rajamesandClaude Opus 5.5
9bfd5071d2
Ruled 2026-10-07. BLOCK, BUFFER, UPDATE, SAVE-BUFFERS and EMPTY-BUFFERS are each one kernel request on port 0, by block number only. The node has a window of four slots in its memory, as a v3 VM has; the kernel copies blocks into it, keeps the record of which block is in which slot, and decides when a block is written (v4/system/blocks.c). The node keeps no record and gives the kernel no address, so a request cannot overwrite the node's code. When a block is written stays FORTH-79's: UPDATE marks it. When the chain of devices changes the slots are let go, as in v3. The window is 512 cells more than the two buffers were; the dictionary space ends that much lower, at 13824. MESH.md 8.5 had said, from the review, that a v3 VM's BLOCK is the kernel's buffer. It is not, and the section now says what was reported, what v3 does, and what was ruled. make -C v4 test, sanitize and hosted-check pass; amd64, aarch64 and riscv64 boot, POST 538 of 538, the same hashes on all six: logs/20261007-092835, -093112, -093456. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
85 lines
4.0 KiB
C
85 lines
4.0 KiB
C
/* blocks.h -- a node asks its kernel for a block.
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* docs/v4.0.0/MESH.md section 8, docs/v4.0.0/ENGINE.md 3.3,
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* docs/v4.0.0/V3-PARITY.md 1d.
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*
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* A node only ever asks for a block by number, and it asks the kernel: a
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* request written to the port where its kernel is, as any kernel word is.
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* This is v3's way (v3/src/word_source/block_words.c). The node has a
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* WINDOW in its memory, V4_BLOCK_SLOTS slots of 256 cells, as a v3 VM has
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* four slots of 1 KiB at the top of its memory. The kernel keeps the
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* record of which block is in which slot and does all the copying, and it
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* writes into the window and nowhere else in the node. The requests, the
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* same for every node:
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*
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* V4_REQ_BLOCK ( n -- waddr status ) the slot that holds block n, read
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* from storage if it is not in one
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* V4_REQ_BUFFER ( n -- waddr status ) a slot for block n, of zeros if it
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* is not in one: nothing is read
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* V4_REQ_UPDATE ( -- status ) the block most recently asked for
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* is marked changed
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* V4_REQ_SAVE_BUFFERS ( -- status ) every block marked is written
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* V4_REQ_EMPTY_BUFFERS ( -- ) every slot is let go; nothing is
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* written
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*
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* Their numbers are below zero: the requests a host names for its own
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* words (KERNEL-WORD) count up from 1.
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*
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* waddr is the word address of the slot, or 0 when the status is not 0.
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* The status is 0; or V4_BLOCK_RANGE, there is no such block; or
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* V4_BLOCK_REFUSED: storage would not have a block that had to be written,
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* the stack did not hold the request's argument, or the window is not all
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* in the node's memory.
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*
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* WHEN A BLOCK IS WRITTEN is FORTH-79's: UPDATE marks it, and it is written
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* by SAVE-BUFFERS or when its slot is wanted for another block. (v3's
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* UPDATE copies the slot to the kernel at once; the standard is followed.)
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* A slot whose block is not marked is taken before one whose block is. A
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* block that storage would not take is let go of: its slot is empty.
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*
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* When the kernel's chain of devices changes, everything in the slots is
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* let go and nothing of it is written, as v3 does (blk_vm_check_epoch).
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*
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* A block is 1024 bytes and 256 cells, four bytes to a cell, the first
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* lowest, whatever the cell width: a block read leaves the rest of each
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* cell zero, and a write takes the low 32 bits.
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*
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* The blocks are the kernel's block subsystem's (v3/src/block_subsystem.c).
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* Who may have which block is not checked here yet (MESH.md 8.4).
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*/
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#ifndef V4_BLOCKS_H
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#define V4_BLOCKS_H
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#include "v4/node.h"
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#define V4_REQ_BLOCK (-1)
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#define V4_REQ_BUFFER (-2)
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#define V4_REQ_UPDATE (-3)
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#define V4_REQ_SAVE_BUFFERS (-4)
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#define V4_REQ_EMPTY_BUFFERS (-5)
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#define V4_BLOCK_OK 0
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#define V4_BLOCK_REFUSED 2
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#define V4_BLOCK_RANGE 3
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#define V4_BLOCK_SLOTS 4u
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/* What the kernel keeps for one node. */
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typedef struct {
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v4_cell window; /* word address of the first slot */
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uint32_t block[V4_BLOCK_SLOTS]; /* the block in each slot; 0: none */
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unsigned char changed[V4_BLOCK_SLOTS]; /* UPDATEd and not yet written */
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unsigned next; /* where the search for a slot to take begins */
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int last; /* the slot most recently asked for; -1: none */
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uint64_t epoch; /* the chain as it was when the slots were filled */
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} v4_blocks;
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/* A node's window is at `window`, and nothing is in it. */
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void v4_blocks_init(v4_blocks *w, v4_cell window);
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/* If `request` is one of the five, serve it for the node and return 1.
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* Otherwise touch nothing and return 0. The node is stopped, blocked at
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* its port, when this is called. */
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int v4_blocks_serve(v4_blocks *w, v4_node *n, v4_cell request);
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#endif /* V4_BLOCKS_H */
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