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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/random.h>
enum { WARMUP = 50, TRIALS = 1000, IDLE = 1 * 1000 };
static unsigned long stamp = 0;
module_param(stamp, ulong, 0);
int dummy;
static char dummy_out[64 * 1024];
static int function(void)
{
get_random_bytes(dummy_out, sizeof(dummy_out));
return dummy_out[sizeof(dummy_out) - 1];
}
static int __init mod_init(void)
{
int ret = 0, i;
cycles_t start, end;
unsigned long flags;
DEFINE_SPINLOCK(lock);
msleep(IDLE);
spin_lock_irqsave(&lock, flags);
for (i = 0; i < WARMUP; ++i)
ret |= function();
start = get_cycles();
for (i = 0; i < TRIALS; ++i)
ret |= function();
end = get_cycles();
spin_unlock_irqrestore(&lock, flags);
pr_err("%lu: %llu cycles per call\n", stamp, (end - start) / TRIALS);
/* Don't let compiler be too clever. */
dummy = ret;
/* We should never actually agree to insert the module. Choosing
* -0x1000 here is an amazing hack. It causes the kernel to not
* actually load the module, while the standard userspace tools
* don't return an error, because it's too big. */
return -0x1000;
}
module_init(mod_init);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("kBench9000 Cycle Counter");
MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
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