dwarf-unwind.c

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// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/types.h>
#include <inttypes.h>
#include <unistd.h>
#include "tests.h"
#include "debug.h"
#include "machine.h"
#include "event.h"
#include "../util/unwind.h"
#include "perf_regs.h"
#include "map.h"
#include "thread.h"
#include "callchain.h"

#if defined (__x86_64__) || defined (__i386__) || defined (__powerpc__)
#include "arch-tests.h"
#endif

/* For bsearch. We try to unwind functions in shared object. */
#include <stdlib.h>

static int mmap_handler(struct perf_tool *tool __maybe_unused,
            union perf_event *event,
            struct perf_sample *sample,
            struct machine *machine)
{
    return machine__process_mmap2_event(machine, event, sample);
}

static int init_live_machine(struct machine *machine)
{
    union perf_event event;
    pid_t pid = getpid();

    return perf_event__synthesize_mmap_events(NULL, &event, pid, pid,
                          mmap_handler, machine, true, 500);
}

/*
 * We need to keep these functions global, despite the
 * fact that they are used only locally in this object,
 * in order to keep them around even if the binary is
 * stripped. If they are gone, the unwind check for
 * symbol fails.
 */
int test_dwarf_unwind__thread(struct thread *thread);
int test_dwarf_unwind__compare(void *p1, void *p2);
int test_dwarf_unwind__krava_3(struct thread *thread);
int test_dwarf_unwind__krava_2(struct thread *thread);
int test_dwarf_unwind__krava_1(struct thread *thread);

#define MAX_STACK 8

static int unwind_entry(struct unwind_entry *entry, void *arg)
{
    unsigned long *cnt = (unsigned long *) arg;
    char *symbol = entry->sym ? entry->sym->name : NULL;
    static const char *funcs[MAX_STACK] = {
        "test__arch_unwind_sample",
        "test_dwarf_unwind__thread",
        "test_dwarf_unwind__compare",
        "bsearch",
        "test_dwarf_unwind__krava_3",
        "test_dwarf_unwind__krava_2",
        "test_dwarf_unwind__krava_1",
        "test__dwarf_unwind"
    };
    /*
     * The funcs[MAX_STACK] array index, based on the
     * callchain order setup.
     */
    int idx = callchain_param.order == ORDER_CALLER ?
          MAX_STACK - *cnt - 1 : *cnt;

    if (*cnt >= MAX_STACK) {
        pr_debug("failed: crossed the max stack value %d\n", MAX_STACK);
        return -1;
    }

    if (!symbol) {
        pr_debug("failed: got unresolved address 0x%" PRIx64 "\n",
             entry->ip);
        return -1;
    }

    (*cnt)++;
    pr_debug("got: %s 0x%" PRIx64 ", expecting %s\n",
         symbol, entry->ip, funcs[idx]);
    return strcmp((const char *) symbol, funcs[idx]);
}

noinline int test_dwarf_unwind__thread(struct thread *thread)
{
    struct perf_sample sample;
    unsigned long cnt = 0;
    int err = -1;

    memset(&sample, 0, sizeof(sample));

    if (test__arch_unwind_sample(&sample, thread)) {
        pr_debug("failed to get unwind sample\n");
        goto out;
    }

    err = unwind__get_entries(unwind_entry, &cnt, thread,
                  &sample, MAX_STACK);
    if (err)
        pr_debug("unwind failed\n");
    else if (cnt != MAX_STACK) {
        pr_debug("got wrong number of stack entries %lu != %d\n",
             cnt, MAX_STACK);
        err = -1;
    }

 out:
    free(sample.user_stack.data);
    free(sample.user_regs.regs);
    return err;
}

static int global_unwind_retval = -INT_MAX;

noinline int test_dwarf_unwind__compare(void *p1, void *p2)
{
    /* Any possible value should be 'thread' */
    struct thread *thread = *(struct thread **)p1;

    if (global_unwind_retval == -INT_MAX) {
        /* Call unwinder twice for both callchain orders. */
        callchain_param.order = ORDER_CALLER;

        global_unwind_retval = test_dwarf_unwind__thread(thread);
        if (!global_unwind_retval) {
            callchain_param.order = ORDER_CALLEE;
            global_unwind_retval = test_dwarf_unwind__thread(thread);
        }
    }

    return p1 - p2;
}

noinline int test_dwarf_unwind__krava_3(struct thread *thread)
{
    struct thread *array[2] = {thread, thread};
    void *fp = &bsearch;
    /*
     * make _bsearch a volatile function pointer to
     * prevent potential optimization, which may expand
     * bsearch and call compare directly from this function,
     * instead of libc shared object.
     */
    void *(*volatile _bsearch)(void *, void *, size_t,
            size_t, int (*)(void *, void *));

    _bsearch = fp;
    _bsearch(array, &thread, 2, sizeof(struct thread **),
         test_dwarf_unwind__compare);
    return global_unwind_retval;
}

noinline int test_dwarf_unwind__krava_2(struct thread *thread)
{
    return test_dwarf_unwind__krava_3(thread);
}

noinline int test_dwarf_unwind__krava_1(struct thread *thread)
{
    return test_dwarf_unwind__krava_2(thread);
}

int test__dwarf_unwind(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    struct machine *machine;
    struct thread *thread;
    int err = -1;

    machine = machine__new_host();
    if (!machine) {
        pr_err("Could not get machine\n");
        return -1;
    }

    if (machine__create_kernel_maps(machine)) {
        pr_err("Failed to create kernel maps\n");
        return -1;
    }

    callchain_param.record_mode = CALLCHAIN_DWARF;
    dwarf_callchain_users = true;

    if (init_live_machine(machine)) {
        pr_err("Could not init machine\n");
        goto out;
    }

    if (verbose > 1)
        machine__fprintf(machine, stderr);

    thread = machine__find_thread(machine, getpid(), getpid());
    if (!thread) {
        pr_err("Could not get thread\n");
        goto out;
    }

    err = test_dwarf_unwind__krava_1(thread);
    thread__put(thread);

 out:
    machine__delete_threads(machine);
    machine__delete(machine);
    return err;
}