On Thu, Feb 06, 2020 at 04:26:23AM -0800, Kees Cook wrote: > I know x86_64 stack alignment is 16 bytes. I cannot find evidence for > what function start alignment should be. It seems the linker is 16 byte > aligning these functions, when I think no alignment is needed for > function starts, so we're wasting some memory (average 8 bytes per > function, at say 50,000 functions, so approaching 512KB) between > functions. If we can specify a 1 byte alignment for these orphan > sections, that would be nice, as mentioned in the cover letter: we lose > a 4 bits of entropy to this alignment, since all randomized function > addresses will have their low bits set to zero. > The default function alignment is 16-bytes for x64 at least with gcc. You can use -falign-functions to specify a different alignment. There was some old discussion on reducing it [1] but it doesn't seem to have been merged. [1] https://lore.kernel.org/lkml/tip-4874fe1eeb40b403a8c9d0ddeb4d166cab3f37ba@xxxxxxxxxxxxxx/
