// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (c) 2015-2017 Daniel Borkmann */
/* Copyright (c) 2018 Netronome Systems, Inc. */

#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <linux/magic.h>
#include <fcntl.h>
#include <sys/vfs.h>

#include "main.h"

#ifndef TRACEFS_MAGIC
# define TRACEFS_MAGIC  0x74726163
#endif

#define _textify(x)     #x
#define textify(x)      _textify(x)

FILE *trace_pipe_fd;
char *buff;

static int validate_tracefs_mnt(const char *mnt, unsigned long magic)
{
        struct statfs st_fs;

        if (statfs(mnt, &st_fs) < 0)
                return -ENOENT;
        if ((unsigned long)st_fs.f_type != magic)
                return -ENOENT;

        return 0;
}

static bool
find_tracefs_mnt_single(unsigned long magic, char *mnt, const char *mntpt)
{
        size_t src_len;

        if (validate_tracefs_mnt(mntpt, magic))
                return false;

        src_len = strlen(mntpt);
        if (src_len + 1 >= PATH_MAX) {
                p_err("tracefs mount point name too long");
                return false;
        }

        strcpy(mnt, mntpt);
        return true;
}

static bool get_tracefs_pipe(char *mnt)
{
        static const char * const known_mnts[] = {
                "/sys/kernel/tracing",
                "/sys/kernel/debug/tracing",
        };
        const char *pipe_name = "/trace_pipe";
        const char *fstype = "tracefs";
        char type[100], format[32];
        const char * const *ptr;
        bool found = false;
        FILE *fp;

        for (ptr = known_mnts; ptr < known_mnts + ARRAY_SIZE(known_mnts); ptr++)
                if (find_tracefs_mnt_single(TRACEFS_MAGIC, mnt, *ptr))
                        goto exit_found;

        fp = fopen("/proc/mounts", "r");
        if (!fp)
                return false;

        /* Allow room for NULL terminating byte and pipe file name */
        snprintf(format, sizeof(format), "%%*s %%%zus %%99s %%*s %%*d %%*d\\n",
                 PATH_MAX - strlen(pipe_name) - 1);
        while (fscanf(fp, format, mnt, type) == 2)
                if (strcmp(type, fstype) == 0) {
                        found = true;
                        break;
                }
        fclose(fp);

        /* The string from fscanf() might be truncated, check mnt is valid */
        if (found && validate_tracefs_mnt(mnt, TRACEFS_MAGIC))
                goto exit_found;

        if (block_mount)
                return false;

        p_info("could not find tracefs, attempting to mount it now");
        strcpy(mnt, known_mnts[0]);
        if (mount_tracefs(mnt))
                return false;

exit_found:
        strcat(mnt, pipe_name);
        return true;
}

static void exit_tracelog(int signum)
{
        fclose(trace_pipe_fd);
        free(buff);

        if (json_output) {
                jsonw_end_array(json_wtr);
                jsonw_destroy(&json_wtr);
        }

        exit(0);
}

int do_tracelog(int argc, char **argv)
{
        const struct sigaction act = {
                .sa_handler = exit_tracelog
        };
        char trace_pipe[PATH_MAX];
        size_t buff_len = 0;

        if (json_output)
                jsonw_start_array(json_wtr);

        if (!get_tracefs_pipe(trace_pipe))
                return -1;

        trace_pipe_fd = fopen(trace_pipe, "r");
        if (!trace_pipe_fd) {
                p_err("could not open trace pipe: %s", strerror(errno));
                return -1;
        }

        sigaction(SIGHUP, &act, NULL);
        sigaction(SIGINT, &act, NULL);
        sigaction(SIGTERM, &act, NULL);
        while (1) {
                ssize_t ret;

                ret = getline(&buff, &buff_len, trace_pipe_fd);
                if (ret <= 0) {
                        p_err("failed to read content from trace pipe: %s",
                              strerror(errno));
                        break;
                }
                if (json_output)
                        jsonw_string(json_wtr, buff);
                else
                        printf("%s", buff);
        }

        fclose(trace_pipe_fd);
        free(buff);
        return -1;
}