之前看到字节团队分享的 “iOS性能优化实践：头条抖音如何实现OOM崩溃率下降50%+”这篇文章，对其实现比较感兴趣，但是没有开源，所以觉得自己花时间探索一下具体实现。
什么是OOM，为什么会发生OOM以及其原因分析，大家去看原文就好了，本文主要分析APP内存使用到达阈值后，如何采集Memory Graph信息并分析。
什么是Memory Graph？
这个时候就进入了断点模式，可以查看issue面板，注意选择右边Runtime：
有很多叹号说明就有问题了。看内存中object的名字，有一条是Closure captures leaked。展开后点击就可以看到这个issue对应的内存图形展示在中间的面板中。
作为一个开发者，有一个学习的氛围跟一个交流圈子特别重要，这是一个我的iOS交流群：413038000，不管你是小白还是大牛欢迎入驻 ，分享BAT,阿里面试题、面试经验，讨论技术， 大家一起交流学习成长！
点击紫色的叹号会出现Xcode分析出来的内存引用图形：
如果我们在线上App中也能采集到Memory Graph的相关信息，那么就可以在监控平台还原用户当时内存信息，帮助开发人员分析和解决问题。
如何内存快照采集
- 虚拟内存节点信息采集
OC/Swift/C++所有实例及其类名- 内存节点之间的引用关系，实例中成员变量类型和它引用其他内存的关系
内存节点的获取
通过 mach 内核的vm_region_recurse/vm_region_recurse64函数我们可以遍历进程内所有VM Region，并通过vm_region_submap_info_64结构体获取以下信息：
-
虚拟地址空间中的地址和大小。
-
Dirty 和 Swapped 内存页数，表示该
VM Region的真实物理内存使用。 -
是否可交换，Text 段、共享 mmap 等只读或随时可以被交换出去的内存，无需关注。
-
user_tag，用户标签，用于提供该
VM Region的用途的更准确信息。
获取所有内存节点信息
kern_return_t krc = KERN_SUCCESS;
vm_address_t address = 0;
vm_size_t size = 0;
uint32_t depth = 1;
pid_t pid = getpid();
char buf[PATH_MAX];
while (1) {
struct vm_region_submap_info_64 info;
mach_msg_type_number_t count = VM_REGION_SUBMAP_INFO_COUNT_64;
krc = vm_region_recurse_64(mach_task_self(), &address, &size, &depth, (vm_region_info_64_t)&info, &count);
if (krc == KERN_INVALID_ADDRESS){
break;
}
if (info.is_submap){
depth++;
} else {
//do stuff
proc_regionfilename(pid, address, buf, sizeof(buf));
printf("Found VM Region: %08x to %08x (depth=%d) user_tag:%s name:%s
", (uint32_t)address, (uint32_t)(address+size), depth, [visualMemoryTypeString(info.user_tag) cStringUsingEncoding:NSUTF8StringEncoding], buf);
address += size;
}
}
复制代码
输出如下：
Found VM Region: 04c68000 to 04c80000 (depth=0) user_tag:(null) name:/private/var/containers/Bundle/Application/70EFA90E-D8EE-4FE9-9D5E-C708F6DB2FE6/OnlineMemoryGraphDemo.app/OnlineMemoryGraphDemo
Found VM Region: 04c80000 to 04c88000 (depth=0) user_tag:(null) name:/private/var/containers/Bundle/Application/70EFA90E-D8EE-4FE9-9D5E-C708F6DB2FE6/OnlineMemoryGraphDemo.app/OnlineMemoryGraphDemo
Found VM Region: 04c88000 to 04ca8000 (depth=0) user_tag:(null) name:/private/var/containers/Bundle/Application/70EFA90E-D8EE-4FE9-9D5E-C708F6DB2FE6/OnlineMemoryGraphDemo.app/OnlineMemoryGraphDemo
Found VM Region: 04ca8000 to 04cac000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04cac000 to 04cb8000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04cbc000 to 04d18000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04d18000 to 04d20000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04d24000 to 04d58000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04d58000 to 04d94000 (depth=0) user_tag:(null) name:/usr/lib/dyld
Found VM Region: 04d98000 to 04da4000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libBacktraceRecording.dylib
Found VM Region: 04da4000 to 04da8000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libBacktraceRecording.dylib
Found VM Region: 04da8000 to 04dac000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libBacktraceRecording.dylib
Found VM Region: 04dac000 to 04db0000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libBacktraceRecording.dylib
Found VM Region: 04db0000 to 04db4000 (depth=0) user_tag:DYLIB name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04db4000 to 04df8000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04df8000 to 04dfc000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04dfc000 to 04e00000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04e00000 to 04f00000 (depth=0) user_tag:DYLIB name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04f00000 to 04f04000 (depth=0) user_tag:(null) name:/Developer/usr/lib/libMainThreadChecker.dylib
Found VM Region: 04f04000 to 04f08000 (depth=0) user_tag:DYLIB name:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
Found VM Region: 04f08000 to 04f40000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
Found VM Region: 04f40000 to 04f48000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
Found VM Region: 04f48000 to 04f5c000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
Found VM Region: 04f5c000 to 04f70000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
Found VM Region: 04f70000 to 04f74000 (depth=0) user_tag:DYLIB name:/usr/lib/system/introspection/libdispatch.dylib
Found VM Region: 04f74000 to 04fbc000 (depth=0) user_tag:(null) name:/usr/lib/system/introspection/libdispatch.dylib
Found VM Region: 04fd4000 to 04fd8000 (depth=0) user_tag:(null) name:/usr/lib/system/introspection/libdispatch.dylib
Found VM Region: 04fd8000 to 04fdc000 (depth=0) user_tag:(null) name:/usr/lib/system/introspection/libdispatch.dylib
Found VM Region: 04fdc000 to 05008000 (depth=0) user_tag:(null) name:/usr/lib/system/introspection/libdispatch.dylib
Found VM Region: 05008000 to 0500c000 (depth=0) user_tag:DYLIB name:/Developer/Library/PrivateFrameworks/DebugHierarchyFoundation.framework/DebugHierarchyFoundation
Found VM Region: 0500c000 to 05030000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DebugHierarchyFoundation.framework/DebugHierarchyFoundation
Found VM Region: 05030000 to 05034000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DebugHierarchyFoundation.framework/DebugHierarchyFoundation
Found VM Region: 05034000 to 0503c000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DebugHierarchyFoundation.framework/DebugHierarchyFoundation
Found VM Region: 0503c000 to 05050000 (depth=0) user_tag:(null) name:/Developer/Library/PrivateFrameworks/DebugHierarchyFoundation.framework/DebugHierarchyFoundation
Found VM Region: 05050000 to 05054000 (depth=0) user_tag:DYLIB name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05054000 to 0505c000 (depth=0) user_tag:OS_ALLOC_ONCE name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 0505c000 to 05060000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05060000 to 05064000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05064000 to 05068000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05068000 to 05070000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05070000 to 05074000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05074000 to 05078000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05080000 to 05084000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05088000 to 0508c000 (depth=0) user_tag:MALLOC name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 05090000 to 050d0000 (depth=0) user_tag:ANALYSIS_TOOL name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 050d8000 to 050dc000 (depth=0) user_tag:MALLOC_LARGE name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 050e0000 to 050e8000 (depth=0) user_tag:MALLOC_LARGE name:/private/var/preferences/Logging/.plist-cache.8czmnDXb
Found VM Region: 050f4000 to 050f8000 (depth=0) user_tag:ANALYSIS_TOOL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 050f8000 to 05100000 (depth=0) user_tag:ANALYSIS_TOOL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05100000 to 05200000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05200000 to 05300000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05300000 to 05340000 (depth=0) user_tag:GENEALOGY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05340000 to 05348000 (depth=0) user_tag:ANALYSIS_TOOL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05348000 to 0534c000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 0534c000 to 05350000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05350000 to 05354000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05354000 to 0535c000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 0535c000 to 05360000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05360000 to 053e0000 (depth=0) user_tag:MALLOC_LARGE name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 053e0000 to 053e4000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 053ec000 to 053f0000 (depth=0) user_tag:MALLOC name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 053f0000 to 053f4000 (depth=0) user_tag:LAYERKIT name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 053f4000 to 053f8000 (depth=0) user_tag:(null) name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 053f8000 to 05400000 (depth=0) user_tag:MALLOC_LARGE name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05400000 to 05500000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05500000 to 05600000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05600000 to 05700000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05700000 to 05800000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 05800000 to 06000000 (depth=0) user_tag:MALLOC_SMALL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 06000000 to 06800000 (depth=0) user_tag:MALLOC_SMALL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 06800000 to 07000000 (depth=0) user_tag:MALLOC_SMALL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 07000000 to 07800000 (depth=0) user_tag:MALLOC_SMALL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 07800000 to 08000000 (depth=0) user_tag:MALLOC_SMALL name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08000000 to 08100000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08100000 to 08200000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08200000 to 08300000 (depth=0) user_tag:MALLOC_TINY name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08300000 to 0830c000 (depth=0) user_tag:(null) name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 0830c000 to 08310000 (depth=0) user_tag:(null) name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08310000 to 08314000 (depth=0) user_tag:DYLIB name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08314000 to 0831c000 (depth=0) user_tag:MALLOC_LARGE name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 0831c000 to 08320000 (depth=0) user_tag:FOUNDATION name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 08320000 to 0832c000 (depth=0) user_tag:(null) name:/usr/lib/libobjc-trampolines.dylib
Found VM Region: 0832c000 to 08334000 (depth=0) user_tag:(null) name:/usr/share/icu/icudt66l.dat
Found VM Region: 08334000 to 08340000 (depth=0) user_tag:MALLOC_LARGE name:/usr/share/icu/icudt66l.dat
Found VM Region: 08340000 to 08344000 (depth=0) user_tag:(null) name:/usr/share/icu/icudt66l.dat
Found VM Region: 08344000 to 0834c000 (depth=0) user_tag:MALLOC_LARGE name:/usr/share/icu/icudt66l.dat
Found VM Region: 0834c000 to 08350000 (depth=0) user_tag:LAYERKIT name:/usr/share/icu/icudt66l.dat
Found VM Region: 08350000 to 08360000 (depth=0) user_tag:MALLOC_LARGE name:/usr/share/icu/icudt66l.dat
Found VM Region: 08400000 to 08500000 (depth=0) user_tag:MALLOC_TINY name:/usr/share/icu/icudt66l.dat
Found VM Region: 08800000 to 09000000 (depth=0) user_tag:MALLOC_SMALL name:/usr/share/icu/icudt66l.dat
Found VM Region: 09000000 to 09800000 (depth=0) user_tag:MALLOC_SMALL name:/usr/share/icu/icudt66l.dat
Found VM Region: 09800000 to 0b750000 (depth=0) user_tag:(null) name:/usr/share/icu/icudt66l.dat
Found VM Region: 0b750000 to 0bf38000 (depth=0) user_tag:(null) name:/System/Library/Fonts/CoreUI/SFUI.ttf
Found VM Region: 0bf38000 to 108cc000 (depth=0) user_tag:(null) name:/System/Library/Fonts/LanguageSupport/PingFang.ttc
Found VM Region: 6b098000 to 6b09c000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b09c000 to 6b198000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b198000 to 6b19c000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b19c000 to 6b224000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b3c8000 to 6b3cc000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b3cc000 to 6b454000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b454000 to 6b458000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b458000 to 6b4e0000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b56c000 to 6b570000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 6b570000 to 6b5f8000 (depth=0) user_tag:STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 8f018000 to 8f388000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 8f388000 to 8f38c000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 8f38c000 to 90000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 90000000 to 911bc000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 911bc000 to 911c0000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 911c0000 to 92000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 92000000 to 93130000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 93130000 to 93134000 (depth=0) user_tag:SHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 93134000 to 94000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 94000000 to a0000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a0000000 to a2ca4000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2ca4000 to a2ca8000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2ca8000 to a2cac000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2cac000 to a2cc0000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2cc0000 to a2cc4000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2cc4000 to a2cc8000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2ccc000 to a2da8000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2da8000 to a2dac000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: a2dac000 to b0000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: b0000000 to c0000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: c0000000 to d0000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: d0000000 to db010000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: dd010000 to de000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: de000000 to e0000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: e0000000 to e2000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: e2000000 to e4000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: e4000000 to e6000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: e6000000 to e8000000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: e8000000 to e9da8000 (depth=0) user_tag:UNSHARED_PMAP name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: ebda8000 to f0000000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: f0000000 to f7150000 (depth=1) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 80000000 to a0000000 (depth=0) user_tag:MALLOC_NANO name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: c0000000 to 00000000 (depth=0) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
Found VM Region: 00000000 to 00000000 (depth=0) user_tag:(null) name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64
复制代码
内存节点大致分为这几类：
-
App的二进制文件在内存的映射（如OnlineMemoryGraphDemo）
-
动态库在内存中的映射（如libBacktraceRecording.dylib，libdispatch.dylib等）
-
系统或自定义字体等资源（SFUI.ttf， PingFang.ttc）
-
栈区（STACK name:/System/Library/Caches/com.apple.dyld/dyld_shared_cache_arm64）
-
Malloc Zone，Malloc Zone分为Nano和Scalable，Nano分配16B～256B(16B的整数倍)的内存，Scalable分配256B以上的大内存
Malloc内存信息的获取
Malloc内就是我们平时开发接触最多的了，我们iOS开发中语言，C/C++， OC， Swift等创建的内存和对象都是在这里分配。
我们可以通过malloc_get_all_zones获取libmalloc内部所有的zone，并遍历每个zone中管理的内存节点，获取 libmalloc 管理的存活的所有内存节点的指针和大小。
获取所有Malloc Zone
vm_address_t *zones = NULL;
unsigned int zoneCount = 0;
kern_return_t result = malloc_get_all_zones(TASK_NULL, memory_reader_callback, &zones, &zoneCount);
if (result == KERN_SUCCESS) {
for (unsigned int i = 0; i < zoneCount; i++) {
malloc_zone_t *zone = (malloc_zone_t *)zones[i];
printf("Found zone name:%s
", zone->zone_name);
}
}
复制代码
输出如下：
Found zone name:DefaultMallocZone // Nano Zone
Found zone name:MallocHelperZone. // Scalable Zone
Found zone name:QuartzCore
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获取Zone内所有分配的节点
malloc_introspection_t *introspection = zone->introspect;
if (!introspection) {
continue;
}
void (*lock_zone)(malloc_zone_t *zone) = introspection->force_lock;
void (*unlock_zone)(malloc_zone_t *zone) = introspection->force_unlock;
// Callback has to unlock the zone so we freely allocate memory inside the given block
malloc_object_enumeration_block_t callback = ^(__unsafe_unretained id object, __unsafe_unretained Class actualClass) {
unlock_zone(zone);
block(object, actualClass);
lock_zone(zone);
};
BOOL lockZoneValid = mallocPointerIsReadable((void *)lock_zone);
BOOL unlockZoneValid = mallocPointerIsReadable((void *)unlock_zone);
// There is little documentation on when and why
// any of these function pointers might be NULL
// or garbage, so we resort to checking for NULL
// and whether the pointer is readable
if (introspection->enumerator && lockZoneValid && unlockZoneValid) {
lock_zone(zone);
introspection->enumerator(TASK_NULL, (void *)&callback, MALLOC_PTR_IN_USE_RANGE_TYPE, (vm_address_t)zone, memory_reader_callback, &vm_range_recorder_callback);
unlock_zone(zone);
}
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判断内存地址中是什么
这里遇到一个问题，遍历Malloc Zone分配的内存节点，只会给一个地址和大小，怎么判断这是一个OC/C++/Swift对象还是只是一个Malloc出来的Buffer呢？
- 判断是OC/Swift对象
- 判断是C++对象
- 一块普通Buffer
如何判断是不是一个OC/Swift对象
Swift在内存布局上兼容了Objective-C，也有isa指针，objc相关方法可以作用于两种语言的对象上。只要保证 isa 指针合法，对象实例大小满足条件即可认为正确。
获取所有OC/SwiftClass类型
CFMutableSetRef registeredClasses;
unsigned int updateRegisteredClasses() {
if (!registeredClasses) {
registeredClasses = CFSetCreateMutable(NULL, 0, NULL);
} else {
CFSetRemoveAllValues(registeredClasses);
}
unsigned int count = 0;
Class *classes = objc_copyClassList(&count);
for (unsigned int i = 0; i < count; i++) {
CFSetAddValue(registeredClasses, (__bridge const void *)(classes[i]));
}
free(classes);
return count;
}
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判断isa是否合法
typedef struct {
Class isa;
} malloc_maybe_object_t;
void vm_range_recorder_callback(task_t task, void *context, unsigned type, vm_range_t *ranges, unsigned rangeCount) {
if (!context) {
return;
}
for (unsigned int i = 0; i < rangeCount; i++) {
vm_range_t range = ranges[i];
malloc_maybe_object_t *tryObject = (malloc_maybe_object_t *)range.address;
Class tryClass = NULL;
#ifdef __arm64__
// See http://www.sealiesoftware.com/blog/archive/2013/09/24/objc_explain_Non-pointer_isa.html
extern uint64_t objc_debug_isa_class_mask WEAK_IMPORT_ATTRIBUTE;
tryClass = (__bridge Class)((void *)((uint64_t)tryObject->isa & objc_debug_isa_class_mask));
#else
tryClass = tryObject->isa;
#endif
// 1. 判断是否为OC/SwiftObject
if (CFSetContainsValue(registeredClasses, (__bridge const void *)(tryClass))) {
(*(malloc_object_enumeration_block_t __unsafe_unretained *)context)((__bridge id)tryObject, tryClass);
}
// 2. 判断是否是一个保护type_info的C++对象
else if ([CPPObjectUtil cppTypeInfoName:(void *)range.address] != NULL) {
NSLog(@"Find a Cpp Object:%s!", [CPPObjectUtil cppTypeInfoName:(void *)range.address]);
}
}
}
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如何判断是不是一个C++对象
C++对象根据是否包含虚表可以分成两类。对于不包含虚表的对象，因为缺乏运行时数据，无法进行处理。对于对于包含虚表的对象，在调研 mach-o 和 C++的 ABI 文档后，可以通过 std::type_info 和以下几个 section 的信息获取对应的类型信息。
[图片上传中...(image-1c32a1-1607149856673-1)]
C++实例以及 vtable，type_info的引用关系示意图
分析MachO文件，我们发现在Dynamic Loader Info段中，发现了C++Type_Info信息
[图片上传中...(image-c2b44f-1607149856672-0)]
获取App二进制加载到内存中起始地址，_dyld_register_func_for_add_image方法当App的二进制或者动态库等MachO格式的文件映射到内存后，启动App时的回调，我们可以通过这个拿到App执行二进制的起始地址，从而拿到段中的C++类型信息。
获取App二进制起始地址
/*
* The following functions allow you to install callbacks which will be called
* by dyld whenever an image is loaded or unloaded. During a call to _dyld_register_func_for_add_image()
* the callback func is called for every existing image. Later, it is called as each new image
* is loaded and bound (but initializers not yet run). The callback registered with
* _dyld_register_func_for_remove_image() is called after any terminators in an image are run
* and before the image is un-memory-mapped.
*/
extern void _dyld_register_func_for_add_image(void (*func)(const struct mach_header* mh, intptr_t vmaddr_slide)) __OSX_AVAILABLE_STARTING(__MAC_10_1, __IPHONE_2_0);
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获取所有C++type_info
typedef std::vector<struct segment_command_64 const *> Segment64Vector;
typedef std::set<uint64_t *> CxxTypeInfoSet;
static Segment64Vector *segments_64 = NULL;
static CxxTypeInfoSet *cxxTypeInfoSet = NULL;
// 记录Data Segment中__const段的有效最大最小地址，合法的C++ type_info地址不会超出这里
uint64_t dataConstMinAddress = NULL;
uint64_t dataConstMaxAddress = NULL;
static void dyld_callback(const struct mach_header *mhp, intptr_t vmaddr_slide)
{
// 这里只分析App的二进制
if (mhp->filetype != MH_EXECUTE) {
return;
}
segments_64 = new Segment64Vector();
cxxTypeInfoSet = new CxxTypeInfoSet();
size_t header_size = sizeof(struct mach_header_64);
uint64_t *load_comandPtr = (uint64_t *)((unsigned char *)mhp + header_size);
uint64_t address = (uint64_t)((uint64_t *)mhp);
uint32_t ptrSize = sizeof(uint64_t);
for (int i=0; i<mhp->ncmds; i++) {
struct load_command *load_command = (struct load_command *)load_comandPtr;
segments_64->push_back((struct segment_command_64 const *)load_command);
NSString *cmdType = loadCommandMap[@(load_command->cmd)];
NSLog(@"dyld_callback load_command cmd:%@", cmdType);
// 分析 Data Segment中__const段，获取有效最大最小地址
if (load_command->cmd == LC_SEGMENT_64) {
struct segment_command_64 *segment_64 = (struct segment_command_64 *)load_command;
if (strcmp(segment_64->segname, "__DATA") == 0) {
const struct section_64 *sec = (struct section_64 *)(segment_64 + 1);
for (int j=0; j<segment_64->nsects; j++) {
if (strcmp(sec[j].sectname, "__const") == 0) {
dataConstMinAddress = (((uint64_t)(uint64_t *)mhp) + sec[j].offset);
dataConstMaxAddress = (((uint64_t)(uint64_t *)mhp) + sec[j].offset + sec[j].size);
}
}
}
}
// 分析动态链接段的信息，获取App内C++ type_info的地址
else if (load_command->cmd == LC_DYLD_INFO ||
load_command->cmd == LC_DYLD_INFO_ONLY) {
struct dyld_info_command *dyldCommand = (struct dyld_info_command *)load_command;
uint8_t *bytePtr = (uint8_t *)((uint8_t *)mhp + dyldCommand->bind_off); // Dynamic Loader Info Bind部分的起始地址
uint64_t dyldMaxAddress = (((uint64_t)(uint64_t *)mhp) + dyldCommand->bind_off + dyldCommand->bind_size);
uint64_t doBindLocation = *((uint64_t *)bytePtr);
int32_t libOrdinal = 0;
uint32_t type = 0;
int64_t addend = 0;
NSString * symbolName = nil;
uint32_t symbolFlags = 0;
BOOL isDone = NO;
while (((uint64_t)(uint64_t *)bytePtr) < dyldMaxAddress) {
uint8_t byte = read_int8(&bytePtr);
uint8_t opcode = byte & BIND_OPCODE_MASK;
uint8_t immediate = byte & BIND_IMMEDIATE_MASK;
NSLog(@"dyld_callback load_command opcode:%d, immediate:%d", opcode, immediate);
switch (opcode)
{
case BIND_OPCODE_DONE:
// The lazy bindings have one of these at the end of each bind.
isDone = YES;
doBindLocation = (*((uint64_t *)bytePtr) + 1);
break;
case BIND_OPCODE_SET_DYLIB_ORDINAL_IMM:
libOrdinal = immediate;
break;
case BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB:
libOrdinal = (uint32_t)read_uleb128(&bytePtr);
break;
case BIND_OPCODE_SET_DYLIB_SPECIAL_IMM:
{
// Special means negative
if (immediate == 0)
{
libOrdinal = 0;
}
else
{
int8_t signExtended = immediate | BIND_OPCODE_MASK; // This sign extends the value
libOrdinal = signExtended;
}
} break;
case BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM:
symbolFlags = immediate;
symbolName = read_string(&bytePtr);
break;
case BIND_OPCODE_SET_TYPE_IMM:
type = immediate;
break;
case BIND_OPCODE_SET_ADDEND_SLEB:
addend = read_sleb128(&bytePtr);
break;
//
case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB:
{
uint32_t segmentIndex = immediate;
uint64_t val = read_uleb128(&bytePtr);
if (segmentIndex < segments_64->size())
{
address += (*segments_64)[segmentIndex]->fileoff + val;
}
} break;
case BIND_OPCODE_ADD_ADDR_ULEB:
{
uint64_t val = read_uleb128(&bytePtr);
address += val;
} break;
case BIND_OPCODE_DO_BIND:
{
// 获取C++ type_info地址
NSLog(@"dyld_callback Bind SymbolName:%@", symbolName);
if ([symbolName hasPrefix:@"__ZTVN10__cxxabi"]) {
std::type_info *type_info = (std::type_info *)address;
NSLog(@"std::type_info name:%s address:%p", type_info->name(), type_info);
cxxTypeInfoSet->insert((uint64_t *)address);
}
doBindLocation = *((uint64_t *)bytePtr);
address += ptrSize;
} break;
case BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB:
{
uint64_t startNextBind = *((uint64_t *)bytePtr);
uint64_t val = read_uleb128(&bytePtr);
doBindLocation = startNextBind;
address += ptrSize + val;
} break;
case BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED:
{
uint32_t scale = immediate;
// 获取C++ type_info地址
if ([symbolName hasPrefix:@"__ZTVN10__cxxabi"]) {
std::type_info *type_info = (std::type_info *)address;
NSLog(@"std::type_info name:%s address:%p", type_info->name(), type_info);
cxxTypeInfoSet->insert((uint64_t *)address);
}
doBindLocation = *((uint64_t *)bytePtr);
address += ptrSize + scale * ptrSize;
} break;
case BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB:
{
uint64_t startNextBind = *((uint64_t *)bytePtr);
uint64_t count = read_uleb128(&bytePtr);
uint64_t skip = read_uleb128(&bytePtr);
for (uint64_t index = 0; index < count; index++)
{
doBindLocation = startNextBind;
address += ptrSize + skip;
}
} break;
default:
break;
}
}
}
load_comandPtr = (uint64_t *)((unsigned char *)load_comandPtr + load_command->cmdsize);
}
}
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输出如下
2020-11-16 11:03:32.879783+0800 OnlineMemoryGraphDemo[9037:1777045] std::type_info name:4Base address:0x104c803c0
2020-11-16 11:03:32.880196+0800 OnlineMemoryGraphDemo[9037:1777045] std::type_info name:5Human address:0x104c803d0
2020-11-16 11:03:32.880761+0800 OnlineMemoryGraphDemo[9037:1777045] std::type_info name:P4Male address:0x104c803f8
2020-11-16 11:03:32.881309+0800 OnlineMemoryGraphDemo[9037:1777045] std::type_info name:4Male address:0x104c803e0
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实际App中关于C++类型的定义
class Human {
public:
int age;
int sex;
void sayHello();
};
class Base
{
public:
Base(int i) :baseI(i){};
int getI(){ return baseI; }
static void countI(){};
virtual ~Base(){}
virtual void basePrint(void){ printf("Base::print()");}
private:
int baseI;
static int baseS;
};
class Male : public Base {
public:
Male(int i): Base(i){
};
void sayHello();
};
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判断一个地址是否为一个C++Object（有type_info的）
typedef std::set<uint64_t *> CxxTypeInfoSet;
static CxxTypeInfoSet *cxxTypeInfoSet = NULL;
+ (const char *) cppTypeInfoName:(void *) ptr {
uint64_t *typeInfoPtr = (uint64_t*)(*((uint64_t *)ptr) - 8);
uint64_t typeInfoAddress = (uint64_t)typeInfoPtr;
if (typeInfoAddress >= dataConstMinAddress && typeInfoAddress < dataConstMaxAddress) {
uint64_t *typeInfo = (uint64_t *)(*typeInfoPtr);
if (cxxTypeInfoSet->find(typeInfo) != cxxTypeInfoSet->end()) {
const char *name = ((std::type_info *)typeInfo)->name();
return name;
}
}
return NULL;
}
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输出如下
2020-11-16 11:03:39.581065+0800 OnlineMemoryGraphDemo[9037:1777252] Find a Cpp Object:4Male!
2020-11-16 11:03:39.581137+0800 OnlineMemoryGraphDemo[9037:1777252] Find a Cpp Object:4Base!
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数据上报和后台分析
这个大家就根据自己情况自己去实现吧。
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