bp_signal.c

Go to the documentation of this file.

// SPDX-License-Identifier: GPL-2.0
/*
 * Inspired by breakpoint overflow test done by
 * Vince Weaver <vincent.weaver@maine.edu> for perf_event_tests
 * (git://github.com/deater/perf_event_tests)
 */

/*
 * Powerpc needs __SANE_USERSPACE_TYPES__ before <linux/types.h> to select
 * 'int-ll64.h' and avoid compile warnings when printing __u64 with %llu.
 */
#define __SANE_USERSPACE_TYPES__

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <time.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/mman.h>
#include <linux/compiler.h>
#include <linux/hw_breakpoint.h>

#include "tests.h"
#include "debug.h"
#include "perf.h"
#include "cloexec.h"

static int fd1;
static int fd2;
static int fd3;
static int overflows;
static int overflows_2;

volatile long the_var;


/*
 * Use ASM to ensure watchpoint and breakpoint can be triggered
 * at one instruction.
 */
#if defined (__x86_64__)
extern void __test_function(volatile long *ptr);
asm (
    ".globl __test_function\n"
    "__test_function:\n"
    "incq (%rdi)\n"
    "ret\n");
#elif defined (__aarch64__)
extern void __test_function(volatile long *ptr);
asm (
    ".globl __test_function\n"
    "__test_function:\n"
    "str x30, [x0]\n"
    "ret\n");

#else
static void __test_function(volatile long *ptr)
{
    *ptr = 0x1234;
}
#endif

static noinline int test_function(void)
{
    __test_function(&the_var);
    the_var++;
    return time(NULL);
}

static void sig_handler_2(int signum __maybe_unused,
              siginfo_t *oh __maybe_unused,
              void *uc __maybe_unused)
{
    overflows_2++;
    if (overflows_2 > 10) {
        ioctl(fd1, PERF_EVENT_IOC_DISABLE, 0);
        ioctl(fd2, PERF_EVENT_IOC_DISABLE, 0);
        ioctl(fd3, PERF_EVENT_IOC_DISABLE, 0);
    }
}

static void sig_handler(int signum __maybe_unused,
            siginfo_t *oh __maybe_unused,
            void *uc __maybe_unused)
{
    overflows++;

    if (overflows > 10) {
        /*
         * This should be executed only once during
         * this test, if we are here for the 10th
         * time, consider this the recursive issue.
         *
         * We can get out of here by disable events,
         * so no new SIGIO is delivered.
         */
        ioctl(fd1, PERF_EVENT_IOC_DISABLE, 0);
        ioctl(fd2, PERF_EVENT_IOC_DISABLE, 0);
        ioctl(fd3, PERF_EVENT_IOC_DISABLE, 0);
    }
}

static int __event(bool is_x, void *addr, int sig)
{
    struct perf_event_attr pe;
    int fd;

    memset(&pe, 0, sizeof(struct perf_event_attr));
    pe.type = PERF_TYPE_BREAKPOINT;
    pe.size = sizeof(struct perf_event_attr);

    pe.config = 0;
    pe.bp_type = is_x ? HW_BREAKPOINT_X : HW_BREAKPOINT_W;
    pe.bp_addr = (unsigned long) addr;
    pe.bp_len = sizeof(long);

    pe.sample_period = 1;
    pe.sample_type = PERF_SAMPLE_IP;
    pe.wakeup_events = 1;

    pe.disabled = 1;
    pe.exclude_kernel = 1;
    pe.exclude_hv = 1;

    fd = sys_perf_event_open(&pe, 0, -1, -1,
                 perf_event_open_cloexec_flag());
    if (fd < 0) {
        pr_debug("failed opening event %llx\n", pe.config);
        return TEST_FAIL;
    }

    fcntl(fd, F_SETFL, O_RDWR|O_NONBLOCK|O_ASYNC);
    fcntl(fd, F_SETSIG, sig);
    fcntl(fd, F_SETOWN, getpid());

    ioctl(fd, PERF_EVENT_IOC_RESET, 0);

    return fd;
}

static int bp_event(void *addr, int sig)
{
    return __event(true, addr, sig);
}

static int wp_event(void *addr, int sig)
{
    return __event(false, addr, sig);
}

static long long bp_count(int fd)
{
    long long count;
    int ret;

    ret = read(fd, &count, sizeof(long long));
    if (ret != sizeof(long long)) {
        pr_debug("failed to read: %d\n", ret);
        return TEST_FAIL;
    }

    return count;
}

int test__bp_signal(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    struct sigaction sa;
    long long count1, count2, count3;

    /* setup SIGIO signal handler */
    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_sigaction = (void *) sig_handler;
    sa.sa_flags = SA_SIGINFO;

    if (sigaction(SIGIO, &sa, NULL) < 0) {
        pr_debug("failed setting up signal handler\n");
        return TEST_FAIL;
    }

    sa.sa_sigaction = (void *) sig_handler_2;
    if (sigaction(SIGUSR1, &sa, NULL) < 0) {
        pr_debug("failed setting up signal handler 2\n");
        return TEST_FAIL;
    }

    /*
     * We create following events:
     *
     * fd1 - breakpoint event on __test_function with SIGIO
     *       signal configured. We should get signal
     *       notification each time the breakpoint is hit
     *
     * fd2 - breakpoint event on sig_handler with SIGUSR1
     *       configured. We should get SIGUSR1 each time when
     *       breakpoint is hit
     *
     * fd3 - watchpoint event on __test_function with SIGIO
     *       configured.
     *
     * Following processing should happen:
     *   Exec:               Action:                       Result:
     *   incq (%rdi)       - fd1 event breakpoint hit   -> count1 == 1
     *                     - SIGIO is delivered
     *   sig_handler       - fd2 event breakpoint hit   -> count2 == 1
     *                     - SIGUSR1 is delivered
     *   sig_handler_2                                  -> overflows_2 == 1  (nested signal)
     *   sys_rt_sigreturn  - return from sig_handler_2
     *   overflows++                                    -> overflows = 1
     *   sys_rt_sigreturn  - return from sig_handler
     *   incq (%rdi)       - fd3 event watchpoint hit   -> count3 == 1       (wp and bp in one insn)
     *                     - SIGIO is delivered
     *   sig_handler       - fd2 event breakpoint hit   -> count2 == 2
     *                     - SIGUSR1 is delivered
     *   sig_handler_2                                  -> overflows_2 == 2  (nested signal)
     *   sys_rt_sigreturn  - return from sig_handler_2
     *   overflows++                                    -> overflows = 2
     *   sys_rt_sigreturn  - return from sig_handler
     *   the_var++         - fd3 event watchpoint hit   -> count3 == 2       (standalone watchpoint)
     *                     - SIGIO is delivered
     *   sig_handler       - fd2 event breakpoint hit   -> count2 == 3
     *                     - SIGUSR1 is delivered
     *   sig_handler_2                                  -> overflows_2 == 3  (nested signal)
     *   sys_rt_sigreturn  - return from sig_handler_2
     *   overflows++                                    -> overflows == 3
     *   sys_rt_sigreturn  - return from sig_handler
     *
     * The test case check following error conditions:
     * - we get stuck in signal handler because of debug
     *   exception being triggered receursively due to
     *   the wrong RF EFLAG management
     *
     * - we never trigger the sig_handler breakpoint due
     *   to the rong RF EFLAG management
     *
     */

    fd1 = bp_event(__test_function, SIGIO);
    fd2 = bp_event(sig_handler, SIGUSR1);
    fd3 = wp_event((void *)&the_var, SIGIO);

    ioctl(fd1, PERF_EVENT_IOC_ENABLE, 0);
    ioctl(fd2, PERF_EVENT_IOC_ENABLE, 0);
    ioctl(fd3, PERF_EVENT_IOC_ENABLE, 0);

    /*
     * Kick off the test by trigering 'fd1'
     * breakpoint.
     */
    test_function();

    ioctl(fd1, PERF_EVENT_IOC_DISABLE, 0);
    ioctl(fd2, PERF_EVENT_IOC_DISABLE, 0);
    ioctl(fd3, PERF_EVENT_IOC_DISABLE, 0);

    count1 = bp_count(fd1);
    count2 = bp_count(fd2);
    count3 = bp_count(fd3);

    close(fd1);
    close(fd2);
    close(fd3);

    pr_debug("count1 %lld, count2 %lld, count3 %lld, overflow %d, overflows_2 %d\n",
         count1, count2, count3, overflows, overflows_2);

    if (count1 != 1) {
        if (count1 == 11)
            pr_debug("failed: RF EFLAG recursion issue detected\n");
        else
            pr_debug("failed: wrong count for bp1%lld\n", count1);
    }

    if (overflows != 3)
        pr_debug("failed: wrong overflow hit\n");

    if (overflows_2 != 3)
        pr_debug("failed: wrong overflow_2 hit\n");

    if (count2 != 3)
        pr_debug("failed: wrong count for bp2\n");

    if (count3 != 2)
        pr_debug("failed: wrong count for bp3\n");

    return count1 == 1 && overflows == 3 && count2 == 3 && overflows_2 == 3 && count3 == 2 ?
        TEST_OK : TEST_FAIL;
}

bool test__bp_signal_is_supported(void)
{
/*
 * The powerpc so far does not have support to even create
 * instruction breakpoint using the perf event interface.
 * Once it's there we can release this.
 */
#if defined(__powerpc__) || defined(__s390x__)
    return false;
#else
    return true;
#endif
}