mu - Soul of a tiny new machine. More thorough tests → More comprehensible and rewrite-friendly software → More resilient society.

	Commit message (Collapse)	Author	Age	Files	Lines
*	.	Kartik Agaram	2021-06-26	1	-4/+4
\| \| \| \| \|	Switch html rendering to my current colorscheme with a little less blue, for night browsing.
*	.	Kartik Agaram	2021-06-24	1	-3/+3
\| \| \| \|	Switch html rendering to a white background.
*	.	Kartik Agaram	2021-06-15	1	-6/+21
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*	.	Kartik Agaram	2021-04-21	1	-3/+3
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*	.	Kartik Agaram	2021-03-23	1	-0/+93

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Mu - linux/104new-segment.subx</title> <meta name="Generator" content="Vim/8.1"> <meta name="plugin-version" content="vim8.1_v1"> <meta name="syntax" content="none"> <meta name="settings" content="number_lines,use_css,no_foldcolumn,expand_tabs,line_ids,prevent_copy="> <meta name="colorscheme" content="minimal-light"> <style type="text/css">  </style> <script type='text/javascript'>  </script> </head> <body onload='JumpToLine();'> <a href='https://github.com/akkartik/mu/blob/main/linux/104new-segment.subx'>https://github.com/akkartik/mu/blob/main/linux/104new-segment.subx</a> <pre id='vimCodeElement'> 1 # Create a new segment (pool of memory for allocating chunks from) in the form 2 # of an *allocation descriptor* that can be passed to the memory allocator 3 # (defined in a later layer). 4 # 5 # Currently an allocation descriptor consists of just the bounds of the pool of 6 # available memory: 7 # 8 # curr: address 9 # end: address 10 # 11 # This isn't enough information to reclaim individual allocations. We can't 12 # support arbitrary reclamation yet. 13 14 == code 15 # instruction effective address register displacement immediate 16 # . op subop mod rm32 base index scale r32 17 # . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes 18 19 Entry: # manual test 20 # var ad/ecx: allocation-descriptor 21 68/push 0/imm32/limit 22 68/push 0/imm32/curr 23 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx 24 # new-segment(0x1000, ad) 25 # . . push args 26 51/push-ecx 27 68/push 0x1000/imm32 28 # . . call 29 e8/call <a href='104new-segment.subx.html#L40'>new-segment</a>/disp32 30 # . . discard args 31 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 32 # var eax: (addr _) = ad->curr 33 8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax 34 # write to *eax to check that we have access to the newly-allocated segment 35 c7 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0x34/imm32 # copy to *eax 36 # syscall(exit, eax) 37 89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx 38 e8/call <a href='000init.subx.html#L18'>syscall_exit</a>/disp32 39 40 new-segment: # len: int, ad: (addr allocation-descriptor) 41 # . prologue 42 55/push-ebp 43 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp 44 # . save registers 45 50/push-eax 46 53/push-ebx 47 # copy len to _mmap-new-segment->len 48 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax 49 89/copy 0/mod/indirect 5/rm32/.disp32 . . 0/r32/eax $_mmap-new-segment:len/disp32 # copy eax to *$_mmap-new-segment:len 50 # mmap(_mmap-new-segment) 51 bb/copy-to-ebx <a href='104new-segment.subx.html#L73'>_mmap-new-segment</a>/imm32 52 e8/call <a href='000init.subx.html#L71'>syscall_mmap</a>/disp32 53 # copy {eax, eax+len} to *ad 54 # . ebx = ad 55 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 3/r32/ebx 0xc/disp8 . # copy *(ebp+12) to ebx 56 # . ad->curr = eax 57 89/copy 0/mod/indirect 3/rm32/ebx . . . 0/r32/eax . . # copy eax to *ebx 58 # . ad->end = eax+len 59 03/add 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # add *(ebp+8) to eax 60 89/copy 1/mod/*+disp8 3/rm32/ebx . . . 0/r32/eax 4/disp8 . # copy eax to *(ebx+4) 61 $new-segment:end: 62 # . restore registers 63 5b/pop-to-ebx 64 58/pop-to-eax 65 # . epilogue 66 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 67 5d/pop-to-ebp 68 c3/return 69 70 == data 71 72 # various constants used here were found in the Linux sources (search for file mman-common.h) 73 _mmap-new-segment: # mmap_arg_struct 74 # addr 75 0/imm32 76 $_mmap-new-segment:len: 77 # len 78 0/imm32 79 # protection flags 80 3/imm32 # PROT_READ | PROT_WRITE 81 # sharing flags 82 0x22/imm32 # MAP_PRIVATE | MAP_ANONYMOUS 83 # fd 84 -1/imm32 # since MAP_ANONYMOUS is specified 85 # offset 86 0/imm32 # since MAP_ANONYMOUS is specified 87 88 # . . vim:nowrap:textwidth=0 </pre> </body> </html>