rdpmc.c

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// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <linux/types.h>
#include "perf.h"
#include "debug.h"
#include "tests/tests.h"
#include "cloexec.h"
#include "util.h"
#include "arch-tests.h"

static u64 rdpmc(unsigned int counter)
{
    unsigned int low, high;

    asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));

    return low | ((u64)high) << 32;
}

static u64 rdtsc(void)
{
    unsigned int low, high;

    asm volatile("rdtsc" : "=a" (low), "=d" (high));

    return low | ((u64)high) << 32;
}

static u64 mmap_read_self(void *addr)
{
    struct perf_event_mmap_page *pc = addr;
    u32 seq, idx, time_mult = 0, time_shift = 0;
    u64 count, cyc = 0, time_offset = 0, enabled, running, delta;

    do {
        seq = pc->lock;
        barrier();

        enabled = pc->time_enabled;
        running = pc->time_running;

        if (enabled != running) {
            cyc = rdtsc();
            time_mult = pc->time_mult;
            time_shift = pc->time_shift;
            time_offset = pc->time_offset;
        }

        idx = pc->index;
        count = pc->offset;
        if (idx)
            count += rdpmc(idx - 1);

        barrier();
    } while (pc->lock != seq);

    if (enabled != running) {
        u64 quot, rem;

        quot = (cyc >> time_shift);
        rem = cyc & (((u64)1 << time_shift) - 1);
        delta = time_offset + quot * time_mult +
            ((rem * time_mult) >> time_shift);

        enabled += delta;
        if (idx)
            running += delta;

        quot = count / running;
        rem = count % running;
        count = quot * enabled + (rem * enabled) / running;
    }

    return count;
}

/*
 * If the RDPMC instruction faults then signal this back to the test parent task:
 */
static void segfault_handler(int sig __maybe_unused,
                 siginfo_t *info __maybe_unused,
                 void *uc __maybe_unused)
{
    exit(-1);
}

static int __test__rdpmc(void)
{
    volatile int tmp = 0;
    u64 i, loops = 1000;
    int n;
    int fd;
    void *addr;
    struct perf_event_attr attr = {
        .type = PERF_TYPE_HARDWARE,
        .config = PERF_COUNT_HW_INSTRUCTIONS,
        .exclude_kernel = 1,
    };
    u64 delta_sum = 0;
        struct sigaction sa;
    char sbuf[STRERR_BUFSIZE];

    sigfillset(&sa.sa_mask);
    sa.sa_sigaction = segfault_handler;
    sa.sa_flags = 0;
    sigaction(SIGSEGV, &sa, NULL);

    fd = sys_perf_event_open(&attr, 0, -1, -1,
                 perf_event_open_cloexec_flag());
    if (fd < 0) {
        pr_err("Error: sys_perf_event_open() syscall returned "
               "with %d (%s)\n", fd,
               str_error_r(errno, sbuf, sizeof(sbuf)));
        return -1;
    }

    addr = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0);
    if (addr == (void *)(-1)) {
        pr_err("Error: mmap() syscall returned with (%s)\n",
               str_error_r(errno, sbuf, sizeof(sbuf)));
        goto out_close;
    }

    for (n = 0; n < 6; n++) {
        u64 stamp, now, delta;

        stamp = mmap_read_self(addr);

        for (i = 0; i < loops; i++)
            tmp++;

        now = mmap_read_self(addr);
        loops *= 10;

        delta = now - stamp;
        pr_debug("%14d: %14Lu\n", n, (long long)delta);

        delta_sum += delta;
    }

    munmap(addr, page_size);
    pr_debug("   ");
out_close:
    close(fd);

    if (!delta_sum)
        return -1;

    return 0;
}

int test__rdpmc(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    int status = 0;
    int wret = 0;
    int ret;
    int pid;

    pid = fork();
    if (pid < 0)
        return -1;

    if (!pid) {
        ret = __test__rdpmc();

        exit(ret);
    }

    wret = waitpid(pid, &status, 0);
    if (wret < 0 || status)
        return -1;

    return 0;
}