* Using get_cycles for add_timer_randomness
@ 2003-08-16 1:03 Arnd Bergmann
2004-08-10 16:24 ` Anton Blanchard
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2003-08-16 1:03 UTC (permalink / raw)
To: linux-kernel
I noticed that only i386 and x86-64 are currently using
a high resolution timer source when adding randomness.
Since many architectures have a working get_cycles()
implementation, it seems rather straightforward to use
that.
Has this been discussed before, or can anyone comment
on the implementation below?
This patch attempts to take into account the size of
cycles_t, which is either 32 or 64 bits wide but
independent of the architecture's word size.
The behavior should be nearly identical to the
old one on i386, x86-64 and all architectures
without a time stamp counter, while finding
more entropy on the other architectures.
Arnd <><
===== drivers/char/random.c 1.35 vs edited =====
--- 1.35/drivers/char/random.c Wed Aug 6 19:59:31 2003
+++ edited/drivers/char/random.c Sat Aug 16 02:05:34 2003
@@ -711,8 +711,8 @@
/* There is one of these per entropy source */
struct timer_rand_state {
- __u32 last_time;
- __s32 last_delta,last_delta2;
+ cycles_t last_time;
+ long last_delta,last_delta2;
int dont_count_entropy:1;
};
@@ -729,27 +729,28 @@
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
- * On the i386, this is assumed to be at most 16 bits, and the high bits
- * are used for a high-resolution timer.
+ * This is assumed to be at most 16 bits, and the high bits are used for
+ * high-resolution timers.
*
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
- __u32 time;
- __s32 delta, delta2, delta3;
+ cycles_t time;
+ long delta, delta2, delta3;
int entropy = 0;
-#if defined (__i386__) || defined (__x86_64__)
- if (cpu_has_tsc) {
- __u32 high;
- rdtsc(time, high);
- num ^= high;
+ /*
+ * Use get_cycles() if implemented, otherwise fall back to
+ * jiffies.
+ */
+ time = get_cycles();
+ if (time != 0) {
+ if (sizeof (time) > 4) {
+ num ^= (u32)(time >> 32);
+ }
} else {
time = jiffies;
}
-#else
- time = jiffies;
-#endif
/*
* Calculate number of bits of randomness we probably added.
===== include/asm-i386/timex.h 1.5 vs edited =====
--- 1.5/include/asm-i386/timex.h Mon Jun 9 14:41:23 2003
+++ edited/include/asm-i386/timex.h Sat Aug 16 02:17:05 2003
@@ -7,7 +7,7 @@
#define _ASMi386_TIMEX_H
#include <linux/config.h>
-#include <asm/msr.h>
+#include <asm/processor.h>
#ifdef CONFIG_X86_PC9800
extern int CLOCK_TICK_RATE;
@@ -44,14 +44,17 @@
static inline cycles_t get_cycles (void)
{
+ unsigned long long ret=0;
+
#ifndef CONFIG_X86_TSC
- return 0;
-#else
- unsigned long long ret;
+ if (!cpu_has_tsc)
+ return 0;
+#endif
+#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
rdtscll(ret);
- return ret;
#endif
+ return ret;
}
extern unsigned long cpu_khz;
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Using get_cycles for add_timer_randomness
2003-08-16 1:03 Using get_cycles for add_timer_randomness Arnd Bergmann
@ 2004-08-10 16:24 ` Anton Blanchard
2004-08-14 18:36 ` Anton Blanchard
0 siblings, 1 reply; 3+ messages in thread
From: Anton Blanchard @ 2004-08-10 16:24 UTC (permalink / raw)
To: Arnd Bergmann; +Cc: linux-kernel, akpm
This sounded like a good idea at the time, any reason we cant merge
this?
Anton
On Sat, Aug 16, 2003 at 03:03:17AM +0200, Arnd Bergmann wrote:
> I noticed that only i386 and x86-64 are currently using
> a high resolution timer source when adding randomness.
> Since many architectures have a working get_cycles()
> implementation, it seems rather straightforward to use
> that.
>
> Has this been discussed before, or can anyone comment
> on the implementation below?
>
> This patch attempts to take into account the size of
> cycles_t, which is either 32 or 64 bits wide but
> independent of the architecture's word size.
>
> The behavior should be nearly identical to the
> old one on i386, x86-64 and all architectures
> without a time stamp counter, while finding
> more entropy on the other architectures.
>
> Arnd <><
>
> ===== drivers/char/random.c 1.35 vs edited =====
> --- 1.35/drivers/char/random.c Wed Aug 6 19:59:31 2003
> +++ edited/drivers/char/random.c Sat Aug 16 02:05:34 2003
> @@ -711,8 +711,8 @@
>
> /* There is one of these per entropy source */
> struct timer_rand_state {
> - __u32 last_time;
> - __s32 last_delta,last_delta2;
> + cycles_t last_time;
> + long last_delta,last_delta2;
> int dont_count_entropy:1;
> };
>
> @@ -729,27 +729,28 @@
> * The number "num" is also added to the pool - it should somehow describe
> * the type of event which just happened. This is currently 0-255 for
> * keyboard scan codes, and 256 upwards for interrupts.
> - * On the i386, this is assumed to be at most 16 bits, and the high bits
> - * are used for a high-resolution timer.
> + * This is assumed to be at most 16 bits, and the high bits are used for
> + * high-resolution timers.
> *
> */
> static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
> {
> - __u32 time;
> - __s32 delta, delta2, delta3;
> + cycles_t time;
> + long delta, delta2, delta3;
> int entropy = 0;
>
> -#if defined (__i386__) || defined (__x86_64__)
> - if (cpu_has_tsc) {
> - __u32 high;
> - rdtsc(time, high);
> - num ^= high;
> + /*
> + * Use get_cycles() if implemented, otherwise fall back to
> + * jiffies.
> + */
> + time = get_cycles();
> + if (time != 0) {
> + if (sizeof (time) > 4) {
> + num ^= (u32)(time >> 32);
> + }
> } else {
> time = jiffies;
> }
> -#else
> - time = jiffies;
> -#endif
>
> /*
> * Calculate number of bits of randomness we probably added.
> ===== include/asm-i386/timex.h 1.5 vs edited =====
> --- 1.5/include/asm-i386/timex.h Mon Jun 9 14:41:23 2003
> +++ edited/include/asm-i386/timex.h Sat Aug 16 02:17:05 2003
> @@ -7,7 +7,7 @@
> #define _ASMi386_TIMEX_H
>
> #include <linux/config.h>
> -#include <asm/msr.h>
> +#include <asm/processor.h>
>
> #ifdef CONFIG_X86_PC9800
> extern int CLOCK_TICK_RATE;
> @@ -44,14 +44,17 @@
>
> static inline cycles_t get_cycles (void)
> {
> + unsigned long long ret=0;
> +
> #ifndef CONFIG_X86_TSC
> - return 0;
> -#else
> - unsigned long long ret;
> + if (!cpu_has_tsc)
> + return 0;
> +#endif
>
> +#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
> rdtscll(ret);
> - return ret;
> #endif
> + return ret;
> }
>
> extern unsigned long cpu_khz;
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Using get_cycles for add_timer_randomness
2004-08-10 16:24 ` Anton Blanchard
@ 2004-08-14 18:36 ` Anton Blanchard
0 siblings, 0 replies; 3+ messages in thread
From: Anton Blanchard @ 2004-08-14 18:36 UTC (permalink / raw)
To: Arnd Bergmann, akpm; +Cc: linux-kernel, richm, tytso
> This sounded like a good idea at the time, any reason we cant merge
> this?
Merged against latest bk. I tested how long it took to do a dd from
/dev/random on ppc64 before and after this patch, while doing a ping
flood from another machine.
before:
# /usr/bin/time dd if=/dev/random of=/dev/zero count=1k
0+51 records in
Command terminated by signal 2
0.00user 0.00system 19:18.46elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
I gave up after 19 minutes.
after:
# /usr/bin/time dd if=/dev/random of=/dev/zero count=1k
0+1024 records in
0.00user 0.00system 0:33.38elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
Just over 33 seconds. Better.
Anton
--
From: Arnd Bergmann <arnd@arndb.de>
I noticed that only i386 and x86-64 are currently using
a high resolution timer source when adding randomness.
Since many architectures have a working get_cycles()
implementation, it seems rather straightforward to use
that.
Has this been discussed before, or can anyone comment
on the implementation below?
This patch attempts to take into account the size of
cycles_t, which is either 32 or 64 bits wide but
independent of the architecture's word size.
The behavior should be nearly identical to the
old one on i386, x86-64 and all architectures
without a time stamp counter, while finding
more entropy on the other architectures.
Signed-off-by: Anton Blanchard <anton@samba.org>
===== drivers/char/random.c 1.45 vs edited =====
--- 1.45/drivers/char/random.c Sun Aug 8 16:43:40 2004
+++ edited/drivers/char/random.c Sun Aug 15 03:13:21 2004
@@ -781,8 +781,8 @@
/* There is one of these per entropy source */
struct timer_rand_state {
- __u32 last_time;
- __s32 last_delta,last_delta2;
+ cycles_t last_time;
+ long last_delta,last_delta2;
int dont_count_entropy:1;
};
@@ -799,14 +799,12 @@
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
- * On the i386, this is assumed to be at most 16 bits, and the high bits
- * are used for a high-resolution timer.
*
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
- __u32 time;
- __s32 delta, delta2, delta3;
+ cycles_t time;
+ long delta, delta2, delta3;
int entropy = 0;
/* if over the trickle threshold, use only 1 in 4096 samples */
@@ -814,17 +812,18 @@
(__get_cpu_var(trickle_count)++ & 0xfff))
return;
-#if defined (__i386__) || defined (__x86_64__)
- if (cpu_has_tsc) {
- __u32 high;
- rdtsc(time, high);
- num ^= high;
+ /*
+ * Use get_cycles() if implemented, otherwise fall back to
+ * jiffies.
+ */
+ time = get_cycles();
+ if (time != 0) {
+ if (sizeof(time) > 4) {
+ num ^= (u32)(time >> 32);
+ }
} else {
time = jiffies;
}
-#else
- time = jiffies;
-#endif
/*
* Calculate number of bits of randomness we probably added.
===== include/asm-i386/timex.h 1.7 vs edited =====
--- 1.7/include/asm-i386/timex.h Fri Jun 18 16:43:58 2004
+++ edited/include/asm-i386/timex.h Sun Aug 15 02:41:55 2004
@@ -7,7 +7,7 @@
#define _ASMi386_TIMEX_H
#include <linux/config.h>
-#include <asm/msr.h>
+#include <asm/processor.h>
#ifdef CONFIG_X86_ELAN
# define CLOCK_TICK_RATE 1189200 /* AMD Elan has different frequency! */
@@ -40,14 +40,17 @@
static inline cycles_t get_cycles (void)
{
+ unsigned long long ret=0;
+
#ifndef CONFIG_X86_TSC
- return 0;
-#else
- unsigned long long ret;
+ if (!cpu_has_tsc)
+ return 0;
+#endif
+#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
rdtscll(ret);
- return ret;
#endif
+ return ret;
}
extern unsigned long cpu_khz;
^ permalink raw reply [flat|nested] 3+ messages in thread
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