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

	Commit message (Expand)	Author	Age	Files	Lines
*	.	Kartik Agaram	2021-05-18	1	-167/+165
*	.	Kartik Agaram	2021-04-21	1	-3/+3
*	.	Kartik Agaram	2021-03-23	1	-0/+230

<!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/103kernel-string-equal.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-dark"> <style type="text/css">  </style> <script type='text/javascript'>  </script> </head> <body onload='JumpToLine();'> <a href='https://github.com/akkartik/mu/blob/main/linux/103kernel-string-equal.subx'>https://github.com/akkartik/mu/blob/main/linux/103kernel-string-equal.subx</a> <pre id='vimCodeElement'> 1 # Checking null-terminated strings. 2 # 3 # By default we create strings as arrays of bytes, and all arrays have a 4-byte 4 # size prefix. 5 # 6 # However, we sometimes need to deal with null-terminated strings when 7 # interacting with the Linux kernel. This layer implements a function for 8 # comparing a null-terminated 'kernel string' with a size-prefixed 'SubX 9 # string'. 10 # 11 # To run (from the subx directory): 12 # $ bootstrap/bootstrap translate 10[0-3]*.subx -o a.elf 13 # $ bootstrap/bootstrap run a.elf # runs a series of tests 14 # ...... # all tests pass 15 # 16 # (We can't yet run the tests when given a "test" commandline argument, 17 # because checking for it would require the function being tested! Breakage 18 # would cause tests to not run, rather than to fail as we'd like.) 19 20 == code 21 # instruction effective address register displacement immediate 22 # . op subop mod rm32 base index scale r32 23 # . 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 24 25 Entry: # run all tests 26 e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. 27 # syscall(exit, Num-test-failures) 28 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/ebx <a href='102test.subx.html#L89'>Num-test-failures</a>/disp32 # copy *Num-test-failures to ebx 29 e8/call <a href='000init.subx.html#L18'>syscall_exit</a>/disp32 30 31 kernel-string-equal?: # s: (addr kernel-string), benchmark: (addr array byte) -> result/eax: boolean 32 # pseudocode: 33 # n = benchmark->size 34 # s1 = s 35 # s2 = benchmark->data 36 # i = 0 37 # while (i < n) 38 # c1 = *s1 39 # c2 = *s2 40 # if (c1 == 0) return false 41 # if (c1 != c2) return false 42 # ++s1, ++s2, ++i 43 # return *s1 == 0 44 # 45 # registers: 46 # i: ecx 47 # n: edx 48 # s1: edi 49 # s2: esi 50 # c1: eax 51 # c2: ebx 52 # 53 # . prologue 54 55/push-ebp 55 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp 56 # . save registers 57 51/push-ecx 58 52/push-edx 59 53/push-ebx 60 56/push-esi 61 57/push-edi 62 # var s1/edi: (addr byte) = s 63 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi 64 # var n/edx: int = benchmark->size 65 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx 66 8b/copy 0/mod/indirect 2/rm32/edx . . . 2/r32/edx . . # copy *edx to edx 67 # var s2/esi: (addr byte) = benchmark->data 68 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0xc/disp8 . # copy *(ebp+12) to esi 69 81 0/subop/add 3/mod/direct 6/rm32/esi . . . . . 4/imm32 # add to esi 70 # var i/ecx: int = 0 71 b9/copy-to-ecx 0/imm32/exit 72 # var c1/eax: byte = 0 73 b8/copy-to-eax 0/imm32 74 # var c2/ebx: byte = 0 75 bb/copy-to-ebx 0/imm32 76 $kernel-string-equal?:loop: 77 # if (i >= n) break 78 39/compare 3/mod/direct 1/rm32/ecx . . . 2/r32/edx . . # compare ecx with edx 79 7d/jump-if->= $kernel-string-equal?:break/disp8 80 # c1 = *s1 81 8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL 82 # c2 = *s2 83 8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 3/r32/BL . . # copy byte at *esi to BL 84 # if (c1 == 0) return false 85 3d/compare-eax-and 0/imm32/null 86 74/jump-if-= $kernel-string-equal?:false/disp8 87 # if (c1 != c2) return false 88 39/compare 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # compare eax and ebx 89 75/jump-if-!= $kernel-string-equal?:false/disp8 90 # ++i 91 41/increment-ecx 92 # ++s1 93 47/increment-edi 94 # ++s2 95 46/increment-esi 96 eb/jump $kernel-string-equal?:loop/disp8 97 $kernel-string-equal?:break: 98 # return *s1 == 0 99 8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL 100 3d/compare-eax-and 0/imm32/null 101 75/jump-if-!= $kernel-string-equal?:false/disp8 102 $kernel-string-equal?:true: 103 b8/copy-to-eax 1/imm32 104 eb/jump $kernel-string-equal?:end/disp8 105 $kernel-string-equal?:false: 106 b8/copy-to-eax 0/imm32 107 $kernel-string-equal?:end: 108 # . restore registers 109 5f/pop-to-edi 110 5e/pop-to-esi 111 5b/pop-to-ebx 112 5a/pop-to-edx 113 59/pop-to-ecx 114 # . epilogue 115 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 116 5d/pop-to-ebp 117 c3/return 118 119 # - tests 120 121 test-compare-null-kernel-string-with-empty-array: 122 # eax = kernel-string-equal?(Null-kernel-string, "") 123 # . . push args 124 68/push ""/imm32 125 68/push <a href='103kernel-string-equal.subx.html#L263'>Null-kernel-string</a>/imm32 126 # . . call 127 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 128 # . . discard args 129 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 130 # check-ints-equal(eax, 1, msg) 131 # . . push args 132 68/push "F - test-compare-null-kernel-string-with-empty-array"/imm32 133 68/push 1/imm32/true 134 50/push-eax 135 # . . call 136 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 137 # . . discard args 138 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 139 c3/return 140 141 test-compare-null-kernel-string-with-non-empty-array: 142 # eax = kernel-string-equal?(Null-kernel-string, "Abc") 143 # . . push args 144 68/push "Abc"/imm32 145 68/push <a href='103kernel-string-equal.subx.html#L263'>Null-kernel-string</a>/imm32 146 # . . call 147 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 148 # . . discard args 149 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 150 # check-ints-equal(eax, 0, msg) 151 # . . push args 152 68/push "F - test-compare-null-kernel-string-with-non-empty-array"/imm32 153 68/push 0/imm32/false 154 50/push-eax 155 # . . call 156 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 157 # . . discard args 158 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 159 c3/return 160 161 test-compare-kernel-string-with-equal-array: 162 # eax = kernel-string-equal?(_test-Abc-kernel-string, "Abc") 163 # . . push args 164 68/push "Abc"/imm32 165 68/push <a href='103kernel-string-equal.subx.html#L266'>_test-Abc-kernel-string</a>/imm32 166 # . . call 167 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 168 # . . discard args 169 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 170 # check-ints-equal(eax, 1, msg) 171 # . . push args 172 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 173 68/push 1/imm32/true 174 50/push-eax 175 # . . call 176 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 177 # . . discard args 178 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 179 c3/return 180 181 test-compare-kernel-string-with-inequal-array: 182 # eax = kernel-string-equal?(_test-Abc-kernel-string, "Adc") 183 # . . push args 184 68/push "Adc"/imm32 185 68/push <a href='103kernel-string-equal.subx.html#L266'>_test-Abc-kernel-string</a>/imm32 186 # . . call 187 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 188 # . . discard args 189 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 190 # check-ints-equal(eax, 0, msg) 191 # . . push args 192 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 193 68/push 0/imm32/false 194 50/push-eax 195 # . . call 196 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 197 # . . discard args 198 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 199 c3/return 200 201 test-compare-kernel-string-with-empty-array: 202 # eax = kernel-string-equal?(_test-Abc-kernel-string, "") 203 # . . push args 204 68/push ""/imm32 205 68/push <a href='103kernel-string-equal.subx.html#L266'>_test-Abc-kernel-string</a>/imm32 206 # . . call 207 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 208 # . . discard args 209 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 210 # check-ints-equal(eax, 0, msg) 211 # . . push args 212 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 213 68/push 0/imm32/false 214 50/push-eax 215 # . . call 216 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 217 # . . discard args 218 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 219 c3/return 220 221 test-compare-kernel-string-with-shorter-array: 222 # eax = kernel-string-equal?(_test-Abc-kernel-string, "Ab") 223 # . . push args 224 68/push "Ab"/imm32 225 68/push <a href='103kernel-string-equal.subx.html#L266'>_test-Abc-kernel-string</a>/imm32 226 # . . call 227 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 228 # . . discard args 229 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 230 # check-ints-equal(eax, 0, msg) 231 # . . push args 232 68/push "F - test-compare-kernel-string-with-shorter-array"/imm32 233 68/push 0/imm32/false 234 50/push-eax 235 # . . call 236 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 237 # . . discard args 238 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 239 c3/return 240 241 test-compare-kernel-string-with-longer-array: 242 # eax = kernel-string-equal?(_test-Abc-kernel-string, "Abcd") 243 # . . push args 244 68/push "Abcd"/imm32 245 68/push <a href='103kernel-string-equal.subx.html#L266'>_test-Abc-kernel-string</a>/imm32 246 # . . call 247 e8/call <a href='103kernel-string-equal.subx.html#L31'>kernel-string-equal?</a>/disp32 248 # . . discard args 249 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 250 # check-ints-equal(eax, 0, msg) 251 # . . push args 252 68/push "F - test-compare-kernel-string-with-longer-array"/imm32 253 68/push 0/imm32/false 254 50/push-eax 255 # . . call 256 e8/call <a href='102test.subx.html#L23'>check-ints-equal</a>/disp32 257 # . . discard args 258 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 259 c3/return 260 261 == data 262 263 Null-kernel-string: # (addr kernel-string) 264 00/null 265 266 _test-Abc-kernel-string: # (addr kernel-string) 267 41/A 62/b 63/c 00/null 268 269 # . . vim:nowrap:textwidth=0 </pre> </body> </html>