cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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cpufreq-test_tsc.c (3124B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * test module to check whether the TSC-based delay routine continues
      4 * to work properly after cpufreq transitions. Needs ACPI to work
      5 * properly.
      6 *
      7 * Based partly on the Power Management Timer (PMTMR) code to be found
      8 * in arch/i386/kernel/timers/timer_pm.c on recent 2.6. kernels, especially
      9 * code written by John Stultz. The read_pmtmr function was copied verbatim
     10 * from that file.
     11 *
     12 * (C) 2004 Dominik Brodowski
     13 *
     14 * To use:
     15 * 1.) pass clock=tsc to the kernel on your bootloader
     16 * 2.) modprobe this module (it'll fail)
     17 * 3.) change CPU frequency
     18 * 4.) modprobe this module again
     19 * 5.) if the third value, "diff_pmtmr", changes between 2. and 4., the
     20 *     TSC-based delay routine on the Linux kernel does not correctly
     21 *     handle the cpufreq transition. Please report this to
     22 *     linux-pm@vger.kernel.org
     23 */
     24
     25#include <linux/kernel.h>
     26#include <linux/module.h>
     27#include <linux/init.h>
     28#include <linux/delay.h>
     29#include <linux/acpi.h>
     30#include <asm/io.h>
     31
     32static int pm_tmr_ioport = 0;
     33
     34/*helper function to safely read acpi pm timesource*/
     35static u32 read_pmtmr(void)
     36{
     37	u32 v1=0,v2=0,v3=0;
     38	/* It has been reported that because of various broken
     39	 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
     40	 * source is not latched, so you must read it multiple
     41	 * times to insure a safe value is read.
     42	 */
     43	do {
     44		v1 = inl(pm_tmr_ioport);
     45		v2 = inl(pm_tmr_ioport);
     46		v3 = inl(pm_tmr_ioport);
     47	} while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
     48		 || (v3 > v1 && v3 < v2));
     49
     50	/* mask the output to 24 bits */
     51	return (v2 & 0xFFFFFF);
     52}
     53
     54static int __init cpufreq_test_tsc(void)
     55{
     56	u32 now, then, diff;
     57	u64 now_tsc, then_tsc, diff_tsc;
     58	int i;
     59
     60	/* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
     61	   of Linux v2.6.25. */
     62
     63	/* detect the location of the ACPI PM Timer */
     64	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
     65		/* FADT rev. 2 */
     66		if (acpi_gbl_FADT.xpm_timer_block.space_id !=
     67		    ACPI_ADR_SPACE_SYSTEM_IO)
     68			return 0;
     69
     70		pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
     71		/*
     72		 * "X" fields are optional extensions to the original V1.0
     73		 * fields, so we must selectively expand V1.0 fields if the
     74		 * corresponding X field is zero.
     75	 	 */
     76		if (!pm_tmr_ioport)
     77			pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
     78	} else {
     79		/* FADT rev. 1 */
     80		pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
     81	}
     82
     83	printk(KERN_DEBUG "start--> \n");
     84	then = read_pmtmr();
     85	then_tsc = rdtsc();
     86	for (i=0;i<20;i++) {
     87		mdelay(100);
     88		now = read_pmtmr();
     89		now_tsc = rdtsc();
     90		diff = (now - then) & 0xFFFFFF;
     91		diff_tsc = now_tsc - then_tsc;
     92		printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
     93		then = now;
     94		then_tsc = now_tsc;
     95	}
     96	printk(KERN_DEBUG "<-- end \n");
     97	return -ENODEV;
     98}
     99
    100static void __exit cpufreq_none(void)
    101{
    102	return;
    103}
    104
    105module_init(cpufreq_test_tsc)
    106module_exit(cpufreq_none)
    107
    108
    109MODULE_AUTHOR("Dominik Brodowski");
    110MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
    111MODULE_LICENSE ("GPL");