mirror of
https://github.com/isfshax/isfshax.git
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136 lines
4.6 KiB
C
136 lines
4.6 KiB
C
/*
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* isfshax.c
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*
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* Copyright (C) 2021 rw-r-r-0644 <rwrr0644@gmail.com>
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*
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* This code is licensed to you under the terms of the GNU GPL, version 2;
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* see file COPYING or http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
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*
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*
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* isfshax is installed to 4 superblock slots for redundancy
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* against ecc errors and nand blocks wear out.
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*
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* when a boot1 superblock recommit attempt (due to ecc errors)
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* is detected, the superblock will be rewritten to the next
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* isfshax slot after correcting ecc errors.
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*
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* the generation number is incremented after each correction;
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* once the maximum allowed genertion number is reached, all
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* isfshax superblocks are rewritten with a lower generation number.
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*
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* if one of the blocks becomes bad during the rewrite,
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* the range of used generations numbers is incremented to ensure
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* the old superblock will not be used:
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* 0 BAD BLOCKS -> generation no. 0xfffffaff-0xfffffbff
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* ...
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* 3 BAD BLOCKS -> generation no. 0xfffffdff-0xfffffeff
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*
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* bad block information is stored along with other informations in a
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* separate isfshax info structure inside of the superblock, since all
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* isfshax slots are already marked as bad to guard against IOSU intervention
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* inside of the normal ISFS cluster allocation table.
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*/
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#include "types.h"
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#include "isfs/isfs.h"
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#include "isfs/super.h"
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#include "isfs/volume.h"
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#include "isfs/isfshax.h"
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#include "malloc.h"
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/* boot1 superblock loading address.
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* this can be used to read the current generation
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* and the list of isfshax superblock slots, but it
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* can't be rewritten directly to nand as it has been
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* modified by the stage1 payload. */
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static const isfshax_super *
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boot1_superblock = (const isfshax_super *)(0x01f80000);
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static isfshax_super
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superblock;
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int isfshax_refresh()
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{
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isfs_ctx *slc = isfs_get_volume(ISFSVOL_SLC);
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u32 curindex, offs, count = 1, written = 0;
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u32 generation;
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/* detect if the superblock contains ecc errors and boot1
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* attempted to recommit the superblock */
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if (boot1_superblock->generation == boot1_superblock->isfshax.generation)
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return 0;
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/* load the newest valid isfshax superblock slot */
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curindex = boot1_superblock->isfshax.index;
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for (offs = 0; offs < ISFSHAX_REDUNDANCY; offs++) {
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u32 index = (curindex + offs) & (ISFSHAX_REDUNDANCY - 1);
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u32 slot = boot1_superblock->isfshax.slots[index] & ~ISFSHAX_BAD_SLOT;
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if (isfs_read_super(slc, &superblock, slot) >= 0) {
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curindex = index;
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break;
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}
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}
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if (offs == ISFSHAX_REDUNDANCY)
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return -2;
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/* if the last valid generation is reached, rewrite/erase all
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* isfshax superblocks with a lower generation number */
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generation = superblock.generation + 1;
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if (generation >= (superblock.isfshax.generationbase + ISFSHAX_GENERATION_RANGE)) {
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generation = superblock.isfshax.generationbase;
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count = ISFSHAX_REDUNDANCY;
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}
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for (offs = 1; (offs <= ISFSHAX_REDUNDANCY) && (written < count); offs++) {
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u32 index = (curindex + offs) & (ISFSHAX_REDUNDANCY - 1);
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u32 slot = superblock.isfshax.slots[index] & ~ISFSHAX_BAD_SLOT;
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/* skip slots that became bad after a superblock rewrite */
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if (superblock.isfshax.slots[index] & ISFSHAX_BAD_SLOT)
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continue;
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/* if the slot currently in use is being rewritten, ensure
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* at least another slot was already successfully written */
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if ((index == curindex) && !written)
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continue;
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/* update superblock informations */
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superblock.isfshax.index = index;
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superblock.isfshax.generation = generation;
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superblock.generation = generation;
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/* rewrite and verify the superblock */
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if (isfs_write_super(slc, &superblock, slot) >= 0)
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{
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generation++;
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written++;
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continue;
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}
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/* block became bad during write operation, mark
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* the block as bad and go to next generation range */
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superblock.isfshax.slots[index] |= ISFSHAX_BAD_SLOT;
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superblock.isfshax.generationbase += ISFSHAX_GENERATION_RANGE;
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generation = superblock.isfshax.generationbase;
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/* the current superblock became bad. ensure the other
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* isfshax superblock are updated with the new generation range
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* and bad slot information. */
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if (index == curindex)
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{
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offs = 1;
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written = 0;
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}
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}
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/* all isfshax superblocks became bad, or the nand writing code stopped
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* working correctly. either way the user should probably be informed. */
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if (!written)
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return -3;
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return 0;
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}
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