827dd4a7fe
One less error that's only in the bootstrap phase. On the other hand, for simplicity I got rid of the ability to override the Entry label. One less special case, but we're also going further from the ability to run subsets of layers. We haven't really been exercising it for a long time, though (commit 7842, March 2021 when we made baremetal the default).
270 lines
12 KiB
Plaintext
270 lines
12 KiB
Plaintext
# Checking null-terminated strings.
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#
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# By default we create strings as arrays of bytes, and all arrays have a 4-byte
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# size prefix.
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#
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# However, we sometimes need to deal with null-terminated strings when
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# interacting with the Linux kernel. This layer implements a function for
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# comparing a null-terminated 'kernel string' with a size-prefixed 'SubX
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# string'.
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#
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# To run (from the subx directory):
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# $ bootstrap/bootstrap translate 10[0-3]*.subx -o a.elf
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# $ bootstrap/bootstrap run a.elf # runs a series of tests
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# ...... # all tests pass
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#
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# (We can't yet run the tests when given a "test" commandline argument,
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# because checking for it would require the function being tested! Breakage
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# would cause tests to not run, rather than to fail as we'd like.)
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== code
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# instruction effective address register displacement immediate
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# . op subop mod rm32 base index scale r32
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# . 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
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#? Entry: # run all tests
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#? e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
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#? # syscall_exit(Num-test-failures)
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#? 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/ebx Num-test-failures/disp32 # copy *Num-test-failures to ebx
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#? e8/call syscall_exit/disp32
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kernel-string-equal?: # s: (addr kernel-string), benchmark: (addr array byte) -> result/eax: boolean
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# pseudocode:
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# n = benchmark->size
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# s1 = s
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# s2 = benchmark->data
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# i = 0
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# while (i < n)
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# c1 = *s1
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# c2 = *s2
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# if (c1 == 0) return false
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# if (c1 != c2) return false
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# ++s1, ++s2, ++i
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# return *s1 == 0
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#
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# registers:
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# i: ecx
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# n: edx
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# s1: edi
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# s2: esi
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# c1: eax
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# c2: ebx
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#
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# . prologue
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55/push-ebp
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89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
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# . save registers
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51/push-ecx
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52/push-edx
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53/push-ebx
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56/push-esi
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57/push-edi
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# var s1/edi: (addr byte) = s
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi
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# var n/edx: int = benchmark->size
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx
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8b/copy 0/mod/indirect 2/rm32/edx . . . 2/r32/edx . . # copy *edx to edx
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# var s2/esi: (addr byte) = benchmark->data
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0xc/disp8 . # copy *(ebp+12) to esi
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81 0/subop/add 3/mod/direct 6/rm32/esi . . . . . 4/imm32 # add to esi
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# var i/ecx: int = 0
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b9/copy-to-ecx 0/imm32/exit
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# var c1/eax: byte = 0
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b8/copy-to-eax 0/imm32
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# var c2/ebx: byte = 0
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bb/copy-to-ebx 0/imm32
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$kernel-string-equal?:loop:
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# if (i >= n) break
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39/compare 3/mod/direct 1/rm32/ecx . . . 2/r32/edx . . # compare ecx with edx
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7d/jump-if->= $kernel-string-equal?:break/disp8
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# c1 = *s1
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8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL
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# c2 = *s2
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8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 3/r32/BL . . # copy byte at *esi to BL
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# if (c1 == 0) return false
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3d/compare-eax-and 0/imm32/null
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74/jump-if-= $kernel-string-equal?:false/disp8
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# if (c1 != c2) return false
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39/compare 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # compare eax and ebx
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75/jump-if-!= $kernel-string-equal?:false/disp8
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# ++i
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41/increment-ecx
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# ++s1
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47/increment-edi
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# ++s2
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46/increment-esi
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eb/jump $kernel-string-equal?:loop/disp8
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$kernel-string-equal?:break:
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# return *s1 == 0
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8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL
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3d/compare-eax-and 0/imm32/null
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75/jump-if-!= $kernel-string-equal?:false/disp8
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$kernel-string-equal?:true:
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b8/copy-to-eax 1/imm32
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eb/jump $kernel-string-equal?:end/disp8
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$kernel-string-equal?:false:
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b8/copy-to-eax 0/imm32
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$kernel-string-equal?:end:
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# . restore registers
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5f/pop-to-edi
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5e/pop-to-esi
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5b/pop-to-ebx
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5a/pop-to-edx
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59/pop-to-ecx
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# . epilogue
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89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
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5d/pop-to-ebp
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c3/return
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# - tests
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test-compare-null-kernel-string-with-empty-array:
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# eax = kernel-string-equal?(Null-kernel-string, "")
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# . . push args
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68/push ""/imm32
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68/push Null-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 1, msg)
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# . . push args
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68/push "F - test-compare-null-kernel-string-with-empty-array"/imm32
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68/push 1/imm32/true
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-null-kernel-string-with-non-empty-array:
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# eax = kernel-string-equal?(Null-kernel-string, "Abc")
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# . . push args
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68/push "Abc"/imm32
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68/push Null-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 0, msg)
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# . . push args
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68/push "F - test-compare-null-kernel-string-with-non-empty-array"/imm32
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68/push 0/imm32/false
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-kernel-string-with-equal-array:
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# eax = kernel-string-equal?(_test-Abc-kernel-string, "Abc")
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# . . push args
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68/push "Abc"/imm32
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68/push _test-Abc-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 1, msg)
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# . . push args
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68/push "F - test-compare-kernel-string-with-equal-array"/imm32
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68/push 1/imm32/true
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-kernel-string-with-inequal-array:
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# eax = kernel-string-equal?(_test-Abc-kernel-string, "Adc")
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# . . push args
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68/push "Adc"/imm32
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68/push _test-Abc-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 0, msg)
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# . . push args
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68/push "F - test-compare-kernel-string-with-equal-array"/imm32
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68/push 0/imm32/false
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-kernel-string-with-empty-array:
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# eax = kernel-string-equal?(_test-Abc-kernel-string, "")
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# . . push args
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68/push ""/imm32
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68/push _test-Abc-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 0, msg)
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# . . push args
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68/push "F - test-compare-kernel-string-with-equal-array"/imm32
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68/push 0/imm32/false
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-kernel-string-with-shorter-array:
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# eax = kernel-string-equal?(_test-Abc-kernel-string, "Ab")
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# . . push args
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68/push "Ab"/imm32
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68/push _test-Abc-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 0, msg)
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# . . push args
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68/push "F - test-compare-kernel-string-with-shorter-array"/imm32
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68/push 0/imm32/false
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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test-compare-kernel-string-with-longer-array:
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# eax = kernel-string-equal?(_test-Abc-kernel-string, "Abcd")
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# . . push args
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68/push "Abcd"/imm32
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68/push _test-Abc-kernel-string/imm32
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# . . call
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e8/call kernel-string-equal?/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-ints-equal(eax, 0, msg)
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# . . push args
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68/push "F - test-compare-kernel-string-with-longer-array"/imm32
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68/push 0/imm32/false
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50/push-eax
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# . . call
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e8/call check-ints-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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c3/return
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== data
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Null-kernel-string: # (addr kernel-string)
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00/null
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_test-Abc-kernel-string: # (addr kernel-string)
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41/A 62/b 63/c 00/null
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# . . vim:nowrap:textwidth=0
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