[apple/libpthread.git] / kern / kern_support.c

/*
 * Copyright (c) 2000-2017 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995-2005 Apple Computer, Inc. All Rights Reserved */
/*
 *      pthread_synch.c
 */

#pragma mark - Front Matter

#define _PTHREAD_CONDATTR_T
#define _PTHREAD_COND_T
#define _PTHREAD_MUTEXATTR_T
#define _PTHREAD_MUTEX_T
#define _PTHREAD_RWLOCKATTR_T
#define _PTHREAD_RWLOCK_T

#undef pthread_mutexattr_t
#undef pthread_mutex_t
#undef pthread_condattr_t
#undef pthread_cond_t
#undef pthread_rwlockattr_t
#undef pthread_rwlock_t

#include <sys/cdefs.h>
#include <os/log.h>

// <rdar://problem/26158937> panic() should be marked noreturn
extern void panic(const char *string, ...) __printflike(1,2) __dead2;

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/resourcevar.h>
//#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/systm.h>
#include <sys/timeb.h>
#include <sys/times.h>
#include <sys/acct.h>
#include <sys/kernel.h>
#include <sys/wait.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/stat.h>
#include <sys/lock.h>
#include <sys/kdebug.h>
//#include <sys/sysproto.h>
#include <sys/vm.h>
#include <sys/user.h>           /* for coredump */
#include <sys/proc_info.h>      /* for fill_procworkqueue */

#include <mach/mach_port.h>
#include <mach/mach_types.h>
#include <mach/semaphore.h>
#include <mach/sync_policy.h>
#include <mach/task.h>
#include <mach/vm_prot.h>
#include <kern/kern_types.h>
#include <kern/task.h>
#include <kern/clock.h>
#include <mach/kern_return.h>
#include <kern/thread.h>
#include <kern/zalloc.h>
#include <kern/sched_prim.h>    /* for thread_exception_return */
#include <kern/processor.h>
#include <kern/assert.h>
#include <mach/mach_vm.h>
#include <mach/mach_param.h>
#include <mach/thread_status.h>
#include <mach/thread_policy.h>
#include <mach/message.h>
#include <mach/port.h>
//#include <vm/vm_protos.h>
#include <vm/vm_fault.h>
#include <vm/vm_map.h>
#include <mach/thread_act.h> /* for thread_resume */
#include <machine/machine_routines.h>
#include <mach/shared_region.h>

#include <libkern/OSAtomic.h>
#include <libkern/libkern.h>

#include "kern_internal.h"

#ifndef WQ_SETUP_EXIT_THREAD
#define WQ_SETUP_EXIT_THREAD    8
#endif

// XXX: Ditto for thread tags from kern/thread.h
#define THREAD_TAG_MAINTHREAD 0x1
#define THREAD_TAG_PTHREAD 0x10
#define THREAD_TAG_WORKQUEUE 0x20

lck_grp_attr_t   *pthread_lck_grp_attr;
lck_grp_t    *pthread_lck_grp;
lck_attr_t   *pthread_lck_attr;

#define C_32_STK_ALIGN          16
#define C_64_STK_ALIGN          16

// WORKQ use the largest alignment any platform needs
#define C_WORKQ_STK_ALIGN       16

#if defined(__arm64__)
/* Pull the pthread_t into the same page as the top of the stack so we dirty one less page.
 * <rdar://problem/19941744> The _pthread struct at the top of the stack shouldn't be page-aligned
 */
#define PTHREAD_T_OFFSET (12*1024)
#else
#define PTHREAD_T_OFFSET 0
#endif

/*
 * Flags filed passed to bsdthread_create and back in pthread_start
31  <---------------------------------> 0
_________________________________________
| flags(8) | policy(8) | importance(16) |
-----------------------------------------
*/

#define PTHREAD_START_CUSTOM            0x01000000 // <rdar://problem/34501401>
#define PTHREAD_START_SETSCHED          0x02000000
// was PTHREAD_START_DETACHED           0x04000000
#define PTHREAD_START_QOSCLASS          0x08000000
#define PTHREAD_START_TSD_BASE_SET      0x10000000
#define PTHREAD_START_SUSPENDED         0x20000000
#define PTHREAD_START_QOSCLASS_MASK     0x00ffffff
#define PTHREAD_START_POLICY_BITSHIFT 16
#define PTHREAD_START_POLICY_MASK 0xff
#define PTHREAD_START_IMPORTANCE_MASK 0xffff

#define SCHED_OTHER      POLICY_TIMESHARE
#define SCHED_FIFO       POLICY_FIFO
#define SCHED_RR         POLICY_RR

#define BASEPRI_DEFAULT 31

uint32_t pthread_debug_tracing = 1;

static uint32_t pthread_mutex_default_policy;

SYSCTL_INT(_kern, OID_AUTO, pthread_mutex_default_policy, CTLFLAG_RW | CTLFLAG_LOCKED,
           &pthread_mutex_default_policy, 0, "");

#pragma mark - Process/Thread Setup/Teardown syscalls

static mach_vm_offset_t
stack_addr_hint(proc_t p, vm_map_t vmap)
{
        mach_vm_offset_t stackaddr;
        mach_vm_offset_t aslr_offset;
        bool proc64bit = proc_is64bit(p);
        bool proc64bit_data = proc_is64bit_data(p);

        // We can't safely take random values % something unless its a power-of-two
        _Static_assert(powerof2(PTH_DEFAULT_STACKSIZE), "PTH_DEFAULT_STACKSIZE is a power-of-two");

#if defined(__i386__) || defined(__x86_64__)
        (void)proc64bit_data;
        if (proc64bit) {
                // Matches vm_map_get_max_aslr_slide_pages's image shift in xnu
                aslr_offset = random() % (1 << 28); // about 512 stacks
        } else {
                // Actually bigger than the image shift, we've got ~256MB to work with
                aslr_offset = random() % (16 * PTH_DEFAULT_STACKSIZE);
        }
        aslr_offset = vm_map_trunc_page_mask(aslr_offset, vm_map_page_mask(vmap));
        if (proc64bit) {
                // Above nanomalloc range (see NANOZONE_SIGNATURE)
                stackaddr = 0x700000000000 + aslr_offset;
        } else {
                stackaddr = SHARED_REGION_BASE_I386 + SHARED_REGION_SIZE_I386 + aslr_offset;
        }
#elif defined(__arm__) || defined(__arm64__)
        user_addr_t main_thread_stack_top = 0;
        if (pthread_kern->proc_get_user_stack) {
                main_thread_stack_top = pthread_kern->proc_get_user_stack(p);
        }
        if (proc64bit && main_thread_stack_top) {
                // The main thread stack position is randomly slid by xnu (c.f.
                // load_main() in mach_loader.c), so basing pthread stack allocations
                // where the main thread stack ends is already ASLRd and doing so
                // avoids creating a gap in the process address space that may cause
                // extra PTE memory usage. rdar://problem/33328206
                stackaddr = vm_map_trunc_page_mask((vm_map_offset_t)main_thread_stack_top,
                                vm_map_page_mask(vmap));
        } else {
                // vm_map_get_max_aslr_slide_pages ensures 1MB of slide, we do better
                aslr_offset = random() % ((proc64bit ? 4 : 2) * PTH_DEFAULT_STACKSIZE);
                aslr_offset = vm_map_trunc_page_mask((vm_map_offset_t)aslr_offset,
                                vm_map_page_mask(vmap));
                if (proc64bit) {
                        // 64 stacks below shared region
                        stackaddr = SHARED_REGION_BASE_ARM64 - 64 * PTH_DEFAULT_STACKSIZE - aslr_offset;
                } else {
                        // If you try to slide down from this point, you risk ending up in memory consumed by malloc
                        if (proc64bit_data) {
                                stackaddr = SHARED_REGION_BASE_ARM64_32;
                        } else {
                                stackaddr = SHARED_REGION_BASE_ARM;
                        }

                        stackaddr -= 32 * PTH_DEFAULT_STACKSIZE + aslr_offset;
                }
        }
#else
#error Need to define a stack address hint for this architecture
#endif
        return stackaddr;
}

static bool
_pthread_priority_to_policy(pthread_priority_t priority,
                thread_qos_policy_data_t *data)
{
        data->qos_tier = _pthread_priority_thread_qos(priority);
        data->tier_importance = _pthread_priority_relpri(priority);
        if (data->qos_tier == THREAD_QOS_UNSPECIFIED || data->tier_importance > 0 ||
                        data->tier_importance < THREAD_QOS_MIN_TIER_IMPORTANCE) {
                return false;
        }
        return true;
}

/**
 * bsdthread_create system call.  Used by pthread_create.
 */
int
_bsdthread_create(struct proc *p,
                __unused user_addr_t user_func, __unused user_addr_t user_funcarg,
                user_addr_t user_stack, user_addr_t user_pthread, uint32_t flags,
                user_addr_t *retval)
{
        kern_return_t kret;
        void * sright;
        int error = 0;
        mach_vm_offset_t th_tsd_base;
        mach_port_name_t th_thport;
        thread_t th;
        task_t ctask = current_task();
        unsigned int policy, importance;
        uint32_t tsd_offset;
        bool start_suspended = (flags & PTHREAD_START_SUSPENDED);

        if (pthread_kern->proc_get_register(p) == 0) {
                return EINVAL;
        }

        PTHREAD_TRACE(pthread_thread_create | DBG_FUNC_START, flags, 0, 0, 0);

        kret = pthread_kern->thread_create(ctask, &th);
        if (kret != KERN_SUCCESS)
                return(ENOMEM);
        thread_reference(th);

        pthread_kern->thread_set_tag(th, THREAD_TAG_PTHREAD);

        sright = (void *)pthread_kern->convert_thread_to_port(th);
        th_thport = pthread_kern->ipc_port_copyout_send(sright, pthread_kern->task_get_ipcspace(ctask));
        if (!MACH_PORT_VALID(th_thport)) {
                error = EMFILE; // userland will convert this into a crash
                goto out;
        }

        if ((flags & PTHREAD_START_CUSTOM) == 0) {
                error = EINVAL;
                goto out;
        }

        PTHREAD_TRACE(pthread_thread_create|DBG_FUNC_NONE, 0, 0, 0, 3);

        tsd_offset = pthread_kern->proc_get_pthread_tsd_offset(p);
        if (tsd_offset) {
                th_tsd_base = user_pthread + tsd_offset;
                kret = pthread_kern->thread_set_tsd_base(th, th_tsd_base);
                if (kret == KERN_SUCCESS) {
                        flags |= PTHREAD_START_TSD_BASE_SET;
                }
        }
        /*
         * Strip PTHREAD_START_SUSPENDED so that libpthread can observe the kernel
         * supports this flag (after the fact).
         */
        flags &= ~PTHREAD_START_SUSPENDED;

        /*
         * Set up registers & function call.
         */
#if defined(__i386__) || defined(__x86_64__)
        if (proc_is64bit_data(p)) {
                x86_thread_state64_t state = {
                        .rip = (uint64_t)pthread_kern->proc_get_threadstart(p),
                        .rdi = (uint64_t)user_pthread,
                        .rsi = (uint64_t)th_thport,
                        .rdx = (uint64_t)user_func,    /* golang wants this */
                        .rcx = (uint64_t)user_funcarg, /* golang wants this */
                        .r8  = (uint64_t)user_stack,   /* golang wants this */
                        .r9  = (uint64_t)flags,

                        .rsp = (uint64_t)user_stack,
                };

                (void)pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state);
        } else {
                x86_thread_state32_t state = {
                        .eip = (uint32_t)pthread_kern->proc_get_threadstart(p),
                        .eax = (uint32_t)user_pthread,
                        .ebx = (uint32_t)th_thport,
                        .ecx = (uint32_t)user_func,    /* golang wants this */
                        .edx = (uint32_t)user_funcarg, /* golang wants this */
                        .edi = (uint32_t)user_stack,   /* golang wants this */
                        .esi = (uint32_t)flags,

                        .esp = (uint32_t)user_stack,
                };

                (void)pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
        }
#elif defined(__arm__) || defined(__arm64__)
        if (proc_is64bit_data(p)) {
#ifdef __arm64__
                arm_thread_state64_t state = {
                        .pc   = (uint64_t)pthread_kern->proc_get_threadstart(p),
                        .x[0] = (uint64_t)user_pthread,
                        .x[1] = (uint64_t)th_thport,
                        .x[2] = (uint64_t)user_func,    /* golang wants this */
                        .x[3] = (uint64_t)user_funcarg, /* golang wants this */
                        .x[4] = (uint64_t)user_stack,   /* golang wants this */
                        .x[5] = (uint64_t)flags,

                        .sp   = (uint64_t)user_stack,
                };

                (void)pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state);
#else
                panic("Shouldn't have a 64-bit thread on a 32-bit kernel...");
#endif // defined(__arm64__)
        } else {
                arm_thread_state_t state = {
                        .pc   = (uint32_t)pthread_kern->proc_get_threadstart(p),
                        .r[0] = (uint32_t)user_pthread,
                        .r[1] = (uint32_t)th_thport,
                        .r[2] = (uint32_t)user_func,    /* golang wants this */
                        .r[3] = (uint32_t)user_funcarg, /* golang wants this */
                        .r[4] = (uint32_t)user_stack,   /* golang wants this */
                        .r[5] = (uint32_t)flags,

                        .sp   = (uint32_t)user_stack,
                };

                (void)pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
        }
#else
#error bsdthread_create  not defined for this architecture
#endif

        if (flags & PTHREAD_START_SETSCHED) {
                /* Set scheduling parameters if needed */
                thread_extended_policy_data_t    extinfo;
                thread_precedence_policy_data_t   precedinfo;

                importance = (flags & PTHREAD_START_IMPORTANCE_MASK);
                policy = (flags >> PTHREAD_START_POLICY_BITSHIFT) & PTHREAD_START_POLICY_MASK;

                if (policy == SCHED_OTHER) {
                        extinfo.timeshare = 1;
                } else {
                        extinfo.timeshare = 0;
                }

                thread_policy_set(th, THREAD_EXTENDED_POLICY, (thread_policy_t)&extinfo, THREAD_EXTENDED_POLICY_COUNT);

                precedinfo.importance = (importance - BASEPRI_DEFAULT);
                thread_policy_set(th, THREAD_PRECEDENCE_POLICY, (thread_policy_t)&precedinfo, THREAD_PRECEDENCE_POLICY_COUNT);
        } else if (flags & PTHREAD_START_QOSCLASS) {
                /* Set thread QoS class if requested. */
                thread_qos_policy_data_t qos;

                if (!_pthread_priority_to_policy(flags & PTHREAD_START_QOSCLASS_MASK, &qos)) {
                        error = EINVAL;
                        goto out;
                }
                pthread_kern->thread_policy_set_internal(th, THREAD_QOS_POLICY,
                                (thread_policy_t)&qos, THREAD_QOS_POLICY_COUNT);
        }

        if (pthread_kern->proc_get_mach_thread_self_tsd_offset) {
                uint64_t mach_thread_self_offset =
                                pthread_kern->proc_get_mach_thread_self_tsd_offset(p);
                if (mach_thread_self_offset && tsd_offset) {
                        bool proc64bit = proc_is64bit(p);
                        if (proc64bit) {
                                uint64_t th_thport_tsd = (uint64_t)th_thport;
                                error = copyout(&th_thport_tsd, user_pthread + tsd_offset +
                                                mach_thread_self_offset, sizeof(th_thport_tsd));
                        } else {
                                uint32_t th_thport_tsd = (uint32_t)th_thport;
                                error = copyout(&th_thport_tsd, user_pthread + tsd_offset +
                                                mach_thread_self_offset, sizeof(th_thport_tsd));
                        }
                        if (error) {
                                goto out;
                        }
                }
        }

        if (!start_suspended) {
                kret = pthread_kern->thread_resume(th);
                if (kret != KERN_SUCCESS) {
                        error = EINVAL;
                        goto out;
                }
        }
        thread_deallocate(th);  /* drop the creator reference */

        PTHREAD_TRACE(pthread_thread_create|DBG_FUNC_END, error, user_pthread, 0, 0);

        *retval = user_pthread;
        return(0);

out:
        (void)pthread_kern->mach_port_deallocate(pthread_kern->task_get_ipcspace(ctask), th_thport);
        if (pthread_kern->thread_will_park_or_terminate) {
                pthread_kern->thread_will_park_or_terminate(th);
        }
        (void)thread_terminate(th);
        (void)thread_deallocate(th);
        return(error);
}

/**
 * bsdthread_terminate system call.  Used by pthread_terminate
 */
int
_bsdthread_terminate(__unused struct proc *p,
                     user_addr_t stackaddr,
                     size_t size,
                     uint32_t kthport,
                     uint32_t sem,
                     __unused int32_t *retval)
{
        mach_vm_offset_t freeaddr;
        mach_vm_size_t freesize;
        kern_return_t kret;
        thread_t th = current_thread();

        freeaddr = (mach_vm_offset_t)stackaddr;
        freesize = size;

        PTHREAD_TRACE(pthread_thread_terminate|DBG_FUNC_START, freeaddr, freesize, kthport, 0xff);

        if ((freesize != (mach_vm_size_t)0) && (freeaddr != (mach_vm_offset_t)0)) {
                if (pthread_kern->thread_get_tag(th) & THREAD_TAG_MAINTHREAD){
                        vm_map_t user_map = pthread_kern->current_map();
                        freesize = vm_map_trunc_page_mask((vm_map_offset_t)freesize - 1, vm_map_page_mask(user_map));
                        kret = mach_vm_behavior_set(user_map, freeaddr, freesize, VM_BEHAVIOR_REUSABLE);
#if MACH_ASSERT
                        if (kret != KERN_SUCCESS && kret != KERN_INVALID_ADDRESS) {
                                os_log_error(OS_LOG_DEFAULT, "unable to make thread stack reusable (kr: %d)", kret);
                        }
#endif
                        kret = kret ? kret : mach_vm_protect(user_map, freeaddr, freesize, FALSE, VM_PROT_NONE);
                        assert(kret == KERN_SUCCESS || kret == KERN_INVALID_ADDRESS);
                } else {
                        kret = mach_vm_deallocate(pthread_kern->current_map(), freeaddr, freesize);
                        if (kret != KERN_SUCCESS) {
                                PTHREAD_TRACE(pthread_thread_terminate|DBG_FUNC_END, kret, 0, 0, 0);
                        }
                }
        }

        if (pthread_kern->thread_will_park_or_terminate) {
                pthread_kern->thread_will_park_or_terminate(th);
        }
        (void)thread_terminate(th);
        if (sem != MACH_PORT_NULL) {
                kret = pthread_kern->semaphore_signal_internal_trap(sem);
                if (kret != KERN_SUCCESS) {
                        PTHREAD_TRACE(pthread_thread_terminate|DBG_FUNC_END, kret, 0, 0, 0);
                }
        }

        if (kthport != MACH_PORT_NULL) {
                pthread_kern->mach_port_deallocate(pthread_kern->task_get_ipcspace(current_task()), kthport);
        }

        PTHREAD_TRACE(pthread_thread_terminate|DBG_FUNC_END, 0, 0, 0, 0);

        pthread_kern->thread_exception_return();
        __builtin_unreachable();
}

/**
 * bsdthread_register system call.  Performs per-process setup.  Responsible for
 * returning capabilitiy bits to userspace and receiving userspace function addresses.
 */
int
_bsdthread_register(struct proc *p,
                    user_addr_t threadstart,
                    user_addr_t wqthread,
                    int pthsize,
                    user_addr_t pthread_init_data,
                    user_addr_t pthread_init_data_size,
                    uint64_t dispatchqueue_offset,
                    int32_t *retval)
{
        struct _pthread_registration_data data = {};
        uint32_t max_tsd_offset;
        kern_return_t kr;
        size_t pthread_init_sz = 0;

        /* syscall randomizer test can pass bogus values */
        if (pthsize < 0 || pthsize > MAX_PTHREAD_SIZE) {
                return(EINVAL);
        }
        /*
         * if we have pthread_init_data, then we use that and target_concptr
         * (which is an offset) get data.
         */
        if (pthread_init_data != 0) {
                if (pthread_init_data_size < sizeof(data.version)) {
                        return EINVAL;
                }
                pthread_init_sz = MIN(sizeof(data), (size_t)pthread_init_data_size);
                int ret = copyin(pthread_init_data, &data, pthread_init_sz);
                if (ret) {
                        return ret;
                }
                if (data.version != (size_t)pthread_init_data_size) {
                        return EINVAL;
                }
        } else {
                data.dispatch_queue_offset = dispatchqueue_offset;
        }

        /* We have to do this before proc_get_register so that it resets after fork */
        mach_vm_offset_t stackaddr = stack_addr_hint(p, pthread_kern->current_map());
        pthread_kern->proc_set_stack_addr_hint(p, (user_addr_t)stackaddr);

        /* prevent multiple registrations */
        if (pthread_kern->proc_get_register(p) != 0) {
                return(EINVAL);
        }

        pthread_kern->proc_set_threadstart(p, threadstart);
        pthread_kern->proc_set_wqthread(p, wqthread);
        pthread_kern->proc_set_pthsize(p, pthsize);
        pthread_kern->proc_set_register(p);

        uint32_t tsd_slot_sz = proc_is64bit(p) ? sizeof(uint64_t) : sizeof(uint32_t);
        if ((uint32_t)pthsize >= tsd_slot_sz &&
                        data.tsd_offset <= (uint32_t)(pthsize - tsd_slot_sz)) {
                max_tsd_offset = ((uint32_t)pthsize - data.tsd_offset - tsd_slot_sz);
        } else {
                data.tsd_offset = 0;
                max_tsd_offset = 0;
        }
        pthread_kern->proc_set_pthread_tsd_offset(p, data.tsd_offset);

        if (data.dispatch_queue_offset > max_tsd_offset) {
                data.dispatch_queue_offset = 0;
        }
        pthread_kern->proc_set_dispatchqueue_offset(p, data.dispatch_queue_offset);

        if (pthread_kern->proc_set_return_to_kernel_offset) {
                if (data.return_to_kernel_offset > max_tsd_offset) {
                        data.return_to_kernel_offset = 0;
                }
                pthread_kern->proc_set_return_to_kernel_offset(p,
                                data.return_to_kernel_offset);
        }

        if (pthread_kern->proc_set_mach_thread_self_tsd_offset) {
                if (data.mach_thread_self_offset > max_tsd_offset) {
                        data.mach_thread_self_offset = 0;
                }
                pthread_kern->proc_set_mach_thread_self_tsd_offset(p,
                                data.mach_thread_self_offset);
        }

        if (pthread_init_data != 0) {
                /* Outgoing data that userspace expects as a reply */
                data.version = sizeof(struct _pthread_registration_data);
                data.main_qos = _pthread_unspecified_priority();

                if (pthread_kern->qos_main_thread_active()) {
                        mach_msg_type_number_t nqos = THREAD_QOS_POLICY_COUNT;
                        thread_qos_policy_data_t qos;
                        boolean_t gd = FALSE;

                        kr = pthread_kern->thread_policy_get(current_thread(),
                                        THREAD_QOS_POLICY, (thread_policy_t)&qos, &nqos, &gd);
                        if (kr != KERN_SUCCESS || qos.qos_tier == THREAD_QOS_UNSPECIFIED) {
                                /*
                                 * Unspecified threads means the kernel wants us
                                 * to impose legacy upon the thread.
                                 */
                                qos.qos_tier = THREAD_QOS_LEGACY;
                                qos.tier_importance = 0;

                                kr = pthread_kern->thread_policy_set_internal(current_thread(),
                                                THREAD_QOS_POLICY, (thread_policy_t)&qos,
                                                THREAD_QOS_POLICY_COUNT);
                        }

                        if (kr == KERN_SUCCESS) {
                                data.main_qos = _pthread_priority_make_from_thread_qos(
                                                qos.qos_tier, 0, 0);
                        }
                }

                data.stack_addr_hint = stackaddr;
                data.mutex_default_policy = pthread_mutex_default_policy;

                kr = copyout(&data, pthread_init_data, pthread_init_sz);
                if (kr != KERN_SUCCESS) {
                        return EINVAL;
                }
        }

        /* return the supported feature set as the return value. */
        *retval = PTHREAD_FEATURE_SUPPORTED;

        return(0);
}


#pragma mark - Workqueue Thread Support

static mach_vm_size_t
workq_thread_allocsize(proc_t p, vm_map_t wq_map,
                mach_vm_size_t *guardsize_out)
{
        mach_vm_size_t guardsize = vm_map_page_size(wq_map);
        mach_vm_size_t pthread_size = vm_map_round_page_mask(
                        pthread_kern->proc_get_pthsize(p) + PTHREAD_T_OFFSET,
                        vm_map_page_mask(wq_map));
        if (guardsize_out) *guardsize_out = guardsize;
        return guardsize + PTH_DEFAULT_STACKSIZE + pthread_size;
}

int
workq_create_threadstack(proc_t p, vm_map_t vmap, mach_vm_offset_t *out_addr)
{
        mach_vm_offset_t stackaddr = pthread_kern->proc_get_stack_addr_hint(p);
        mach_vm_size_t guardsize, th_allocsize;
        kern_return_t kret;

        th_allocsize = workq_thread_allocsize(p, vmap, &guardsize);
        kret = mach_vm_map(vmap, &stackaddr, th_allocsize, page_size - 1,
                        VM_MAKE_TAG(VM_MEMORY_STACK) | VM_FLAGS_ANYWHERE, NULL, 0, FALSE,
                        VM_PROT_DEFAULT, VM_PROT_ALL, VM_INHERIT_DEFAULT);

        if (kret != KERN_SUCCESS) {
                kret = mach_vm_allocate(vmap, &stackaddr, th_allocsize,
                                VM_MAKE_TAG(VM_MEMORY_STACK) | VM_FLAGS_ANYWHERE);
        }

        if (kret != KERN_SUCCESS) {
                goto fail;
        }

        /*
         * The guard page is at the lowest address
         * The stack base is the highest address
         */
        kret = mach_vm_protect(vmap, stackaddr, guardsize, FALSE, VM_PROT_NONE);
        if (kret != KERN_SUCCESS) {
                goto fail_vm_deallocate;
        }

        if (out_addr) {
                *out_addr = stackaddr;
        }
        return 0;

fail_vm_deallocate:
        (void)mach_vm_deallocate(vmap, stackaddr, th_allocsize);
fail:
        return kret;
}

int
workq_destroy_threadstack(proc_t p, vm_map_t vmap, mach_vm_offset_t stackaddr)
{
        return mach_vm_deallocate(vmap, stackaddr,
                        workq_thread_allocsize(p, vmap, NULL));
}

void
workq_markfree_threadstack(proc_t OS_UNUSED p, thread_t OS_UNUSED th,
                vm_map_t vmap, user_addr_t stackaddr)
{
        // Keep this in sync with workq_setup_thread()
        const vm_size_t       guardsize = vm_map_page_size(vmap);
        const user_addr_t     freeaddr = (user_addr_t)stackaddr + guardsize;
        const vm_map_offset_t freesize = vm_map_trunc_page_mask(
                        (PTH_DEFAULT_STACKSIZE + guardsize + PTHREAD_T_OFFSET) - 1,
                        vm_map_page_mask(vmap)) - guardsize;

        __assert_only kern_return_t kr = mach_vm_behavior_set(vmap, freeaddr,
                        freesize, VM_BEHAVIOR_REUSABLE);
#if MACH_ASSERT
        if (kr != KERN_SUCCESS && kr != KERN_INVALID_ADDRESS) {
                os_log_error(OS_LOG_DEFAULT, "unable to make thread stack reusable (kr: %d)", kr);
        }
#endif
}

struct workq_thread_addrs {
        user_addr_t self;
        user_addr_t stack_bottom;
        user_addr_t stack_top;
};

static inline void
workq_thread_set_top_addr(struct workq_thread_addrs *th_addrs, user_addr_t addr)
{
        th_addrs->stack_top = (addr & -C_WORKQ_STK_ALIGN);
}

static void
workq_thread_get_addrs(vm_map_t map, user_addr_t stackaddr,
                                           struct workq_thread_addrs *th_addrs)
{
        const vm_size_t guardsize = vm_map_page_size(map);

        th_addrs->self = (user_addr_t)(stackaddr + PTH_DEFAULT_STACKSIZE +
                        guardsize + PTHREAD_T_OFFSET);
        workq_thread_set_top_addr(th_addrs, th_addrs->self);
        th_addrs->stack_bottom = (user_addr_t)(stackaddr + guardsize);
}

static inline void
workq_set_register_state(proc_t p, thread_t th,
                struct workq_thread_addrs *addrs, mach_port_name_t kport,
                user_addr_t kevent_list, uint32_t upcall_flags, int kevent_count)
{
        user_addr_t wqstart_fnptr = pthread_kern->proc_get_wqthread(p);
        if (!wqstart_fnptr) {
                panic("workqueue thread start function pointer is NULL");
        }

#if defined(__i386__) || defined(__x86_64__)
        if (proc_is64bit_data(p) == 0) {
                x86_thread_state32_t state = {
                        .eip = (unsigned int)wqstart_fnptr,
                        .eax = /* arg0 */ (unsigned int)addrs->self,
                        .ebx = /* arg1 */ (unsigned int)kport,
                        .ecx = /* arg2 */ (unsigned int)addrs->stack_bottom,
                        .edx = /* arg3 */ (unsigned int)kevent_list,
                        .edi = /* arg4 */ (unsigned int)upcall_flags,
                        .esi = /* arg5 */ (unsigned int)kevent_count,

                        .esp = (int)((vm_offset_t)addrs->stack_top),
                };

                int error = pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
                if (error != KERN_SUCCESS) {
                        panic(__func__ ": thread_set_wq_state failed: %d", error);
                }
        } else {
                x86_thread_state64_t state64 = {
                        // x86-64 already passes all the arguments in registers, so we just put them in their final place here
                        .rip = (uint64_t)wqstart_fnptr,
                        .rdi = (uint64_t)addrs->self,
                        .rsi = (uint64_t)kport,
                        .rdx = (uint64_t)addrs->stack_bottom,
                        .rcx = (uint64_t)kevent_list,
                        .r8  = (uint64_t)upcall_flags,
                        .r9  = (uint64_t)kevent_count,

                        .rsp = (uint64_t)(addrs->stack_top)
                };

                int error = pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state64);
                if (error != KERN_SUCCESS) {
                        panic(__func__ ": thread_set_wq_state failed: %d", error);
                }
        }
#elif defined(__arm__) || defined(__arm64__)
        if (!proc_is64bit_data(p)) {
                arm_thread_state_t state = {
                        .pc = (int)wqstart_fnptr,
                        .r[0] = (unsigned int)addrs->self,
                        .r[1] = (unsigned int)kport,
                        .r[2] = (unsigned int)addrs->stack_bottom,
                        .r[3] = (unsigned int)kevent_list,
                        // will be pushed onto the stack as arg4/5
                        .r[4] = (unsigned int)upcall_flags,
                        .r[5] = (unsigned int)kevent_count,

                        .sp = (int)(addrs->stack_top)
                };

                int error = pthread_kern->thread_set_wq_state32(th, (thread_state_t)&state);
                if (error != KERN_SUCCESS) {
                        panic(__func__ ": thread_set_wq_state failed: %d", error);
                }
        } else {
#if defined(__arm64__)
                arm_thread_state64_t state = {
                        .pc = (uint64_t)wqstart_fnptr,
                        .x[0] = (uint64_t)addrs->self,
                        .x[1] = (uint64_t)kport,
                        .x[2] = (uint64_t)addrs->stack_bottom,
                        .x[3] = (uint64_t)kevent_list,
                        .x[4] = (uint64_t)upcall_flags,
                        .x[5] = (uint64_t)kevent_count,

                        .sp = (uint64_t)((vm_offset_t)addrs->stack_top),
                };

                int error = pthread_kern->thread_set_wq_state64(th, (thread_state_t)&state);
                if (error != KERN_SUCCESS) {
                        panic(__func__ ": thread_set_wq_state failed: %d", error);
                }
#else /* defined(__arm64__) */
                panic("Shouldn't have a 64-bit thread on a 32-bit kernel...");
#endif /* defined(__arm64__) */
        }
#else
#error setup_wqthread  not defined for this architecture
#endif
}

static inline int
workq_kevent(proc_t p, struct workq_thread_addrs *th_addrs,
                user_addr_t eventlist, int nevents, int kevent_flags,
                user_addr_t *kevent_list_out, int *kevent_count_out)
{
        int ret;

        user_addr_t kevent_list = th_addrs->self -
                        WQ_KEVENT_LIST_LEN * sizeof(struct kevent_qos_s);
        user_addr_t data_buf = kevent_list - WQ_KEVENT_DATA_SIZE;
        user_size_t data_available = WQ_KEVENT_DATA_SIZE;

        ret = pthread_kern->kevent_workq_internal(p, eventlist, nevents,
                        kevent_list, WQ_KEVENT_LIST_LEN,
                        data_buf, &data_available,
                        kevent_flags, kevent_count_out);

        // squash any errors into just empty output
        if (ret != 0 || *kevent_count_out == -1) {
                *kevent_list_out = NULL;
                *kevent_count_out = 0;
                return ret;
        }

        workq_thread_set_top_addr(th_addrs, data_buf + data_available);
        *kevent_list_out = kevent_list;
        return ret;
}

/**
 * configures initial thread stack/registers to jump into:
 * _pthread_wqthread(pthread_t self, mach_port_t kport, void *stackaddr, void *keventlist, int upcall_flags, int nkevents);
 * to get there we jump through assembily stubs in pthread_asm.s.  Those
 * routines setup a stack frame, using the current stack pointer, and marshall
 * arguments from registers to the stack as required by the ABI.
 *
 * One odd thing we do here is to start the pthread_t 4k below what would be the
 * top of the stack otherwise.  This is because usually only the first 4k of the
 * pthread_t will be used and so we want to put it on the same 16k page as the
 * top of the stack to save memory.
 *
 * When we are done the stack will look like:
 * |-----------| th_stackaddr + th_allocsize
 * |pthread_t  | th_stackaddr + DEFAULT_STACKSIZE + guardsize + PTHREAD_STACK_OFFSET
 * |kevent list| optionally - at most WQ_KEVENT_LIST_LEN events
 * |kevent data| optionally - at most WQ_KEVENT_DATA_SIZE bytes
 * |stack gap  | bottom aligned to 16 bytes
 * |   STACK   |
 * |     ⇓     |
 * |           |
 * |guard page | guardsize
 * |-----------| th_stackaddr
 */
__attribute__((noreturn,noinline))
void
workq_setup_thread(proc_t p, thread_t th, vm_map_t map, user_addr_t stackaddr,
                mach_port_name_t kport, int th_qos __unused, int setup_flags, int upcall_flags)
{
        struct workq_thread_addrs th_addrs;
        bool first_use = (setup_flags & WQ_SETUP_FIRST_USE);
        user_addr_t kevent_list = NULL;
        int kevent_count = 0;

        workq_thread_get_addrs(map, stackaddr, &th_addrs);

        if (first_use) {
                uint32_t tsd_offset = pthread_kern->proc_get_pthread_tsd_offset(p);
                if (tsd_offset) {
                        mach_vm_offset_t th_tsd_base = th_addrs.self + tsd_offset;
                        kern_return_t kret = pthread_kern->thread_set_tsd_base(th,
                                        th_tsd_base);
                        if (kret == KERN_SUCCESS) {
                                upcall_flags |= WQ_FLAG_THREAD_TSD_BASE_SET;
                        }
                }

                /*
                 * Pre-fault the first page of the new thread's stack and the page that will
                 * contain the pthread_t structure.
                 */
                vm_map_offset_t mask = vm_map_page_mask(map);
                vm_map_offset_t th_page = vm_map_trunc_page_mask(th_addrs.self, mask);
                vm_map_offset_t stk_page = vm_map_trunc_page_mask(th_addrs.stack_top - 1, mask);
                if (th_page != stk_page) {
                        vm_fault(map, stk_page, VM_PROT_READ | VM_PROT_WRITE, FALSE, THREAD_UNINT, NULL, 0);
                }
                vm_fault(map, th_page, VM_PROT_READ | VM_PROT_WRITE, FALSE, THREAD_UNINT, NULL, 0);
        }

        if (setup_flags & WQ_SETUP_EXIT_THREAD) {
                kevent_count = WORKQ_EXIT_THREAD_NKEVENT;
        } else if (upcall_flags & WQ_FLAG_THREAD_KEVENT) {
                unsigned int flags = KEVENT_FLAG_STACK_DATA | KEVENT_FLAG_IMMEDIATE;
                workq_kevent(p, &th_addrs, NULL, 0, flags, &kevent_list, &kevent_count);
        }

        workq_set_register_state(p, th, &th_addrs, kport,
                        kevent_list, upcall_flags, kevent_count);

        if (first_use) {
                pthread_kern->thread_bootstrap_return();
        } else {
                pthread_kern->unix_syscall_return(EJUSTRETURN);
        }
        __builtin_unreachable();
}

int
workq_handle_stack_events(proc_t p, thread_t th, vm_map_t map,
                user_addr_t stackaddr, mach_port_name_t kport,
                user_addr_t events, int nevents, int upcall_flags)
{
        struct workq_thread_addrs th_addrs;
        user_addr_t kevent_list = NULL;
        int kevent_count = 0, error;
        __assert_only kern_return_t kr;

        workq_thread_get_addrs(map, stackaddr, &th_addrs);

        unsigned int flags = KEVENT_FLAG_STACK_DATA | KEVENT_FLAG_IMMEDIATE |
                        KEVENT_FLAG_PARKING;
        error = workq_kevent(p, &th_addrs, events, nevents, flags,
                        &kevent_list, &kevent_count);

        if (error || kevent_count == 0) {
                return error;
        }

        kr = pthread_kern->thread_set_voucher_name(MACH_PORT_NULL);
        assert(kr == KERN_SUCCESS);

        workq_set_register_state(p, th, &th_addrs, kport,
                        kevent_list, upcall_flags, kevent_count);

        pthread_kern->unix_syscall_return(EJUSTRETURN);
        __builtin_unreachable();
}

int
_thread_selfid(__unused struct proc *p, uint64_t *retval)
{
        thread_t thread = current_thread();
        *retval = thread_tid(thread);
        return KERN_SUCCESS;
}

void
_pthread_init(void)
{
        pthread_lck_grp_attr = lck_grp_attr_alloc_init();
        pthread_lck_grp = lck_grp_alloc_init("pthread", pthread_lck_grp_attr);

        /*
         * allocate the lock attribute for pthread synchronizers
         */
        pthread_lck_attr = lck_attr_alloc_init();
        pthread_list_mlock = lck_mtx_alloc_init(pthread_lck_grp, pthread_lck_attr);

        pth_global_hashinit();
        psynch_thcall = thread_call_allocate(psynch_wq_cleanup, NULL);
        psynch_zoneinit();

        int policy_bootarg;
        if (PE_parse_boot_argn("pthread_mutex_default_policy", &policy_bootarg, sizeof(policy_bootarg))) {
                pthread_mutex_default_policy = policy_bootarg;
        }

        sysctl_register_oid(&sysctl__kern_pthread_mutex_default_policy);
}