Per-process address spaces (AddressSpace = a PML4 with an empty user
half and the shared kernel half copied in; create/destroy in paging.zig)
with CR3 switched on context switch and TSS.rsp0/kernel_rsp published per
switch. The GS base now points at an arch per-CPU block and every ring
transition observes the swapgs discipline, so a ring-3 `mov %ax,%gs` can
no longer poison per-CPU access. syscall/sysret is the primary user entry
(int 0x80 kept as a test path); one handler, installed once at boot,
serves both and dispatches on whether the caller is a scheduled process
or a borrowed test thread. spawnProcess loads an ELF into a fresh address
space and schedules it; exit frees the address space after switching to
the kernel tables. New `process` test: init runs twice as a real process
(create/exit/recreate) on its own page tables, coexisting with a kernel
task under preemption. Suite 28/28.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
paging.init now maps only the physmap, the framebuffer/LAPIC windows,
and the kernel's own segments; the entire low canonical half is left to
user space. Every higher-half PML4 entry is pre-created so a per-process
address space can share the kernel half by copying PML4[256..512), with
an assert against late top-half entries and a 4 GiB guard on
pre-switch table frames. The AP trampoline's low identity page is now
created transiently by arm() and unmapped by disarm(); startAp asserts
the page-table root is 32-bit addressable. Docs (paging.md) updated.
Suite 27/27; 4-core normal boot reaches /sbin/init.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
paging.init now builds the physmap (physToVirt(phys)) alongside the low
identity map, so both addressing modes resolve during the transition.
tableAt (the page-table walk hinge), the pmm bitmap, the framebuffer,
LAPIC/IOAPIC/HPET/PM-timer/SPCR MMIO, the ACPI table walk, AML
OperationRegions, the ACPI power registers, the user-ELF frame fills,
and the AP trampoline arm/disarm all reach physical memory through the
physmap. Hal.mapMmio now maps into the physmap and returns the virtual
address, so the device layer never learns the layout. boot_info and its
pointees are converted at kmain entry. The kernel still links and runs
low; identity is the safety net until it's removed. Suite 27/27.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Ring 3 works: user GDT descriptors (sysret-ready layout), TSS.rsp0,
U/S-bit user mappings (W^X preserved), an int 0x80 syscall gate with a
mutable trap frame, and a setjmp-style enter/exit path. /sbin/init is a
real freestanding Zig binary built from sbin/, shipped on the ESP,
loaded by the bootloader (BootInfo.init_base/len), validated and mapped
by an in-kernel user-ELF loader, and run at CPL 3 — syscalls: exit,
ping, write. Tests: user, user-pf (U/S isolation proof, error code
0x5), init. Suite 27/27.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
fault-ap-df pins a #DF to an AP (its own IST must catch it); affinity checks a pinned task never migrates. onException now names the core, so an AP fault is attributed and shown contained. Both teeth-checked.
Add a discovery case (asserts stable ACPI/MADT/FADT/AML facts) and a wx case (audits R+X code vs NX data/rodata/heap/stack via arch.pageExecutable). Wire the existing poweroff/reboot cases into the harness. Suite: 18 -> 22.
Adds paging.isExecutable and arch.trampolinePage; the smp case now asserts the frame is zeroed and non-executable after bring-up. Teeth-checked against a no-op disarm.
Daniel SamsonandClaude Fable 5
daniel