namespaces.c

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/*
 * 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>

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;

    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;

    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;

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

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

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

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

errout:
    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)
        return;

    setns(nc->oldns, CLONE_NEWNS);

    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;
}