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authorDaniel Borkmann <dborkman@redhat.com>2015-02-13 14:36:21 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-13 21:21:35 -0800
commitf5e38b9284e13e28c1ef00e508238f279cf0ac3a (patch)
tree0067a65ff5a293c80593117840550c182c158814 /lib
parent7f590657937f1c59163ff14a13062439a18e4a37 (diff)
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')
-rw-r--r--lib/gen_crc32table.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index 71fcfcd9641..d83a372fa76 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,