f5e38b9284
Commit 8f243af42a ("sections: fix const sections for crc32 table")
removed the compile-time generated crc32 tables from the RO sections,
because it conflicts with the definition of __cacheline_aligned which
puts all such aligned data into .data..cacheline_aligned section
optimized for wasting less space, and can cause alignment issues when
used in combination with const with some gcc versions like 4.7.0 due to
a gcc bug [1].
Given that most gcc versions should have the fix by now, we can just use
____cacheline_aligned, which only aligns the data but doesn't move it
into specific sections as opposed to __cacheline_aligned. In case of
gcc versions having the mentioned bug, the alignment attribute will have
no effect, but the data will still be made RO.
After patch tables are in RO:
$ nm -v lib/crc32.o | grep -1 -E "crc32c?table"
0000000000000000 t arch_local_irq_enable
0000000000000000 r crc32ctable_le
0000000000000000 t crc32_exit
--
0000000000000960 t test_buf
0000000000002000 r crc32table_be
0000000000004000 r crc32table_le
000000001d1056e5 A __crc_crc32_be
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
140 lines
3.2 KiB
C
140 lines
3.2 KiB
C
#include <stdio.h>
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#include "../include/generated/autoconf.h"
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#include "crc32defs.h"
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#include <inttypes.h>
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#define ENTRIES_PER_LINE 4
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#if CRC_LE_BITS > 8
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# define LE_TABLE_ROWS (CRC_LE_BITS/8)
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# define LE_TABLE_SIZE 256
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#else
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# define LE_TABLE_ROWS 1
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# define LE_TABLE_SIZE (1 << CRC_LE_BITS)
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#endif
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#if CRC_BE_BITS > 8
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# define BE_TABLE_ROWS (CRC_BE_BITS/8)
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# define BE_TABLE_SIZE 256
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#else
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# define BE_TABLE_ROWS 1
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# define BE_TABLE_SIZE (1 << CRC_BE_BITS)
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#endif
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static uint32_t crc32table_le[LE_TABLE_ROWS][256];
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static uint32_t crc32table_be[BE_TABLE_ROWS][256];
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static uint32_t crc32ctable_le[LE_TABLE_ROWS][256];
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/**
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* crc32init_le() - allocate and initialize LE table data
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*
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* crc is the crc of the byte i; other entries are filled in based on the
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* fact that crctable[i^j] = crctable[i] ^ crctable[j].
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*
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*/
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static void crc32init_le_generic(const uint32_t polynomial,
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uint32_t (*tab)[256])
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{
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unsigned i, j;
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uint32_t crc = 1;
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tab[0][0] = 0;
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for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
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crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
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for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
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tab[0][i + j] = crc ^ tab[0][j];
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}
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for (i = 0; i < LE_TABLE_SIZE; i++) {
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crc = tab[0][i];
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for (j = 1; j < LE_TABLE_ROWS; j++) {
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crc = tab[0][crc & 0xff] ^ (crc >> 8);
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tab[j][i] = crc;
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}
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}
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}
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static void crc32init_le(void)
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{
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crc32init_le_generic(CRCPOLY_LE, crc32table_le);
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}
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static void crc32cinit_le(void)
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{
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crc32init_le_generic(CRC32C_POLY_LE, crc32ctable_le);
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}
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/**
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* crc32init_be() - allocate and initialize BE table data
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*/
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static void crc32init_be(void)
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{
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unsigned i, j;
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uint32_t crc = 0x80000000;
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crc32table_be[0][0] = 0;
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for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
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crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
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for (j = 0; j < i; j++)
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crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
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}
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for (i = 0; i < BE_TABLE_SIZE; i++) {
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crc = crc32table_be[0][i];
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for (j = 1; j < BE_TABLE_ROWS; j++) {
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crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
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crc32table_be[j][i] = crc;
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}
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}
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}
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static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
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{
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int i, j;
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for (j = 0 ; j < rows; j++) {
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printf("{");
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for (i = 0; i < len - 1; i++) {
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if (i % ENTRIES_PER_LINE == 0)
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printf("\n");
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printf("%s(0x%8.8xL), ", trans, table[j][i]);
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}
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printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
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}
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}
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int main(int argc, char** argv)
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{
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printf("/* this file is generated - do not edit */\n\n");
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if (CRC_LE_BITS > 1) {
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crc32init_le();
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printf("static const u32 ____cacheline_aligned "
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"crc32table_le[%d][%d] = {",
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LE_TABLE_ROWS, LE_TABLE_SIZE);
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output_table(crc32table_le, LE_TABLE_ROWS,
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LE_TABLE_SIZE, "tole");
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printf("};\n");
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}
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if (CRC_BE_BITS > 1) {
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crc32init_be();
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printf("static const u32 ____cacheline_aligned "
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"crc32table_be[%d][%d] = {",
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BE_TABLE_ROWS, BE_TABLE_SIZE);
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output_table(crc32table_be, LE_TABLE_ROWS,
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BE_TABLE_SIZE, "tobe");
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printf("};\n");
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}
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if (CRC_LE_BITS > 1) {
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crc32cinit_le();
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printf("static const u32 ____cacheline_aligned "
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"crc32ctable_le[%d][%d] = {",
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LE_TABLE_ROWS, LE_TABLE_SIZE);
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output_table(crc32ctable_le, LE_TABLE_ROWS,
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LE_TABLE_SIZE, "tole");
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printf("};\n");
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}
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return 0;
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}
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