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
*	5924	Kartik Agaram	2020-01-27	1	-2/+2
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*	5897 - rename comparison instructions	Kartik Agaram	2020-01-16	1	-1/+1
\| \| \| \| \| \| \|	Signed and unsigned don't quite capture the essence of what the different combinations of x86 flags are doing for SubX. The crucial distinction is that one set of comparison operators is for integers and the second is for addresses.
*	5876 - address -> addr	Kartik Agaram	2020-01-03	1	-1/+1
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*	5804	Kartik Agaram	2019-12-08	1	-2/+2
\| \| \| \| \|	Try to make the comments consistent with the type system we'll eventually have.
*	5790	Kartik Agaram	2019-12-05	1	-8/+8
\| \| \| \| \| \|	Standardize conventions for labels within objects in the data segment. We're going to use this in a new tool.
*	5714	Kartik Agaram	2019-10-25	1	-16/+8
\| \| \| \|	Replace calculations of constants with labels.
*	5700	Kartik Agaram	2019-10-17	1	-1/+1
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*	5698	Kartik Agaram	2019-10-15	1	-2/+2
\| \| \| \|	Thanks Andrew Owen for reporting this typo.
*	5675 - move helpers from subx-common into layers	Kartik Agaram	2019-09-19	1	-0/+249
	This undoes 5672 in favor of a new plan: Layers 000 - 099 are for running without syntax sugar. We use them for building syntax-sugar passes. Layers 100 and up are for running with all syntax sugar. The layers are arranged in approximate order so more phases rely on earlier layers than later ones. I plan to not use intermediate syntax sugar (just sigils without calls, or sigils and calls without braces) anywhere except in the specific passes implementing them.

# Helper to dynamically allocate memory on the heap. # # We'd like to be able to write tests for functions that allocate memory, # making assertions on the precise addresses used. To achieve this we'll pass # in an *allocation descriptor* to allocate from. # # Allocation descriptors are also useful outside of tests. Assembly and machine # code are of necessity unsafe languages, and one of the most insidious kinds # of bugs unsafe languages expose us to are dangling pointers to memory that # has been freed and potentially even reused for something totally different. # To reduce the odds of such "use after free" errors, SubX programs tend to not # reclaim and reuse dynamically allocated memory. (Running out of memory is far # easier to debug.) Long-running programs that want to reuse memory are mostly # on their own to be careful. However, they do get one bit of help: they can # carve out chunks of memory and then allocate from them manually using this # very same 'allocate' helper. They just need a new allocation descriptor for # their book-keeping. == data # A default allocation descriptor for programs to use. Heap: # (ref allocation-descriptor) # curr 0/imm32 # limit 0/imm32 # a reasonable default Heap-size: # (ref int) 0x200000/imm32/2MB == 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 # Let's start initializing the default allocation descriptor. Entry: # initialize heap # . Heap = new-segment(Heap-size) # . . push args 68/push Heap/imm32 ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Heap-size/disp32 # push *Heap-size # . . call e8/call new-segment/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. $array-equal-main:end: # syscall(exit, Num-test-failures) 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/ebx Num-test-failures/disp32 # copy *Num-test-failures to ebx b8/copy-to-eax 1/imm32/exit cd/syscall 0x80/imm8 # Claim the next 'n' bytes of memory starting at ad->curr and update ad->curr. # Abort if there isn't enough memory in 'ad'. allocate: # ad : (address allocation-descriptor), n : int -> address-or-null/eax : (address _) # . 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 # ecx = ad 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx # save ad->curr 8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax # check if there's enough space # . edx = ad->curr + n 89/copy 3/mod/direct 2/rm32/edx . . . 0/r32/eax . . # copy eax to edx 03/add 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # add *(ebp+12) to edx 3b/compare 1/mod/*+disp8 1/rm32/ecx . . . 2/r32/edx 4/disp8 . # compare edx with *(ecx+4) 73/jump-if-greater-or-equal-signed $allocate:abort/disp8 $allocate:commit: # update ad->curr 89/copy 0/mod/indirect 1/rm32/ecx . . . 2/r32/edx . . # copy edx to *ecx $allocate:end: # . restore registers 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 $allocate:abort: # . _write(2/stderr, error) # . . push args 68/push "allocate: failed to allocate\n"/imm32 68/push 2/imm32/stderr # . . call e8/call _write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . syscall(exit, 1) bb/copy-to-ebx 1/imm32 b8/copy-to-eax 1/imm32/exit cd/syscall 0x80/imm8 # never gets here test-allocate-success: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var ad/ecx : (ref allocation-descriptor) = {11, 15} 68/push 0xf/imm32/limit 68/push 0xb/imm32/curr 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # var eax : (handle byte) = allocate(ad, 3) # . . push args 68/push 3/imm32 51/push-ecx # . . call e8/call allocate/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # check-ints-equal(eax, 11, msg) # . . push args 68/push "F - test-allocate-success: returns current pointer of allocation descriptor"/imm32 68/push 0xb/imm32 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 # check-ints-equal(ad->curr, 14, msg) # . . push args 68/push "F - test-allocate-success: updates allocation descriptor"/imm32 68/push 0xe/imm32 ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return _pending-test-allocate-failure: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var ad/ecx : (ref allocation-descriptor) = {11, 15} 68/push 0xf/imm32/limit 68/push 0xb/imm32/curr 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # var eax : (handle byte) = allocate(ad, 6) # . . push args 68/push 6/imm32 51/push-ecx # . . call e8/call allocate/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-allocate-failure: returns null"/imm32 68/push 0/imm32 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 # no change to ad->curr # . check-ints-equal(ad->curr, 11) # . . push args 68/push "F - test-allocate-failure: updates allocation descriptor"/imm32 68/push 0xb/imm32 ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # helper: create a nested allocation descriptor (useful for tests) allocate-region: # ad : (address allocation-descriptor), n : int -> new-ad : (handle allocation-descriptor) # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx # eax = allocate(ad, n) # . . push args ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) # . . call e8/call allocate/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # if (eax == 0) abort 3d/compare-eax-and 0/imm32 74/jump-if-equal $allocate-region:abort/disp8 # earmark 8 bytes at the start for a new allocation descriptor # . *eax = eax + 8 89/copy 3/mod/direct 1/rm32/ecx . . . 0/r32/eax . . # copy eax to ecx 81 0/subop/add 3/mod/direct 1/rm32/ecx . . . . . 8/imm32 # add to ecx 89/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy ecx to *eax # . *(eax+4) = eax + n 89/copy 3/mod/direct 1/rm32/ecx . . . 0/r32/eax . . # copy eax to ecx 03/add 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0xc/disp8 . # add *(ebp+12) to ecx 89/copy 1/mod/*+disp8 0/rm32/eax . . . 1/r32/ecx 4/disp8 . # copy ecx to *(eax+4) # . restore registers 59/pop-to-ecx # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # We could create a more general '$abort' jump target, but then we'd need to do # a conditional jump followed by loading the error message and an unconditional # jump. Or we'd need to unconditionally load the error message before a # conditional jump, even if it's unused the vast majority of the time. This way # we bloat a potentially cold segment in RAM so we can abort with a single # instruction. $allocate-region:abort: # . _write(2/stderr, error) # . . push args 68/push "allocate-region: failed to allocate\n"/imm32 68/push 2/imm32/stderr # . . call e8/call _write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . syscall(exit, 1) bb/copy-to-ebx 1/imm32 b8/copy-to-eax 1/imm32/exit cd/syscall 0x80/imm8 # never gets here # . . vim:nowrap:textwidth=0