我看了http://iphonedevwiki.net/
里面有这么一段
What has changed in iOS 9? (Classes, frameworks, etc.)
Entitlements
Every dylib meant for injection has to be signed to work on iOS, even if no entitlements are required. Please make sure that your toolchain of choice is producing signed dylibs, if it is a fat binary, make sure that all slices are signed.
Use ldid to sign:
ldid -S Tweak.dylib
Failure to do this will invalidate the process and make it lose all entitlements. The standard symptom is the following, but frankly, it is confusing why any binaries are in the wild that haven't at least been passed through ldid, so please don't rely on this symptom and just fix your build environment.
应该就是签名的问题了。iOS9中所有dylib都需要签名。我用ldid -S libusb-1.0.0.dylib手动签名以后，就没有出现上述问题。