random: Add support for architectural random hooks

commit 63d77173 upstream.

Add support for architecture-specific hooks into the kernel-directed
random number generator interfaces.  This patchset does not use the
architecture random number generator interfaces for the
userspace-directed interfaces (/dev/random and /dev/urandom), thus
eliminating the need to distinguish between them based on a pool
pointer.

Changes in version 3:
- Moved the hooks from extract_entropy() to get_random_bytes().
- Changes the hooks to inlines.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Theodore Ts'o" <tytso@mit.edu>
[PG: .34 already had "unsigned int ret" in get_random_int, so the
 diffstat here is slightly smaller than that of 63d77173. ]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

drivers/char/random.c

@@ -932,7 +932,21 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
  */
 void get_random_bytes(void *buf, int nbytes)
 {
-	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+	char *p = buf;
+
+	while (nbytes) {
+		unsigned long v;
+		int chunk = min(nbytes, (int)sizeof(unsigned long));
+
+		if (!arch_get_random_long(&v))
+			break;
+
+		memcpy(buf, &v, chunk);
+		p += chunk;
+		nbytes -= chunk;
+	}
+
+	extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
 }
 EXPORT_SYMBOL(get_random_bytes);
 
@@ -1360,9 +1374,14 @@ late_initcall(random_int_secret_init);
 DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
 unsigned int get_random_int(void)
 {
-	__u32 *hash = get_cpu_var(get_random_int_hash);
+	__u32 *hash;
 	unsigned int ret;
 
+	if (arch_get_random_int(&ret))
+		return ret;
+
+	hash = get_cpu_var(get_random_int_hash);
+
 	hash[0] += current->pid + jiffies + get_cycles();
 	md5_transform(hash, random_int_secret);
 	ret = hash[0];

include/linux/random.h

@@ -63,6 +63,19 @@ unsigned long randomize_range(unsigned long start, unsigned long end, unsigned l
 u32 random32(void);
 void srandom32(u32 seed);
 
+#ifdef CONFIG_ARCH_RANDOM
+# include <asm/archrandom.h>
+#else
+static inline int arch_get_random_long(unsigned long *v)
+{
+	return 0;
+}
+static inline int arch_get_random_int(unsigned int *v)
+{
+	return 0;
+}
+#endif
+
 #endif /* __KERNEL___ */
 
 #endif /* _LINUX_RANDOM_H */