Hi Wolfgang,
Dear Lukasz,
In message 1399295277-28334-1-git-send-email-l.majewski@samsung.com you wrote:
The current approach set the initial value of crc32 calculation to zero, which is correct for calculating checksum of the whole chunk of data.
It however, lacks the flexibility, when one wants to calculate CRC32 of a file comprised of many smaller parts received separately.
In the proposed approach the output value is used as a starting condition for the proper crc32 calculation at crc32_wd function. This behavior is identical to the one provided by crc32() method implementation.
Additionally, comments were appropriately updated.
Signed-off-by: Lukasz Majewski l.majewski@samsung.com Cc: Marek Vasut marex@denx.de Cc: Simon Glass sjg@chromium.org
include/hash.h | 2 +- include/u-boot/crc.h | 3 ++- lib/crc32.c | 2 +- 3 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/include/hash.h b/include/hash.h index dc21678..abf704d 100644 --- a/include/hash.h +++ b/include/hash.h @@ -101,7 +101,7 @@ int hash_command(const char *algo_name, int flags, cmd_tbl_t *cmdtp, int flag,
- @algo_name: Hash algorithm to use
- @data: Data to hash
- @len: Lengh of data to hash in bytes
- @output: Place to put hash value
- @output: Place to put hash value - also the
initial value (crc32)
- @output_size: On entry, pointer to the number of bytes
available in
output. On exit, pointer to the numberof bytes used.
If NULL, then it is assumed that thecaller has diff --git a/include/u-boot/crc.h b/include/u-boot/crc.h index 754ac72..7a87911 100644 --- a/include/u-boot/crc.h +++ b/include/u-boot/crc.h @@ -19,7 +19,8 @@ uint32_t crc32_no_comp (uint32_t, const unsigned char *, uint); *
- @input: Input buffer
- @ilen: Input buffer length
- @output: Place to put checksum result (4 bytes)
- @output: Place to provide initial CRC32 value and
afterwards
put checksum result (4 bytes)- @chunk_sz: Trigger watchdog after processing this many
bytes */ void crc32_wd_buf(const unsigned char *input, uint ilen, diff --git a/lib/crc32.c b/lib/crc32.c index 9759212..f6266c7 100644 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -257,7 +257,7 @@ void crc32_wd_buf(const unsigned char *input, unsigned int ilen, { uint32_t crc;
- crc = crc32_wd(0, input, ilen, chunk_sz);
- crc = crc32_wd(*(uint32_t *)output, input, ilen, chunk_sz); crc = htonl(crc); memcpy(output, &crc, sizeof(crc));
This looks wrong to me, in a number of ways.
First, the *(uint32_t *)output cast, is likely to trigger unaligned accesses with the resulting problems on some platforms. Never, never ever cast a character pointer into something that requires any alignment!
I admit that I was thinking about my (particular) platform.
Instead, I should memcpy the output to crc variable, which is defined as uint32_t, and pass it to the crc32_wd.
Seconds, where exactly do you now initialize the CRC vlaue to start with 0 ?
The proposed approach (with setting initial value of CRC32) is working fine with crc32() function at least in the DFU. Zeroing out of relevant variable is performed there.
The venerable crc32() implementation allows passing initial value of crc. As it is now, the hash_block() doesn't.
Finally we should keep in mind (this is nothing caused by your patch, but when touching this area we really should consider it) that we have a number of (slightly) different CRC implementations thare cry for cleanup / unification: in addition to lib/crc32.c we have disk/part_efi.c (which provides efi_crc32()), drivers/mtd/ubi/crc32.c (which provides crc32_le() and crc32_be()), net/eth.c (which uses ether_crc()), we have BZ2_crc32Table[256] in lib/bzlib_private.h / lib/bzlib_crctable.c (which appears to be unsued), and we have tools/pblimage.c (which provides pbl_crc32()).
As Marek pointed out, we shall start using hash_block (from #include <hash.h>).
However, as I pointed out in this patch hash_block (at least for crc32) needs to be modified to preserve the functionality of bare metal crc32() function.
To unify, we also may be forced to introduce some flags - like output crc endianess (big, little). But this may wait for the moment.
What a mess :-(
+1
Best regards,
Wolfgang Denk