rewritten setjmp: compiler now gives a bit more support
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ceriel
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1 changed files with 83 additions and 126 deletions
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@ -1,161 +1,118 @@
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#
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mes 2,EM_WSIZE,EM_PSIZE
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;
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; layout of a setjmp buffer:
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;
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; -----------------
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; | signal mask | (only for Berkeley 4.2)
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; -----------------
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; | PC of caller |
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; -----------------
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; | |
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; | GTO descriptor |
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; | (SP, LB, PC) |
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; | |
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; -----------------
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;
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; setjmp saves the signalmask, PC, SP, and LB of caller, and creates a
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; GTO descriptor with a program counter indicating a piece of code that
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; gets the return value right before jumping to the caller of setjmp in
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; the setjmp buffer, which has a layout as displayed above.
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; The big problem here is how to het the return address, i.e. the PC of
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; the caller; This problem is solved by the front-end, which must pass
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; it as an extra parameter to setjmp.
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gtobuf
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bss 3*EM_PSIZE,0,0
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retval
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bss EM_WSIZE,0,0
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jmpbuf_addr
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bss EM_PSIZE,0,0
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inp $fill_ret_area
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exp $setjmp
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pro $setjmp,3*EM_WSIZE
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; setjmp saves the StackPointer and the LocalBase, and the chunk of
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; memory between the StackPointer and the ArgumentBase, + its size in a
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; buffer, pointed to by the parameter.
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; longjump can then restore this buffer and return.
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; Notice that this does not work on EM implementations in which every
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; procedure frame has a different fragment in memory, because in this case
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; the ArgumentBase will point into the fragment of the caller.
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; What really is needed is a way to find out the size of the return
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; status block.
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; On EM-implementations in which the stack grows upwards it is untested,
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; as there are no such implementations available now.
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; This implementation of setjmp/longjmp
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; depends on the assumption that the routine calling
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; setjmp does not have register variables, and that it saves all registers
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; that are available for variables.
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pro $setjmp,0
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mes 11
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#ifdef __BSD4_2
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loc 0
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cal $sigblock
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asp EM_WSIZE
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lfr EM_WSIZE
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stl -3*EM_WSIZE
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lal 0
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loi EM_PSIZE
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stf 4*EM_PSIZE
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#endif
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loc 0
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stl -2*EM_WSIZE
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lor 1 ; load StackPointer
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; create GTO descriptor for longjmp
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lxl 0
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dch ; Local Base of caller
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lxa 0 ; Stackpointer of caller
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.1
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rom *1
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lae .1
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loi EM_PSIZE ; where the longjmp ends up
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lal 0
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loi EM_PSIZE
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sti EM_PSIZE ; save it
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lxl 0 ; load LocalBase
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sti 3*EM_PSIZE ; stored in jmpbuf
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; also save return address, which has been supplied by the compiler
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lal EM_PSIZE
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loi EM_PSIZE
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lal 0
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loi EM_PSIZE
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adp EM_PSIZE
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sti EM_PSIZE ; save it
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lxa 0 ; load ArgumentBase
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lal 0
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loi EM_PSIZE
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loi EM_PSIZE ; load saved StackPointer
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sbs EM_WSIZE ; gives size of block that is to be saved, or negative size
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dup EM_WSIZE
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zgt *5
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ngi EM_WSIZE
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loc 1
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stl -2*EM_WSIZE; one if the stack grows upwards
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5
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stl -EM_WSIZE ; save size of block in local
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lol -EM_WSIZE
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lal 0
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loi EM_PSIZE
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adp 2*EM_PSIZE
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sti EM_WSIZE ; and also in the buffer
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lal 0
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loi EM_PSIZE
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loi EM_PSIZE ; load saved StackPointer
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lol -2*EM_WSIZE; positive if the stack grows upwards
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zle *6
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asp EM_PSIZE
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lxa 0
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adp EM_WSIZE ; in this case the source address = ArgumentBase+EM_WSIZE
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6
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lal 0
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loi EM_PSIZE
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adp 2*EM_PSIZE+EM_WSIZE
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; destination address
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lol -EM_WSIZE ; count
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bls EM_WSIZE ; block copy
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adp 3*EM_PSIZE
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sti EM_PSIZE
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loc 0
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ret EM_WSIZE
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end 3*EM_WSIZE
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exp $longjmp
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pro $longjmp,3*EM_WSIZE
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; first, find out wether the stack grows upwards
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loc 0
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stl -2*EM_WSIZE
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lxa 0
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lxl 0
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cmp
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zge *7
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loc 1
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stl -2*EM_WSIZE; this local contains 1 if it does, otherwise it contains 0
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7
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; then, adjust StackPointer until it is below the saved StackPointer (or
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; above if it grows upwards)
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; then push parameters
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; then copy the saved block in its proper place
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; notice that the parameters can not be used anymore now
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; then restore the LocalBase and the Stackpointer and return.
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1
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loc 0
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2
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lor 1
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lal 0
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; so, the longjmp returns here.
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; now, create a GTO descriptor for the final GTO
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lae jmpbuf_addr
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loi EM_PSIZE
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loi EM_PSIZE ; saved StackPointer
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cmp ; compare with current one
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lol -2*EM_WSIZE
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zle *8
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zlt *1
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bra *10
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8
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zgt *1
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10
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lal 0
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adp 3*EM_PSIZE
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loi EM_PSIZE
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loi EM_PSIZE ; push saved StackPointer
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lol EM_PSIZE ; push value to be returned by longjmp
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lal 0
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lae gtobuf
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sti EM_PSIZE ; this is the return address
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lae jmpbuf_addr
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loi EM_PSIZE
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adp EM_PSIZE
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loi EM_PSIZE ; push saved LocalBase
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loi 2*EM_PSIZE
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lae gtobuf+EM_PSIZE
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sti 2*EM_PSIZE ; that's it, the GTO descriptor is ready;
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; now take care of the return value ...
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cal $fill_ret_area
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gto gtobuf ; there we go ...
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end 0
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pro $fill_ret_area,0
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loe retval
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ret EM_WSIZE
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end 0
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exp $longjmp
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pro $longjmp,?
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lal 0
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loi EM_PSIZE
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adp 2*EM_PSIZE+EM_WSIZE
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; source address
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lal 0
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loi EM_PSIZE
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loi EM_PSIZE ; saved stackpointer
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lol -2*EM_WSIZE
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zle *9 ; if not positive, this is the destination address,
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; otherwise subtract the size of the saved area and add EM_WSIZE
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adp EM_WSIZE
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lal 0
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loi EM_PSIZE
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adp 2*EM_PSIZE
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loi EM_WSIZE
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ngi EM_WSIZE
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ads EM_WSIZE
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9 ; destination address
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lal 0
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loi EM_PSIZE
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adp 2*EM_PSIZE
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loi EM_WSIZE ; size
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bls EM_WSIZE ; now we have a frame exactly as it was in setjmp,
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; and exactly at the same place
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str 0 ; restore LocalBase
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stl -EM_WSIZE ; saves the return value
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str 1 ; restores the StackPointer
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#ifdef __BSD4_2
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lol -3*EM_WSIZE
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dup EM_PSIZE
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lof 4*EM_PSIZE
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cal $sigsetmask
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asp EM_WSIZE
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lfr EM_WSIZE
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asp EM_WSIZE
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#endif
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lol -EM_WSIZE
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lae jmpbuf_addr
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sti EM_PSIZE ; save address of jmpbuf
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lol EM_PSIZE
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dup EM_WSIZE
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zne *3
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; of course, longjmp may not return 0!
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asp EM_WSIZE
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loc 1
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3
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ret EM_WSIZE
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end 3*EM_WSIZE
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ste retval ; save return value
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lal 0
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loi EM_PSIZE
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lae gtobuf
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blm 3*EM_PSIZE ; create GTO descriptor
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gto gtobuf ; and GTO
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end 0
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