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134 lines
4.9 KiB
134 lines
4.9 KiB
//
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// FLEXHeapEnumerator.m
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// Flipboard
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//
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// Created by Ryan Olson on 5/28/14.
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// Copyright (c) 2014 Flipboard. All rights reserved.
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//
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#import "FLEXHeapEnumerator.h"
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#import <malloc/malloc.h>
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#import <mach/mach.h>
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#import <objc/runtime.h>
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static CFMutableSetRef registeredClasses;
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// Mimics the objective-c object structure for checking if a range of memory is an object.
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typedef struct {
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Class isa;
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} flex_maybe_object_t;
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@implementation FLEXHeapEnumerator
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static void range_callback(task_t task, void *context, unsigned type, vm_range_t *ranges, unsigned rangeCount)
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{
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if (!context) {
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return;
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}
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for (unsigned int i = 0; i < rangeCount; i++) {
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vm_range_t range = ranges[i];
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flex_maybe_object_t *tryObject = (flex_maybe_object_t *)range.address;
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Class tryClass = NULL;
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#ifdef __arm64__
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// See http://www.sealiesoftware.com/blog/archive/2013/09/24/objc_explain_Non-pointer_isa.html
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extern uint64_t objc_debug_isa_class_mask WEAK_IMPORT_ATTRIBUTE;
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tryClass = (__bridge Class)((void *)((uint64_t)tryObject->isa & objc_debug_isa_class_mask));
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#else
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tryClass = tryObject->isa;
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#endif
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// If the class pointer matches one in our set of class pointers from the runtime, then we should have an object.
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if (CFSetContainsValue(registeredClasses, (__bridge const void *)(tryClass))) {
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(*(flex_object_enumeration_block_t __unsafe_unretained *)context)((__bridge id)tryObject, tryClass);
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}
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}
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}
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static kern_return_t reader(__unused task_t remote_task, vm_address_t remote_address, __unused vm_size_t size, void **local_memory)
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{
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*local_memory = (void *)remote_address;
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return KERN_SUCCESS;
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}
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+ (void)enumerateLiveObjectsUsingBlock:(flex_object_enumeration_block_t)block
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{
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if (!block) {
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return;
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}
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// Refresh the class list on every call in case classes are added to the runtime.
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[self updateRegisteredClasses];
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// Inspired by:
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// https://llvm.org/svn/llvm-project/lldb/tags/RELEASE_34/final/examples/darwin/heap_find/heap/heap_find.cpp
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// https://gist.github.com/samdmarshall/17f4e66b5e2e579fd396
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vm_address_t *zones = NULL;
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unsigned int zoneCount = 0;
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kern_return_t result = malloc_get_all_zones(TASK_NULL, reader, &zones, &zoneCount);
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if (result == KERN_SUCCESS) {
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for (unsigned int i = 0; i < zoneCount; i++) {
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malloc_zone_t *zone = (malloc_zone_t *)zones[i];
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malloc_introspection_t *introspection = zone->introspect;
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// This may explain why some zone functions are
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// sometimes invalid; perhaps not all zones support them?
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if (!introspection) {
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continue;
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}
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void (*lock_zone)(malloc_zone_t *zone) = introspection->force_lock;
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void (*unlock_zone)(malloc_zone_t *zone) = introspection->force_unlock;
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// Callback has to unlock the zone so we freely allocate memory inside the given block
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flex_object_enumeration_block_t callback = ^(__unsafe_unretained id object, __unsafe_unretained Class actualClass) {
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unlock_zone(zone);
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block(object, actualClass);
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lock_zone(zone);
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};
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// The largest realistic memory address varies by platform.
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// Only 48 bits are used by 64 bit machines while
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// 32 bit machines use all bits.
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//
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// __LP64__ is defined as 1 for both arm64 and x86_64
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// via: clang -dM -arch [arm64|x86_64] -E -x c /dev/null | grep LP
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#if __LP64__
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static uintptr_t MAX_REALISTIC_ADDRESS = 0x0000FFFFFFFFFFFF;
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BOOL lockZoneValid = lock_zone != nil && (uintptr_t)lock_zone < MAX_REALISTIC_ADDRESS;
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BOOL unlockZoneValid = unlock_zone != nil && (uintptr_t)unlock_zone < MAX_REALISTIC_ADDRESS;
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#else
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BOOL lockZoneValid = lock_zone != nil;
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BOOL unlockZoneValid = unlock_zone != nil;
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#endif
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// There is little documentation on when and why
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// any of these function pointers might be NULL
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// or garbage, so we resort to checking for NULL
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// and impossible memory addresses at least
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if (introspection->enumerator && lockZoneValid && unlockZoneValid) {
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lock_zone(zone);
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introspection->enumerator(TASK_NULL, (void *)&callback, MALLOC_PTR_IN_USE_RANGE_TYPE, (vm_address_t)zone, reader, &range_callback);
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unlock_zone(zone);
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}
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}
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}
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}
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+ (void)updateRegisteredClasses
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{
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if (!registeredClasses) {
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registeredClasses = CFSetCreateMutable(NULL, 0, NULL);
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} else {
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CFSetRemoveAllValues(registeredClasses);
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}
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unsigned int count = 0;
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Class *classes = objc_copyClassList(&count);
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for (unsigned int i = 0; i < count; i++) {
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CFSetAddValue(registeredClasses, (__bridge const void *)(classes[i]));
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}
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free(classes);
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}
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@end
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