84 lines
3.6 KiB
Plaintext
84 lines
3.6 KiB
Plaintext
crypto-API support for z990 Message Security Assist (MSA) instructions
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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AUTHOR: Thomas Spatzier (tspat@de.ibm.com)
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1. Introduction crypto-API
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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See Documentation/crypto/api-intro.txt for an introduction/description of the
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kernel crypto API.
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According to api-intro.txt support for z990 crypto instructions has been added
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in the algorithm api layer of the crypto API. Several files containing z990
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optimized implementations of crypto algorithms are placed in the
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arch/s390/crypto directory.
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2. Probing for availability of MSA
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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It should be possible to use Kernels with the z990 crypto implementations both
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on machines with MSA available and on those without MSA (pre z990 or z990
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without MSA). Therefore a simple probing mechanism has been implemented:
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In the init function of each crypto module the availability of MSA and of the
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respective crypto algorithm in particular will be tested. If the algorithm is
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available the module will load and register its algorithm with the crypto API.
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If the respective crypto algorithm is not available, the init function will
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return -ENOSYS. In that case a fallback to the standard software implementation
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of the crypto algorithm must be taken ( -> the standard crypto modules are
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also built when compiling the kernel).
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3. Ensuring z990 crypto module preference
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If z990 crypto instructions are available the optimized modules should be
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preferred instead of standard modules.
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3.1. compiled-in modules
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~~~~~~~~~~~~~~~~~~~~~~~~
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For compiled-in modules it has to be ensured that the z990 modules are linked
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before the standard crypto modules. Then, on system startup the init functions
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of z990 crypto modules will be called first and query for availability of z990
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crypto instructions. If instruction is available, the z990 module will register
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its crypto algorithm implementation -> the load of the standard module will fail
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since the algorithm is already registered.
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If z990 crypto instruction is not available the load of the z990 module will
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fail -> the standard module will load and register its algorithm.
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3.2. dynamic modules
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~~~~~~~~~~~~~~~~~~~~
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A system administrator has to take care of giving preference to z990 crypto
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modules. If MSA is available appropriate lines have to be added to
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/etc/modprobe.conf.
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Example: z990 crypto instruction for SHA1 algorithm is available
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add the following line to /etc/modprobe.conf (assuming the
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z990 crypto modules for SHA1 is called sha1_z990):
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alias sha1 sha1_z990
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-> when the sha1 algorithm is requested through the crypto API
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(which has a module autoloader) the z990 module will be loaded.
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TBD: a userspace module probing mechanism
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something like 'probe sha1 sha1_z990 sha1' in modprobe.conf
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-> try module sha1_z990, if it fails to load standard module sha1
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the 'probe' statement is currently not supported in modprobe.conf
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4. Currently implemented z990 crypto algorithms
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The following crypto algorithms with z990 MSA support are currently implemented.
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The name of each algorithm under which it is registered in crypto API and the
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name of the respective module is given in square brackets.
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- SHA1 Digest Algorithm [sha1 -> sha1_z990]
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- DES Encrypt/Decrypt Algorithm (64bit key) [des -> des_z990]
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- Triple DES Encrypt/Decrypt Algorithm (128bit key) [des3_ede128 -> des_z990]
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- Triple DES Encrypt/Decrypt Algorithm (192bit key) [des3_ede -> des_z990]
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In order to load, for example, the sha1_z990 module when the sha1 algorithm is
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requested (see 3.2.) add 'alias sha1 sha1_z990' to /etc/modprobe.conf.
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