coredump的裁剪方法

coredump默认情况下会将进程内的所有匿名内存页给dump出来。

/* coredump filter bits */
#define MMF_DUMP_ANON_PRIVATE      2
#define MMF_DUMP_ANON_SHARED       3
#define MMF_DUMP_MAPPED_PRIVATE    4
#define MMF_DUMP_MAPPED_SHARED     5
#define MMF_DUMP_ELF_HEADERS       6
#define MMF_DUMP_HUGETLB_PRIVATE   7
#define MMF_DUMP_HUGETLB_SHARED    8

#define MMF_DUMP_FILTER_SHIFT      MMF_DUMPABLE_BITS
#define MMF_DUMP_FILTER_BITS       7
#define MMF_DUMP_FILTER_MASK       (((1 << MMF_DUMP_FILTER_BITS) - 1) << MMF_DUMP_FILTER_SHIFT)
#define MMF_DUMP_FILTER_DEFAULT    ((1 << MMF_DUMP_ANON_PRIVATE) | (1 << MMF_DUMP_ANON_SHARED) | (1 << MMF_DUMP_HUGETLB_PRIVATE) | MMF_DUMP_MASK_DEFAULT_ELF)

64位下一般app进程中的匿名页大小都会非常庞大，都是1G以上的。

以SystemUI为例：

core文件	压缩前大小	压缩后大小
core-ndroid.systemui-1801	1339M	17.3M

压缩前1339M，压缩后17.3M。

按照coredump中占有的大小排匿名页：

file_offset        virtual addr       file_size          mem_size
...
0x00000000467a7000 0x0000007f6051f000 0x0000000000103000 0x0000000000103000  RW  [stack:4303]
0x00000000469f7000 0x0000007f607e9000 0x0000000000103000 0x0000000000103000  RW  [stack:4321]
0x00000000466a3000 0x0000007f6041a000 0x0000000000103000 0x0000000000103000  RW  [stack:4322]
0x0000000045658000 0x0000007f5cde5000 0x0000000000103000 0x0000000000103000  RW  [stack:4354]
0x0000000045164000 0x0000007f5afba000 0x0000000000103000 0x0000000000103000  RW  [stack:4364]
0x0000000047eaa000 0x0000007f632f3000 0x0000000000103000 0x0000000000103000  RW  [stack:4471]
0x0000000020f61000 0x000000007545a000 0x0000000000180000 0x0000000000180000  RW  /dev/ashmem/dalvik-zygote space (deleted)
0x00000000516fc000 0x0000007f7e465000 0x0000000000185000 0x0000000000185000  R   /dev/ashmem/dalvik-classes.dex extracted in memory from /system/priv-app/MiuiSystemUI/MiuiSystemUI.apk (deleted)
0x0000000044f63000 0x0000007f5ac00000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x0000000047006000 0x0000007f60e00000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x00000000481b5000 0x0000007f63600000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000004dbcd000 0x0000007f72800000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000004de39000 0x0000007f74c00000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000004e05f000 0x0000007f77800000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x0000000000031000 0x0000000012c00000 0x0000000000208000 0x0000000000208000  RW  /dev/ashmem/dalvik-main space (deleted)
0x000000004d8e9000 0x0000007f717a1000 0x000000000027e000 0x000000000027e000  RW  /system/vendor/lib64/egl/libGLESv2_adreno.so
0x0000000045da3000 0x0000007f5fa00000 0x0000000000400000 0x0000000000400000  RW  [anon:libc_malloc]
0x00000000462a2000 0x0000007f60000000 0x0000000000400000 0x0000000000400000  RW  [anon:libc_malloc]
0x00000000526ea000 0x0000007f7fc00000 0x0000000000400000 0x0000000000400000  RW  [anon:libc_malloc]
0x0000000000239000 0x0000000012e08000 0x00000000006b2000 0x00000000006b2000  RW  /dev/ashmem/dalvik-main space (deleted)
0x0000000052f4b000 0x0000007fd91bc000 0x00000000007ff000 0x00000000007ff000  RW  
0x0000000024762000 0x0000000078c5b000 0x00000000007ff000 0x00000000007ff000  RW  /dev/ashmem/dalvik-non moving space (deleted)
0x000000004d0e2000 0x0000007f69007000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space live-bitmap 3 (deleted)
0x000000004c8e2000 0x0000007f68807000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space mark-bitmap 3 (deleted)
0x000000004ed62000 0x0000007f7aac1000 0x0000000000801000 0x0000000000801000  RW  /dev/ashmem/dalvik-allocation stack (deleted)
0x000000004e561000 0x0000007f7a2c0000 0x0000000000801000 0x0000000000801000  RW  /dev/ashmem/dalvik-live stack (deleted)
0x0000000020031000 0x000000006f961000 0x0000000000f2f000 0x0000000000f2f000  RW  /data/dalvik-cache/arm64/system@framework@boot.art
0x000000004a8e2000 0x0000007f66807000 0x0000000002000000 0x0000000002000000  R E /dev/ashmem/dalvik-jit-code-cache (deleted)
0x00000000488e2000 0x0000007f64807000 0x0000000002000000 0x0000000002000000  RW  /dev/ashmem/dalvik-data-code-cache (deleted)
0x000000004f5a3000 0x0000007f7b302000 0x0000000002001000 0x0000000002001000  RW  /dev/ashmem/dalvik-card table (deleted)
0x0000000021171000 0x000000007566a000 0x00000000035f1000 0x00000000035f1000      /dev/ashmem/dalvik-non moving space (deleted)
0x00000000008eb000 0x00000000134ba000 0x000000001f746000 0x000000001f746000      /dev/ashmem/dalvik-main space (deleted)
0x0000000024f61000 0x000000007945a000 0x0000000020000000 0x0000000020000000  RW  /dev/ashmem/dalvik-free list large object space (deleted)

可以看到排行靠前的基本都是虚拟机相关的匿名页。

而我们用coredump分析的大部分是native的问题，且native的heap和java的heap是独立分开的，

因此java相关的内存一般是不需要的，也就是可以被裁剪掉的。

如何裁剪呢？

我们只需要在NE的进程退出前，将需要裁剪的内存段设置为MADV_DONTDUMP就可以了。

如下代码：

typedef enum {
    TRIM_TYPE_RESERVED = (1 << 0),
    TRIM_TYPE_JAVA     = (1 << 1),
    TRIM_TYPE_LIB_CODE = (1 << 2),
    TRIM_TYPE_FONT     = (1 << 3),
    TRIM_TYPE_USR      = (1 << 4),
    TRIM_TYPE_FOR_FULL_DUMP = (TRIM_TYPE_RESERVED|TRIM_TYPE_LIB_CODE|TRIM_TYPE_FONT|TRIM_TYPE_USR),
    TRIM_TYPE_MAX
} TRIM_TYPE;


static void skip_segment(uintptr_t start, uintptr_t end) {
    if (end > start) {
        int rc = madvise((void*)start, end - start, MADV_DONTDUMP);
        if (rc == -1) {
            MILOGI("madvise err! start=%p, end=%p, errno=%d",(void*)start, (void*)end, errno);
        }
    }
}

static int permision_c_to_i(const char* ptr){
    int perm = 0;
    if (ptr[0] == 'r')
        perm |= 0x4;
    if (ptr[1] == 'w')
        perm |= 0x2;
    if (ptr[2] == 'x')
        perm |= 0x1;
    return perm;
}

static void trim_core(uintptr_t trim_type) {
    FILE* maps = fopen("/proc/self/maps", "r");
    if (maps == nullptr) {
        return;
    }
    char line[4096];
    while (fgets(line, sizeof(line), maps)) {
        uintptr_t start, end;
        int name_pos;
        char perms[5];

        if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4s %*x %*x:%*x %*d %n", &start, &end, perms, &name_pos) == 3) {
            const char* name = &line[name_pos];
            int perm = permision_c_to_i(perms);

#define CHECK_TRIM(_trim, _perm, _name) 
    do { 
        if ((trim_type & _trim) == _trim) { 
            if ((_perm == 0xf || perm == _perm) && strncmp(name, _name, sizeof(_name)-1) == 0) { 
                skip_segment(start, end); 
                continue; 
            } 
        } 
    } while(0)
            CHECK_TRIM(TRIM_TYPE_JAVA,     0xf, "/dev/ashmem/dalvik");
            CHECK_TRIM(TRIM_TYPE_JAVA,     0xf, "/data/dalvik-cache/");
            CHECK_TRIM(TRIM_TYPE_RESERVED, 0x0, "/dev/ashmem/dalvik");
            CHECK_TRIM(TRIM_TYPE_FONT,     0x4, "/system/fonts/");
            CHECK_TRIM(TRIM_TYPE_USR,      0x4, "/system/usr/");
#ifdef __aarch64__
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/lib64/");
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/vendor/lib64/");
#else
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/lib/");
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/vendor/lib/");
#endif
        }
    }
    fclose(maps);
}

extern "C" void trim_core_dump(uintptr_t dump_java) {

    if (dump_java) {
        trim_core(TRIM_TYPE_FOR_FULL_DUMP);
    } else {
        trim_core(TRIM_TYPE_JAVA);
    }
}

裁剪完java相关的heap后的coredump大小如下：

core文件	压缩前	压缩后
core-ndroid.systemui-1801	121.5M	3.7M

裁剪前后对比如下：

	压缩前	压缩后
裁剪前	1339M	17.3M
裁剪后	121.5M	3.7M
比率	9%	21.3%

有时候我们需要通过coredump分析java堆相关的问题，

这时候除了要在core里面保留java heap相关内容，还要将boot.art、boot.oat等文件映射的内存页也给dump粗来。

默认情况下coredump不会dump文件映射，因此我们得需要动态修改filter：

static void core_set_filter(pid_t pid, bool is_full)
{
    char path[PATH_MAX];

    snprintf(path,sizeof(path),"/proc/%d/coredump_filter",pid);

    int fd = open(path, O_WRONLY);

    if (fd > 0) {
        if (is_full) {
            write(fd, "39", 2);    /*0x27 MMF_DUMP_ANON_PRIVATE|MMF_DUMP_ANON_SHARED|MMF_DUMP_MAPPED_PRIVATE|MMF_DUMP_HUGETLB_PRIVATE*/
        } else {
            write(fd, "35", 2);    /*0x23 MMF_DUMP_ANON_PRIVATE|MMF_DUMP_ANON_SHARED|MMF_DUMP_HUGETLB_PRIVATE*/
        }
        close(fd);
    }
}

修改filer后就能dump文件映射内存段(MMF_DUMP_MAPPED_PRIVATE)。

而此时的coredump文件非常大，一般都是2~3G，以SystemUI为例： 

core文件	压缩前	压缩后
core-ndroid.systemui-1801	2184M	154.3M

按照coredump中占有的大小排匿名页：

file_offset        virtual addr       file_size          mem_size

...
0x000000006dd4f000 0x0000007f60986000 0x0000000000103000 0x0000000000103000  RW  [stack:2268]
0x000000006dc49000 0x0000007f6087a000 0x0000000000103000 0x0000000000103000  RW  [stack:2275]
0x000000006d73d000 0x0000007f602fd000 0x0000000000103000 0x0000000000103000  RW  [stack:2276]
0x000000006a3ce000 0x0000007f5cf31000 0x0000000000103000 0x0000000000103000  RW  [stack:2348]
0x0000000069e72000 0x0000007f5b0b9000 0x0000000000103000 0x0000000000103000  RW  [stack:2875]
0x000000006f284000 0x0000007f62dda000 0x0000000000103000 0x0000000000103000  RW  [stack:4189]
0x000000006f389000 0x0000007f62edf000 0x0000000000103000 0x0000000000103000  RW  [stack:4205]
0x0000000084a07000 0x0000007f8024d000 0x0000000000104000 0x0000000000104000  R E /system/lib64/libcrypto.so (BuildId: a6e63a0db9e7619d2ad33c4f028d5c6c)
0x000000006d534000 0x0000007f600e5000 0x0000000000109000 0x0000000000109000  R E /system/lib64/libblas.so (BuildId: f951af52fad1aa7d561d021ab1c80cab)
0x0000000069d30000 0x0000007f5af52000 0x000000000011d000 0x000000000011d000  R   /system/priv-app/SecurityCenter/SecurityCenter.apk
0x0000000083dc6000 0x0000007f7f603000 0x0000000000137000 0x0000000000137000  R E /system/lib64/libart.so (BuildId: bf9347900a4e1fa84e9df75618d54db6) (load base 0x23000)
0x000000007c10a000 0x0000007f77679000 0x0000000000141000 0x0000000000141000  R E /system/lib64/libxml2.so (BuildId: eadb3a4e20d6e9b12715ae2b5ff356d8) (load base 0x3000)
0x000000007c6f1000 0x0000007f77c6b000 0x0000000000163000 0x0000000000163000  R E /data/dalvik-cache/arm64/system@framework@android-support-v13.jar@classes.dex (load base 0x178000)
0x00000000877ca000 0x0000007f830a0000 0x000000000016a000 0x000000000016a000  R E /system/lib64/libicuuc.so (BuildId: affece9f885adfad1e8f976d2edb4940) (load base 0x19000)
0x000000007c579000 0x0000007f77af3000 0x0000000000178000 0x0000000000178000  R   /data/dalvik-cache/arm64/system@framework@android-support-v13.jar@classes.dex
0x0000000085871000 0x0000007f8112d000 0x0000000000178000 0x0000000000178000  R E /system/lib64/libandroid_runtime.so (BuildId: 944b9208a384a65f9a8ed8c140aaaa19) (load base 0x30000)
0x0000000045b2a000 0x000000007545a000 0x0000000000180000 0x0000000000180000  RW  /dev/ashmem/dalvik-zygote space (deleted)
0x0000000082c3d000 0x0000007f7e462000 0x0000000000185000 0x0000000000185000  R   /dev/ashmem/dalvik-classes.dex extracted in memory from /system/priv-app/MiuiSystemUI/MiuiSystemUI.apk (deleted)
0x000000007e330000 0x0000007f798ac000 0x000000000018d000 0x000000000018d000  R E /system/vendor/lib64/lib-imsqimf.so (BuildId: f5c244699ac36464c3624f113b5bdac0) (load base 0x5000)
0x0000000084c08000 0x0000007f804ba000 0x0000000000191000 0x0000000000191000  R E /system/lib64/libstagefright.so (BuildId: 9c75c09de4c3b843fcdde036230fa5ac) (load base 0x46000)
0x000000006eaf0000 0x0000007f61753000 0x00000000001e4000 0x00000000001e4000  R E /data/dalvik-cache/arm64/system@priv-app@MiuiKeyguard@MiuiKeyguard.apk@classes.dex (load base 0x223000)
0x00000000775c6000 0x0000007f72b2e000 0x00000000001ec000 0x00000000001ec000  R   /system/framework/framework-res.apk
0x0000000070a57000 0x0000007f645ea000 0x00000000001f6000 0x00000000001f6000  R E /data/dalvik-cache/arm64/system@framework@miuipushsdkshared.jar@classes.dex (load base 0x207000)
0x0000000069b30000 0x0000007f5ac00000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000006fa9e000 0x0000007f63600000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000007729b000 0x0000007f72800000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x0000000079691000 0x0000007f74c00000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x000000007c291000 0x0000007f77800000 0x0000000000200000 0x0000000000200000  RW  [anon:libc_malloc]
0x0000000070850000 0x0000007f643e3000 0x0000000000207000 0x0000000000207000  R   /data/dalvik-cache/arm64/system@framework@miuipushsdkshared.jar@classes.dex
0x0000000000031000 0x0000000012c00000 0x0000000000208000 0x0000000000208000  RW  /dev/ashmem/dalvik-main space (deleted)
0x0000000084f41000 0x0000007f807f4000 0x0000000000218000 0x0000000000218000  R E /system/lib64/libicui18n.so (BuildId: 568e215ae7171b7d181b019a97360459) (load base 0x1a000)
0x000000006e8cd000 0x0000007f61530000 0x0000000000223000 0x0000000000223000  R   /data/dalvik-cache/arm64/system@priv-app@MiuiKeyguard@MiuiKeyguard.apk@classes.dex
0x000000007623d000 0x0000007f717a1000 0x000000000027e000 0x000000000027e000  RW  /system/vendor/lib64/egl/libGLESv2_adreno.so
0x0000000078027000 0x0000007f73596000 0x000000000032d000 0x000000000032d000  R   /system/fonts/Miui-Light.ttf
0x00000000704d3000 0x0000007f64066000 0x000000000033b000 0x000000000033b000  R E /data/dalvik-cache/arm64/system@framework@cloud-common.jar@classes.dex (load base 0x365000)
0x0000000079a9b000 0x0000007f7500a000 0x0000000000355000 0x0000000000355000  R   /system/fonts/NotoColorEmoji.ttf
0x000000007016e000 0x0000007f63d01000 0x0000000000365000 0x0000000000365000  R   /data/dalvik-cache/arm64/system@framework@cloud-common.jar@classes.dex
0x0000000079df0000 0x0000007f7535f000 0x000000000037d000 0x000000000037d000  R   /system/fonts/Miui-Regular.ttf
0x000000007ddc7000 0x0000007f79341000 0x00000000003ba000 0x00000000003ba000  R E /system/lib64/libart-compiler.so (BuildId: 9d4bc4d801f3664a60f498526017376f) (load base 0x32000)
0x000000006d840000 0x0000007f60400000 0x0000000000400000 0x0000000000400000  RW  [anon:libc_malloc]
0x00000000843c2000 0x0000007f7fc00000 0x0000000000400000 0x0000000000400000  RW  [anon:libc_malloc]
0x0000000075db1000 0x0000007f71315000 0x000000000048c000 0x000000000048c000  R E /system/vendor/lib64/egl/libGLESv2_adreno.so (load base 0x39000)
0x0000000083efe000 0x0000007f7f73b000 0x00000000004af000 0x00000000004af000  R E /system/lib64/libart.so
0x00000000852de000 0x0000007f80b97000 0x00000000004bc000 0x00000000004bc000  R E /system/lib64/libpdfium.so (BuildId: d233271a0367337979041d0a9cceefbb) (load base 0x1c000)
0x0000000085a13000 0x0000007f812d0000 0x000000000054d000 0x000000000054d000  R E /system/lib64/libskia.so (BuildId: a8644d98d760e4fc9fdbcb139416d616) (load base 0x4d000)
0x0000000077a89000 0x0000007f72ff8000 0x000000000059e000 0x000000000059e000  R   /system/fonts/Miui-Bold.ttf
0x000000006ce97000 0x0000007f5fa00000 0x0000000000600000 0x0000000000600000  RW  [anon:libc_malloc]
0x0000000000239000 0x0000000012e08000 0x000000000066c000 0x000000000066c000  RW  /dev/ashmem/dalvik-main space (deleted)
0x000000008817c000 0x0000007fd91bc000 0x00000000007ff000 0x00000000007ff000  RW  
0x000000004932b000 0x0000000078c5b000 0x00000000007ff000 0x00000000007ff000  RW  /dev/ashmem/dalvik-non moving space (deleted)
0x00000000823e3000 0x0000007f7dc03000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space 1 live-bitmap 2 (deleted)
0x0000000081be3000 0x0000007f7d403000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space 1 mark-bitmap 2 (deleted)
0x0000000075474000 0x0000007f69007000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space live-bitmap 3 (deleted)
0x0000000074c74000 0x0000007f68807000 0x0000000000800000 0x0000000000800000  RW  /dev/ashmem/dalvik-allocspace main rosalloc space mark-bitmap 3 (deleted)
0x000000007f2a1000 0x0000007f7aac1000 0x0000000000801000 0x0000000000801000  RW  /dev/ashmem/dalvik-allocation stack (deleted)
0x000000007eaa0000 0x0000007f7a2c0000 0x0000000000801000 0x0000000000801000  RW  /dev/ashmem/dalvik-live stack (deleted)
0x00000000764bf000 0x0000007f71a23000 0x0000000000d2d000 0x0000000000d2d000  R E /system/vendor/lib64/libllvm-glnext.so (BuildId: 3e03677902b12a49330c14952aa887e9) (load base 0x5b000)
0x0000000040031000 0x000000006f961000 0x0000000000f2f000 0x0000000000f2f000  RW  /data/dalvik-cache/arm64/system@framework@boot.art
0x0000000086478000 0x0000007f81d4b000 0x00000000010f5000 0x00000000010f5000  R E /system/lib64/libLLVM.so (BuildId: 571f26c70c35873d3c0da4e3a037055c) (load base 0xa3000)
0x00000000784c1000 0x0000007f73a30000 0x00000000011d0000 0x00000000011d0000  R   /system/fonts/NotoSansCJK-Regular.ttc
0x000000007abde000 0x0000007f7614d000 0x000000000152c000 0x000000000152c000  R   /system/usr/icu/icudt56l.dat
0x000000007c89b000 0x0000007f77e15000 0x000000000152c000 0x000000000152c000  R   /system/usr/icu/icudt56l.dat
0x0000000043e3c000 0x000000007376c000 0x0000000001cec000 0x0000000001cec000  R E /data/dalvik-cache/arm64/system@framework@boot.oat (load base 0x7376c000)
0x0000000072c74000 0x0000007f66807000 0x0000000002000000 0x0000000002000000  R E /dev/ashmem/dalvik-jit-code-cache (deleted)
0x0000000070c74000 0x0000007f64807000 0x0000000002000000 0x0000000002000000  RW  /dev/ashmem/dalvik-data-code-cache (deleted)
0x000000007fae2000 0x0000007f7b302000 0x0000000002001000 0x0000000002001000  RW  /dev/ashmem/dalvik-card table (deleted)
0x000000006a6c9000 0x0000007f5d22e000 0x00000000022c8000 0x00000000022c8000  R E /system/vendor/lib64/libllvm-qcom.so (BuildId: d04f0c912709b2087e42af548465996a) (load base 0x1a0000)
0x0000000040f60000 0x0000000070890000 0x0000000002edc000 0x0000000002edc000  R   /data/dalvik-cache/arm64/system@framework@boot.oat
0x0000000045d40000 0x0000000075670000 0x00000000035eb000 0x00000000035eb000      /dev/ashmem/dalvik-non moving space (deleted)
0x00000000008a5000 0x0000000013474000 0x000000001f78c000 0x000000001f78c000      /dev/ashmem/dalvik-main space (deleted)
0x0000000020032000 0x0000000032c01000 0x000000001ffff000 0x000000001ffff000      /dev/ashmem/dalvik-main space 1 (deleted)
0x0000000049b2a000 0x000000007945a000 0x0000000020000000 0x0000000020000000  RW  /dev/ashmem/dalvik-free list large object space (deleted)

从上面的列表中可以看到，core文件中除了我们想要的boot.oat和boot.art和其他虚拟机相关的内存段外，

还有其他不必要的文件映射，如so的可执行段、font目录下的ttc文件、usr目录下的dat文件，没有访问权限的数据段等。

我们同样也可以通过mdevice()将这些没用的段给去掉。如下面代码中的红色部分：

static void trim_core(uintptr_t trim_type) {
    FILE* maps = fopen("/proc/self/maps", "r");
    if (maps == nullptr) {
        return;
    }
    char line[4096];
    while (fgets(line, sizeof(line), maps)) {
        uintptr_t start, end;
        int name_pos;
        char perms[5];

        if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4s %*x %*x:%*x %*d %n", &start, &end, perms, &name_pos) == 3) {
            const char* name = &line[name_pos];
            int perm = permision_c_to_i(perms);

#define CHECK_TRIM(_trim, _perm, _name) 
    do { 
        if ((trim_type & _trim) == _trim) { 
            if ((_perm == 0xf || perm == _perm) && strncmp(name, _name, sizeof(_name)-1) == 0) { 
                skip_segment(start, end); 
                continue; 
            } 
        } 
    } while(0)
            CHECK_TRIM(TRIM_TYPE_JAVA,     0xf, "/dev/ashmem/dalvik");
            CHECK_TRIM(TRIM_TYPE_JAVA,     0xf, "/data/dalvik-cache/");
            CHECK_TRIM(TRIM_TYPE_RESERVED, 0x0, "/dev/ashmem/dalvik");
            CHECK_TRIM(TRIM_TYPE_FONT,     0x4, "/system/fonts/");
            CHECK_TRIM(TRIM_TYPE_USR,      0x4, "/system/usr/");
#ifdef __aarch64__
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/lib64/");
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/vendor/lib64/");
#else
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/lib/");
            CHECK_TRIM(TRIM_TYPE_LIB_CODE, 0x5, "/system/vendor/lib/");
#endif
        }
    }
    fclose(maps);
}

裁剪后的大小如下:

core文件	压缩前	压缩后
core-ndroid.systemui-1801	900M	51.3M

裁剪前后对比如下：

	压缩前	压缩后
裁剪前	2184M	154.3M
裁剪后	900M	51.3M
比率	41.2%	33.2%