Remove multikernel stubs - #511
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Mirrors the existing x86_64 common-os support in arch/aarch64/mm: * New software-defined PT-entry flag COW_MARKER (bit 58) plus the `copy_on_write()`, `user()`, `kernel()`, `execute_enable()` helpers on PageTableEntryFlags, and a PageTableEntryFlagsExt trait that matches the x86_64 API so common-os callers compile unchanged. * `mark_user_pages_copy_on_write()` walks the active TTBR0_EL1 user L0 entry and marks every writable user page READ_ONLY+COW_MARKER — the prep step before duplicating a page table for fork(). * `create_new_root_page_table` / `copy_current_root_page_table` / `drop_user_space` / `clear_user_space` / `copy_kernel_stack_to` manage per-process root tables. Kernel L0 entries (#0 kernel image, hermit-os#256+ kernel heap, hermit-os#511 self-ref) are SHARED across every task; only the user slot (#2 = LOADER_START >> 39) is private and deep-copied on fork. clear_l0 only walks the user slot and only frees a sub-table when the user-page sweep leaves it fully empty, so the kernel's own heap and stacks (which live in shared L0 entries) stay mapped. * L0 self-reference at 0x0000_FFFF_FFFF_F000 lets PT walks reach any level via virtual addresses, matching the existing x86_64 recursive PML4 idiom. mm/physicalmem.rs and scheduler/{mod,task/mod}.rs lift the `x86_64 + common-os` cfg-gates around frame_ref_inc/dec, copy_page, RootPageTable, Heap and the related Task fields to plain `feature = "common-os"`. Items still architecturally x86_64-only (fork(), spawn_thread, prepare_fork_child_stack, sys_fork/sys_waitpid) remain re-gated; aarch64 picks them up incrementally in the later stages of this series.
stlankes
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Mirrors the existing x86_64 common-os support in arch/aarch64/mm: * New software-defined PT-entry flag COW_MARKER (bit 58) plus the `copy_on_write()`, `user()`, `kernel()`, `execute_enable()` helpers on PageTableEntryFlags, and a PageTableEntryFlagsExt trait that matches the x86_64 API so common-os callers compile unchanged. * `mark_user_pages_copy_on_write()` walks the active TTBR0_EL1 user L0 entry and marks every writable user page READ_ONLY+COW_MARKER — the prep step before duplicating a page table for fork(). * `create_new_root_page_table` / `copy_current_root_page_table` / `drop_user_space` / `clear_user_space` / `copy_kernel_stack_to` manage per-process root tables. Kernel L0 entries (#0 kernel image, hermit-os#256+ kernel heap, hermit-os#511 self-ref) are SHARED across every task; only the user slot (#2 = LOADER_START >> 39) is private and deep-copied on fork. clear_l0 only walks the user slot and only frees a sub-table when the user-page sweep leaves it fully empty, so the kernel's own heap and stacks (which live in shared L0 entries) stay mapped. * L0 self-reference at 0x0000_FFFF_FFFF_F000 lets PT walks reach any level via virtual addresses, matching the existing x86_64 recursive PML4 idiom. mm/physicalmem.rs and scheduler/{mod,task/mod}.rs lift the `x86_64 + common-os` cfg-gates around frame_ref_inc/dec, copy_page, RootPageTable, Heap and the related Task fields to plain `feature = "common-os"`. Items still architecturally x86_64-only (fork(), spawn_thread, prepare_fork_child_stack, sys_fork/sys_waitpid) remain re-gated; aarch64 picks them up incrementally in the later stages of this series.
stlankes
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Aug 13, 2026
Mirrors the existing x86_64 common-os support in arch/aarch64/mm: * New software-defined PT-entry flag COW_MARKER (bit 58) plus the `copy_on_write()`, `user()`, `kernel()`, `execute_enable()` helpers on PageTableEntryFlags, and a PageTableEntryFlagsExt trait that matches the x86_64 API so common-os callers compile unchanged. * `mark_user_pages_copy_on_write()` walks the active TTBR0_EL1 user L0 entry and marks every writable user page READ_ONLY+COW_MARKER — the prep step before duplicating a page table for fork(). * `create_new_root_page_table` / `copy_current_root_page_table` / `drop_user_space` / `clear_user_space` / `copy_kernel_stack_to` manage per-process root tables. Kernel L0 entries (#0 kernel image, hermit-os#256+ kernel heap, hermit-os#511 self-ref) are SHARED across every task; only the user slot (#2 = LOADER_START >> 39) is private and deep-copied on fork. clear_l0 only walks the user slot and only frees a sub-table when the user-page sweep leaves it fully empty, so the kernel's own heap and stacks (which live in shared L0 entries) stay mapped. * L0 self-reference at 0x0000_FFFF_FFFF_F000 lets PT walks reach any level via virtual addresses, matching the existing x86_64 recursive PML4 idiom. mm/physicalmem.rs and scheduler/{mod,task/mod}.rs lift the `x86_64 + common-os` cfg-gates around frame_ref_inc/dec, copy_page, RootPageTable, Heap and the related Task fields to plain `feature = "common-os"`. Items still architecturally x86_64-only (fork(), spawn_thread, prepare_fork_child_stack, sys_fork/sys_waitpid) remain re-gated; aarch64 picks them up incrementally in the later stages of this series.
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Since multikernel support is nonexistent as far as I know, we might remove any remains of older multikernel plans.