/* * lib/ts_bm.c Boyer-Moore text search implementation * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * Authors: Pablo Neira Ayuso * * ========================================================================== * * Implements Boyer-Moore string matching algorithm: * * [1] A Fast String Searching Algorithm, R.S. Boyer and Moore. * Communications of the Association for Computing Machinery, * 20(10), 1977, pp. 762-772. * http://www.cs.utexas.edu/users/moore/publications/fstrpos.pdf * * [2] Handbook of Exact String Matching Algorithms, Thierry Lecroq, 2004 * http://www-igm.univ-mlv.fr/~lecroq/string/string.pdf * * Note: Since Boyer-Moore (BM) performs searches for matchings from right * to left, it's still possible that a matching could be spread over * multiple blocks, in that case this algorithm won't find any coincidence. * * If you're willing to ensure that such thing won't ever happen, use the * Knuth-Pratt-Morris (KMP) implementation instead. In conclusion, choose * the proper string search algorithm depending on your setting. * * Say you're using the textsearch infrastructure for filtering, NIDS or * any similar security focused purpose, then go KMP. Otherwise, if you * really care about performance, say you're classifying packets to apply * Quality of Service (QoS) policies, and you don't mind about possible * matchings spread over multiple fragments, then go BM. */ #include #include #include #include #include #include /* Alphabet size, use ASCII */ #define ASIZE 256 #if 0 #define DEBUGP printk #else #define DEBUGP(args, format...) #endif struct ts_bm { u8 * pattern; unsigned int patlen; unsigned int bad_shift[ASIZE]; unsigned int good_shift[0]; }; static unsigned int bm_find(struct ts_config *conf, struct ts_state *state) { struct ts_bm *bm = ts_config_priv(conf); unsigned int i, text_len, consumed = state->offset; const u8 *text; int shift = bm->patlen - 1, bs; const u8 icase = conf->flags & TS_IGNORECASE; for (;;) { text_len = conf->get_next_block(consumed, &text, conf, state); if (unlikely(text_len == 0)) break; while (shift < text_len) { DEBUGP("Searching in position %d (%c)\n", shift, text[shift]); for (i = 0; i < bm->patlen; i++) if ((icase ? toupper(text[shift-i]) : text[shift-i]) != bm->pattern[bm->patlen-1-i]) goto next; /* London calling... */ DEBUGP("found!\n"); return consumed += (shift-(bm->patlen-1)); next: bs = bm->bad_shift[text[shift-i]]; /* Now jumping to... */ shift = max_t(int, shift-i+bs, shift+bm->good_shift[i]); } consumed += text_len; } return UINT_MAX; } static int subpattern(u8 *pattern, int i, int j, int g) { int x = i+g-1, y = j+g-1, ret = 0; while(pattern[x--] == pattern[y--]) { if (y < 0) { ret = 1; break; } if (--g == 0) { ret = pattern[i-1] != pattern[j-1]; break; } } return ret; } static void compute_prefix_tbl(struct ts_bm *bm, int flags) { int i, j, g; for (i = 0; i < ASIZE; i++) bm->bad_shift[i] = bm->patlen; for (i = 0; i < bm->patlen - 1; i++) { bm->bad_shift[bm->pattern[i]] = bm->patlen - 1 - i; if (flags & TS_IGNORECASE) bm->bad_shift[tolower(bm->pattern[i])] = bm->patlen - 1 - i; } /* Compute the good shift array, used to match reocurrences * of a subpattern */ bm->good_shift[0] = 1; for (i = 1; i < bm->patlen; i++) bm->good_shift[i] = bm->patlen; for (i = bm->patlen-1, g = 1; i > 0; g++, i--) { for (j = i-1; j >= 1-g ; j--) if (subpattern(bm->pattern, i, j, g)) { bm->good_shift[g] = bm->patlen-j-g; break; } } } static struct ts_config *bm_init(const void *pattern, unsigned int len, gfp_t gfp_mask, int flags) { struct ts_config *conf; struct ts_bm *bm; int i; unsigned int prefix_tbl_len = len * sizeof(unsigned int); size_t priv_size = sizeof(*bm) + len + prefix_tbl_len; conf = alloc_ts_config(priv_size, gfp_mask); if (IS_ERR(conf)) return conf; conf->flags = flags; bm = ts_config_priv(conf); bm->patlen = len; bm->pattern = (u8 *) bm->good_shift + prefix_tbl_len; if (flags & TS_IGNORECASE) for (i = 0; i < len; i++) bm->pattern[i] = toupper(((u8 *)pattern)[i]); else memcpy(bm->pattern, pattern, len); compute_prefix_tbl(bm, flags); return conf; } static void *bm_get_pattern(struct ts_config *conf) { struct ts_bm *bm = ts_config_priv(conf); return bm->pattern; } static unsigned int bm_get_pattern_len(struct ts_config *conf) { struct ts_bm *bm = ts_config_priv(conf); return bm->patlen; } static struct ts_ops bm_ops = { .name = "bm", .find = bm_find, .init = bm_init, .get_pattern = bm_get_pattern, .get_pattern_len = bm_get_pattern_len, .owner = THIS_MODULE, .list = LIST_HEAD_INIT(bm_ops.list) }; static int __init init_bm(void) { return textsearch_register(&bm_ops); } static void __exit exit_bm(void) { textsearch_unregister(&bm_ops); } MODULE_LICENSE("GPL"); module_init(init_bm); module_exit(exit_bm); 3a50fbc746ed9b415c25e92'>d53fbdac9d0781e39a13b2ac6b2bd258cf3b4140 /fs/xfs/libxfs/xfs_ag_resv.c parentbf29bddf0417a4783da3b24e8c9e017ac649326f (diff)
efi/fdt: Avoid FDT manipulation after ExitBootServices()
Some AArch64 UEFI implementations disable the MMU in ExitBootServices(), after which unaligned accesses to RAM are no longer supported. Commit: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel") fixed an issue in the memory map handling of the stub FDT code, but inadvertently created an issue with such firmware, by moving some of the FDT manipulation to after the invocation of ExitBootServices(). Given that the stub's libfdt implementation uses the ordinary, accelerated string functions, which rely on hardware handling of unaligned accesses, manipulating the FDT with the MMU off may result in alignment faults. So fix the situation by moving the update_fdt_memmap() call into the callback function invoked by efi_exit_boot_services() right before it calls the ExitBootServices() UEFI service (which is arguably a better place for it anyway) Note that disabling the MMU in ExitBootServices() is not compliant with the UEFI spec, and carries great risk due to the fact that switching from cached to uncached memory accesses halfway through compiler generated code (i.e., involving a stack) can never be done in a way that is architecturally safe. Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel") Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Riku Voipio <riku.voipio@linaro.org> Cc: <stable@vger.kernel.org> Cc: mark.rutland@arm.com Cc: linux-efi@vger.kernel.org Cc: matt@codeblueprint.co.uk Cc: leif.lindholm@linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'fs/xfs/libxfs/xfs_ag_resv.c')