uClibc Compatibility Shim for Ingenic Libraries

Overview

This project provides a small compatibility shim that lets Ingenic SDK binary libraries (libimp, libalog, libsysutils, ...) run on systems built with a modern uClibc-ng toolchain.

Modern uClibc-ng exports nearly everything the blobs reference, so the shim has shrunk to the two pieces uClibc-ng genuinely does not provide:

• mmap offset workaround: Ingenic libraries map rmem with byte offsets that are not always page aligned. uClibc-ng's mmap rejects those with EINVAL; the shim's mmap silently truncates to the containing page via the mmap2 syscall, matching the vendor libc behaviour the blobs were built against. The blobs pass a 32-bit byte offset (pre-LFS off_t ABI).
• Bare ctype table pointers (__ctype_b, __ctype_tolower, __ctype_toupper): a glibc 2.2 era interface also exported by uClibc 0.9.x but dropped by uClibc-ng. Still referenced by gcc 4.7.2 era blobs (for example T10/T20/T21/T30 libalog). The shim points them at uClibc-ng's own C locale tables, which use the same 1<<n mask encoding those blobs were compiled with.

Do not add libc wrappers back

Earlier versions also defined fopen64, open64, fseeko64, mmap64, __fgetc_unlocked, __fputc_unlocked, __assert, __pthread_register_cancel and __pthread_unregister_cancel. uClibc-ng provides all of them natively, and redefining the LFS ones is fatal: uClibc-ng force-enables _FILE_OFFSET_BITS=64, so its headers redirect fopen to fopen64, open to open64 and fseeko to fseeko64 at compile time (asm renames on the declarations, immune to #undef). A wrapper like fopen64() { return fopen(...); } compiles into a call to itself, and since the shim precedes libc in symbol lookup order, every caller in the process hangs in an infinite tail-call loop on the first file open.

For the same reason uclibc_shim.c must never include <sys/mman.h>: the header would rename the shim's mmap definition to mmap64.

Requirements

• A uClibc-ng toolchain with LFS (mandatory in current uClibc-ng) and NPTL threads. Both are checked at compile time.
• An Ingenic platform: xburst1 (T10 through T33, C100) or xburst2 (T40/T41/A1).

Building

Build as a shared library:

${CROSS_COMPILE}gcc -fPIC -shared -o libuclibcshim.so uclibc_shim.c

Or as a static archive:

${CROSS_COMPILE}gcc -c -o uclibc_shim.o uclibc_shim.c
${CROSS_COMPILE}gcc-ar rcs libuclibcshim.a uclibc_shim.o

Usage

Link your application with -luclibcshim alongside the Ingenic SDK libraries:

LDFLAGS += -limp -lalog -lsysutils -luclibcshim

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests through GitHub.

License

This project is licensed under the MIT License.