[apple/xnu.git] / osfmk / kern / stack.c

/*
 * Copyright (c) 2003-2007 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@
 */
/*
 *      Kernel stack management routines.
 */

#include <mach/mach_host.h>
#include <mach/mach_types.h>
#include <mach/processor_set.h>

#include <kern/kern_types.h>
#include <kern/mach_param.h>
#include <kern/processor.h>
#include <kern/thread.h>
#include <kern/zalloc.h>
#include <kern/kalloc.h>
#include <kern/ledger.h>

#include <vm/vm_map.h>
#include <vm/vm_kern.h>

#include <mach_debug.h>

/*
 *      We allocate stacks from generic kernel VM.
 *
 *      The stack_free_list can only be accessed at splsched,
 *      because stack_alloc_try/thread_invoke operate at splsched.
 */

decl_simple_lock_data(static,stack_lock_data)
#define stack_lock()            simple_lock(&stack_lock_data)
#define stack_unlock()          simple_unlock(&stack_lock_data)

#define STACK_CACHE_SIZE        2

static vm_offset_t              stack_free_list;

static unsigned int             stack_free_count, stack_free_hiwat;             /* free list count */
static unsigned int             stack_hiwat;
unsigned int                    stack_total;                            /* current total count */
unsigned long long              stack_allocs;                           /* total count of allocations */

static int                      stack_fake_zone_index = -1;     /* index in zone_info array */

static unsigned int             stack_free_target;
static int                              stack_free_delta;

static unsigned int             stack_new_count;                                                /* total new stack allocations */

static vm_offset_t              stack_addr_mask;

unsigned int                    kernel_stack_pages;
vm_offset_t                     kernel_stack_size;
vm_offset_t                     kernel_stack_mask;
vm_offset_t                     kernel_stack_depth_max;

static inline void
STACK_ZINFO_PALLOC(thread_t thread)
{
        ledger_credit(thread->t_ledger, task_ledgers.tkm_private, kernel_stack_size);
}

static inline void
STACK_ZINFO_PFREE(thread_t thread)
{
        ledger_debit(thread->t_ledger, task_ledgers.tkm_private, kernel_stack_size);
}

static inline void
STACK_ZINFO_HANDOFF(thread_t from, thread_t to)
{
        ledger_debit(from->t_ledger, task_ledgers.tkm_private, kernel_stack_size);
        ledger_credit(to->t_ledger, task_ledgers.tkm_private, kernel_stack_size);
}

/*
 *      The next field is at the base of the stack,
 *      so the low end is left unsullied.
 */
#define stack_next(stack)       \
        (*((vm_offset_t *)((stack) + kernel_stack_size) - 1))

static inline int
log2(vm_offset_t size)
{
        int     result;
        for (result = 0; size > 0; result++)
                size >>= 1;
        return result;
}

static inline vm_offset_t
roundup_pow2(vm_offset_t size)
{
        return 1UL << (log2(size - 1) + 1); 
}

static vm_offset_t stack_alloc_internal(void);
static void stack_free_stack(vm_offset_t);

void
stack_init(void)
{
        simple_lock_init(&stack_lock_data, 0);
        
        kernel_stack_pages = KERNEL_STACK_SIZE / PAGE_SIZE;
        kernel_stack_size = KERNEL_STACK_SIZE;
        kernel_stack_mask = -KERNEL_STACK_SIZE;
        kernel_stack_depth_max = 0;

        if (PE_parse_boot_argn("kernel_stack_pages",
                               &kernel_stack_pages,
                               sizeof (kernel_stack_pages))) {
                kernel_stack_size = kernel_stack_pages * PAGE_SIZE;
                printf("stack_init: kernel_stack_pages=%d kernel_stack_size=%p\n",
                        kernel_stack_pages, (void *) kernel_stack_size);
        }

        if (kernel_stack_size < round_page(kernel_stack_size))
                panic("stack_init: stack size %p not a multiple of page size %d\n",
                        (void *) kernel_stack_size, PAGE_SIZE);
        
        stack_addr_mask = roundup_pow2(kernel_stack_size) - 1;
        kernel_stack_mask = ~stack_addr_mask;
}

/*
 *      stack_alloc:
 *
 *      Allocate a stack for a thread, may
 *      block.
 */

static vm_offset_t 
stack_alloc_internal(void)
{
        vm_offset_t             stack;
        spl_t                   s;
        int                     guard_flags;

        s = splsched();
        stack_lock();
        stack_allocs++;
        stack = stack_free_list;
        if (stack != 0) {
                stack_free_list = stack_next(stack);
                stack_free_count--;
        }
        else {
                if (++stack_total > stack_hiwat)
                        stack_hiwat = stack_total;
                stack_new_count++;
        }
        stack_free_delta--;
        stack_unlock();
        splx(s);
                
        if (stack == 0) {

                /*
                 * Request guard pages on either side of the stack.  Ask
                 * kernel_memory_allocate() for two extra pages to account
                 * for these.
                 */

                guard_flags = KMA_GUARD_FIRST | KMA_GUARD_LAST;
                if (kernel_memory_allocate(kernel_map, &stack,
                                           kernel_stack_size + (2*PAGE_SIZE),
                                           stack_addr_mask,
                                           KMA_KSTACK | KMA_KOBJECT | guard_flags,
                                           VM_KERN_MEMORY_STACK)
                    != KERN_SUCCESS)
                        panic("stack_alloc: kernel_memory_allocate");

                /*
                 * The stack address that comes back is the address of the lower
                 * guard page.  Skip past it to get the actual stack base address.
                 */

                stack += PAGE_SIZE;
        }
        return stack;
}

void
stack_alloc(
        thread_t        thread)
{

        assert(thread->kernel_stack == 0);
        machine_stack_attach(thread, stack_alloc_internal());
        STACK_ZINFO_PALLOC(thread);
}

void
stack_handoff(thread_t from, thread_t to)
{
        assert(from == current_thread());
        machine_stack_handoff(from, to);
        STACK_ZINFO_HANDOFF(from, to);
}

/*
 *      stack_free:
 *
 *      Detach and free the stack for a thread.
 */
void
stack_free(
        thread_t        thread)
{
    vm_offset_t         stack = machine_stack_detach(thread);

        assert(stack);
        if (stack != thread->reserved_stack) {
                STACK_ZINFO_PFREE(thread);
                stack_free_stack(stack);
        }
}

void
stack_free_reserved(
        thread_t        thread)
{
        if (thread->reserved_stack != thread->kernel_stack) {
                stack_free_stack(thread->reserved_stack);
                STACK_ZINFO_PFREE(thread);
        }
}

static void
stack_free_stack(
        vm_offset_t             stack)
{
        struct stack_cache      *cache;
        spl_t                           s;

        s = splsched();
        cache = &PROCESSOR_DATA(current_processor(), stack_cache);
        if (cache->count < STACK_CACHE_SIZE) {
                stack_next(stack) = cache->free;
                cache->free = stack;
                cache->count++;
        }
        else {
                stack_lock();
                stack_next(stack) = stack_free_list;
                stack_free_list = stack;
                if (++stack_free_count > stack_free_hiwat)
                        stack_free_hiwat = stack_free_count;
                stack_free_delta++;
                stack_unlock();
        }
        splx(s);
}

/*
 *      stack_alloc_try:
 *
 *      Non-blocking attempt to allocate a
 *      stack for a thread.
 *
 *      Returns TRUE on success.
 *
 *      Called at splsched.
 */
boolean_t
stack_alloc_try(
        thread_t                thread)
{
        struct stack_cache      *cache;
        vm_offset_t                     stack;

        cache = &PROCESSOR_DATA(current_processor(), stack_cache);
        stack = cache->free;
        if (stack != 0) {
                STACK_ZINFO_PALLOC(thread);
                cache->free = stack_next(stack);
                cache->count--;
        }
        else {
                if (stack_free_list != 0) {
                        stack_lock();
                        stack = stack_free_list;
                        if (stack != 0) {
                                STACK_ZINFO_PALLOC(thread);
                                stack_free_list = stack_next(stack);
                                stack_free_count--;
                                stack_free_delta--;
                        }
                        stack_unlock();
                }
        }

        if (stack != 0 || (stack = thread->reserved_stack) != 0) {
                machine_stack_attach(thread, stack);
                return (TRUE);
        }

        return (FALSE);
}

static unsigned int             stack_collect_tick, last_stack_tick;

/*
 *      stack_collect:
 *
 *      Free excess kernel stacks, may
 *      block.
 */
void
stack_collect(void)
{
        if (stack_collect_tick != last_stack_tick) {
                unsigned int    target;
                vm_offset_t             stack;
                spl_t                   s;

                s = splsched();
                stack_lock();

                target = stack_free_target + (STACK_CACHE_SIZE * processor_count);
                target += (stack_free_delta >= 0)? stack_free_delta: -stack_free_delta;

                while (stack_free_count > target) {
                        stack = stack_free_list;
                        stack_free_list = stack_next(stack);
                        stack_free_count--; stack_total--;
                        stack_unlock();
                        splx(s);

                        /*
                         * Get the stack base address, then decrement by one page
                         * to account for the lower guard page.  Add two extra pages
                         * to the size to account for the guard pages on both ends
                         * that were originally requested when the stack was allocated
                         * back in stack_alloc().
                         */

                        stack = (vm_offset_t)vm_map_trunc_page(
                                stack,
                                VM_MAP_PAGE_MASK(kernel_map));
                        stack -= PAGE_SIZE;
                        if (vm_map_remove(
                                    kernel_map,
                                    stack,
                                    stack + kernel_stack_size+(2*PAGE_SIZE),
                                    VM_MAP_REMOVE_KUNWIRE)
                            != KERN_SUCCESS)
                                panic("stack_collect: vm_map_remove");
                        stack = 0;

                        s = splsched();
                        stack_lock();

                        target = stack_free_target + (STACK_CACHE_SIZE * processor_count);
                        target += (stack_free_delta >= 0)? stack_free_delta: -stack_free_delta;
                }

                last_stack_tick = stack_collect_tick;

                stack_unlock();
                splx(s);
        }
}

/*
 *      compute_stack_target:
 *
 *      Computes a new target free list count
 *      based on recent alloc / free activity.
 *
 *      Limits stack collection to once per
 *      computation period.
 */
void
compute_stack_target(
__unused void           *arg)
{
        spl_t           s;

        s = splsched();
        stack_lock();

        if (stack_free_target > 5)
                stack_free_target = (4 * stack_free_target) / 5;
        else
        if (stack_free_target > 0)
                stack_free_target--;

        stack_free_target += (stack_free_delta >= 0)? stack_free_delta: -stack_free_delta;

        stack_free_delta = 0;
        stack_collect_tick++;

        stack_unlock();
        splx(s);
}

void
stack_fake_zone_init(int zone_index)
{
        stack_fake_zone_index = zone_index;
}

void
stack_fake_zone_info(int *count, 
                     vm_size_t *cur_size, vm_size_t *max_size, vm_size_t *elem_size, vm_size_t *alloc_size,
                     uint64_t *sum_size, int *collectable, int *exhaustable, int *caller_acct)
{
        unsigned int    total, hiwat, free;
        unsigned long long all;
        spl_t                   s;

        s = splsched();
        stack_lock();
        all = stack_allocs;
        total = stack_total;
        hiwat = stack_hiwat;
        free = stack_free_count;
        stack_unlock();
        splx(s);

        *count      = total - free;
        *cur_size   = kernel_stack_size * total;
        *max_size   = kernel_stack_size * hiwat;
        *elem_size  = kernel_stack_size;
        *alloc_size = kernel_stack_size;
        *sum_size = all * kernel_stack_size;

        *collectable = 1;
        *exhaustable = 0;
        *caller_acct = 1;
}

/* OBSOLETE */
void    stack_privilege(
                        thread_t        thread);

void
stack_privilege(
        __unused thread_t       thread)
{
        /* OBSOLETE */
}

/*
 * Return info on stack usage for threads in a specific processor set
 */
kern_return_t
processor_set_stack_usage(
        processor_set_t pset,
        unsigned int    *totalp,
        vm_size_t       *spacep,
        vm_size_t       *residentp,
        vm_size_t       *maxusagep,
        vm_offset_t     *maxstackp)
{
#if !MACH_DEBUG
        return KERN_NOT_SUPPORTED;
#else
        unsigned int total;
        vm_size_t maxusage;
        vm_offset_t maxstack;

        thread_t *thread_list;
        thread_t thread;

        unsigned int actual;    /* this many things */
        unsigned int i;

        vm_size_t size, size_needed;
        void *addr;

        if (pset == PROCESSOR_SET_NULL || pset != &pset0)
                return KERN_INVALID_ARGUMENT;

        size = 0;
        addr = NULL;

        for (;;) {
                lck_mtx_lock(&tasks_threads_lock);

                actual = threads_count;

                /* do we have the memory we need? */

                size_needed = actual * sizeof(thread_t);
                if (size_needed <= size)
                        break;

                lck_mtx_unlock(&tasks_threads_lock);

                if (size != 0)
                        kfree(addr, size);

                assert(size_needed > 0);
                size = size_needed;

                addr = kalloc(size);
                if (addr == 0)
                        return KERN_RESOURCE_SHORTAGE;
        }

        /* OK, have memory and list is locked */
        thread_list = (thread_t *) addr;
        for (i = 0, thread = (thread_t)(void *) queue_first(&threads);
                                        !queue_end(&threads, (queue_entry_t) thread);
                                        thread = (thread_t)(void *) queue_next(&thread->threads)) {
                thread_reference_internal(thread);
                thread_list[i++] = thread;
        }
        assert(i <= actual);

        lck_mtx_unlock(&tasks_threads_lock);

        /* calculate maxusage and free thread references */

        total = 0;
        maxusage = 0;
        maxstack = 0;
        while (i > 0) {
                thread_t threadref = thread_list[--i];

                if (threadref->kernel_stack != 0)
                        total++;

                thread_deallocate(threadref);
        }

        if (size != 0)
                kfree(addr, size);

        *totalp = total;
        *residentp = *spacep = total * round_page(kernel_stack_size);
        *maxusagep = maxusage;
        *maxstackp = maxstack;
        return KERN_SUCCESS;

#endif  /* MACH_DEBUG */
}

vm_offset_t min_valid_stack_address(void)
{
        return (vm_offset_t)vm_map_min(kernel_map);
}

vm_offset_t max_valid_stack_address(void)
{
        return (vm_offset_t)vm_map_max(kernel_map);
}