lib/crc32: make crc32c() go directly to lib

Now that the lower level __crc32c_le() library function is optimized for
each architecture, make crc32c() just call that instead of taking an
inefficient and error-prone detour through the shash API.

Note: a future cleanup should make crc32c_le() be the actual library
function instead of __crc32c_le().  That will require updating callers
of __crc32c_le() to use crc32c_le() instead, and updating callers of
crc32c_le() that expect a 'const void *' arg to expect 'const u8 *'
instead.  Similarly, a future cleanup should remove LIBCRC32C by making
everyone who is selecting it just select CRC32 directly instead.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-16-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

include/linux/crc32c.h

@@ -2,9 +2,12 @@
 #ifndef _LINUX_CRC32C_H
 #define _LINUX_CRC32C_H
 
-#include <linux/types.h>
+#include <linux/crc32.h>
 
-extern u32 crc32c(u32 crc, const void *address, unsigned int length);
+static inline u32 crc32c(u32 crc, const void *address, unsigned int length)
+{
+	return __crc32c_le(crc, address, length);
+}
 
 /* This macro exists for backwards-compatibility. */
 #define crc32c_le crc32c

lib/Kconfig

@@ -310,14 +310,10 @@ config CRC7
 
 config LIBCRC32C
 	tristate "CRC32c (Castagnoli, et al) Cyclic Redundancy-Check"
-	select CRYPTO
-	select CRYPTO_CRC32C
+	select CRC32
 	help
-	  This option is provided for the case where no in-kernel-tree
-	  modules require CRC32c functions, but a module built outside the
-	  kernel tree does. Such modules that use library CRC32c functions
-	  require M here.  See Castagnoli93.
-	  Module will be libcrc32c.
+	  This option just selects CRC32 and is provided for compatibility
+	  purposes until the users are updated to select CRC32 directly.
 
 config CRC8
 	tristate "CRC8 function"

lib/Makefile

@@ -167,7 +167,6 @@ obj-$(CONFIG_CRC64)     += crc64.o
 obj-$(CONFIG_CRC32_SELFTEST)	+= crc32test.o
 obj-$(CONFIG_CRC4)	+= crc4.o
 obj-$(CONFIG_CRC7)	+= crc7.o
-obj-$(CONFIG_LIBCRC32C)	+= libcrc32c.o
 obj-$(CONFIG_CRC8)	+= crc8.o
 obj-$(CONFIG_CRC64_ROCKSOFT) += crc64-rocksoft.o
 obj-$(CONFIG_XXHASH)	+= xxhash.o