Android Changes For Ndk Developers

grep TEXTREL 0x00000016 (TEXTREL) 0x0 0x0000001e (FLAGS) SYMBOLIC TEXTREL BIND_NOW $ Note: it is technically possible to have a shared object with the TEXTREL entry/flag but without any actual text relocations. This doesn’t happen with the NDK, but if you’re generating ELF files yourself make sure you’re not generating ELF files that claim to have text relocations, because the Android dynamic linker trusts the entry/flag. Potential problems: Relocations enforce code pages being writable, and wastefully increase the number of dirty pages in memory. The dynamic linker has issued warnings about text relocations since Android K (API 19), but on API 23 and above it refuses to load code with text relocations. Resolution: rewrite assembler to be position independent to ensure no text relocations are necessary. Check the href="https://wiki.gentoo.org/wiki/Hardened/Textrels_Guide">Gentoo documentation for cookbook recipes. Invalid DT_NEEDED Entries (Enforced since API 23) While library dependencies (DT_NEEDED entries in the ELF headers) can be absolute paths, that doesn’t make sense on Android because you have no control over where your library will be installed by the system. A DT_NEEDED entry should be the same as the needed library’s SONAME, leaving the business of finding the library at runtime to the dynamic linker. Before API 23, Android’s dynamic linker ignored the full path, and used only the basename (the part after the last ‘/’) when looking up the required libraries. Since API 23 the runtime linker will gaji the DT_NEEDED exactly and so it won’t be able to load the library if it is not present in that exact location on the device. Even worse, some build systems have bugs that cause them to insert DT_NEEDED entries that point to a file on the build host, something that cannot be found on the device. $ readelf --dynamic libSample.so