Robert Allan JamesandClaude Sonnet 5
57ac3fc304
Second stage of the preemptive context-switching plan. Every VM (Hera, every capsule_birth_baby()-born VM including WIREBIND identities) now gets its own dedicated 2 MiB native C stack at birth -- but nothing runs on it yet, that's Stage 2. Pure allocation-machinery proof. Design correction made before writing code: the plan called for cloning sk_vm_arena_alloc()'s guard-page pattern, but that pattern turns out to be Mama-only -- host_services.c's kernel_alloc() gives every baby VM a plain kmalloc() block for its dictionary arena, not a real guarded PMM allocation. Stacks get the real treatment instead (new sk_vm_native_stack_alloc()/_free() in arena.c): independent pmm_alloc_contiguous() + guard pages for every VM without exception, no singleton, no kmalloc fallback -- a stack overflow is exactly the failure mode guard pages exist for, and a corrupted stack could corrupt whatever saved context Stage 2 trusts. 2 MiB size matches this project's own established kernel-stack convention (g_kernel_stack/g_rpi5_native_stack), not a guess -- that one shared 2 MiB stack today already carries all VMs' combined nested VM-EXEC recursion. Three new VM struct fields, freed in vm_cleanup() alongside the existing call_stack free. Allocation failure is non-fatal to birth. All 3 architectures re-verified clean boot to ok>, no native-stack allocation failures for any Tripod-fleet VM. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016UNhH1mhi52i6Qihh7ZV5S
97 lines
3.5 KiB
C
97 lines
3.5 KiB
C
/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* arena.h - VM arena management for StarKernel builds.
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*
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* Hosted builds never include this header. Kernel integration layers use it
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* to provision the PMM-backed VM arena before handing memory to the VM core.
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*/
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#ifndef STARKERNEL_VM_ARENA_H
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#define STARKERNEL_VM_ARENA_H
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#ifdef __STARKERNEL__
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#include <stddef.h>
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#include <stdint.h>
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uint64_t sk_vm_arena_alloc(void);
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void sk_vm_arena_free(void);
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uint8_t *sk_vm_arena_ptr(void);
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size_t sk_vm_arena_size(void);
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int sk_vm_arena_is_initialized(void);
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void sk_vm_arena_assert_guards(const char *tag);
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/**
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* sk_vm_native_stack_t - one VM's own dedicated native (C) stack.
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*
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* FABRIC-3.md §XXVIII (Stage 1, preemptive-context-switch per-VM native
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* stacks, 2026-09-13). Unlike sk_vm_arena_alloc() -- whose PMM+guard-page
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* path is exercised only for Hera; every baby VM's "arena" is actually a
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* plain kmalloc block, per host_services.c's kernel_alloc() -- every native
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* stack, for every VM without exception, gets its own real, independent
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* pmm_alloc_contiguous() allocation with guard pages. A stack overflow is
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* exactly the failure mode guard pages exist for, and unlike the dictionary
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* arena, a corrupted stack can also corrupt whatever saved context Stage 2
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* later trusts -- worth the extra PMM pages every VM, not just Hera.
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*
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* Caller owns this struct (stored directly on the VM, mirroring how
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* vm->memory already holds its own arena pointer directly rather than going
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* through any module-level registry) and passes it back unchanged to
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* sk_vm_native_stack_free().
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*/
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typedef struct {
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uint64_t paddr; /* physical base (for pmm_free_contiguous) */
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uint64_t guard_vaddr; /* virtual base of the whole guarded region */
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uint64_t stack_top; /* initial SP value -- stacks grow down on all
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* 3 arches, so this is guard_vaddr + one guard
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* page + the full stack size */
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} sk_vm_native_stack_t;
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int sk_vm_native_stack_alloc(sk_vm_native_stack_t *out);
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void sk_vm_native_stack_free(const sk_vm_native_stack_t *stack);
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#endif /* __STARKERNEL__ */
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#endif /* STARKERNEL_VM_ARENA_H */
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