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Date: Thu, 22 Dec 2016 19:07:41 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: tytso@....edu,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Cc: "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 2/2] random: convert get_random_int/long into get_random_u32/u64
Many times, when a user wants a random number, he wants a random number
of a guaranteed size. So, thinking of get_random_int and get_random_long
in terms of get_random_u32 and get_random_u64 makes it much easier to
achieve this. It also makes the code simpler.
On 32-bit platforms, get_random_int and get_random_long are both aliased
to get_random_u32. On 64-bit platforms, int->u32 and long->u64.
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Cc: Theodore Ts'o <tytso@....edu>
---
I personally would find this extremely useful in my own code, where I
currently wind up doing something ugly like:
(u64)get_random_int() << 32 | get_random_int()
But if you have some aversion, don't hesitate to just take 1/2 without
this 2/2. But hopefully you'll like this 2/2.
drivers/char/random.c | 55 +++++++++++++++++++++++++-------------------------
include/linux/random.h | 17 ++++++++++++++--
2 files changed, 42 insertions(+), 30 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 08d1dd58c0d2..ee737ef41ce9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2044,8 +2044,8 @@ struct ctl_table random_table[] = {
struct batched_entropy {
union {
- unsigned long entropy_long[CHACHA20_BLOCK_SIZE / sizeof(unsigned long)];
- unsigned int entropy_int[CHACHA20_BLOCK_SIZE / sizeof(unsigned int)];
+ u64 entropy_u64[CHACHA20_BLOCK_SIZE / sizeof(u64)];
+ u32 entropy_u32[CHACHA20_BLOCK_SIZE / sizeof(u32)];
};
unsigned int position;
};
@@ -2055,52 +2055,51 @@ struct batched_entropy {
* number is either as good as RDRAND or as good as /dev/urandom, with the
* goal of being quite fast and not depleting entropy.
*/
-static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_long);
-unsigned long get_random_long(void)
+static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
+u64 get_random_u64(void)
{
- unsigned long ret;
+ u64 ret;
struct batched_entropy *batch;
- if (arch_get_random_long(&ret))
+#if BITS_PER_LONG == 64
+ if (arch_get_random_long((unsigned long *)&ret))
return ret;
+#else
+ if (arch_get_random_long((unsigned long *)&ret) &&
+ arch_get_random_long((unsigned long *)&ret + 1))
+ return ret;
+#endif
- batch = &get_cpu_var(batched_entropy_long);
- if (batch->position % ARRAY_SIZE(batch->entropy_long) == 0) {
- extract_crng((u8 *)batch->entropy_long);
+ batch = &get_cpu_var(batched_entropy_u64);
+ if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
+ extract_crng((u8 *)batch->entropy_u64);
batch->position = 0;
}
- ret = batch->entropy_long[batch->position++];
- put_cpu_var(batched_entropy_long);
+ ret = batch->entropy_u64[batch->position++];
+ put_cpu_var(batched_entropy_u64);
return ret;
}
-EXPORT_SYMBOL(get_random_long);
+EXPORT_SYMBOL(get_random_u64);
-#if BITS_PER_LONG == 32
-unsigned int get_random_int(void)
-{
- return get_random_long();
-}
-#else
-static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_int);
-unsigned int get_random_int(void)
+static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
+u32 get_random_u32(void)
{
- unsigned int ret;
+ u32 ret;
struct batched_entropy *batch;
if (arch_get_random_int(&ret))
return ret;
- batch = &get_cpu_var(batched_entropy_int);
- if (batch->position % ARRAY_SIZE(batch->entropy_int) == 0) {
- extract_crng((u8 *)batch->entropy_int);
+ batch = &get_cpu_var(batched_entropy_u32);
+ if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
+ extract_crng((u8 *)batch->entropy_u32);
batch->position = 0;
}
- ret = batch->entropy_int[batch->position++];
- put_cpu_var(batched_entropy_int);
+ ret = batch->entropy_u32[batch->position++];
+ put_cpu_var(batched_entropy_u32);
return ret;
}
-#endif
-EXPORT_SYMBOL(get_random_int);
+EXPORT_SYMBOL(get_random_u32);
/**
* randomize_page - Generate a random, page aligned address
diff --git a/include/linux/random.h b/include/linux/random.h
index 16ab429735a7..ed5c3838780d 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -42,8 +42,21 @@ extern void get_random_bytes_arch(void *buf, int nbytes);
extern const struct file_operations random_fops, urandom_fops;
#endif
-unsigned int get_random_int(void);
-unsigned long get_random_long(void);
+u32 get_random_u32(void);
+u64 get_random_u64(void);
+static inline unsigned int get_random_int(void)
+{
+ return get_random_u32();
+}
+static inline unsigned long get_random_long(void)
+{
+#if BITS_PER_LONG == 64
+ return get_random_u64();
+#else
+ return get_random_u32();
+#endif
+}
+
unsigned long randomize_page(unsigned long start, unsigned long range);
u32 prandom_u32(void);
--
2.11.0
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