On Tue, Aug 13, 2019 at 01:16:59PM +0100, Matthias Maennich wrote: > This change allows growing struct kernel_symbol without wasting bytes to > alignment. It also concretized the alignment of ksymtab entries if > relative references are used for ksymtab entries. > > struct kernel_symbol was already implicitly being aligned to the word > size, except on x86_64 and m68k, where it is aligned to 16 and 2 bytes, > respectively. > > As far as I can tell there is no requirement for aligning struct > kernel_symbol to 16 bytes on x86_64, but gcc aligns structs to their > size, and the linker aligns the custom __ksymtab sections to the largest > data type contained within, so setting KSYM_ALIGN to 16 was necessary to > stay consistent with the code generated for non-ASM EXPORT_SYMBOL(). Now > that non-ASM EXPORT_SYMBOL() explicitly aligns to word size (8), > KSYM_ALIGN is no longer necessary. > > In case of relative references, the alignment has been changed > accordingly to not waste space when adding new struct members. > > As for m68k, struct kernel_symbol is aligned to 2 bytes even though the > structure itself is 8 bytes; using a 4-byte alignment shouldn't hurt. > > I manually verified the output of the __ksymtab sections didn't change > on x86, x86_64, arm, arm64 and m68k. As expected, the section contents > didn't change, and the ELF section alignment only changed on x86_64 and > m68k. Feedback from other archs more than welcome. > > Co-developed-by: Martijn Coenen <maco@xxxxxxxxxxx> > Signed-off-by: Martijn Coenen <maco@xxxxxxxxxxx> > Signed-off-by: Matthias Maennich <maennich@xxxxxxxxxx> Ick, messy, nice fix. Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
