danielandClaude Fable 5
5db2bd4c7c
MontaukOS binaries could not use thread-local storage: the ELF loader ignored PT_TLS and no FS base was ever programmed, so any %fs access (initial-exec/local-exec TLS, e.g. libbfd's _Thread_local error state) page faulted at address 0. This is the kernel prerequisite for cc1plus/libstdc++ in the GCC port. ELF loader: parse PT_TLS and build the main thread's TLS block above the loaded image (x86-64 variant II ABI: block below the thread pointer, TP = base + align_up(memsz, align), .tdata copied from the template, .tbss zeroed, ABI self-pointer stored at [TP]). The template description is kept on the process for thread spawns. Scheduler: fsBase per thread, loaded into IA32_FS_BASE at every dispatch site through a per-CPU cache - TLS-free processes cost one MSR write per CPU ever, and userspace cannot desync the cache since CR4.FSGSBASE stays off. SYS_THREAD_SPAWN gives each new thread its own TLS block copied from the template (allocated from the process heap; reclaimed at process teardown). Ships tls-test.elf in the SDK (built by the devkit target): checks .tdata values, .tbss zeroing, and the %fs:0 self-pointer, exiting nonzero on failure. Boot-smoke verified; existing TLS-free programs are unaffected. Co-Authored-By: Claude Fable 5 <[email protected]>
MontaukOS Toolchains
Two cross toolchains live here, both installed to toolchain/local/:
| Script | Triple | Purpose |
|---|---|---|
build-toolchain.sh |
x86_64-elf |
Bare-metal compiler for the kernel |
build-montauk-toolchain.sh |
x86_64-montauk |
OS-aware compiler for userspace programs |
Both use Binutils 2.43.1 + GCC 14.2.0 and share the source trees in
src/. The Montauk target is added by the patches in patches/ plus
the target header files/montauk.h (installed as
gcc/config/montauk.h in the GCC tree).
The x86_64-montauk target
x86_64-montauk-gcc knows the Montauk userspace ABI, so a hosted
program builds with no special flags:
toolchain/local/bin/x86_64-montauk-gcc hello.c -o hello.elf
What the target does by default:
- Links static, non-PIE
ET_EXECbinaries (what the kernel ELF loader inkernel/src/Sched/ElfLoader.cppaccepts), text at 0x400000. -z max-page-size=0x1000— the loader maps 4 KiB pages; the x86-64 default of 2 MiB segment alignment would bloat every binary.- Startup/link line:
crt1.o crti.o crtbegin.o ... -lc crtend.o crtn.otaken from the sysroot (toolchain/sysroot/usr/lib), which is assembled fromprograms/lib/libcby the build script. - Headers resolve against the sysroot (
toolchain/sysroot/usr/include), assembled fromprograms/include/libcplus themontauk/SDK headers.#include <stdio.h>just works; no-nostdincneeded. -mno-red-zone(the project-wide userspace convention). Standard hard-float SysV ABI otherwise; pass-mno-sseetc. per program if wanted.- Defines
__montauk__/__MONTAUK__.
C++ works with -fno-exceptions -fno-rtti (the project convention).
There is no libstdc++ yet — only libgcc is built. A hosted libstdc++
needs a more complete libc and is the next step toward self-hosting.
Refreshing the sysroot
The sysroot is rebuilt every time build-montauk-toolchain.sh runs
(the compiler build steps are skipped once installed). After changing
libc headers or the libc itself, re-run the script to refresh it.
Layout
toolchain/
build-toolchain.sh # bare-metal x86_64-elf (kernel)
build-montauk-toolchain.sh # x86_64-montauk (userspace)
patches/ # Montauk target patches (checked in)
files/montauk.h # GCC target header (checked in)
src/ # downloaded + patched sources (ignored)
build/ # build trees (ignored)
local/ # install prefix (ignored)
sysroot/ # generated target sysroot (ignored)
Native binutils (runs on MontaukOS)
Binutils can be cross-compiled to run on MontaukOS itself
(--host=x86_64-montauk), the first step toward a self-hosted GCC:
mkdir -p toolchain/build/binutils-native && cd toolchain/build/binutils-native
export PATH=$PWD/../../local/bin:$PATH
../../src/binutils-2.43.1/configure \
--build=x86_64-pc-linux-gnu --host=x86_64-montauk \
--target=x86_64-montauk --prefix=/sdk \
--disable-nls --disable-werror --disable-gprofng --disable-gold \
--disable-plugins --disable-shared --enable-static
make -j$(nproc) all-gas all-ld all-binutils
make install-strip-gas install-strip-ld install-strip-binutils \
DESTDIR=$PWD/../../native
Notes:
- Build only
all-gas all-ld all-binutils. gprof needs fscanf with %[] scansets (not in the Montauk libc); gold and gprofng are disabled outright. - The libc gained a large POSIX surface for this port (fd functions, full errno/signal sets, struct stat, sys/wait.h, utime.h, wchar.h, sys/param.h, memory.h, bsearch, sscanf field widths, ...). pex-style process spawning (fork/exec/pipe) is stubbed to fail with ENOSYS: the tools themselves never spawn, and real process plumbing is the posix_spawn milestone that needs kernel support (exit codes in SYS_WAITPID, fd redirection wiring).
- The
devkittarget in programs/GNUmakefile ships the staged tools into the OS image at 0:/sdk/bin (as.elf, ld.elf, ar.elf, ...) with a target-side sysroot at 0:/sdk/include + 0:/sdk/lib (libc.a, crt objects, empty libm/libstdc++) - the Montauk SDK. The kernel resolves driveless absolute paths ("/sdk/lib") against the cwd drive, so the --prefix=/sdk layout works natively. The shell searches 0:/sdk/bin and tab-completes it. Future ports configure with --prefix=/sdk. If toolchain/native/ has not been built the devkit step is skipped and the image builds without it.