On Sun, May 8, 2022 at 12:09 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol > versions into ELF objects. Then, modpost extracts the version CRCs > from them. > > The following figures show how it currently works, and how I am trying > to change it. > > Current implementation > ====================== > |----------| > embed CRC -------------------------->| final | > $(CC) $(LD) / |---------| | link for | > -----> *.o -------> *.o -->| modpost | | vmlinux | > / / | |-- *.mod.c -->| or | > / genksyms / |---------| | module | > *.c ------> *.symversions |----------| > > Genksyms outputs the calculated CRCs in the form of linker script > (*.symversions), which is used by $(LD) to update the object. > > If CONFIG_LTO_CLANG=y, the build process is much more complex. Embedding > the CRCs is postponed until the LLVM bitcode is converted into ELF, > creating another intermediate *.prelink.o. > > However, this complexity is unneeded. There is no reason why we must > embed version CRCs in objects so early. > > There is final link stage for vmlinux (scripts/link-vmlinux.sh) and > modules (scripts/Makefile.modfinal). We can link CRCs at the very last > moment. > > New implementation > ================== > |----------| > --------------------------------------->| final | > $(CC) / |---------| | link for | > -----> *.o ---->| | | vmlinux | > / | modpost |--- .vmlinux.export.c -->| or | > / genksyms | |--- *.mod.c ------------>| module | > *.c ------> *.cmd -->|---------| |----------| > > Pass the symbol versions to modpost as separate text data, which are > available in *.cmd files. > > This commit changes modpost to extract CRCs from *.cmd files instead of > from ELF objects. > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx> > Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> This looks good to me, it's great to get rid of the .symversions files! Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Sami
