// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/zalloc.h>
#include <inttypes.h>
#include <limits.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 "symbol.h"
#include "thread.h"
#include "callchain.h"
#include "util/synthetic-events.h"

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

/*
 * The test will assert frames are on the stack but tail call optimizations lose
 * the frame of the caller. Clang can disable this optimization on a called
 * function but GCC currently (11/2020) lacks this attribute. The barrier is
 * used to inhibit tail calls in these cases.
 */
#ifdef __has_attribute
#if __has_attribute(disable_tail_calls)
#define NO_TAIL_CALL_ATTRIBUTE __attribute__((disable_tail_calls))
#define NO_TAIL_CALL_BARRIER
#endif
#endif
#ifndef NO_TAIL_CALL_ATTRIBUTE
#define NO_TAIL_CALL_ATTRIBUTE
#define NO_TAIL_CALL_BARRIER __asm__ __volatile__("" : : : "memory");
#endif

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();

        memset(&event, 0, sizeof(event));
        return perf_event__synthesize_mmap_events(NULL, &event, pid, pid,
                                                  mmap_handler, machine, true);
}

/*
 * 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->ms.sym ? entry->ms.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]);
}

NO_TAIL_CALL_ATTRIBUTE 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:
        zfree(&sample.user_stack.data);
        zfree(&sample.user_regs.regs);
        return err;
}

static int global_unwind_retval = -INT_MAX;

NO_TAIL_CALL_ATTRIBUTE 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;
}

NO_TAIL_CALL_ATTRIBUTE 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;
}

NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_2(struct thread *thread)
{
        int ret;

        ret =  test_dwarf_unwind__krava_3(thread);
        NO_TAIL_CALL_BARRIER;
        return ret;
}

NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread *thread)
{
        int ret;

        ret =  test_dwarf_unwind__krava_2(thread);
        NO_TAIL_CALL_BARRIER;
        return ret;
}

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;
}