diff options
Diffstat (limited to 'linux/ex11.subx')
| -rw-r--r-- | linux/ex11.subx | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/linux/ex11.subx b/linux/ex11.subx new file mode 100644 index 00000000..9ff43a73 --- /dev/null +++ b/linux/ex11.subx @@ -0,0 +1,355 @@ +# Null-terminated vs size-prefixed ascii strings. +# +# By default we create strings with a 4-byte size prefix rather than a null suffix. +# However we still need null-prefixed strings when interacting with the Linux +# kernel in a few places. This layer implements a function for comparing +# a null-terminated 'kernel string' with a size-prefixed 'SubX string'. +# +# To run: +# $ ./bootstrap translate init.linux apps/ex11.subx -o apps/ex11 +# $ ./bootstrap run apps/ex11 # runs a series of tests +# ...... # all tests pass +# +# (We can't yet run the tests when given a "test" commandline argument, +# because checking for it would require the function being tested! Breakage +# would cause tests to not run, rather than to fail as we'd like.) + +== code +# instruction effective address register displacement immediate +# . op subop mod rm32 base index scale r32 +# . 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 + +Entry: # run all tests + e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. + # exit(eax) + 89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx + e8/call syscall_exit/disp32 + +# compare a null-terminated ascii string with a more idiomatic size-prefixed byte array +# reason for the name: the only place we should have null-terminated ascii strings is from commandline args +kernel-string-equal?: # s: null-terminated ascii string, benchmark: size-prefixed ascii string -> eax: boolean + # pseudocode: + # n = benchmark->size + # s1 = s + # s2 = benchmark->data + # i = 0 + # while i < n + # c1 = *s1 + # c2 = *s2 + # if (c1 == 0) return false + # if (c1 != c2) return false + # ++s1, ++s2, ++i + # return *s1 == 0 + # + # registers: + # i: ecx + # n: edx + # s1: edi + # s2: esi + # c1: eax + # c2: ebx + # + # . prologue + 55/push-ebp + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + # . save registers + 51/push-ecx + 52/push-edx + 53/push-ebx + 56/push-esi + 57/push-edi + # s1/edi = s + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi + # n/edx = benchmark->size + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx + 8b/copy 0/mod/indirect 2/rm32/edx . . . 2/r32/edx . . # copy *edx to edx + # s2/esi = benchmark->data + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0xc/disp8 . # copy *(ebp+12) to esi + 81 0/subop/add 3/mod/direct 6/rm32/esi . . . . . 4/imm32 # add to esi + # i/ecx = c1/eax = c2/ebx = 0 + b9/copy-to-ecx 0/imm32/exit + b8/copy-to-eax 0/imm32 + bb/copy-to-ebx 0/imm32 +$kernel-string-equal?:loop: + # if (i >= n) break + 39/compare 3/mod/direct 1/rm32/ecx . . . 2/r32/edx . . # compare ecx with edx + 7d/jump-if->= $kernel-string-equal?:break/disp8 + # c1 = *s1 + 8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL + # c2 = *s2 + 8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 3/r32/BL . . # copy byte at *esi to BL + # if (c1 == 0) return false + 3d/compare-eax-and 0/imm32/null + 74/jump-if-= $kernel-string-equal?:false/disp8 + # if (c1 != c2) return false + 39/compare 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # compare eax and ebx + 75/jump-if-!= $kernel-string-equal?:false/disp8 + # ++i + 41/increment-ecx + # ++s1 + 47/increment-edi + # ++s2 + 46/increment-esi + eb/jump $kernel-string-equal?:loop/disp8 +$kernel-string-equal?:break: + # return *s1 == 0 + 8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 0/r32/AL . . # copy byte at *edi to AL + 3d/compare-eax-and 0/imm32/null + 75/jump-if-!= $kernel-string-equal?:false/disp8 +$kernel-string-equal?:true: + b8/copy-to-eax 1/imm32 + eb/jump $kernel-string-equal?:end/disp8 +$kernel-string-equal?:false: + b8/copy-to-eax 0/imm32 +$kernel-string-equal?:end: + # . restore registers + 5f/pop-to-edi + 5e/pop-to-esi + 5b/pop-to-ebx + 5a/pop-to-edx + 59/pop-to-ecx + # . epilogue + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +# - tests + +test-compare-null-kernel-string-with-empty-array: + # eax = kernel-string-equal?(Null-kernel-string, "") + # . . push args + 68/push ""/imm32 + 68/push Null-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 1, msg) + # . . push args + 68/push "F - test-compare-null-kernel-string-with-empty-array"/imm32 + 68/push 1/imm32/true + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-null-kernel-string-with-non-empty-array: + # eax = kernel-string-equal?(Null-kernel-string, "Abc") + # . . push args + 68/push "Abc"/imm32 + 68/push Null-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-compare-null-kernel-string-with-non-empty-array"/imm32 + 68/push 0/imm32/false + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-kernel-string-with-equal-array: + # eax = kernel-string-equal?(_test-Abc-kernel-string, "Abc") + # . . push args + 68/push "Abc"/imm32 + 68/push _test-Abc-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 1, msg) + # . . push args + 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 + 68/push 1/imm32/true + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-kernel-string-with-inequal-array: + # eax = kernel-string-equal?(_test-Abc-kernel-string, "Adc") + # . . push args + 68/push "Adc"/imm32 + 68/push _test-Abc-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 + 68/push 0/imm32/false + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-kernel-string-with-empty-array: + # eax = kernel-string-equal?(_test-Abc-kernel-string, "") + # . . push args + 68/push ""/imm32 + 68/push _test-Abc-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-compare-kernel-string-with-equal-array"/imm32 + 68/push 0/imm32/false + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-kernel-string-with-shorter-array: + # eax = kernel-string-equal?(_test-Abc-kernel-string, "Ab") + # . . push args + 68/push "Ab"/imm32 + 68/push _test-Abc-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-compare-kernel-string-with-shorter-array"/imm32 + 68/push 0/imm32/false + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +test-compare-kernel-string-with-longer-array: + # eax = kernel-string-equal?(_test-Abc-kernel-string, "Abcd") + # . . push args + 68/push "Abcd"/imm32 + 68/push _test-Abc-kernel-string/imm32 + # . . call + e8/call kernel-string-equal?/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-ints-equal(eax, 0, msg) + # . . push args + 68/push "F - test-compare-kernel-string-with-longer-array"/imm32 + 68/push 0/imm32/false + 50/push-eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + c3/return + +# - helpers + +# print msg to stderr if a != b, otherwise print "." +check-ints-equal: # (a: int, b: int, msg: (addr array byte)) -> boolean + # . prologue + 55/push-ebp + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + # . save registers + 51/push-ecx + 53/push-ebx + # load args into eax, ebx and ecx + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 3/r32/ebx 0xc/disp8 . # copy *(ebp+12) to ebx + # if (eax == b/ebx) print('.') and return + 39/compare 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # compare eax and ebx + 75/jump-if-unequal $check-ints-equal:else/disp8 + # . write-stderr('.') + # . . push args + 68/push "."/imm32 + # . . call + e8/call write-stderr/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # . return + eb/jump $check-ints-equal:end/disp8 + # otherwise print(msg) +$check-ints-equal:else: + # copy msg into ecx + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0x10/disp8 . # copy *(ebp+16) to ecx + # print(ecx) + # . . push args + 51/push-ecx + # . . call + e8/call write-stderr/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # print newline + # . . push args + 68/push Newline/imm32 + # . . call + e8/call write-stderr/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp +$check-ints-equal:end: + # . restore registers + 5b/pop-to-ebx + 59/pop-to-ecx + # end + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +write-stderr: # s: (addr array byte) -> <void> + # . prologue + 55/push-ebp + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + # . save registers + 50/push-eax + 51/push-ecx + 52/push-edx + 53/push-ebx + # syscall(write, 2/stderr, (data) s+4, (size) *s) + # . . fd = 2 (stderr) + bb/copy-to-ebx 2/imm32 + # . . x = s+4 + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx + 81 0/subop/add 3/mod/direct 1/rm32/ecx . . . . . 4/imm32 # add to ecx + # . . size = *s + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 8/disp8 . # copy *(ebp+8) to edx + 8b/copy 0/mod/indirect 2/rm32/edx . . . 2/r32/edx . . # copy *edx to edx + # . . syscall + e8/call syscall_write/disp32 + # . restore registers + 5b/pop-to-ebx + 5a/pop-to-edx + 59/pop-to-ecx + 58/pop-to-eax + # . end + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +== data + +Newline: + # size + 1/imm32 + # data + 0a/newline + +# for kernel-string-equal tests +Null-kernel-string: + 00/null + +_test-Abc-kernel-string: + 41/A 62/b 63/c 00/null + +# . . vim:nowrap:textwidth=0 |