From 71e4f3812982dba2efb471283d310224e8db363e Mon Sep 17 00:00:00 2001 From: "Kartik K. Agaram" Date: Wed, 3 Mar 2021 22:09:50 -0800 Subject: 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. --- linux/ex12.subx | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 linux/ex12.subx (limited to 'linux/ex12.subx') diff --git a/linux/ex12.subx b/linux/ex12.subx new file mode 100644 index 00000000..0c0d4315 --- /dev/null +++ b/linux/ex12.subx @@ -0,0 +1,43 @@ +# Example showing mmap syscall. +# Create a new segment using mmap, save the address, write to it. +# +# To run: +# $ ./bootstrap translate init.linux apps/ex12.subx -o apps/ex12 +# $ ./bootstrap run apps/ex12 +# You shouldn't get a segmentation fault. + +== 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: + # mmap(Mmap-new-segment->len) + bb/copy-to-ebx Mmap-new-segment/imm32 + e8/call syscall_mmap/disp32 + + # write to *eax to check that we have access to the newly-allocated segment + c7 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0x34/imm32 # copy to *eax + + # exit(eax) + 89/copy 3/mod/direct 3/rm32/ebx . . . 0/r32/eax . . # copy eax to ebx + e8/call syscall_exit/disp32 + +== data + +# various constants used here were found in the Linux sources (search for file mman-common.h) +Mmap-new-segment: # type mmap_arg_struct + # addr + 0/imm32 + # len + 0x100/imm32 + # protection flags + 3/imm32 # PROT_READ | PROT_WRITE + # sharing flags + 0x22/imm32 # MAP_PRIVATE | MAP_ANONYMOUS + # fd + -1/imm32 # since MAP_ANONYMOUS is specified + # offset + 0/imm32 # since MAP_ANONYMOUS is specified + +# . . vim:nowrap:textwidth=0 -- cgit 1.4.1-2-gfad0 lt'>
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