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author | Kartik K. Agaram <vc@akkartik.com> | 2021-03-03 22:09:50 -0800 |
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committer | Kartik K. Agaram <vc@akkartik.com> | 2021-03-03 22:21:03 -0800 |
commit | 71e4f3812982dba2efb471283d310224e8db363e (patch) | |
tree | ea111a1acb8b8845dbda39c0e1b4bac1d198143b /linux/ex9.subx | |
parent | c6b928be29ac8cdb4e4d6e1eaa20420ff03e5a4c (diff) | |
download | mu-71e4f3812982dba2efb471283d310224e8db363e.tar.gz |
7842 - new directory organization
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.
Diffstat (limited to 'linux/ex9.subx')
-rw-r--r-- | linux/ex9.subx | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/linux/ex9.subx b/linux/ex9.subx new file mode 100644 index 00000000..232178a0 --- /dev/null +++ b/linux/ex9.subx @@ -0,0 +1,52 @@ +# Example showing arg order on the stack. +# +# Show difference between ascii codes of first letter of first arg and first +# letter of second arg. +# +# To run: +# $ ./bootstrap translate init.linux apps/ex9.subx -o apps/ex9 +# $ ./bootstrap run apps/ex9 z x +# Expected result: +# $ echo $? +# 2 +# +# At the start of a SubX program: +# argc: *esp +# argv[0]: *(esp+4) +# argv[1]: *(esp+8) +# ... +# Locals start from esp-4 downwards. + +== 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: + # . prologue + 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp + # ascii-difference(argv[1], argv[2]) + # . . push argv[2] + ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) + # . . push argv[1] + ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) + # . . call + e8/call ascii-difference/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # exit(eax) + 89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx + e8/call syscall_exit/disp32 + +ascii-difference: # (s1, s2): null-terminated ascii strings + # a = first letter of s1 (ecx) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none . 0/r32/eax 4/disp8 . # copy *(esp+4) to eax + 8b/copy 0/mod/indirect 0/rm32/eax . . . 0/r32/eax . . # copy *eax to eax + # b = first letter of s2 (edx) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none . 1/r32/ecx 8/disp8 # copy *(esp+8) to ecx + 8b/copy 0/mod/indirect 1/rm32/ecx . . . 1/r32/ecx . . # copy *ecx to ecx + # a-b + 29/subtract 3/mod/direct 0/rm32/eax . . . 1/r32/ecx . . # subtract ecx from eax + c3/return + +# . . vim:nowrap:textwidth=0 |