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https://github.com/Zeal-Operating-System/ZealOS.git
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50 lines
1.1 KiB
HolyC
50 lines
1.1 KiB
HolyC
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asm {
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PUT_DEC_U64::
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//RAX is number to print in decimal.
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//Preserves all regs.
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PUSH RBP
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MOV RBP,RSP
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SUB RSP,24 //24 char buffer on stack
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//$LK,"Save regs",A="FF:::/Kernel/KernelA.HH,PUSH_C_REGS"$ which C code is free to clobber. We don't have to for C callers,
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//but this function will be nice for ASM callers if it saves all regs.
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PUSH_C_REGS
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PUSH RSI //See $LK,"REGG_LOCAL_VARS",A="MN:REGG_LOCAL_VARS"$&$LK,"REGG_LOCAL_NON_PTR_VARS",A="MN:REGG_LOCAL_NON_PTR_VARS"$
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LEA RSI,-1[RBP] //Load addr of end of buffer.
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//We picked RSI because of PUT_STR
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//We'll move bwd
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MOV U8 [RSI],0 //Terminator
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TEST RAX,RAX //Special case -- zero
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JNZ @@05
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DEC RSI
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MOV U8 [RSI],'0'
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JMP @@15
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@@05: MOV RBX,10 //Divides by 10
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@@10: XOR RDX,RDX
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DIV RBX //RAX=(RDX:RAX)/RBX with remainder in RDX
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ADD RDX,'0'
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DEC RSI
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MOV U8 [RSI],DL
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TEST RAX,RAX
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JNZ @@10
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@@15: CALL PUT_STR
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POP RSI
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POP_C_REGS
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LEAVE
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RET
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_DO_IT:: //The convention is C-callable routines have underscores.
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MOV RAX,122333221
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CALL PUT_DEC_U64
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MOV RAX,'\n'
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CALL PUT_CHARS
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RET
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}
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Call(_DO_IT);
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