On Thu, Aug 23, 2018 at 08:54:17PM +0200, Adam Borowski wrote: > On Thu, Aug 23, 2018 at 10:43:59AM -0700, Paul E. McKenney wrote: > > The mkinitramfs approach results in about 40MB of initrd, and dracut > > about 10MB. Most of this is completely useless for rcutorture, which > > isn't interested in mounting filesystems, opening devices, and almost > > all of the other interesting things that mkinitramfs and dracut enable. > > > > Those who know me will not be at all surprised to learn that I went > > overboard making the resulting initrd as small as possible. I started > > by throwing out everything not absolutely needed by the dash and sleep > > binaries, which got me down to about 2.5MB, 1.8MB of which was libc. > > This situation of course prompted me to create an initrd containing > > a statically linked binary named "init" and absolutely nothing else > > (not even /dev or /tmp directories), which weighs in at not quite 800KB. > > This is a great improvement over 10MB, to say nothing of 40MB, but 800KB > > for a C-language "for" loop containing nothing more than a single call to > > sleep()? > > .globl _start > .data > req: .8byte 999999999, 999999999 > .text > _start: > mov $35, %rax # syscall: nanosleep > mov $req, %rdi > xor %rsi, %rsi > syscall > jmp _start > > > as sl.s -o sl.o > ld sl.o -o init > > 'Ere you go, no libc needed. If your arch is not amd64, just say so.
"pause" ($34) would also suffice, and would not require an argument or a .data section. - Josh Triplett
