endianness and sparse warnings

From: Geert Uytterhoeven
Date: Fri Aug 29 2008 - 10:54:39 EST

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With `make C=1 CF="-D__CHECK_ENDIAN__"', you can let sparse check for bad
handling of endian-annotated data.

Unfortunately several of the accessors for endian-annotated data do not cause
sparse warnings.

Summarized:
- [bl]e{16,32,64}_to_cpu() is OK
- [bl]e{16,32,64}_to_cpup() (aka get_aligned_[bl]e{16,32,64}() ;-) is OK
- get_unaligned_[bl]e{16,32,64} is not OK
- __get_unaligned_[bl]e() is partially OK, as long as you don't use it on
non-annotated data, but
o it's meant for internal use only
o it incorrectly causes sparse warnings when assigning the resulting
value to a non-annotated variable

To check it for yourself, plug in the code below into any kernel source file.

#include <asm/unaligned.h>

__u8 d8;
__u16 d16;
__u32 d32;
__u64 d64;

__be16 be16;
__be32 be32;
__be64 be64;

__le16 le16;
__le32 le32;
__le64 le64;

char dr[16];

#define get_aligned_be16 be16_to_cpup
#define get_aligned_be32 be32_to_cpup
#define get_aligned_be64 be64_to_cpup
#define get_aligned_le16 le16_to_cpup
#define get_aligned_le32 le32_to_cpup
#define get_aligned_le64 le64_to_cpup

int test(void)
{
u64 x = 0;

x ^= d8;

// ----------------------------------------------------------------------------

x ^= d16; /* OK */
x ^= d32; /* OK */
x ^= d64; /* OK */
x ^= be16; /* sparse warning */
x ^= be32; /* sparse warning */
x ^= be64; /* sparse warning */
x ^= le16; /* sparse warning */
x ^= le32; /* sparse warning */
x ^= le64; /* sparse warning */

// ----------------------------------------------------------------------------

x ^= be16_to_cpu(d16); /* sparse warning */
x ^= be16_to_cpu(d32); /* sparse warning */
x ^= be16_to_cpu(d64); /* sparse warning */
x ^= be16_to_cpu(be16); /* OK */
x ^= be16_to_cpu(be32); /* sparse warning */
x ^= be16_to_cpu(be64); /* sparse warning */
x ^= be16_to_cpu(le16); /* sparse warning */
x ^= be16_to_cpu(le32); /* sparse warning */
x ^= be16_to_cpu(le64); /* sparse warning */

x ^= be32_to_cpu(d16); /* sparse warning */
x ^= be32_to_cpu(d32); /* sparse warning */
x ^= be32_to_cpu(d64); /* sparse warning */
x ^= be32_to_cpu(be16); /* sparse warning */
x ^= be32_to_cpu(be32); /* OK */
x ^= be32_to_cpu(be64); /* sparse warning */
x ^= be32_to_cpu(le16); /* sparse warning */
x ^= be32_to_cpu(le32); /* sparse warning */
x ^= be32_to_cpu(le64); /* sparse warning */

x ^= be64_to_cpu(d16); /* sparse warning */
x ^= be64_to_cpu(d32); /* sparse warning */
x ^= be64_to_cpu(d64); /* sparse warning */
x ^= be64_to_cpu(be16); /* sparse warning */
x ^= be64_to_cpu(be32); /* sparse warning */
x ^= be64_to_cpu(be64); /* OK */
x ^= be64_to_cpu(le16); /* sparse warning */
x ^= be64_to_cpu(le32); /* sparse warning */
x ^= be64_to_cpu(le64); /* sparse warning */

x ^= le16_to_cpu(d16); /* sparse warning */
x ^= le16_to_cpu(d32); /* sparse warning */
x ^= le16_to_cpu(d64); /* sparse warning */
x ^= le16_to_cpu(be16); /* sparse warning */
x ^= le16_to_cpu(be32); /* sparse warning */
x ^= le16_to_cpu(be64); /* sparse warning */
x ^= le16_to_cpu(le16); /* OK */
x ^= le16_to_cpu(le32); /* sparse warning */
x ^= le16_to_cpu(le64); /* sparse warning */

x ^= le32_to_cpu(d16); /* sparse warning */
x ^= le32_to_cpu(d32); /* sparse warning */
x ^= le32_to_cpu(d64); /* sparse warning */
x ^= le32_to_cpu(be16); /* sparse warning */
x ^= le32_to_cpu(be32); /* sparse warning */
x ^= le32_to_cpu(be64); /* sparse warning */
x ^= le32_to_cpu(le16); /* sparse warning */
x ^= le32_to_cpu(le32); /* OK */
x ^= le32_to_cpu(le64); /* sparse warning */

x ^= le64_to_cpu(d16); /* sparse warning */
x ^= le64_to_cpu(d32); /* sparse warning */
x ^= le64_to_cpu(d64); /* sparse warning */
x ^= le64_to_cpu(be16); /* sparse warning */
x ^= le64_to_cpu(be32); /* sparse warning */
x ^= le64_to_cpu(be64); /* sparse warning */
x ^= le64_to_cpu(le16); /* sparse warning */
x ^= le64_to_cpu(le32); /* sparse warning */
x ^= le64_to_cpu(le64); /* OK */

// ----------------------------------------------------------------------------

x ^= get_unaligned_be16(&d16); /* NO WARNING!! */
x ^= get_unaligned_be16(&d32); /* NO WARNING!! */
x ^= get_unaligned_be16(&d64); /* NO WARNING!! */
x ^= get_unaligned_be16(&be16); /* OK */
x ^= get_unaligned_be16(&be32); /* NO WARNING!! */
x ^= get_unaligned_be16(&be64); /* NO WARNING!! */
x ^= get_unaligned_be16(&le16); /* NO WARNING!! */
x ^= get_unaligned_be16(&le32); /* NO WARNING!! */
x ^= get_unaligned_be16(&le64); /* NO WARNING!! */
x ^= get_unaligned_be16(&dr[1]); /* OK */

x ^= get_unaligned_be32(&d16); /* NO WARNING!! */
x ^= get_unaligned_be32(&d32); /* NO WARNING!! */
x ^= get_unaligned_be32(&d64); /* NO WARNING!! */
x ^= get_unaligned_be32(&be16); /* NO WARNING!! */
x ^= get_unaligned_be32(&be32); /* OK */
x ^= get_unaligned_be32(&be64); /* NO WARNING!! */
x ^= get_unaligned_be32(&le16); /* NO WARNING!! */
x ^= get_unaligned_be32(&le32); /* NO WARNING!! */
x ^= get_unaligned_be32(&le64); /* NO WARNING!! */
x ^= get_unaligned_be32(&dr[1]); /* OK */

x ^= get_unaligned_be64(&d16); /* NO WARNING!! */
x ^= get_unaligned_be64(&d32); /* NO WARNING!! */
x ^= get_unaligned_be64(&d64); /* NO WARNING!! */
x ^= get_unaligned_be64(&be16); /* NO WARNING!! */
x ^= get_unaligned_be64(&be32); /* NO WARNING!! */
x ^= get_unaligned_be64(&be64); /* OK */
x ^= get_unaligned_be64(&le16); /* NO WARNING!! */
x ^= get_unaligned_be64(&le32); /* NO WARNING!! */
x ^= get_unaligned_be64(&le64); /* NO WARNING!! */
x ^= get_unaligned_be64(&dr[1]); /* OK */

x ^= get_unaligned_le16(&d16); /* NO WARNING!! */
x ^= get_unaligned_le16(&d32); /* NO WARNING!! */
x ^= get_unaligned_le16(&d64); /* NO WARNING!! */
x ^= get_unaligned_le16(&be16); /* NO WARNING!! */
x ^= get_unaligned_le16(&be32); /* NO WARNING!! */
x ^= get_unaligned_le16(&be64); /* NO WARNING!! */
x ^= get_unaligned_le16(&le16); /* OK */
x ^= get_unaligned_le16(&le32); /* NO WARNING!! */
x ^= get_unaligned_le16(&le64); /* NO WARNING!! */
x ^= get_unaligned_le16(&dr[1]); /* OK */

x ^= get_unaligned_le32(&d16); /* NO WARNING!! */
x ^= get_unaligned_le32(&d32); /* NO WARNING!! */
x ^= get_unaligned_le32(&d64); /* NO WARNING!! */
x ^= get_unaligned_le32(&be16); /* NO WARNING!! */
x ^= get_unaligned_le32(&be32); /* NO WARNING!! */
x ^= get_unaligned_le32(&be64); /* NO WARNING!! */
x ^= get_unaligned_le32(&le16); /* NO WARNING!! */
x ^= get_unaligned_le32(&le32); /* OK */
x ^= get_unaligned_le32(&le64); /* NO WARNING!! */
x ^= get_unaligned_le16(&dr[1]); /* OK */

x ^= get_unaligned_le64(&d16); /* NO WARNING!! */
x ^= get_unaligned_le64(&d32); /* NO WARNING!! */
x ^= get_unaligned_le64(&d64); /* NO WARNING!! */
x ^= get_unaligned_le64(&be16); /* NO WARNING!! */
x ^= get_unaligned_le64(&be32); /* NO WARNING!! */
x ^= get_unaligned_le64(&be64); /* NO WARNING!! */
x ^= get_unaligned_le64(&le16); /* NO WARNING!! */
x ^= get_unaligned_le64(&le32); /* NO WARNING!! */
x ^= get_unaligned_le64(&le64); /* OK */
x ^= get_unaligned_le16(&dr[1]); /* OK */

// ----------------------------------------------------------------------------

x ^= get_unaligned(&d16); /* OK */
x ^= get_unaligned(&d32); /* OK */
x ^= get_unaligned(&d64); /* OK */
x ^= get_unaligned(&be16); /* sparse warning */
x ^= get_unaligned(&be32); /* sparse warning */
x ^= get_unaligned(&be64); /* sparse warning */
x ^= get_unaligned(&le16); /* sparse warning */
x ^= get_unaligned(&le32); /* sparse warning */
x ^= get_unaligned(&le64); /* sparse warning */
x ^= get_unaligned(&dr[1]); /* OK */

x ^= __get_unaligned_be(&d16); /* NO WARNING!! */
x ^= __get_unaligned_be(&d32); /* NO WARNING!! */
x ^= __get_unaligned_be(&d64); /* NO WARNING!! */
x ^= __get_unaligned_be(&be16); /* sparse warning */
x ^= __get_unaligned_be(&be32); /* sparse warning */
x ^= __get_unaligned_be(&be64); /* sparse warning */
x ^= __get_unaligned_be(&le16); /* sparse warning */
x ^= __get_unaligned_be(&le32); /* sparse warning */
x ^= __get_unaligned_be(&le64); /* sparse warning */
x ^= __get_unaligned_be(&dr[1]); /* NO WARNING!! */

x ^= __get_unaligned_le(&d16); /* NO WARNING!! */
x ^= __get_unaligned_le(&d32); /* NO WARNING!! */
x ^= __get_unaligned_le(&d64); /* NO WARNING!! */
x ^= __get_unaligned_le(&be16); /* sparse warning */
x ^= __get_unaligned_le(&be32); /* sparse warning */
x ^= __get_unaligned_le(&be64); /* sparse warning */
x ^= __get_unaligned_le(&le16); /* sparse warning */
x ^= __get_unaligned_le(&le32); /* sparse warning */
x ^= __get_unaligned_le(&le64); /* sparse warning */
x ^= __get_unaligned_le(&dr[1]); /* NO WARNING!! */

// ----------------------------------------------------------------------------

x ^= get_aligned_be16(&d16); /* sparse warning */
x ^= get_aligned_be16(&d32); /* gcc/sparse warning */
x ^= get_aligned_be16(&d64); /* gcc/sparse warning */
x ^= get_aligned_be16(&be16); /* OK */
x ^= get_aligned_be16(&be32); /* gcc/sparse warning */
x ^= get_aligned_be16(&be64); /* gcc/sparse warning */
x ^= get_aligned_be16(&le16); /* sparse warning */
x ^= get_aligned_be16(&le32); /* gcc/sparse warning */
x ^= get_aligned_be16(&le64); /* gcc/sparse warning */
x ^= get_aligned_be16(&dr[1]); /* gcc/sparse warning */

x ^= get_aligned_be32(&d16); /* gcc/sparse warning */
x ^= get_aligned_be32(&d32); /* sparse warning */
x ^= get_aligned_be32(&d64); /* gcc/sparse warning */
x ^= get_aligned_be32(&be16); /* gcc/sparse warning */
x ^= get_aligned_be32(&be32); /* OK */
x ^= get_aligned_be32(&be64); /* gcc/sparse warning */
x ^= get_aligned_be32(&le16); /* gcc/sparse warning */
x ^= get_aligned_be32(&le32); /* sparse warning */
x ^= get_aligned_be32(&le64); /* gcc/sparse warning */
x ^= get_aligned_be32(&dr[1]); /* gcc/sparse warning */

x ^= get_aligned_be64(&d16); /* gcc/sparse warning */
x ^= get_aligned_be64(&d32); /* gcc/sparse warning */
x ^= get_aligned_be64(&d64); /* sparse warning */
x ^= get_aligned_be64(&be16); /* gcc/sparse warning */
x ^= get_aligned_be64(&be32); /* gcc/sparse warning */
x ^= get_aligned_be64(&be64); /* OK */
x ^= get_aligned_be64(&le16); /* gcc/sparse warning */
x ^= get_aligned_be64(&le32); /* gcc/sparse warning */
x ^= get_aligned_be64(&le64); /* sparse warning */
x ^= get_aligned_be64(&dr[1]); /* gcc/sparse warning */

x ^= get_aligned_le16(&d16); /* sparse warning */
x ^= get_aligned_le16(&d32); /* gcc/sparse warning */
x ^= get_aligned_le16(&d64); /* gcc/sparse warning */
x ^= get_aligned_le16(&be16); /* sparse warning */
x ^= get_aligned_le16(&be32); /* gcc/sparse warning */
x ^= get_aligned_le16(&be64); /* gcc/sparse warning */
x ^= get_aligned_le16(&le16); /* OK */
x ^= get_aligned_le16(&le32); /* gcc/sparse warning */
x ^= get_aligned_le16(&le64); /* gcc/sparse warning */
x ^= get_aligned_le16(&dr[1]); /* gcc/sparse warning */

x ^= get_aligned_le32(&d16); /* gcc/sparse warning */
x ^= get_aligned_le32(&d32); /* sparse warning */
x ^= get_aligned_le32(&d64); /* gcc/sparse warning */
x ^= get_aligned_le32(&be16); /* gcc/sparse warning */
x ^= get_aligned_le32(&be32); /* sparse warning */
x ^= get_aligned_le32(&be64); /* gcc/sparse warning */
x ^= get_aligned_le32(&le16); /* gcc/sparse warning */
x ^= get_aligned_le32(&le32); /* OK */
x ^= get_aligned_le32(&le64); /* gcc/sparse warning */
x ^= get_aligned_le16(&dr[1]); /* gcc/sparse warning */

x ^= get_aligned_le64(&d16); /* gcc/sparse warning */
x ^= get_aligned_le64(&d32); /* gcc/sparse warning */
x ^= get_aligned_le64(&d64); /* sparse warning */
x ^= get_aligned_le64(&be16); /* gcc/sparse warning */
x ^= get_aligned_le64(&be32); /* gcc/sparse warning */
x ^= get_aligned_le64(&be64); /* sparse warning */
x ^= get_aligned_le64(&le16); /* gcc/sparse warning */
x ^= get_aligned_le64(&le32); /* gcc/sparse warning */
x ^= get_aligned_le64(&le64); /* OK */
x ^= get_aligned_le16(&dr[1]); /* gcc/sparse warning */

// ----------------------------------------------------------------------------

return x;
}

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village Â Da Vincilaan 7-D1 Â B-1935 Zaventem Â Belgium

Phone: +32 (0)2 700 8453
Fax: +32 (0)2 700 8622
E-mail: Geert.Uytterhoeven@xxxxxxxxxxx
Internet: http://www.sony-europe.com/

A division of Sony Europe (Belgium) N.V.
VAT BE 0413.825.160 Â RPR Brussels
Fortis Â BIC GEBABEBB Â IBAN BE41293037680010

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