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fae29f135e
quality field is currently documented as being 'per mill'. In fact the
math involved is:
add_hwgenerator_randomness((void *)rng_fillbuf, rc,
rc * current_quality * 8 >> 10);
thus the actual definition is "bits of entropy per 1024 bits of input".
The current documentation seems to have confused multiple people
in the past, let's fix the documentation to match code.
An alternative is to change core to match driver expectations, replacing
rc * current_quality * 8 >> 10
with
rc * current_quality / 1000
but that has performance costs, so probably isn't a good option.
Fixes: 0f734e6e76 ("hwrng: add per-device entropy derating")
Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
/*
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Hardware Random Number Generator
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Please read Documentation/hw_random.txt for details on use.
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----------------------------------------------------------
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This software may be used and distributed according to the terms
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of the GNU General Public License, incorporated herein by reference.
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*/
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#ifndef LINUX_HWRANDOM_H_
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#define LINUX_HWRANDOM_H_
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#include <linux/completion.h>
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/kref.h>
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/**
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* struct hwrng - Hardware Random Number Generator driver
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* @name: Unique RNG name.
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* @init: Initialization callback (can be NULL).
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* @cleanup: Cleanup callback (can be NULL).
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* @data_present: Callback to determine if data is available
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* on the RNG. If NULL, it is assumed that
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* there is always data available. *OBSOLETE*
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* @data_read: Read data from the RNG device.
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* Returns the number of lower random bytes in "data".
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* Must not be NULL. *OBSOLETE*
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* @read: New API. drivers can fill up to max bytes of data
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* into the buffer. The buffer is aligned for any type
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* and max is a multiple of 4 and >= 32 bytes.
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* @priv: Private data, for use by the RNG driver.
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* @quality: Estimation of true entropy in RNG's bitstream
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* (in bits of entropy per 1024 bits of input;
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* valid values: 1 to 1024, or 0 for unknown).
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*/
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struct hwrng {
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const char *name;
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int (*init)(struct hwrng *rng);
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void (*cleanup)(struct hwrng *rng);
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int (*data_present)(struct hwrng *rng, int wait);
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int (*data_read)(struct hwrng *rng, u32 *data);
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int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
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unsigned long priv;
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unsigned short quality;
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/* internal. */
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struct list_head list;
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struct kref ref;
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struct completion cleanup_done;
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};
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struct device;
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/** Register a new Hardware Random Number Generator driver. */
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extern int hwrng_register(struct hwrng *rng);
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extern int devm_hwrng_register(struct device *dev, struct hwrng *rng);
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/** Unregister a Hardware Random Number Generator driver. */
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extern void hwrng_unregister(struct hwrng *rng);
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extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng);
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/** Feed random bits into the pool. */
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extern void add_hwgenerator_randomness(const char *buffer, size_t count, size_t entropy);
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#endif /* LINUX_HWRANDOM_H_ */
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