Other problems encountered in debugging fingerprints

Other problems encountered when debugging fingerprints

1.SELinux

android 8.0 SELinux Great changes have taken place , at present SELinux Compile it , Will be generated in two directories ：

1.system/etc/sepolicy
2.vendor/etc/sepolicy

compile SELinux You can't just compile as before bootimage. Now compile bootimage It can't be generated Selinux Of documents ,
For the time being, I can only think of all the compilation methods .

test SeLinux Whether to compile to ：

1.android 8.0 Before , You can take a look at this out/project/obj/sepolicy_interdaiates/policy.conf Is there... In this file
Self written selinux The rules

2.android 8.0 after , look down system/etc/sepolicy perhaps vendor/etc/sepolicy Have you written it yourself selinux The rules

2. Close... From the source code SELinux The security policy

Code location ：/system/core/init/init.cpp

modify selinux_is_enforcing() The function is as follows

static bool selinux_is_enforcing(void){
    return false; //force set selinux permissive.
    if (ALLOW_PERMISSIVE_SELINUX) {
        return selinux_status_from_cmdline() == SELINUX_ENFORCING;
    }
    return true;
}

3.app load jni compiled .so Report the wrong question

If you app It is compiled in the system , And then you install Installed , It's easy to have this problem

1. The details of error reporting are as follows :

java.lang.UnsatisfiedLinkError: dlopen failed: library "xx.so"
("/system/lib/xx.so") needed or dlopened by
"/system/lib/libnativeloader.so" is not accessible for the namespace
"classloader-namespace"at java.lang.Runtime.loadLibrary0(Runtime.java:977)
 at java.lang.System.loadLibrary(System.java:1602)

reason ：android 7.0, There are some behavioral changes ,app You cannot call the private of the system .so file . You can only call the public of the system .so

Solution ：

Put yourself jni Generated .so Put it in /system/etc/public.libraries.txt perhaps /vendor/etc/public.libraries.txt In the middle .

And then put public.libraries.txt push go in