arch/arm64/include/asm/archrandom.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_ARCHRANDOM_H
   3 #define _ASM_ARCHRANDOM_H
   4
   5 #ifdef CONFIG_ARCH_RANDOM
   6
   7 #include <linux/random.h>
   8 #include <asm/cpufeature.h>
   9
  10 static inline bool __arm64_rndr(unsigned long *v)
  11 {
  12         bool ok;
  13
  14         /*
  15          * Reads of RNDR set PSTATE.NZCV to 0b0000 on success,
  16          * and set PSTATE.NZCV to 0b0100 otherwise.
  17          */
  18         asm volatile(
  19                 __mrs_s("%0", SYS_RNDR_EL0) "\n"
  20         "       cset %w1, ne\n"
  21         : "=r" (*v), "=r" (ok)
  22         :
  23         : "cc");
  24
  25         return ok;
  26 }
  27
  28 static inline bool __must_check arch_get_random_long(unsigned long *v)
  29 {
  30         return false;
  31 }
  32
  33 static inline bool __must_check arch_get_random_int(unsigned int *v)
  34 {
  35         return false;
  36 }
  37
  38 static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
  39 {
  40         /*
  41          * Only support the generic interface after we have detected
  42          * the system wide capability, avoiding complexity with the
  43          * cpufeature code and with potential scheduling between CPUs
  44          * with and without the feature.
  45          */
  46         if (!cpus_have_const_cap(ARM64_HAS_RNG))
  47                 return false;
  48
  49         return __arm64_rndr(v);
  50 }
  51
  52
  53 static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
  54 {
  55         unsigned long val;
  56         bool ok = arch_get_random_seed_long(&val);
  57
  58         *v = val;
  59         return ok;
  60 }
  61
  62 static inline bool __init __early_cpu_has_rndr(void)
  63 {
  64         /* Open code as we run prior to the first call to cpufeature. */
  65         unsigned long ftr = read_sysreg_s(SYS_ID_AA64ISAR0_EL1);
  66         return (ftr >> ID_AA64ISAR0_RNDR_SHIFT) & 0xf;
  67 }
  68
  69 #else
  70
  71 static inline bool __arm64_rndr(unsigned long *v) { return false; }
  72 static inline bool __init __early_cpu_has_rndr(void) { return false; }
  73
  74 #endif /* CONFIG_ARCH_RANDOM */
  75 #endif /* _ASM_ARCHRANDOM_H */