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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pmae_handling_test.c (2098B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Copyright 2014, Michael Ellerman, IBM Corp.
      4 */
      5
      6#include <sched.h>
      7#include <signal.h>
      8#include <stdbool.h>
      9#include <stdio.h>
     10#include <stdlib.h>
     11
     12#include "ebb.h"
     13
     14
     15/*
     16 * Test that the kernel properly handles PMAE across context switches.
     17 *
     18 * We test this by calling into the kernel inside our EBB handler, where PMAE
     19 * is clear. A cpu eater companion thread is running on the same CPU as us to
     20 * encourage the scheduler to switch us.
     21 *
     22 * The kernel must make sure that when it context switches us back in, it
     23 * honours the fact that we had PMAE clear.
     24 *
     25 * Observed to hit the failing case on the first EBB with a broken kernel.
     26 */
     27
     28static bool mmcr0_mismatch;
     29static uint64_t before, after;
     30
     31static void syscall_ebb_callee(void)
     32{
     33	uint64_t val;
     34
     35	val = mfspr(SPRN_BESCR);
     36	if (!(val & BESCR_PMEO)) {
     37		ebb_state.stats.spurious++;
     38		goto out;
     39	}
     40
     41	ebb_state.stats.ebb_count++;
     42	count_pmc(1, sample_period);
     43
     44	before = mfspr(SPRN_MMCR0);
     45
     46	/* Try and get ourselves scheduled, to force a PMU context switch */
     47	sched_yield();
     48
     49	after = mfspr(SPRN_MMCR0);
     50	if (before != after)
     51		mmcr0_mismatch = true;
     52
     53out:
     54	reset_ebb();
     55}
     56
     57static int test_body(void)
     58{
     59	struct event event;
     60
     61	SKIP_IF(!ebb_is_supported());
     62
     63	event_init_named(&event, 0x1001e, "cycles");
     64	event_leader_ebb_init(&event);
     65
     66	event.attr.exclude_kernel = 1;
     67	event.attr.exclude_hv = 1;
     68	event.attr.exclude_idle = 1;
     69
     70	FAIL_IF(event_open(&event));
     71
     72	setup_ebb_handler(syscall_ebb_callee);
     73	ebb_global_enable();
     74
     75	FAIL_IF(ebb_event_enable(&event));
     76
     77	mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
     78
     79	while (ebb_state.stats.ebb_count < 20 && !mmcr0_mismatch)
     80		FAIL_IF(core_busy_loop());
     81
     82	ebb_global_disable();
     83	ebb_freeze_pmcs();
     84
     85	dump_ebb_state();
     86
     87	if (mmcr0_mismatch)
     88		printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
     89
     90	event_close(&event);
     91
     92	FAIL_IF(ebb_state.stats.ebb_count == 0);
     93	FAIL_IF(mmcr0_mismatch);
     94
     95	return 0;
     96}
     97
     98int pmae_handling(void)
     99{
    100	return eat_cpu(test_body);
    101}
    102
    103int main(void)
    104{
    105	return test_harness(pmae_handling, "pmae_handling");
    106}