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| author | Daniel Borkmann <dborkman@redhat.com> | 2015-02-13 14:36:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-13 21:21:35 -0800 |
| commit | f5e38b9284e13e28c1ef00e508238f279cf0ac3a (patch) | |
| tree | 0067a65ff5a293c80593117840550c182c158814 /lib/gen_crc32table.c | |
| parent | 7f590657937f1c59163ff14a13062439a18e4a37 (diff) | |
| download | lwn-f5e38b9284e13e28c1ef00e508238f279cf0ac3a.tar.gz lwn-f5e38b9284e13e28c1ef00e508238f279cf0ac3a.zip | |
lib: crc32: constify crc32 lookup table
Commit 8f243af42ade ("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>
Diffstat (limited to 'lib/gen_crc32table.c')
| -rw-r--r-- | lib/gen_crc32table.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c index 71fcfcd96410..d83a372fa76f 100644 --- a/lib/gen_crc32table.c +++ b/lib/gen_crc32table.c @@ -109,7 +109,7 @@ int main(int argc, char** argv) if (CRC_LE_BITS > 1) { crc32init_le(); - printf("static u32 __cacheline_aligned " + printf("static const u32 ____cacheline_aligned " "crc32table_le[%d][%d] = {", LE_TABLE_ROWS, LE_TABLE_SIZE); output_table(crc32table_le, LE_TABLE_ROWS, @@ -119,7 +119,7 @@ int main(int argc, char** argv) if (CRC_BE_BITS > 1) { crc32init_be(); - printf("static u32 __cacheline_aligned " + printf("static const u32 ____cacheline_aligned " "crc32table_be[%d][%d] = {", BE_TABLE_ROWS, BE_TABLE_SIZE); output_table(crc32table_be, LE_TABLE_ROWS, @@ -128,7 +128,7 @@ int main(int argc, char** argv) } if (CRC_LE_BITS > 1) { crc32cinit_le(); - printf("static u32 __cacheline_aligned " + printf("static const u32 ____cacheline_aligned " "crc32ctable_le[%d][%d] = {", LE_TABLE_ROWS, LE_TABLE_SIZE); output_table(crc32ctable_le, LE_TABLE_ROWS, |