.text
.global __clone
.hidden __clone
.type __clone, %function
__clone:
# int clone(
# fn, a = r2
# stack, b = r3
# flags, c = r4
# arg, d = r5
# ptid, e = r6
# tls, f = *(r15+160)
# ctid) g = *(r15+168)
#
# pseudo C code:
# tid = syscall(SYS_clone,b,c,e,g,f);
# if (!tid) syscall(SYS_exit, a(d));
# return tid;
# preserve call-saved register used as syscall arg
stg %r6, 48(%r15)
# create initial stack frame for new thread
nill %r3, 0xfff8
aghi %r3, -160
lghi %r0, 0
stg %r0, 0(%r3)
# save fn and arg to child stack
stg %r2, 8(%r3)
stg %r5, 16(%r3)
# shuffle args into correct registers and call SYS_clone
lgr %r2, %r3
lgr %r3, %r4
lgr %r4, %r6
lg %r5, 168(%r15)
lg %r6, 160(%r15)
svc 120
# restore call-saved register
lg %r6, 48(%r15)
# if error or if we're the parent, return
ltgr %r2, %r2
bnzr %r14
# we're the child. call fn(arg)
lg %r1, 8(%r15)
lg %r2, 16(%r15)
basr %r14, %r1
# call SYS_exit. exit code is already in r2 from fn return value
svc 1
