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linux/tools/perf/util/namespaces.c
Arnaldo Carvalho de Melo 2d1acd3f10 perf namespaces: Introduce nsinfo__mntns_path() accessor to avoid accessing ->mntns_path directly
To reduce the use of RC_CHK_ACCESS(nsi).

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2023-04-17 22:22:24 -03:00

377 lines
7.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
*
* Copyright (C) 2017 Hari Bathini, IBM Corporation
*/
#include "namespaces.h"
#include "event.h"
#include "get_current_dir_name.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;
}
pid_t nsinfo__in_pidns(const struct nsinfo *nsi)
{
return RC_CHK_ACCESS(nsi)->in_pidns;
}
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 (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(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;
}