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Merge branch 'for-next/rng' into for-next/core

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* for-next/rng:
  arm64: random: implement arch_get_random_int/_long based on RNDR
This commit is contained in:
Will Deacon 2022-03-14 19:01:52 +00:00
commit 92051a107a
1 changed files with 39 additions and 6 deletions
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45
arch/arm64/include/asm/archrandom.h
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@ -42,13 +42,47 @@ static inline bool __arm64_rndr(unsigned long *v)
return ok;
}
static inline bool __arm64_rndrrs(unsigned long *v)
{
bool ok;
/*
* Reads of RNDRRS set PSTATE.NZCV to 0b0000 on success,
* and set PSTATE.NZCV to 0b0100 otherwise.
*/
asm volatile(
__mrs_s("%0", SYS_RNDRRS_EL0) "\n"
" cset %w1, ne\n"
: "=r" (*v), "=r" (ok)
:
: "cc");
return ok;
}
static inline bool __must_check arch_get_random_long(unsigned long *v)
{
/*
* Only support the generic interface after we have detected
* the system wide capability, avoiding complexity with the
* cpufeature code and with potential scheduling between CPUs
* with and without the feature.
*/
if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
return true;
return false;
}
static inline bool __must_check arch_get_random_int(unsigned int *v)
{
if (cpus_have_const_cap(ARM64_HAS_RNG)) {
unsigned long val;
if (__arm64_rndr(&val)) {
*v = val;
return true;
}
}
return false;
}
@ -71,12 +105,11 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
}
/*
* Only support the generic interface after we have detected
* the system wide capability, avoiding complexity with the
* cpufeature code and with potential scheduling between CPUs
* with and without the feature.
* RNDRRS is not backed by an entropy source but by a DRBG that is
* reseeded after each invocation. This is not a 100% fit but good
* enough to implement this API if no other entropy source exists.
*/
if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))
return true;
return false;
@ -96,7 +129,7 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
}
if (cpus_have_const_cap(ARM64_HAS_RNG)) {
if (__arm64_rndr(&val)) {
if (__arm64_rndrrs(&val)) {
*v = val;
return true;
}