// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Copyright (C) 2017 Hari Bathini, IBM Corporation
 */

#include "namespaces.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>
#include <linux/kernel.h>
#include <linux/zalloc.h>

static const char *perf_ns__names[] = {
        [NET_NS_INDEX]          = "net",
        [UTS_NS_INDEX]          = "uts",
        [IPC_NS_INDEX]          = "ipc",
        [PID_NS_INDEX]          = "pid",
        [USER_NS_INDEX]         = "user",
        [MNT_NS_INDEX]          = "mnt",
        [CGROUP_NS_INDEX]       = "cgroup",
};

const char *perf_ns__name(unsigned int id)
{
        if (id >= ARRAY_SIZE(perf_ns__names))
                return "UNKNOWN";
        return perf_ns__names[id];
}

struct namespaces *namespaces__new(struct perf_record_namespaces *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);
}

static int nsinfo__get_nspid(pid_t *tgid, pid_t *nstgid, bool *in_pidns, const char *path)
{
        FILE *f = NULL;
        char *statln = NULL;
        size_t linesz = 0;
        char *nspid;

        f = fopen(path, "r");
        if (f == NULL)
                return -1;

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

                if (strstr(statln, "NStgid:") != NULL) {
                        nspid = strrchr(statln, '\t');
                        *nstgid = (pid_t)strtol(nspid, NULL, 10);
                        /*
                         * If innermost tgid is not the first, process is in a different
                         * PID namespace.
                         */
                        *in_pidns = (statln + sizeof("NStgid:") - 1) != nspid;
                        break;
                }
        }

        fclose(f);
        free(statln);
        return 0;
}

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

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

        if (asprintf(&newns, "/proc/%d/ns/mnt", nsinfo__pid(nsi)) == -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) {
                RC_CHK_ACCESS(nsi)->need_setns = true;
                RC_CHK_ACCESS(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", nsinfo__pid(nsi)) >= PATH_MAX)
                goto out;

        rv = nsinfo__get_nspid(&RC_CHK_ACCESS(nsi)->tgid, &RC_CHK_ACCESS(nsi)->nstgid,
                               &RC_CHK_ACCESS(nsi)->in_pidns, spath);

out:
        free(newns);
        return rv;
}

static struct nsinfo *nsinfo__alloc(void)
{
        struct nsinfo *res;
        RC_STRUCT(nsinfo) *nsi;

        nsi = calloc(1, sizeof(*nsi));
        if (ADD_RC_CHK(res, nsi))
                refcount_set(&nsi->refcnt, 1);

        return res;
}

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

        if (pid == 0)
                return NULL;

        nsi = nsinfo__alloc();
        if (!nsi)
                return NULL;

        RC_CHK_ACCESS(nsi)->pid = pid;
        RC_CHK_ACCESS(nsi)->tgid = pid;
        RC_CHK_ACCESS(nsi)->nstgid = pid;
        nsinfo__clear_need_setns(nsi);
        RC_CHK_ACCESS(nsi)->in_pidns = 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)
                nsinfo__clear_need_setns(nsi);

        return nsi;
}

static const char *nsinfo__mntns_path(const struct nsinfo *nsi)
{
        return RC_CHK_ACCESS(nsi)->mntns_path;
}

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

        if (nsi == NULL)
                return NULL;

        nnsi = nsinfo__alloc();
        if (!nnsi)
                return NULL;

        RC_CHK_ACCESS(nnsi)->pid = nsinfo__pid(nsi);
        RC_CHK_ACCESS(nnsi)->tgid = nsinfo__tgid(nsi);
        RC_CHK_ACCESS(nnsi)->nstgid = nsinfo__nstgid(nsi);
        RC_CHK_ACCESS(nnsi)->need_setns = nsinfo__need_setns(nsi);
        RC_CHK_ACCESS(nnsi)->in_pidns = nsinfo__in_pidns(nsi);
        if (nsinfo__mntns_path(nsi)) {
                RC_CHK_ACCESS(nnsi)->mntns_path = strdup(nsinfo__mntns_path(nsi));
                if (!RC_CHK_ACCESS(nnsi)->mntns_path) {
                        nsinfo__put(nnsi);
                        return NULL;
                }
        }

        return nnsi;
}

static refcount_t *nsinfo__refcnt(struct nsinfo *nsi)
{
        return &RC_CHK_ACCESS(nsi)->refcnt;
}

static void nsinfo__delete(struct nsinfo *nsi)
{
        if (nsi) {
                WARN_ONCE(refcount_read(nsinfo__refcnt(nsi)) != 0, "nsinfo refcnt unbalanced\n");
                zfree(&RC_CHK_ACCESS(nsi)->mntns_path);
                RC_CHK_FREE(nsi);
        }
}

struct nsinfo *nsinfo__get(struct nsinfo *nsi)
{
        struct nsinfo *result;

        if (RC_CHK_GET(result, nsi))
                refcount_inc(nsinfo__refcnt(nsi));

        return result;
}

void nsinfo__put(struct nsinfo *nsi)
{
        if (nsi && refcount_dec_and_test(nsinfo__refcnt(nsi)))
                nsinfo__delete(nsi);
        else
                RC_CHK_PUT(nsi);
}

bool nsinfo__need_setns(const struct nsinfo *nsi)
{
        return RC_CHK_ACCESS(nsi)->need_setns;
}

void nsinfo__clear_need_setns(struct nsinfo *nsi)
{
        RC_CHK_ACCESS(nsi)->need_setns = false;
}

pid_t nsinfo__tgid(const struct nsinfo  *nsi)
{
        return RC_CHK_ACCESS(nsi)->tgid;
}

pid_t nsinfo__nstgid(const struct nsinfo  *nsi)
{
        return RC_CHK_ACCESS(nsi)->nstgid;
}

pid_t nsinfo__pid(const struct nsinfo  *nsi)
{
        return RC_CHK_ACCESS(nsi)->pid;
}

bool nsinfo__in_pidns(const struct nsinfo *nsi)
{
        return RC_CHK_ACCESS(nsi)->in_pidns;
}

void nsinfo__set_in_pidns(struct nsinfo *nsi)
{
        RC_CHK_ACCESS(nsi)->in_pidns = true;
}

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 || !nsinfo__need_setns(nsi))
                return;

        if (!getcwd(curpath, sizeof(curpath)))
                return;

        oldcwd = strdup(curpath);
        if (!oldcwd)
                return;

        oldns = open("/proc/self/ns/mnt", O_RDONLY);
        if (oldns < 0)
                goto errout;

        newns = open(nsinfo__mntns_path(nsi), 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;
}

int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi)
{
        int ret;
        struct nscookie nsc;

        nsinfo__mountns_enter(nsi, &nsc);
        ret = stat(filename, st);
        nsinfo__mountns_exit(&nsc);

        return ret;
}

bool nsinfo__is_in_root_namespace(void)
{
        pid_t tgid = 0, nstgid = 0;
        bool in_pidns = false;

        nsinfo__get_nspid(&tgid, &nstgid, &in_pidns, "/proc/self/status");
        return !in_pidns;
}