From 2049dbb6fe55b6bd42e18dc9853c5b9dafc5149d Mon Sep 17 00:00:00 2001 From: Alexander Shiyan Date: Sun, 19 Jun 2016 21:52:52 +0300 Subject: [PATCH] crypto: crc32: Optimize dynamic CRC table generation In barebox we have an option for dynamic formation of the CRC32 table (DYNAMIC_CRC_TABLE), but the source code declares a static array which is simply filled with data, the resulting code becomes even more than without DYNAMIC_CRC_TABLE option, due to the BSS usage. CONFIG_DYNAMIC_CRC_TABLE=n text data bss dec hex filename 1884 0 0 1884 75c crc32.o CONFIG_DYNAMIC_CRC_TABLE=y text data bss dec hex filename 1066 4 1024 2094 82e crc32.o This patch provides dynamic buffer allocation for the CRC table, which saves about 1 Kbyte, as it should be. CONFIG_DYNAMIC_CRC_TABLE=y text data bss dec hex filename 1062 0 4 1066 42a crc32.o Signed-off-by: Alexander Shiyan Signed-off-by: Sascha Hauer --- crypto/crc32.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/crypto/crc32.c b/crypto/crc32.c index 3bff6feb2..232c023ad 100644 --- a/crypto/crc32.c +++ b/crypto/crc32.c @@ -24,9 +24,7 @@ #ifdef CONFIG_DYNAMIC_CRC_TABLE -static int crc_table_empty = 1; -static ulong crc_table[256]; -static void make_crc_table(void); +static ulong *crc_table; /* Generate a table for a byte-wise 32-bit CRC calculation on the polynomial: @@ -65,6 +63,8 @@ static void make_crc_table(void) for (n = 0; n < sizeof(p)/sizeof(char); n++) poly |= 1L << (31 - p[n]); + crc_table = xmalloc(sizeof(ulong) * 256); + for (n = 0; n < 256; n++) { c = (ulong)n; @@ -72,7 +72,6 @@ static void make_crc_table(void) c = c & 1 ? poly ^ (c >> 1) : c >> 1; crc_table[n] = c; } - crc_table_empty = 0; } #else /* ======================================================================== @@ -147,8 +146,8 @@ STATIC uint32_t crc32(uint32_t crc, const void *_buf, unsigned int len) const unsigned char *buf = _buf; #ifdef CONFIG_DYNAMIC_CRC_TABLE - if (crc_table_empty) - make_crc_table(); + if (!crc_table) + make_crc_table(); #endif crc = crc ^ 0xffffffffL; while (len >= 8) @@ -173,8 +172,8 @@ STATIC uint32_t crc32_no_comp(uint32_t crc, const void *_buf, unsigned int len) const unsigned char *buf = _buf; #ifdef CONFIG_DYNAMIC_CRC_TABLE - if (crc_table_empty) - make_crc_table(); + if (!crc_table) + make_crc_table(); #endif while (len >= 8) {