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The x86 glue helper module is starting to show its age: - It relies heavily on function pointers to invoke asm helper functions that operate on fixed input sizes that are relatively small. This means the performance is severely impacted by retpolines. - It goes to great lengths to amortize the cost of kernel_fpu_begin()/end() over as much work as possible, which is no longer necessary now that FPU save/restore is done lazily, and doing so may cause unbounded scheduling blackouts due to the fact that enabling the FPU in kernel mode disables preemption. - The CBC mode decryption helper makes backward strides through the input, in order to avoid a single block size memcpy() between chunks. Consuming the input in this manner is highly likely to defeat any hardware prefetchers, so it is better to go through the data linearly, and perform the extra memcpy() where needed (which is turned into direct loads and stores by the compiler anyway). Note that benchmarks won't show this effect, given that the memory they use is always cache hot. - It implements blockwise XOR in terms of le128 pointers, which imply an alignment that is not guaranteed by the API, violating the C standard. GCC does not seem to be smart enough to elide the indirect calls when the function pointers are passed as arguments to static inline helper routines modeled after the existing ones. So instead, let's create some CPP macros that encapsulate the core of the ECB and CBC processing, so we can wire them up for existing users of the glue helper module, i.e., Camellia, Serpent, Twofish and CAST6. Acked-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.