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mu/apps/ex11.subx
Kartik Agaram bfcc0f858a 6182 - start of support for safe handles 
So far it's unclear how to do this in a series of small commits. Still
nibbling around the edges. In this commit we standardize some terminology:

The length of an array or stream is denominated in the high-level elements.
The _size_ is denominated in bytes.

The thing we encode into the type is always the size, not the length.

There's still an open question of what to do about the Mu `length` operator.
I'd like to modify it to provide the length. Currently it provides the
size. If I can't fix that I'll rename it.
2020-04-03 12:35:53 -07:00

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# 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
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