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.text
.global __clone
.type __clone, %function
__clone:
# int clone(fn, stack, flags, arg, ptid, tls, ctid)
# a b c d e f g
# 3 4 5 6 7 8 9
# pseudo C code:
# tid = syscall(SYS_clone,c,b,e,f,g);
# if (!tid) syscall(SYS_exit, a(d));
# return tid;
# SYS_clone = 120
# SYS_exit = 1
# in order that the child can find the start func and its arg, we need to store it into
# non-volative regs. to do so, we have to store those 2 regs into our stackframe, so
# we can restore them later.
subi 1, 1, 16
stw 30, 12(1)
stw 31, 8(1)
# save r3 (func) into r30, and r6(arg) into r31
mr 30, 3
mr 31, 6
#move c into first arg
mr 3, 5
#mr 4, 4
mr 5, 7
mr 6, 8
mr 7, 9
# move syscall number into r0
li 0, 120
sc
# check for syscall error
#this code should be more efficient, but it borks
#bns+ 1f # jump to label 1 if no summary overflow.
#else
#neg 3, 3 #negate the result (errno)
#b 2f # jump to epilogue
# this error check code at least does not spoil the clone call.
#mfcr 0 # Check for an error
#rlwinm 4, 0, 0, 3, 3 # by checking for bit 28.
#cmplwi 0, 4, 0 # It is an error if non-zero.
#beq 0, 1f # Jump if not an error.
#neg 3, 3 # Negate the error number.
#b 2f # jump to epilogue
1:
# compare sc result with 0
cmpwi cr7, 3, 0
# if not 0, jump to end
bne cr7, 2f
#else: we're the child
#call funcptr
# move arg (d) into r3
mr 3, 31
#move r30 (funcptr) into CTR reg
mtctr 30
# call CTR reg
bctrl
# mov SYS_exit into r0 (the exit param is already in r3)
li 0, 1
sc
2:
# restore stack
lwz 30, 12(1)
lwz 31, 8(1)
addi 1, 1, 16
blr
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