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