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Unlike many other structure types defined in the crypto API, the 'shash_desc' structure is permitted to live on the stack, which implies its contents may not be accessed by DMA masters. (This is due to the fact that the stack may be located in the vmalloc area, which requires a different virtual-to-physical translation than the one implemented by the DMA subsystem) Our definition of CRYPTO_MINALIGN_ATTR is based on ARCH_KMALLOC_MINALIGN, which may take DMA constraints into account on architectures that support non-cache coherent DMA such as ARM and arm64. In this case, the value is chosen to reflect the largest cacheline size in the system, in order to ensure that explicit cache maintenance as required by non-coherent DMA masters does not affect adjacent, unrelated slab allocations. On arm64, this value is currently set at 128 bytes. This means that applying CRYPTO_MINALIGN_ATTR to struct shash_desc is both unnecessary (as it is never used for DMA), and undesirable, given that it wastes stack space (on arm64, performing the alignment costs 112 bytes in the worst case, and the hole between the 'tfm' and '__ctx' members takes up another 120 bytes, resulting in an increased stack footprint of up to 232 bytes.) So instead, let's switch to the minimum SLAB alignment, which does not take DMA constraints into account. Note that this is a no-op for x86. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> |
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| 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.