lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/

Rework how lib/crc/ supports arch-optimized code.  First, instead of the
arch-optimized CRC code being in arch/$(SRCARCH)/lib/, it will now be in
lib/crc/$(SRCARCH)/.  Second, the API functions (e.g. crc32c()),
arch-optimized functions (e.g. crc32c_arch()), and generic functions
(e.g. crc32c_base()) will now be part of a single module for each CRC
type, allowing better inlining and dead code elimination.  The second
change is made possible by the first.

As an example, consider CONFIG_CRC32=m on x86.  We'll now have just
crc32.ko instead of both crc32-x86.ko and crc32.ko.  The two modules
were already coupled together and always both got loaded together via
direct symbol dependency, so the separation provided no benefit.

Note: later I'd like to apply the same design to lib/crypto/ too, where
often the API functions are out-of-line so this will work even better.
In those cases, for each algorithm we currently have 3 modules all
coupled together, e.g. libsha256.ko, libsha256-generic.ko, and
sha256-x86.ko.  We should have just one, inline things properly, and
rely on the compiler's dead code elimination to decide the inclusion of
the generic code instead of manually setting it via kconfig.

Having arch-specific code outside arch/ was somewhat controversial when
Zinc proposed it back in 2018.  But I don't think the concerns are
warranted.  It's better from a technical perspective, as it enables the
improvements mentioned above.  This model is already successfully used
in other places in the kernel such as lib/raid6/.  The community of each
architecture still remains free to work on the code, even if it's not in
arch/.  At the time there was also a desire to put the library code in
the same files as the old-school crypto API, but that was a mistake; now
that the library is separate, that's no longer a constraint either.

Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-3-ebiggers@kernel.org
Link: https://lore.kernel.org/r/20250612054514.142728-1-ebiggers@kernel.org
Link: https://lore.kernel.org/r/20250621012221.4351-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

diff --git a/Documentation/core-api/kernel-api.rst b/Documentation/core-api/kernel-api.rst
index c4642d9f13a9cd42bf24769d7d77f075f476b2ec..9c8370891a39bb2c796cf3b572e1c1b2d5f1cde2 100644 (file)
--- a/Documentation/core-api/kernel-api.rst
+++ b/Documentation/core-api/kernel-api.rst
@@ -148,7 +148,7 @@ CRC Functions
 .. kernel-doc:: lib/crc/crc16.c
    :export:
 
-.. kernel-doc:: lib/crc/crc32.c
+.. kernel-doc:: lib/crc/crc32-main.c
 
 .. kernel-doc:: lib/crc/crc-ccitt.c
    :export:

diff --git a/MAINTAINERS b/MAINTAINERS
index b0ec17dfbe0353a79e91175f2669ffb3db7dee86..d75676e17ac78ee3389209e6f9cf99daa050432a 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6359,7 +6359,6 @@ L:        linux-crypto@vger.kernel.org
 S:     Maintained
 T:     git https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git crc-next
 F:     Documentation/staging/crc*
-F:     arch/*/lib/crc*
 F:     include/linux/crc*
 F:     lib/crc/
 F:     scripts/gen-crc-consts.py

diff --git a/include/linux/crc-t10dif.h b/include/linux/crc-t10dif.h
index a559fdff3f7e201b93cad6dd867983cbb28ac094..ecc8bc2dd7f4c2c7cafafe49f03d1d2e106e030d 100644 (file)
--- a/include/linux/crc-t10dif.h
+++ b/include/linux/crc-t10dif.h
@@ -4,15 +4,7 @@
 
 #include <linux/types.h>
 
-u16 crc_t10dif_arch(u16 crc, const u8 *p, size_t len);
-u16 crc_t10dif_generic(u16 crc, const u8 *p, size_t len);
-
-static inline u16 crc_t10dif_update(u16 crc, const u8 *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC_T10DIF_ARCH))
-               return crc_t10dif_arch(crc, p, len);
-       return crc_t10dif_generic(crc, p, len);
-}
+u16 crc_t10dif_update(u16 crc, const u8 *p, size_t len);
 
 static inline u16 crc_t10dif(const u8 *p, size_t len)
 {

diff --git a/include/linux/crc32.h b/include/linux/crc32.h
index 36bbc0405aa0445878c63c000d22f1a61667b1f2..22dbe7144eb44d9b2889ae097973d8cbae914f2f 100644 (file)
--- a/include/linux/crc32.h
+++ b/include/linux/crc32.h
@@ -5,33 +5,9 @@
 #include <linux/types.h>
 #include <linux/bitrev.h>
 
-u32 crc32_le_arch(u32 crc, const u8 *p, size_t len);
-u32 crc32_le_base(u32 crc, const u8 *p, size_t len);
-u32 crc32_be_arch(u32 crc, const u8 *p, size_t len);
-u32 crc32_be_base(u32 crc, const u8 *p, size_t len);
-u32 crc32c_arch(u32 crc, const u8 *p, size_t len);
-u32 crc32c_base(u32 crc, const u8 *p, size_t len);
-
-static inline u32 crc32_le(u32 crc, const void *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC32_ARCH))
-               return crc32_le_arch(crc, p, len);
-       return crc32_le_base(crc, p, len);
-}
-
-static inline u32 crc32_be(u32 crc, const void *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC32_ARCH))
-               return crc32_be_arch(crc, p, len);
-       return crc32_be_base(crc, p, len);
-}
-
-static inline u32 crc32c(u32 crc, const void *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC32_ARCH))
-               return crc32c_arch(crc, p, len);
-       return crc32c_base(crc, p, len);
-}
+u32 crc32_le(u32 crc, const void *p, size_t len);
+u32 crc32_be(u32 crc, const void *p, size_t len);
+u32 crc32c(u32 crc, const void *p, size_t len);
 
 /*
  * crc32_optimizations() returns flags that indicate which CRC32 library

diff --git a/include/linux/crc64.h b/include/linux/crc64.h
index b6aa290a79312fe2f52138f1a0ff441fde0cf1ff..fc0c06ab1993c39bf90fac1ce6b461dc8aa82fef 100644 (file)
--- a/include/linux/crc64.h
+++ b/include/linux/crc64.h
@@ -4,11 +4,6 @@
 
 #include <linux/types.h>
 
-u64 crc64_be_arch(u64 crc, const u8 *p, size_t len);
-u64 crc64_be_generic(u64 crc, const u8 *p, size_t len);
-u64 crc64_nvme_arch(u64 crc, const u8 *p, size_t len);
-u64 crc64_nvme_generic(u64 crc, const u8 *p, size_t len);
-
 /**
  * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
  * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
@@ -16,12 +11,7 @@ u64 crc64_nvme_generic(u64 crc, const u8 *p, size_t len);
  * @p: pointer to buffer over which CRC64 is run
  * @len: length of buffer @p
  */
-static inline u64 crc64_be(u64 crc, const void *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC64_ARCH))
-               return crc64_be_arch(crc, p, len);
-       return crc64_be_generic(crc, p, len);
-}
+u64 crc64_be(u64 crc, const void *p, size_t len);
 
 /**
  * crc64_nvme - Calculate CRC64-NVME
@@ -33,11 +23,6 @@ static inline u64 crc64_be(u64 crc, const void *p, size_t len)
  * This computes the CRC64 defined in the NVME NVM Command Set Specification,
  * *including the bitwise inversion at the beginning and end*.
  */
-static inline u64 crc64_nvme(u64 crc, const void *p, size_t len)
-{
-       if (IS_ENABLED(CONFIG_CRC64_ARCH))
-               return ~crc64_nvme_arch(~crc, p, len);
-       return ~crc64_nvme_generic(~crc, p, len);
-}
+u64 crc64_nvme(u64 crc, const void *p, size_t len);
 
 #endif /* _LINUX_CRC64_H */

diff --git a/lib/crc/Kconfig b/lib/crc/Kconfig
index e0e7168b74c75c57370dc8ac215fcfe0935de32b..04c7aeb0fc8e6fcfced51179b9ad508f9632717c 100644 (file)
--- a/lib/crc/Kconfig
+++ b/lib/crc/Kconfig
@@ -48,8 +48,8 @@ config ARCH_HAS_CRC_T10DIF
        bool
 
 config CRC_T10DIF_ARCH
-       tristate
-       default CRC_T10DIF if ARCH_HAS_CRC_T10DIF && CRC_OPTIMIZATIONS
+       bool
+       depends on CRC_T10DIF && CRC_OPTIMIZATIONS
 
 config CRC32
        tristate
@@ -62,8 +62,8 @@ config ARCH_HAS_CRC32
        bool
 
 config CRC32_ARCH
-       tristate
-       default CRC32 if ARCH_HAS_CRC32 && CRC_OPTIMIZATIONS
+       bool
+       depends on CRC32 && CRC_OPTIMIZATIONS
 
 config CRC64
        tristate
@@ -75,11 +75,12 @@ config ARCH_HAS_CRC64
        bool
 
 config CRC64_ARCH
-       tristate
-       default CRC64 if ARCH_HAS_CRC64 && CRC_OPTIMIZATIONS
+       bool
+       depends on CRC64 && CRC_OPTIMIZATIONS
 
 config CRC_OPTIMIZATIONS
        bool "Enable optimized CRC implementations" if EXPERT
+       depends on !UML
        default y
        help
          Disabling this option reduces code size slightly by disabling the

diff --git a/lib/crc/Makefile b/lib/crc/Makefile
index ff4c30dda452846574a053910cd4541738b86075..926edc3b035f6351d9ee0f6c550556c5f8a99525 100644 (file)
--- a/lib/crc/Makefile
+++ b/lib/crc/Makefile
@@ -8,16 +8,32 @@ obj-$(CONFIG_CRC8) += crc8.o
 obj-$(CONFIG_CRC16) += crc16.o
 obj-$(CONFIG_CRC_CCITT) += crc-ccitt.o
 obj-$(CONFIG_CRC_ITU_T) += crc-itu-t.o
+
 obj-$(CONFIG_CRC_T10DIF) += crc-t10dif.o
+crc-t10dif-y := crc-t10dif-main.o
+ifeq ($(CONFIG_CRC_T10DIF_ARCH),y)
+CFLAGS_crc-t10dif-main.o += -I$(src)/$(SRCARCH)
+endif
+
 obj-$(CONFIG_CRC32) += crc32.o
+crc32-y := crc32-main.o
+ifeq ($(CONFIG_CRC32_ARCH),y)
+CFLAGS_crc32-main.o += -I$(src)/$(SRCARCH)
+endif
+
 obj-$(CONFIG_CRC64) += crc64.o
+crc64-y := crc64-main.o
+ifeq ($(CONFIG_CRC64_ARCH),y)
+CFLAGS_crc64-main.o += -I$(src)/$(SRCARCH)
+endif
+
 obj-y += tests/
 
 hostprogs := gen_crc32table gen_crc64table
 clean-files := crc32table.h crc64table.h
 
-$(obj)/crc32.o: $(obj)/crc32table.h
-$(obj)/crc64.o: $(obj)/crc64table.h
+$(obj)/crc32-main.o: $(obj)/crc32table.h
+$(obj)/crc64-main.o: $(obj)/crc64table.h
 
 quiet_cmd_crc32 = GEN     $@
       cmd_crc32 = $< > $@

diff --git a/lib/crc/crc-t10dif.c b/lib/crc/crc-t10dif-main.c
similarity index 78%
rename from lib/crc/crc-t10dif.c
rename to lib/crc/crc-t10dif-main.c
index 311c2ab829f1524069abf495890574f7a472549d..bc91f388818485585397261ecf52cd50c06db944 100644 (file)
--- a/lib/crc/crc-t10dif.c
+++ b/lib/crc/crc-t10dif-main.c
@@ -50,16 +50,39 @@ static const u16 t10_dif_crc_table[256] = {
        0xF0D8, 0x7B6F, 0x6C01, 0xE7B6, 0x42DD, 0xC96A, 0xDE04, 0x55B3
 };
 
-u16 crc_t10dif_generic(u16 crc, const u8 *p, size_t len)
+static inline u16 __maybe_unused
+crc_t10dif_generic(u16 crc, const u8 *p, size_t len)
 {
-       size_t i;
+       while (len--)
+               crc = (crc << 8) ^ t10_dif_crc_table[(crc >> 8) ^ *p++];
+       return crc;
+}
 
-       for (i = 0; i < len; i++)
-               crc = (crc << 8) ^ t10_dif_crc_table[(crc >> 8) ^ p[i]];
+#ifdef CONFIG_CRC_T10DIF_ARCH
+#include "crc-t10dif.h" /* $(SRCARCH)/crc-t10dif.h */
+#else
+#define crc_t10dif_arch crc_t10dif_generic
+#endif
 
-       return crc;
+u16 crc_t10dif_update(u16 crc, const u8 *p, size_t len)
+{
+       return crc_t10dif_arch(crc, p, len);
+}
+EXPORT_SYMBOL(crc_t10dif_update);
+
+#ifdef crc_t10dif_mod_init_arch
+static int __init crc_t10dif_mod_init(void)
+{
+       crc_t10dif_mod_init_arch();
+       return 0;
+}
+subsys_initcall(crc_t10dif_mod_init);
+
+static void __exit crc_t10dif_mod_exit(void)
+{
 }
-EXPORT_SYMBOL(crc_t10dif_generic);
+module_exit(crc_t10dif_mod_exit);
+#endif
 
-MODULE_DESCRIPTION("T10 DIF CRC calculation");
+MODULE_DESCRIPTION("CRC-T10DIF library functions");
 MODULE_LICENSE("GPL");

diff --git a/lib/crc/crc32.c b/lib/crc/crc32-main.c
similarity index 58%
rename from lib/crc/crc32.c
rename to lib/crc/crc32-main.c
index 6811b37df2aada61ecb143b53a66a4b0643c7715..7843512ffef4332f6b6f395632130a0ce8584ce6 100644 (file)
--- a/lib/crc/crc32.c
+++ b/lib/crc/crc32-main.c
@@ -30,30 +30,75 @@
 
 #include "crc32table.h"
 
-MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
-MODULE_DESCRIPTION("Various CRC32 calculations");
-MODULE_LICENSE("GPL");
-
-u32 crc32_le_base(u32 crc, const u8 *p, size_t len)
+static inline u32 __maybe_unused
+crc32_le_base(u32 crc, const u8 *p, size_t len)
 {
        while (len--)
                crc = (crc >> 8) ^ crc32table_le[(crc & 255) ^ *p++];
        return crc;
 }
-EXPORT_SYMBOL(crc32_le_base);
 
-u32 crc32c_base(u32 crc, const u8 *p, size_t len)
+static inline u32 __maybe_unused
+crc32_be_base(u32 crc, const u8 *p, size_t len)
 {
        while (len--)
-               crc = (crc >> 8) ^ crc32ctable_le[(crc & 255) ^ *p++];
+               crc = (crc << 8) ^ crc32table_be[(crc >> 24) ^ *p++];
        return crc;
 }
-EXPORT_SYMBOL(crc32c_base);
 
-u32 crc32_be_base(u32 crc, const u8 *p, size_t len)
+static inline u32 __maybe_unused
+crc32c_base(u32 crc, const u8 *p, size_t len)
 {
        while (len--)
-               crc = (crc << 8) ^ crc32table_be[(crc >> 24) ^ *p++];
+               crc = (crc >> 8) ^ crc32ctable_le[(crc & 255) ^ *p++];
        return crc;
 }
-EXPORT_SYMBOL(crc32_be_base);
+
+#ifdef CONFIG_CRC32_ARCH
+#include "crc32.h" /* $(SRCARCH)/crc32.h */
+
+u32 crc32_optimizations(void)
+{
+       return crc32_optimizations_arch();
+}
+EXPORT_SYMBOL(crc32_optimizations);
+#else
+#define crc32_le_arch crc32_le_base
+#define crc32_be_arch crc32_be_base
+#define crc32c_arch crc32c_base
+#endif
+
+u32 crc32_le(u32 crc, const void *p, size_t len)
+{
+       return crc32_le_arch(crc, p, len);
+}
+EXPORT_SYMBOL(crc32_le);
+
+u32 crc32_be(u32 crc, const void *p, size_t len)
+{
+       return crc32_be_arch(crc, p, len);
+}
+EXPORT_SYMBOL(crc32_be);
+
+u32 crc32c(u32 crc, const void *p, size_t len)
+{
+       return crc32c_arch(crc, p, len);
+}
+EXPORT_SYMBOL(crc32c);
+
+#ifdef crc32_mod_init_arch
+static int __init crc32_mod_init(void)
+{
+       crc32_mod_init_arch();
+       return 0;
+}
+subsys_initcall(crc32_mod_init);
+
+static void __exit crc32_mod_exit(void)
+{
+}
+module_exit(crc32_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("CRC32 library functions");
+MODULE_LICENSE("GPL");

diff --git a/lib/crc/crc64.c b/lib/crc/crc64-main.c
similarity index 66%
rename from lib/crc/crc64.c
rename to lib/crc/crc64-main.c
index 5b1b17057f0aef3dd5d2cc5afd3ab576fe82c3c9..038afc7f4d444fb840d1eb8cca41545208d50e04 100644 (file)
--- a/lib/crc/crc64.c
+++ b/lib/crc/crc64-main.c
@@ -38,21 +38,54 @@
 #include <linux/crc64.h>
 #include "crc64table.h"
 
-MODULE_DESCRIPTION("CRC64 calculations");
-MODULE_LICENSE("GPL v2");
-
-u64 crc64_be_generic(u64 crc, const u8 *p, size_t len)
+static inline u64 __maybe_unused
+crc64_be_generic(u64 crc, const u8 *p, size_t len)
 {
        while (len--)
                crc = (crc << 8) ^ crc64table[(crc >> 56) ^ *p++];
        return crc;
 }
-EXPORT_SYMBOL_GPL(crc64_be_generic);
 
-u64 crc64_nvme_generic(u64 crc, const u8 *p, size_t len)
+static inline u64 __maybe_unused
+crc64_nvme_generic(u64 crc, const u8 *p, size_t len)
 {
        while (len--)
                crc = (crc >> 8) ^ crc64nvmetable[(crc & 0xff) ^ *p++];
        return crc;
 }
-EXPORT_SYMBOL_GPL(crc64_nvme_generic);
+
+#ifdef CONFIG_CRC64_ARCH
+#include "crc64.h" /* $(SRCARCH)/crc64.h */
+#else
+#define crc64_be_arch crc64_be_generic
+#define crc64_nvme_arch crc64_nvme_generic
+#endif
+
+u64 crc64_be(u64 crc, const void *p, size_t len)
+{
+       return crc64_be_arch(crc, p, len);
+}
+EXPORT_SYMBOL_GPL(crc64_be);
+
+u64 crc64_nvme(u64 crc, const void *p, size_t len)
+{
+       return ~crc64_nvme_arch(~crc, p, len);
+}
+EXPORT_SYMBOL_GPL(crc64_nvme);
+
+#ifdef crc64_mod_init_arch
+static int __init crc64_mod_init(void)
+{
+       crc64_mod_init_arch();
+       return 0;
+}
+subsys_initcall(crc64_mod_init);
+
+static void __exit crc64_mod_exit(void)
+{
+}
+module_exit(crc64_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("CRC64 library functions");
+MODULE_LICENSE("GPL");