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
*	7842 - new directory organization	Kartik K. Agaram	2021-03-03	1	-0/+121
	Baremetal is now the default build target and therefore has its sources at the top-level. Baremetal programs build using the phase-2 Mu toolchain that requires a Linux kernel. This phase-2 codebase which used to be at the top-level is now under the linux/ directory. Finally, the phase-2 toolchain, while self-hosting, has a way to bootstrap from a C implementation, which is now stored in linux/bootstrap. The bootstrap C implementation uses some literate programming tools that are now in linux/bootstrap/tools. So the whole thing has gotten inverted. Each directory should build one artifact and include the main sources (along with standard library). Tools used for building it are relegated to sub-directories, even though those tools are often useful in their own right, and have had lots of interesting programs written using them. A couple of things have gotten dropped in this process: - I had old ways to run on just a Linux kernel, or with a Soso kernel. No more. - I had some old tooling for running a single test at the cursor. I haven't used that lately. Maybe I'll bring it back one day. The reorg isn't done yet. Still to do: - redo documentation everywhere. All the README files, all other markdown, particularly vocabulary.md. - clean up how-to-run comments at the start of programs everywhere - rethink what to do with the html/ directory. Do we even want to keep supporting it? In spite of these shortcomings, all the scripts at the top-level, linux/ and linux/bootstrap are working. The names of the scripts also feel reasonable. This is a good milestone to take stock at.

# read: analogously to write, support reading from in-memory streams in # addition to file descriptors. # # We can pass it either a file descriptor or an address to a stream. If a # file descriptor is passed in, we _read from it using the right syscall. If a # stream is passed in (a fake file descriptor), we read from it instead. This # lets us initialize input for tests. # # A little counter-intuitively, the output of 'read' ends up in.. a stream. So # tests end up doing a redundant copy. Why? Well, consider the alternatives: # # a) Reading into a string, and returning a pointer to the end of the read # region, or a count of bytes written. Now this count or end pointer must be # managed separately by the caller, which can be error-prone. # # b) Having 'read' return a buffer that it allocates. But there's no way to # know in advance how large to make the buffer. If you read less than the # size of the buffer you again end up needing to manage initialized vs # uninitialized memory. # # c) Creating more helpful variants like 'read-byte' or 'read-until' which # also can take a file descriptor or stream, just like 'write'. But such # primitives don't exist in the Linux kernel, so we'd be implementing them # somehow, either with more internal buffering or by making multiple # syscalls. # # Reading into a stream avoids these problems. The buffer is externally # provided and the caller has control over where it's allocated, its lifetime, # and so on. The buffer's read and write pointers are internal to it so it's # easier to keep in a consistent state. And it can now be passed directly to # helpers like 'read-byte' or 'read-until' that only need to support streams, # never file descriptors. # # Like with 'write', we assume our data segment will never begin at an address # shorter than 0x08000000, so any smaller arguments are assumed to be real # file descriptors. # # As a reminder, a stream looks like this: # write: int # index at which to write to next # read: int # index at which to read next # data: (array byte) # prefixed by size as usual == 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 read: # f: fd or (addr stream byte), s: (addr stream byte) -> num-bytes-read/eax: int # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # if (f < 0x08000000) return _read(f, s) # f can't be a user-mode address, so treat it as a kernel file descriptor 81 7/subop/compare 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 0x08000000/imm32 # compare *(ebp+8) 73/jump-if-addr>= $read:fake/disp8 # . . 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 _read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # return eb/jump $read:end/disp8 $read:fake: # otherwise, treat 'f' as a stream to scan from # . save registers 56/push-esi 57/push-edi # esi = f 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi # edi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 0xc/disp8 . # copy *(ebp+12) to esi # eax = _buffer-4(out = &s->data[s->write], outend = &s->data[s->size], # in = &f->data[f->read], inend = &f->data[f->write]) # . . push &f->data[f->write] 8b/copy 0/mod/indirect 6/rm32/esi . . . 0/r32/eax . . # copy *esi to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 6/base/esi 0/index/eax . 0/r32/eax 0xc/disp8 . # copy esi+eax+12 to eax 50/push-eax # . . push &f->data[f->read] 8b/copy 1/mod/*+disp8 6/rm32/esi . . . 0/r32/eax 4/disp8 . # copy *(esi+4) to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 6/base/esi 0/index/eax . 0/r32/eax 0xc/disp8 . # copy esi+eax+12 to eax 50/push-eax # . . push &s->data[s->size] 8b/copy 1/mod/*+disp8 7/rm32/edi . . . 0/r32/eax 8/disp8 . # copy *(edi+8) to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/edi 0/index/eax . 0/r32/eax 0xc/disp8 . # copy edi+eax+12 to eax 50/push-eax # . . push &s->data[s->write] 8b/copy 0/mod/indirect 7/rm32/edi . . . 0/r32/eax . . # copy *edi to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/edi 0/index/eax . 0/r32/eax 0xc/disp8 . # copy edi+eax+12 to eax 50/push-eax # . . call e8/call _buffer-4/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/imm32 # add to esp # s->write += eax 01/add 0/mod/indirect 7/rm32/edi . . . 0/r32/eax . . # add eax to *edi # f->read += eax 01/add 1/mod/*+disp8 6/rm32/esi . . . 0/r32/eax 4/disp8 . # add eax to *(esi+4) # . restore registers 5f/pop-to-edi 5e/pop-to-esi $read:end: # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # - helpers # '_buffer' is like '_append', but silently stops instead of aborting when it runs out of space # 3-argument variant of _buffer _buffer-3: # out: address, outend: address, s: (array byte) -> num_bytes_buffered/eax # . 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 = _buffer-4(out, outend, &s->data[0], &s->data[s->size]) # . . push &s->data[s->size] 8b/copy 1/mod/*+disp8 5/rm32/ebp . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax 8b/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy *eax to ecx 8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/eax 1/index/ecx . 1/r32/ecx 4/disp8 . # copy eax+ecx+4 to ecx 51/push-ecx # . . push &s->data[0] 8d/copy-address 1/mod/*+disp8 0/rm32/eax . . . 1/r32/ecx 4/disp8 . # copy eax+4 to ecx 51/push-ecx # . . push outend ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) # . . push out ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) # . . call e8/call _buffer-4/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/imm32 # add to esp $_buffer-3:end: # . 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 # 4-argument variant of _buffer _buffer-4: # out: address, outend: address, in: address, inend: address -> num_bytes_buffered/eax # . 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 # eax/num_bytes_buffered = 0 b8/copy-to-eax 0/imm32 # edi = out 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi # edx = outend 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx # esi = in 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0x10/disp8 . # copy *(ebp+16) to esi # ecx = inend 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0x14/disp8 . # copy *(ebp+20) to ecx $_buffer-4:loop: # if (in >= inend) break 39/compare 3/mod/direct 6/rm32/esi . . . 1/r32/ecx . . # compare esi with ecx 73/jump-if-addr>= $_buffer-4:end/disp8 # if (out >= outend) break # for now silently ignore filled up buffer 39/compare 3/mod/direct 7/rm32/edi . . . 2/r32/edx . . # compare edi with edx 73/jump-if-addr>= $_buffer-4:end/disp8 # *out = *in 8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 3/r32/BL . . # copy byte at *esi to BL 88/copy-byte 0/mod/indirect 7/rm32/edi . . . 3/r32/BL . . # copy byte at BL to *edi # ++num_bytes_buffered 40/increment-eax # ++in 46/increment-esi # ++out 47/increment-edi eb/jump $_buffer-4:loop/disp8 $_buffer-4: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 # idea: a clear-if-empty method on streams that clears only if f->read == f->write # Unclear how I'd use it, though. Callers seem to need the check anyway. # Maybe a better helper would be 'empty-stream?' _read: # fd: int, s: (addr stream byte) -> num-bytes-read/eax: int # . 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 # esi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0xc/disp8 . # copy *(ebp+12) to esi # eax = s->write 8b/copy 0/mod/indirect 6/rm32/esi . . . 0/r32/eax . . # copy *esi to eax # edx = s->size 8b/copy 1/mod/*+disp8 6/rm32/esi . . . 2/r32/edx 8/disp8 . # copy *(esi+8) to edx # syscall(read, fd, &s->data[s->write], s->size - s->write) # . . fd: ebx 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 3/r32/ebx 8/disp8 . # copy *(ebp+8) to ebx # . . data: ecx = &s->data[s->write] 8d/copy-address 1/mod/*+disp8 4/rm32/sib 6/base/esi 0/index/eax . 1/r32/ecx 0xc/disp8 . # copy esi+eax+12 to ecx # . . size: edx = s->size - s->write 29/subtract 3/mod/direct 2/rm32/edx . . . 0/r32/eax . . # subtract eax from edx # . . syscall e8/call syscall_read/disp32 # add the result eax to s->write 01/add 0/mod/indirect 6/rm32/esi . . . 0/r32/eax . . # add eax to *esi $_read:end: # . restore registers 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 # Two options: # 1 (what we have above): # ecx = s # eax = s->write # edx = s->size # # syscall # ecx = lea ecx+eax+12 # edx = sub edx eax # # 2: # ecx = s # edx = s->size # ecx = &s->data # # syscall # ecx = add ecx, s->write # edx = sub edx, s->write # # Not much to choose between the two? Option 2 performs a duplicate load to # use one less register, but doesn't increase the amount of spilling (ecx # and edx must be used, and eax must be clobbered anyway). # - tests test-read-single: # - write a single character into _test-stream, then read from it # clear-stream(_test-stream) # . . push args 68/push _test-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # clear-stream(_test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # write(_test-stream, "Ab") # . . push args 68/push "Ab"/imm32 68/push _test-stream/imm32 # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # eax = read(_test-stream, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-stream/imm32 # . . call e8/call read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # check-ints-equal(eax, 2, msg) # . . push args 68/push "F - test-read-single: return value"/imm32 68/push 2/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-stream-equal(_test-tmp-stream, "Ab", msg) # . . push args 68/push "F - test-read-single"/imm32 68/push "Ab"/imm32 68/push _test-tmp-stream/imm32 # . . call e8/call check-stream-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # end c3/return test-read-is-stateful: # - make two consecutive reads, check that their results are appended # clear-stream(_test-stream) # . . push args 68/push _test-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # clear-stream(_test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # write(_test-stream, "C") # . . push args 68/push "C"/imm32 68/push _test-stream/imm32 # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # read(_test-stream, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-stream/imm32 # . . call e8/call read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # write(_test-stream, "D") # . . push args 68/push "D"/imm32 68/push _test-stream/imm32 # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # read(_test-stream, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-stream/imm32 # . . call e8/call read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # check-stream-equal(_test-tmp-stream, "CD", msg) # . . push args 68/push "F - test-read-is-stateful"/imm32 68/push "CD"/imm32 68/push _test-tmp-stream/imm32 # . . call e8/call check-stream-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # end c3/return test-read-returns-0-on-end-of-file: # - read after hitting end-of-file, check that result is 0 # setup # . clear-stream(_test-stream) # . . push args 68/push _test-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . clear-stream(_test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . write(_test-stream, "Ab") # . . push args 68/push "Ab"/imm32 68/push _test-stream/imm32 # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # first read gets to end-of-file # . read(_test-stream, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-stream/imm32 # . . call e8/call read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # second read # . read(_test-stream, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-stream/imm32 # . . call e8/call read/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-read-returns-0-on-end-of-file"/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 # end c3/return == data _test-tmp-stream: # (stream byte) # current write index 0/imm32 # current read index 0/imm32 # size 8/imm32 # data 00 00 00 00 00 00 00 00 # 8 bytes # . . vim:nowrap:textwidth=0