On Sat, 7 Jun 2025, kikairoya via Cygwin wrote: > Dear Cygwin team, > > I’ve found that rebase.exe makes certain assumptions that do not conform > to the PE specification. > > 1. Incorrect handling of COFF File Header position > When checking the 'Characteristics' field in the COFF File Header, > rebase.exe assumes this field is always at a fixed offset. However, the > PE specification states that the COFF File Header is located immediately > after the PE signature in the image file. > > https://cygwin.com/cgit/cygwin-apps/rebase/tree/rebase.c#n1739 > At this point, the code should perform a relative seek of 18 bytes, not > an absolute seek with SEEK_SET. > > This causes incompatibility with DLLs linked using LLVM's lld, which > uses a PE stub of a different size. As a result, such DLLs cannot be > rebased. > > > 2. Limiting file size too conservatively > https://cygwin.com/cgit/cygwin-apps/rebase/tree/pechecksum.c#n81 > > Here, the image size is limited to 1 GiB, while the PE specification > allows for up to 2 GiB. Large DLLs with debug information (e.g., > `cygLLVM*.dll`, `cygclang-cpp*.dll`, etc.) can easily exceed the 1 GiB > limit. > > > I hope these issues can be addressed to improve compatibility with > LLVM-based toolchains and enhance the robustness of development > workflows.
Would you like to make a patch for these? There may be another issue because peflags says "checksum update failed" on a small lld-created exe even when not modifying the binary. > > Regards, > > -- > Tomohiro Kashiwada (@kikairoya) > -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
