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| author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2017-09-29 12:24:10 +0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2017-09-29 12:24:10 +0300 |
| commit | cf09e3c904bf424f8b6a8203958e09bf7d9bcbc0 (patch) | |
| tree | 5e9936b3de36aa222b52a9bca366a43d98730ffd /include/linux/bitmap.h | |
| parent | d5426f4c2ebac8cf05de43988c3fccddbee13d28 (diff) | |
| parent | e19b205be43d11bff638cad4487008c48d21c103 (diff) | |
| download | linux-cf09e3c904bf424f8b6a8203958e09bf7d9bcbc0.tar.xz | |
Merge tag 'v4.14-rc2' into patchwork
Linux 4.14-rc2
* tag 'v4.14-rc2': (12066 commits)
Linux 4.14-rc2
tpm: ibmvtpm: simplify crq initialization and document crq format
tpm: replace msleep() with usleep_range() in TPM 1.2/2.0 generic drivers
Documentation: tpm: add powered-while-suspended binding documentation
tpm: tpm_crb: constify acpi_device_id.
tpm: vtpm: constify vio_device_id
security: fix description of values returned by cap_inode_need_killpriv
x86/asm: Fix inline asm call constraints for Clang
objtool: Handle another GCC stack pointer adjustment bug
inet: fix improper empty comparison
net: use inet6_rcv_saddr to compare sockets
net: set tb->fast_sk_family
net: orphan frags on stand-alone ptype in dev_queue_xmit_nit
MAINTAINERS: update git tree locations for ieee802154 subsystem
SMB3: Don't ignore O_SYNC/O_DSYNC and O_DIRECT flags
SMB3: handle new statx fields
arch: remove unused *_segments() macros/functions
parisc: Unbreak bootloader due to gcc-7 optimizations
parisc: Reintroduce option to gzip-compress the kernel
apparmor: fix apparmorfs DAC access permissions
...
Diffstat (limited to 'include/linux/bitmap.h')
| -rw-r--r-- | include/linux/bitmap.h | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 5797ca6fdfe2..700cf5f67118 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -361,6 +361,38 @@ static inline int bitmap_parse(const char *buf, unsigned int buflen, } /* + * BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap. + * + * Linux bitmaps are internally arrays of unsigned longs, i.e. 32-bit + * integers in 32-bit environment, and 64-bit integers in 64-bit one. + * + * There are four combinations of endianness and length of the word in linux + * ABIs: LE64, BE64, LE32 and BE32. + * + * On 64-bit kernels 64-bit LE and BE numbers are naturally ordered in + * bitmaps and therefore don't require any special handling. + * + * On 32-bit kernels 32-bit LE ABI orders lo word of 64-bit number in memory + * prior to hi, and 32-bit BE orders hi word prior to lo. The bitmap on the + * other hand is represented as an array of 32-bit words and the position of + * bit N may therefore be calculated as: word #(N/32) and bit #(N%32) in that + * word. For example, bit #42 is located at 10th position of 2nd word. + * It matches 32-bit LE ABI, and we can simply let the compiler store 64-bit + * values in memory as it usually does. But for BE we need to swap hi and lo + * words manually. + * + * With all that, the macro BITMAP_FROM_U64() does explicit reordering of hi and + * lo parts of u64. For LE32 it does nothing, and for BE environment it swaps + * hi and lo words, as is expected by bitmap. + */ +#if __BITS_PER_LONG == 64 +#define BITMAP_FROM_U64(n) (n) +#else +#define BITMAP_FROM_U64(n) ((unsigned long) ((u64)(n) & ULONG_MAX)), \ + ((unsigned long) ((u64)(n) >> 32)) +#endif + +/* * bitmap_from_u64 - Check and swap words within u64. * @mask: source bitmap * @dst: destination bitmap |
