random: Add arch_has_random[_seed]()

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>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
index 801beba..bde5311 100644 (file)
--- 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 6ad7f6d..69f1366 100644 (file)
--- a/arch/x86/include/asm/archrandom.h
+++ b/arch/x86/include/asm/archrandom.h
@@ -114,6 +114,9 @@ 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)
+
 #else
 
 static inline int rdrand_long(unsigned long *v)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index c35cee2..6b75713 100644 (file)
--- 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 c2f0813..57fbbff 100644 (file)
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -88,6 +88,10 @@ 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;
@@ -96,6 +100,10 @@ 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. */