[PATCH v2 4/4] random: Add arch_has_random[_seed]()

H. Peter Anvin
2014-03-17T23:37:36Z

Add predicate functions for having arch_get_random[_seed]*(). The
only current use is to avoid the loop in arch_random_refill() when
arch_get_random_seed_long() is unavailable.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <michael@ellerman.id.au>
---
arch/powerpc/include/asm/archrandom.h | 9 +++++++++
arch/x86/include/asm/archrandom.h | 3 +++
drivers/char/random.c | 3 +++
include/linux/random.h | 8 ++++++++
4 files changed, 23 insertions(+)

diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
index 801beba..bde5311 100644
--- a/arch/powerpc/include/asm/archrandom.h
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -25,6 +25,11 @@ static inline int arch_get_random_int(unsigned int *v)
return rc;
}

+static inline int arch_has_random(void)
+{
+ return !!ppc_md.get_random_long;
+}
+
int powernv_get_random_long(unsigned long *v);

static inline int arch_get_random_seed_long(unsigned long *v)
@@ -35,6 +40,10 @@ static inline int arch_get_random_seed_int(unsigned int *v)
{
return 0;
}
+static inline int arch_has_random_seed(void)
+{
+ return 0;
+}

#endif /* CONFIG_ARCH_RANDOM */

diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
index ba064d5..c7ed4a6 100644
--- a/arch/x86/include/asm/archrandom.h
+++ b/arch/x86/include/asm/archrandom.h
@@ -100,6 +100,9 @@ GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);

#endif /* CONFIG_X86_64 */

+#define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND)
+#define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED)
+
#endif /* CONFIG_ARCH_RANDOM */

extern void x86_init_rdrand(struct cpuinfo_x86 *c);
diff --git a/drivers/char/random.c b/drivers/char/random.c
index c35cee2..6b75713 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1307,6 +1307,9 @@ static int arch_random_refill(void)
unsigned int i;
unsigned long buf[nlongs];

+ if (!arch_has_random_seed())
+ return 0;
+
for (i = 0; i < nlongs; i++) {
if (arch_get_random_seed_long(&buf[n]))
n++;
diff --git a/include/linux/random.h b/include/linux/random.h
index ddaddec..e7a221a 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -72,6 +72,10 @@ static inline int arch_get_random_int(unsigned int *v)
{
return 0;
}
+static inline int arch_has_random(void)
+{
+ return 0;
+}
static inline int arch_get_random_seed_long(unsigned long *v)
{
return 0;
@@ -80,6 +84,10 @@ static inline int arch_get_random_seed_int(unsigned int *v)
{
return 0;
}
+static inline int arch_has_random_seed(void)
+{
+ return 0;
+}
#endif

/* Pseudo random number generator from numerical recipes. */
--
1.8.5.3