Hi Kees, I love your patch! Perhaps something to improve:
[auto build test WARNING on linus/master] [also build test WARNING on v4.17-rc7 next-20180530] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Kees-Cook/lib-bch-Remove-VLA-usage/20180531-055540 reproduce: # apt-get install sparse make ARCH=x86_64 allmodconfig make C=1 CF=-D__CHECK_ENDIAN__ sparse warnings: (new ones prefixed by >>) >> lib/bch.c:237:26: sparse: restricted __be32 degrades to integer vim +237 lib/bch.c 437aa565 Ivan Djelic 2011-03-11 171 437aa565 Ivan Djelic 2011-03-11 172 /** 437aa565 Ivan Djelic 2011-03-11 173 * encode_bch - calculate BCH ecc parity of data 437aa565 Ivan Djelic 2011-03-11 174 * @bch: BCH control structure 437aa565 Ivan Djelic 2011-03-11 175 * @data: data to encode 437aa565 Ivan Djelic 2011-03-11 176 * @len: data length in bytes 437aa565 Ivan Djelic 2011-03-11 177 * @ecc: ecc parity data, must be initialized by caller 437aa565 Ivan Djelic 2011-03-11 178 * 437aa565 Ivan Djelic 2011-03-11 179 * The @ecc parity array is used both as input and output parameter, in order to 437aa565 Ivan Djelic 2011-03-11 180 * allow incremental computations. It should be of the size indicated by member 437aa565 Ivan Djelic 2011-03-11 181 * @ecc_bytes of @bch, and should be initialized to 0 before the first call. 437aa565 Ivan Djelic 2011-03-11 182 * 437aa565 Ivan Djelic 2011-03-11 183 * The exact number of computed ecc parity bits is given by member @ecc_bits of 437aa565 Ivan Djelic 2011-03-11 184 * @bch; it may be less than m*t for large values of t. 437aa565 Ivan Djelic 2011-03-11 185 */ 437aa565 Ivan Djelic 2011-03-11 186 void encode_bch(struct bch_control *bch, const uint8_t *data, 437aa565 Ivan Djelic 2011-03-11 187 unsigned int len, uint8_t *ecc) 437aa565 Ivan Djelic 2011-03-11 188 { 437aa565 Ivan Djelic 2011-03-11 189 const unsigned int l = BCH_ECC_WORDS(bch)-1; 437aa565 Ivan Djelic 2011-03-11 190 unsigned int i, mlen; 437aa565 Ivan Djelic 2011-03-11 191 unsigned long m; da5dc7be Kees Cook 2018-05-29 192 uint32_t w; 437aa565 Ivan Djelic 2011-03-11 193 const uint32_t * const tab0 = bch->mod8_tab; 437aa565 Ivan Djelic 2011-03-11 194 const uint32_t * const tab1 = tab0 + 256*(l+1); 437aa565 Ivan Djelic 2011-03-11 195 const uint32_t * const tab2 = tab1 + 256*(l+1); 437aa565 Ivan Djelic 2011-03-11 196 const uint32_t * const tab3 = tab2 + 256*(l+1); 437aa565 Ivan Djelic 2011-03-11 197 const uint32_t *pdata, *p0, *p1, *p2, *p3; 437aa565 Ivan Djelic 2011-03-11 198 437aa565 Ivan Djelic 2011-03-11 199 if (ecc) { 437aa565 Ivan Djelic 2011-03-11 200 /* load ecc parity bytes into internal 32-bit buffer */ 437aa565 Ivan Djelic 2011-03-11 201 load_ecc8(bch, bch->ecc_buf, ecc); 437aa565 Ivan Djelic 2011-03-11 202 } else { da5dc7be Kees Cook 2018-05-29 203 memset(bch->ecc_work, 0, bch->ecc_bytes); 437aa565 Ivan Djelic 2011-03-11 204 } 437aa565 Ivan Djelic 2011-03-11 205 437aa565 Ivan Djelic 2011-03-11 206 /* process first unaligned data bytes */ 437aa565 Ivan Djelic 2011-03-11 207 m = ((unsigned long)data) & 3; 437aa565 Ivan Djelic 2011-03-11 208 if (m) { 437aa565 Ivan Djelic 2011-03-11 209 mlen = (len < (4-m)) ? len : 4-m; 437aa565 Ivan Djelic 2011-03-11 210 encode_bch_unaligned(bch, data, mlen, bch->ecc_buf); 437aa565 Ivan Djelic 2011-03-11 211 data += mlen; 437aa565 Ivan Djelic 2011-03-11 212 len -= mlen; 437aa565 Ivan Djelic 2011-03-11 213 } 437aa565 Ivan Djelic 2011-03-11 214 437aa565 Ivan Djelic 2011-03-11 215 /* process 32-bit aligned data words */ 437aa565 Ivan Djelic 2011-03-11 216 pdata = (uint32_t *)data; 437aa565 Ivan Djelic 2011-03-11 217 mlen = len/4; 437aa565 Ivan Djelic 2011-03-11 218 data += 4*mlen; 437aa565 Ivan Djelic 2011-03-11 219 len -= 4*mlen; da5dc7be Kees Cook 2018-05-29 220 memcpy(bch->ecc_work, bch->ecc_buf, bch->ecc_bytes); 437aa565 Ivan Djelic 2011-03-11 221 437aa565 Ivan Djelic 2011-03-11 222 /* 437aa565 Ivan Djelic 2011-03-11 223 * split each 32-bit word into 4 polynomials of weight 8 as follows: 437aa565 Ivan Djelic 2011-03-11 224 * 437aa565 Ivan Djelic 2011-03-11 225 * 31 ...24 23 ...16 15 ... 8 7 ... 0 437aa565 Ivan Djelic 2011-03-11 226 * xxxxxxxx yyyyyyyy zzzzzzzz tttttttt 437aa565 Ivan Djelic 2011-03-11 227 * tttttttt mod g = r0 (precomputed) 437aa565 Ivan Djelic 2011-03-11 228 * zzzzzzzz 00000000 mod g = r1 (precomputed) 437aa565 Ivan Djelic 2011-03-11 229 * yyyyyyyy 00000000 00000000 mod g = r2 (precomputed) 437aa565 Ivan Djelic 2011-03-11 230 * xxxxxxxx 00000000 00000000 00000000 mod g = r3 (precomputed) 437aa565 Ivan Djelic 2011-03-11 231 * xxxxxxxx yyyyyyyy zzzzzzzz tttttttt mod g = r0^r1^r2^r3 437aa565 Ivan Djelic 2011-03-11 232 */ 437aa565 Ivan Djelic 2011-03-11 233 while (mlen--) { da5dc7be Kees Cook 2018-05-29 234 uint32_t *r = bch->ecc_work; da5dc7be Kees Cook 2018-05-29 235 437aa565 Ivan Djelic 2011-03-11 236 /* input data is read in big-endian format */ 437aa565 Ivan Djelic 2011-03-11 @237 w = r[0]^cpu_to_be32(*pdata++); 437aa565 Ivan Djelic 2011-03-11 238 p0 = tab0 + (l+1)*((w >> 0) & 0xff); 437aa565 Ivan Djelic 2011-03-11 239 p1 = tab1 + (l+1)*((w >> 8) & 0xff); 437aa565 Ivan Djelic 2011-03-11 240 p2 = tab2 + (l+1)*((w >> 16) & 0xff); 437aa565 Ivan Djelic 2011-03-11 241 p3 = tab3 + (l+1)*((w >> 24) & 0xff); 437aa565 Ivan Djelic 2011-03-11 242 437aa565 Ivan Djelic 2011-03-11 243 for (i = 0; i < l; i++) 437aa565 Ivan Djelic 2011-03-11 244 r[i] = r[i+1]^p0[i]^p1[i]^p2[i]^p3[i]; 437aa565 Ivan Djelic 2011-03-11 245 437aa565 Ivan Djelic 2011-03-11 246 r[l] = p0[l]^p1[l]^p2[l]^p3[l]; 437aa565 Ivan Djelic 2011-03-11 247 } da5dc7be Kees Cook 2018-05-29 248 memcpy(bch->ecc_buf, bch->ecc_work, bch->ecc_bytes); 437aa565 Ivan Djelic 2011-03-11 249 437aa565 Ivan Djelic 2011-03-11 250 /* process last unaligned bytes */ 437aa565 Ivan Djelic 2011-03-11 251 if (len) 437aa565 Ivan Djelic 2011-03-11 252 encode_bch_unaligned(bch, data, len, bch->ecc_buf); 437aa565 Ivan Djelic 2011-03-11 253 437aa565 Ivan Djelic 2011-03-11 254 /* store ecc parity bytes into original parity buffer */ 437aa565 Ivan Djelic 2011-03-11 255 if (ecc) 437aa565 Ivan Djelic 2011-03-11 256 store_ecc8(bch, ecc, bch->ecc_buf); 437aa565 Ivan Djelic 2011-03-11 257 } 437aa565 Ivan Djelic 2011-03-11 258 EXPORT_SYMBOL_GPL(encode_bch); 437aa565 Ivan Djelic 2011-03-11 259 :::::: The code at line 237 was first introduced by commit :::::: 437aa565e2656776a7104aaacd792fe789ea8b2d lib: add shared BCH ECC library :::::: TO: Ivan Djelic <ivan.dje...@parrot.com> :::::: CC: David Woodhouse <david.woodho...@intel.com> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
