71e4f38129
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.
91 lines
2.8 KiB
Plaintext
91 lines
2.8 KiB
Plaintext
# Some OS-specific preliminaries for Linux.
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# Memory layout
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#
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# 0 - 0x08047ffff - reserved for the kernel
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# 0x08048000 - 0xbffffffff - available for user programs
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# 0xc0000000 - 0xfffffffff - reserved for the kernel
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== code 0x09000000
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== data 0x0a000000
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# Syscalls
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#
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# We don't have libc, so we need to know Linux's precise syscall layout.
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# These are not real functions. Pass arguments in specific registers.
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== code
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# http://man7.org/linux/man-pages/man2/exit.2.html
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syscall_exit: # status/ebx: int
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b8/copy-to-eax 1/imm32
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cd/syscall 0x80/imm8
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# http://man7.org/linux/man-pages/man2/read.2.html
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syscall_read: # fd/ebx: int, buf/ecx: addr, size/edx: int -> nbytes-or-error/eax: int
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b8/copy-to-eax 3/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/write.2.html
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syscall_write: # fd/ebx: int, buf/ecx: addr, size/edx: int -> nbytes-or-error/eax: int
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b8/copy-to-eax 4/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/open.2.html
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syscall_open: # filename/ebx: (addr kernel-string), flags/ecx: int, dummy=0x180/edx -> fd-or-error/eax: int
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b8/copy-to-eax 5/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/close.2.html
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syscall_close: # fd/ebx: int -> status/eax
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b8/copy-to-eax 6/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/lseek.2.html
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syscall_lseek: # fd/ebx: int, offset/ecx: int, whence/edx: int
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b8/copy-to-eax 0x13/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/creat.2.html
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syscall_creat: # filename/ebx: (addr kernel-string) -> fd-or-error/eax: int
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b8/copy-to-eax 8/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/unlink.2.html
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syscall_unlink: # filename/ebx: (addr kernel-string) -> status/eax: int
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b8/copy-to-eax 0xa/imm32
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cd/syscall 0x80/imm8
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c3/return
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# http://man7.org/linux/man-pages/man2/rename.2.html
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syscall_rename: # source/ebx: (addr kernel-string), dest/ecx: (addr kernel-string) -> status/eax: int
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b8/copy-to-eax 0x26/imm32
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cd/syscall 0x80/imm8
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c3/return
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# https://github.com/torvalds/linux/blob/fa121bb3fed6313b1f0af23952301e06cf6d32ed/mm/nommu.c#L1352
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syscall_mmap: # arg/ebx: (addr mmap_arg_struct) -> status/eax: int
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# the important thing: ebx+4 contains the 32-bit size to be allocated
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b8/copy-to-eax 0x5a/imm32
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cd/syscall 0x80/imm8
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c3/return
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syscall_ioctl: # fd/ebx: int, cmd/ecx: int, arg/edx: (addr _)
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b8/copy-to-eax 0x36/imm32
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cd/syscall 0x80/imm8
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c3/return
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syscall_nanosleep: # req/ebx: (addr timespec)
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b8/copy-to-eax 0xa2/imm32 # 162
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cd/syscall 0x80/imm8
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c3/return
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syscall_clock_gettime: # clock/ebx: int, out/ecx: (addr timespec)
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b8/copy-to-eax 0x109/imm32 # 265
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cd/syscall 0x80/imm8
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c3/return
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