// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <elfutils/libdw.h>
#include <elfutils/libdwfl.h>
#include <inttypes.h>
#include <errno.h>
#include "debug.h"
#include "unwind.h"
#include "unwind-libdw.h"
#include "machine.h"
#include "thread.h"
#include <linux/types.h>
#include "event.h"
#include "perf_regs.h"
#include "callchain.h"
#include "util.h"

static char *debuginfo_path;

static const Dwfl_Callbacks offline_callbacks = {
        .find_debuginfo         = dwfl_standard_find_debuginfo,
        .debuginfo_path         = &debuginfo_path,
        .section_address        = dwfl_offline_section_address,
};

static int __report_module(struct addr_location *al, u64 ip,
                            struct unwind_info *ui)
{
        Dwfl_Module *mod;
        struct dso *dso = NULL;

        thread__find_addr_location(ui->thread,
                                   PERF_RECORD_MISC_USER,
                                   MAP__FUNCTION, ip, al);

        if (al->map)
                dso = al->map->dso;

        if (!dso)
                return 0;

        mod = dwfl_addrmodule(ui->dwfl, ip);
        if (mod) {
                Dwarf_Addr s;

                dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
                if (s != al->map->start)
                        mod = 0;
        }

        if (!mod)
                mod = dwfl_report_elf(ui->dwfl, dso->short_name,
                                      (dso->symsrc_filename ? dso->symsrc_filename : dso->long_name), -1, al->map->start,
                                      false);

        return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
}

static int report_module(u64 ip, struct unwind_info *ui)
{
        struct addr_location al;

        return __report_module(&al, ip, ui);
}

/*
 * Store all entries within entries array,
 * we will process it after we finish unwind.
 */
static int entry(u64 ip, struct unwind_info *ui)

{
        struct unwind_entry *e = &ui->entries[ui->idx++];
        struct addr_location al;

        if (__report_module(&al, ip, ui))
                return -1;

        e->ip  = al.addr;
        e->map = al.map;
        e->sym = al.sym;

        pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
                 al.sym ? al.sym->name : "''",
                 ip,
                 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
        return 0;
}

static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
{
        /* We want only single thread to be processed. */
        if (*thread_argp != NULL)
                return 0;

        *thread_argp = arg;
        return dwfl_pid(dwfl);
}

static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
                          Dwarf_Word *data)
{
        struct addr_location al;
        ssize_t size;

        thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
                              MAP__FUNCTION, addr, &al);
        if (!al.map) {
                /*
                 * We've seen cases (softice) where DWARF unwinder went
                 * through non executable mmaps, which we need to lookup
                 * in MAP__VARIABLE tree.
                 */
                thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
                                      MAP__VARIABLE, addr, &al);
        }

        if (!al.map) {
                pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
                return -1;
        }

        if (!al.map->dso)
                return -1;

        size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
                                   addr, (u8 *) data, sizeof(*data));

        return !(size == sizeof(*data));
}

static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
                        void *arg)
{
        struct unwind_info *ui = arg;
        struct stack_dump *stack = &ui->sample->user_stack;
        u64 start, end;
        int offset;
        int ret;

        ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
        if (ret)
                return false;

        end = start + stack->size;

        /* Check overflow. */
        if (addr + sizeof(Dwarf_Word) < addr)
                return false;

        if (addr < start || addr + sizeof(Dwarf_Word) > end) {
                ret = access_dso_mem(ui, addr, result);
                if (ret) {
                        pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
                                 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
                                addr, start, end);
                        return false;
                }
                return true;
        }

        offset  = addr - start;
        *result = *(Dwarf_Word *)&stack->data[offset];
        pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
                 addr, (unsigned long)*result, offset);
        return true;
}

static const Dwfl_Thread_Callbacks callbacks = {
        .next_thread            = next_thread,
        .memory_read            = memory_read,
        .set_initial_registers  = libdw__arch_set_initial_registers,
};

static int
frame_callback(Dwfl_Frame *state, void *arg)
{
        struct unwind_info *ui = arg;
        Dwarf_Addr pc;
        bool isactivation;

        if (!dwfl_frame_pc(state, &pc, NULL)) {
                pr_err("%s", dwfl_errmsg(-1));
                return DWARF_CB_ABORT;
        }

        // report the module before we query for isactivation
        report_module(pc, ui);

        if (!dwfl_frame_pc(state, &pc, &isactivation)) {
                pr_err("%s", dwfl_errmsg(-1));
                return DWARF_CB_ABORT;
        }

        if (!isactivation)
                --pc;

        return entry(pc, ui) || !(--ui->max_stack) ?
               DWARF_CB_ABORT : DWARF_CB_OK;
}

int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
                        struct thread *thread,
                        struct perf_sample *data,
                        int max_stack)
{
        struct unwind_info *ui, ui_buf = {
                .sample         = data,
                .thread         = thread,
                .machine        = thread->mg->machine,
                .cb             = cb,
                .arg            = arg,
                .max_stack      = max_stack,
        };
        Dwarf_Word ip;
        int err = -EINVAL, i;

        if (!data->user_regs.regs)
                return -EINVAL;

        ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
        if (!ui)
                return -ENOMEM;

        *ui = ui_buf;

        ui->dwfl = dwfl_begin(&offline_callbacks);
        if (!ui->dwfl)
                goto out;

        err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
        if (err)
                goto out;

        err = report_module(ip, ui);
        if (err)
                goto out;

        err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
        if (err)
                goto out;

        err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);

        if (err && ui->max_stack != max_stack)
                err = 0;

        /*
         * Display what we got based on the order setup.
         */
        for (i = 0; i < ui->idx && !err; i++) {
                int j = i;

                if (callchain_param.order == ORDER_CALLER)
                        j = ui->idx - i - 1;

                err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
        }

 out:
        if (err)
                pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));

        dwfl_end(ui->dwfl);
        free(ui);
        return 0;
}