/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * Copyright (C) 2017 Hari Bathini, IBM Corporation
 */

#include "namespaces.h"
#include "util.h"
#include "event.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <limits.h>
#include <sched.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <asm/bug.h>

struct namespaces *namespaces__new(struct namespaces_event *event)
{
        struct namespaces *namespaces;
        u64 link_info_size = ((event ? event->nr_namespaces : NR_NAMESPACES) *
                              sizeof(struct perf_ns_link_info));

        namespaces = zalloc(sizeof(struct namespaces) + link_info_size);
        if (!namespaces)
                return NULL;

        namespaces->end_time = -1;

        if (event)
                memcpy(namespaces->link_info, event->link_info, link_info_size);

        return namespaces;
}

void namespaces__free(struct namespaces *namespaces)
{
        free(namespaces);
}

int nsinfo__init(struct nsinfo *nsi)
{
        char oldns[PATH_MAX];
        char spath[PATH_MAX];
        char *newns = NULL;
        char *statln = NULL;
        struct stat old_stat;
        struct stat new_stat;
        FILE *f = NULL;
        size_t linesz = 0;
        int rv = -1;

        if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
                return rv;

        if (asprintf(&newns, "/proc/%d/ns/mnt", nsi->pid) == -1)
                return rv;

        if (stat(oldns, &old_stat) < 0)
                goto out;

        if (stat(newns, &new_stat) < 0)
                goto out;

        /* Check if the mount namespaces differ, if so then indicate that we
         * want to switch as part of looking up dso/map data.
         */
        if (old_stat.st_ino != new_stat.st_ino) {
                nsi->need_setns = true;
                nsi->mntns_path = newns;
                newns = NULL;
        }

        /* If we're dealing with a process that is in a different PID namespace,
         * attempt to work out the innermost tgid for the process.
         */
        if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsi->pid) >= PATH_MAX)
                goto out;

        f = fopen(spath, "r");
        if (f == NULL)
                goto out;

        while (getline(&statln, &linesz, f) != -1) {
                /* Use tgid if CONFIG_PID_NS is not defined. */
                if (strstr(statln, "Tgid:") != NULL) {
                        nsi->tgid = (pid_t)strtol(strrchr(statln, '\t'),
                                                     NULL, 10);
                        nsi->nstgid = nsi->tgid;
                }

                if (strstr(statln, "NStgid:") != NULL) {
                        nsi->nstgid = (pid_t)strtol(strrchr(statln, '\t'),
                                                     NULL, 10);
                        break;
                }
        }
        rv = 0;

out:
        if (f != NULL)
                (void) fclose(f);
        free(statln);
        free(newns);
        return rv;
}

struct nsinfo *nsinfo__new(pid_t pid)
{
        struct nsinfo *nsi;

        if (pid == 0)
                return NULL;

        nsi = calloc(1, sizeof(*nsi));
        if (nsi != NULL) {
                nsi->pid = pid;
                nsi->tgid = pid;
                nsi->nstgid = pid;
                nsi->need_setns = false;
                /* Init may fail if the process exits while we're trying to look
                 * at its proc information.  In that case, save the pid but
                 * don't try to enter the namespace.
                 */
                if (nsinfo__init(nsi) == -1)
                        nsi->need_setns = false;

                refcount_set(&nsi->refcnt, 1);
        }

        return nsi;
}

struct nsinfo *nsinfo__copy(struct nsinfo *nsi)
{
        struct nsinfo *nnsi;

        if (nsi == NULL)
                return NULL;

        nnsi = calloc(1, sizeof(*nnsi));
        if (nnsi != NULL) {
                nnsi->pid = nsi->pid;
                nnsi->tgid = nsi->tgid;
                nnsi->nstgid = nsi->nstgid;
                nnsi->need_setns = nsi->need_setns;
                if (nsi->mntns_path) {
                        nnsi->mntns_path = strdup(nsi->mntns_path);
                        if (!nnsi->mntns_path) {
                                free(nnsi);
                                return NULL;
                        }
                }
                refcount_set(&nnsi->refcnt, 1);
        }

        return nnsi;
}

void nsinfo__delete(struct nsinfo *nsi)
{
        zfree(&nsi->mntns_path);
        free(nsi);
}

struct nsinfo *nsinfo__get(struct nsinfo *nsi)
{
        if (nsi)
                refcount_inc(&nsi->refcnt);
        return nsi;
}

void nsinfo__put(struct nsinfo *nsi)
{
        if (nsi && refcount_dec_and_test(&nsi->refcnt))
                nsinfo__delete(nsi);
}

void nsinfo__mountns_enter(struct nsinfo *nsi,
                                  struct nscookie *nc)
{
        char curpath[PATH_MAX];
        int oldns = -1;
        int newns = -1;
        char *oldcwd = NULL;

        if (nc == NULL)
                return;

        nc->oldns = -1;
        nc->newns = -1;

        if (!nsi || !nsi->need_setns)
                return;

        if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
                return;

        oldcwd = get_current_dir_name();
        if (!oldcwd)
                return;

        oldns = open(curpath, O_RDONLY);
        if (oldns < 0)
                goto errout;

        newns = open(nsi->mntns_path, O_RDONLY);
        if (newns < 0)
                goto errout;

        if (setns(newns, CLONE_NEWNS) < 0)
                goto errout;

        nc->oldcwd = oldcwd;
        nc->oldns = oldns;
        nc->newns = newns;
        return;

errout:
        free(oldcwd);
        if (oldns > -1)
                close(oldns);
        if (newns > -1)
                close(newns);
}

void nsinfo__mountns_exit(struct nscookie *nc)
{
        if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
                return;

        setns(nc->oldns, CLONE_NEWNS);

        if (nc->oldcwd) {
                WARN_ON_ONCE(chdir(nc->oldcwd));
                zfree(&nc->oldcwd);
        }

        if (nc->oldns > -1) {
                close(nc->oldns);
                nc->oldns = -1;
        }

        if (nc->newns > -1) {
                close(nc->newns);
                nc->newns = -1;
        }
}

char *nsinfo__realpath(const char *path, struct nsinfo *nsi)
{
        char *rpath;
        struct nscookie nsc;

        nsinfo__mountns_enter(nsi, &nsc);
        rpath = realpath(path, NULL);
        nsinfo__mountns_exit(&nsc);

        return rpath;
}