mirror of
https://github.com/eledio-devices/thirdparty-littlefs.git
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Initial implementation of forward-looking erase-state CRCs
This change is necessary to handle out-of-order writes found by pjsg's fuzzing work. The problem is that it is possible for (non-NOR) block devices to write pages in any order, or to even write random data in the case of a power-loss. This breaks littlefs's use of the first bit in a page to indicate the erase-state. pjsg notes this behavior is documented in the W25Q here: https://community.cypress.com/docs/DOC-10507 --- The basic idea here is to CRC the next page, and use this "erase-state CRC" to check if the next page is erased and ready to accept programs. .------------------. \ commit | metadata | | | | +---. | | | | |------------------| | | | erase-state CRC -----. | |------------------| | | | | commit CRC ---|-|-' |------------------| / | | padding | | padding (doesn't need CRC) | | | |------------------| \ | next prog | erased? | +-' | | | | | v | / | | | | '------------------' This is made a bit annoying since littlefs doesn't actually store the page (prog_size) in the superblock, since it doesn't need to know the size for any other operation. We can work around this by storing both the CRC and size of the next page when necessary. Another interesting note is that we don't need to any bit tweaking information, since we read the next page every time we would need to know how to clobber the erase-state CRC. And since we only read prog_size, this works really well with our caching, since the caches must be a multiple of prog_size. This also brings back the internal lfs_bd_crc function, in which we can use some optimizations added to lfs_bd_cmp. Needs some cleanup but the idea is passing most relevant tests.
This commit is contained in:
Christopher Haster
171
tests/test_powerloss.toml
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171
tests/test_powerloss.toml
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# There are already a number of tests that test general operations under
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# power-loss (see the reentrant attribute). These tests are for explicitly
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# testing specific corner cases.
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[[case]] # only a revision count
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code = '''
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lfs_format(&lfs, &cfg) => 0;
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lfs_mount(&lfs, &cfg) => 0;
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lfs_mkdir(&lfs, "notebook") => 0;
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lfs_file_open(&lfs, &file, "notebook/paper",
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LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
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strcpy((char*)buffer, "hello");
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size = strlen("hello");
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for (int i = 0; i < 5; i++) {
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lfs_file_write(&lfs, &file, buffer, size) => size;
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lfs_file_sync(&lfs, &file) => 0;
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}
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lfs_file_close(&lfs, &file) => 0;
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char rbuffer[256];
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_unmount(&lfs) => 0;
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// get pair/rev count
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lfs_mount(&lfs, &cfg) => 0;
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lfs_dir_open(&lfs, &dir, "notebook") => 0;
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lfs_block_t pair[2] = {dir.m.pair[0], dir.m.pair[1]};
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uint32_t rev = dir.m.rev;
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lfs_dir_close(&lfs, &dir) => 0;
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lfs_unmount(&lfs) => 0;
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// write just the revision count
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uint8_t bbuffer[LFS_BLOCK_SIZE];
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cfg.read(&cfg, pair[1], 0, bbuffer, LFS_BLOCK_SIZE) => 0;
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memcpy(bbuffer, &(uint32_t){lfs_tole32(rev+1)}, sizeof(uint32_t));
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cfg.erase(&cfg, pair[1]) => 0;
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cfg.prog(&cfg, pair[1], 0, bbuffer, LFS_BLOCK_SIZE) => 0;
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lfs_mount(&lfs, &cfg) => 0;
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// can read?
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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// can write?
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lfs_file_open(&lfs, &file, "notebook/paper",
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LFS_O_WRONLY | LFS_O_APPEND) => 0;
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strcpy((char*)buffer, "goodbye");
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size = strlen("goodbye");
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for (int i = 0; i < 5; i++) {
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lfs_file_write(&lfs, &file, buffer, size) => size;
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lfs_file_sync(&lfs, &file) => 0;
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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strcpy((char*)buffer, "hello");
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size = strlen("hello");
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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strcpy((char*)buffer, "goodbye");
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size = strlen("goodbye");
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_unmount(&lfs) => 0;
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'''
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[[case]] # partial prog, may not be byte in order!
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define.BYTE_OFF = ["0", "LFS_PROG_SIZE-1", "LFS_PROG_SIZE/2"]
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define.BYTE_VALUE = [0x33, 0xcc]
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in = "lfs.c"
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code = '''
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lfs_format(&lfs, &cfg) => 0;
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lfs_mount(&lfs, &cfg) => 0;
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lfs_mkdir(&lfs, "notebook") => 0;
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lfs_file_open(&lfs, &file, "notebook/paper",
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LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
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strcpy((char*)buffer, "hello");
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size = strlen("hello");
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for (int i = 0; i < 5; i++) {
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lfs_file_write(&lfs, &file, buffer, size) => size;
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lfs_file_sync(&lfs, &file) => 0;
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}
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lfs_file_close(&lfs, &file) => 0;
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char rbuffer[256];
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_unmount(&lfs) => 0;
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// imitate a partial prog, value should not matter, if littlefs
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// doesn't notice the partial prog testbd will assert
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// get offset to next prog
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lfs_mount(&lfs, &cfg) => 0;
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lfs_dir_open(&lfs, &dir, "notebook") => 0;
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lfs_block_t block = dir.m.pair[0];
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lfs_off_t off = dir.m.off;
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lfs_dir_close(&lfs, &dir) => 0;
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lfs_unmount(&lfs) => 0;
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// tweak byte
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uint8_t bbuffer[LFS_BLOCK_SIZE];
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cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
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bbuffer[off + BYTE_OFF] = BYTE_VALUE;
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cfg.erase(&cfg, block) => 0;
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cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
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lfs_mount(&lfs, &cfg) => 0;
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// can read?
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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// can write?
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lfs_file_open(&lfs, &file, "notebook/paper",
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LFS_O_WRONLY | LFS_O_APPEND) => 0;
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strcpy((char*)buffer, "goodbye");
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size = strlen("goodbye");
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for (int i = 0; i < 5; i++) {
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lfs_file_write(&lfs, &file, buffer, size) => size;
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lfs_file_sync(&lfs, &file) => 0;
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
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strcpy((char*)buffer, "hello");
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size = strlen("hello");
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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strcpy((char*)buffer, "goodbye");
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size = strlen("goodbye");
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for (int i = 0; i < 5; i++) {
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lfs_file_read(&lfs, &file, rbuffer, size) => size;
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assert(memcmp(rbuffer, buffer, size) == 0);
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}
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lfs_file_close(&lfs, &file) => 0;
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lfs_unmount(&lfs) => 0;
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'''
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