                tcq = malloc(sizeof(*tcq), M_TEMP, M_WAITOK | M_ZERO);
                fp = NULL;
                error = fget_write(td, pc->pc_fd, &cap_write_rights, &fp);
                if (error != 0)
                        goto coredump_cleanup_nofp;
                if (fp->f_type != DTYPE_VNODE || fp->f_vnode->v_type != VREG) {
                        error = EPIPE;
                        goto coredump_cleanup;
                }

                PROC_LOCK(p);
                error = proc_can_ptrace(td, p);
                if (error != 0)
                        goto coredump_cleanup_locked;

                td2 = ptrace_sel_coredump_thread(p);
                if (td2 == NULL) {
                        error = EBUSY;
                        goto coredump_cleanup_locked;
                }
                KASSERT((td2->td_dbgflags & (TDB_COREDUMPREQ |
                    TDB_SCREMOTEREQ)) == 0,
                    ("proc %d tid %d req coredump", p->p_pid, td2->td_tid));

                tcq->tc_vp = fp->f_vnode;
                tcq->tc_limit = pc->pc_limit == 0 ? OFF_MAX : pc->pc_limit;
                tcq->tc_flags = SVC_PT_COREDUMP;
                if ((pc->pc_flags & PC_COMPRESS) == 0)
                        tcq->tc_flags |= SVC_NOCOMPRESS;
                if ((pc->pc_flags & PC_ALL) != 0)
                        tcq->tc_flags |= SVC_ALL;
                td2->td_remotereq = tcq;
                td2->td_dbgflags |= TDB_COREDUMPREQ;
                thread_run_flash(td2);
                while ((td2->td_dbgflags & TDB_COREDUMPREQ) != 0)
                        msleep(p, &p->p_mtx, PPAUSE, "crdmp", 0);
                error = tcq->tc_error;
coredump_cleanup_locked:
                PROC_UNLOCK(p);
coredump_cleanup:
                fdrop(fp, td);
coredump_cleanup_nofp:
                free(tcq, M_TEMP);
                PROC_LOCK(p);
                break;

        case PT_SC_REMOTE:
                pscr = addr;
                CTR2(KTR_PTRACE, "PT_SC_REMOTE: pid %d, syscall %d",
                    p->p_pid, pscr->pscr_syscall);
                if ((td2->td_dbgflags & TDB_BOUNDARY) == 0) {
                        error = EBUSY;
                        break;
                }
                PROC_UNLOCK(p);
                MPASS(pscr->pscr_nargs <= nitems(td->td_sa.args));

                tsr = malloc(sizeof(struct thr_syscall_req), M_TEMP,
                    M_WAITOK | M_ZERO);

                tsr->ts_sa.code = pscr->pscr_syscall;
                tsr->ts_nargs = pscr->pscr_nargs;
                memcpy(&tsr->ts_sa.args, pscr->pscr_args,
                    sizeof(syscallarg_t) * tsr->ts_nargs);

                PROC_LOCK(p);
                error = proc_can_ptrace(td, p);
                if (error != 0) {
                        free(tsr, M_TEMP);
                        break;
                }
                if (td2->td_proc != p) {
                        free(tsr, M_TEMP);
                        error = ESRCH;
                        break;
                }
                KASSERT((td2->td_dbgflags & (TDB_COREDUMPREQ |
                    TDB_SCREMOTEREQ)) == 0,
                    ("proc %d tid %d req coredump", p->p_pid, td2->td_tid));

                td2->td_remotereq = tsr;
                td2->td_dbgflags |= TDB_SCREMOTEREQ;
                thread_run_flash(td2);
                while ((td2->td_dbgflags & TDB_SCREMOTEREQ) != 0)
                        msleep(p, &p->p_mtx, PPAUSE, "pscrx", 0);
                error = 0;
                memcpy(&pscr->pscr_ret, &tsr->ts_ret, sizeof(tsr->ts_ret));
                free(tsr, M_TEMP);
                break;

        default:
#ifdef __HAVE_PTRACE_MACHDEP
                if (req >= PT_FIRSTMACH) {
                        PROC_UNLOCK(p);
                        error = cpu_ptrace(td2, req, addr, data);
                        PROC_LOCK(p);
                } else
#endif
                        /* Unknown request. */
                        error = EINVAL;
                break;
        }
out:
        /* Drop our hold on this process now that the request has completed. */
        _PRELE(p);
fail:
        if (p2_req_set) {
                if ((p->p_flag2 & P2_PTRACEREQ) != 0)
                        wakeup(&p->p_flag2);
                p->p_flag2 &= ~P2_PTRACEREQ;
        }
        PROC_UNLOCK(p);
        if (proctree_locked)
                sx_xunlock(&proctree_lock);
        return (error);
}
#undef PROC_READ
#undef PROC_WRITE