133 lines
4.2 KiB
Markdown
133 lines
4.2 KiB
Markdown
# DVX Loader
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Bootstrap loader for the DVX desktop environment. Builds as `dvx.exe`
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-- the only native executable in the system. Everything else is a
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dynamically loaded DXE3 module.
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## What It Does
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1. Changes working directory to the directory containing `dvx.exe`
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2. Truncates `dvx.log` and initializes logging
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3. Calls `platformInit()` to suppress Ctrl+C and install signal handlers
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4. Calls `platformRegisterDxeExports()` to register platform and C
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runtime symbols (libc, libm, libgcc) for DXE module resolution
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5. Scans and loads all modules in two phases (see below)
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6. Finds `shellMain()` via `dlsym` across loaded modules
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7. Calls `shellMain()` -- the shell takes over from here
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8. On return, closes all module handles in reverse load order
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## Two-Phase Module Loading
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### Phase 1: Libraries (libs/*.lib)
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Recursively scans the `LIBS/` directory for `.lib` files. Each module may have a
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`.dep` file (same base name, `.dep` extension) listing base names of
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modules that must load first. The loader resolves the dependency graph
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and loads in topological order.
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Load order (via dep files):
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```
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libtasks.lib (no deps)
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libdvx.lib (deps: libtasks)
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texthelp.lib (deps: libtasks, libdvx)
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listhelp.lib (deps: libtasks, libdvx)
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dvxshell.lib (deps: libtasks, libdvx, texthelp, listhelp)
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taskmgr.lib (deps: dvxshell, libtasks, libdvx, texthelp, listhelp)
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```
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### Phase 2: Widgets (widgets/*.wgt)
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Recursively scans the `WIDGETS/` directory for `.wgt` files. Widget modules may
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also have `.dep` files (e.g., `textinpt.dep` lists `texthelp`).
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Loaded in topological order, same as libs.
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After loading each module, the loader checks for a `wgtRegister`
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export. If present, it is called immediately so the widget registers
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its class(es) and API with the core.
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## Dependency File Format
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Plain text, one dependency base name per line. Empty lines and lines
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starting with `#` are ignored. Names are case-insensitive.
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Example (`combobox.dep`):
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```
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texthelp
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listhelp
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```
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## Hosted Components
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### dvxLog()
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The global logging function is defined in `loaderMain.c` and exported
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to all DXE modules. It appends a line to `dvx.log`, opening and
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closing the file per write so it is never held open.
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```c
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void dvxLog(const char *fmt, ...);
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```
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### stb_ds
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The `STB_DS_IMPLEMENTATION` is compiled into the loader with
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`STBDS_REALLOC` and `STBDS_FREE` overridden to use `dvxRealloc` and
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`dvxFree`. This means all `arrput`/`hmput`/`arrfree` calls in DXE
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code route through the per-app memory tracker, so stb_ds memory is
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attributed correctly in the Task Manager's memory column. stb_ds
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functions are exported to all DXE modules via the platform export
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table.
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### Platform Layer
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`dvxPlatformDos.c` is compiled into the loader (not into libdvx.lib).
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All platform functions are exported to DXE modules. This includes:
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* Video: VESA VBE init, LFB mapping, mode enumeration
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* Input: INT 33h mouse, INT 16h keyboard, CuteMouse wheel API
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* Spans: `rep stosl`/`rep movsd` asm inner loops (8/16/32 bpp)
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* DXE: symbol registration, symbol overrides
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* Crash: signal handler installation, register dump logging
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* System: memory info, directory creation, path utilities
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### Per-App Memory Tracking
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The DXE export table maps standard C allocation symbols to tracked
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wrappers:
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| C Symbol | Mapped To | Effect |
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|----------|-----------|--------|
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| `malloc` | `dvxMalloc` | Allocations attributed to `currentAppId` |
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| `calloc` | `dvxCalloc` | Same |
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| `realloc` | `dvxRealloc` | Transfers attribution on resize |
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| `free` | `dvxFree` | Decrements app's tracked usage |
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| `strdup` | `dvxStrdup` | Tracks the duplicated string |
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This is transparent to DXE code -- apps call `malloc` normally and the
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tracked wrapper runs instead. The Task Manager reads per-app usage via
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`dvxMemGetAppUsage()`. When an app is reaped, `dvxMemResetApp()` zeroes
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its counter.
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## Files
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| File | Description |
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|------|-------------|
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| `loaderMain.c` | Entry point, module scanner, dependency resolver, logger |
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| `Makefile` | Builds `bin/dvx.exe` |
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## Build
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```
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make # builds bin/dvx.exe
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make clean # removes objects and binary
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```
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The loader links `loaderMain.c` + `dvxPlatformDos.c` into a native
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DJGPP executable. The CWSDPMI stub is prepended via exe2coff +
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CWSDSTUB.EXE for standalone execution.
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