#include <common/compat/dlfcn.h>
#include <unistd.h>
+#include <stdbool.h>
#include <stdio.h>
#include <signal.h>
#include <sched.h>
#include <stdlib.h>
#include <errno.h>
+#include <pthread.h>
+
#include <lttng/ust-fork.h>
#include <urcu/uatomic.h>
+#include "common/macros.h"
+
+struct libc_pointer {
+ void **procedure;
+ const char *symbol;
+};
+
+#define DEFINE_LIBC_POINTER(name) { (void**)&plibc_## name, #name }
+
+#ifdef __linux__
+
+struct user_desc;
+
+static int (*plibc_clone)(int (*fn)(void *), void *child_stack,
+ int flags, void *arg, pid_t *ptid,
+ struct user_desc *tls, pid_t *ctid) = NULL;
+
+static int (*plibc_setns)(int fd, int nstype) = NULL;
+
+static int (*plibc_setresgid)(gid_t rgid, gid_t egid, gid_t sgid) = NULL;
+
+static int (*plibc_setresuid)(uid_t ruid, uid_t euid, uid_t suid) = NULL;
+
+static int (*plibc_unshare)(int flags) = NULL;
+
+#elif defined (__FreeBSD__)
+
+static pid_t (*plibc_rfork)(int flags) = NULL;
+
+#endif
+
+static int (*plibc_daemon)(int nochdir, int noclose) = NULL;
+
+static pid_t (*plibc_fork)(void) = NULL;
+
+static int (*plibc_setegid)(gid_t egid) = NULL;
+
+static int (*plibc_seteuid)(uid_t euid) = NULL;
+
+static int (*plibc_setgid)(gid_t gid) = NULL;
+
+static int (*plibc_setregid)(gid_t rgid, gid_t egid) = NULL;
+
+static int (*plibc_setreuid)(uid_t ruid, uid_t euid) = NULL;
+
+static int (*plibc_setuid)(uid_t uid) = NULL;
+
+static void lttng_ust_fork_wrapper_ctor(void)
+ __attribute__((constructor));
+
+static pthread_mutex_t initialization_guard = PTHREAD_MUTEX_INITIALIZER;
+static bool was_initialized = false;
+
+/*
+ * Must be called with initialization_guard held.
+ */
+static void initialize(void)
+{
+ const struct libc_pointer libc_pointers[] = {
+#ifdef __linux__
+ DEFINE_LIBC_POINTER(clone),
+ DEFINE_LIBC_POINTER(setns),
+ DEFINE_LIBC_POINTER(setresgid),
+ DEFINE_LIBC_POINTER(setresuid),
+ DEFINE_LIBC_POINTER(unshare),
+#elif defined (__FreeBSD__)
+ DEFINE_LIBC_POINTER(rfork),
+#endif
+ DEFINE_LIBC_POINTER(daemon),
+ DEFINE_LIBC_POINTER(fork),
+ DEFINE_LIBC_POINTER(setegid),
+ DEFINE_LIBC_POINTER(seteuid),
+ DEFINE_LIBC_POINTER(setgid),
+ DEFINE_LIBC_POINTER(setregid),
+ DEFINE_LIBC_POINTER(setreuid),
+ DEFINE_LIBC_POINTER(setuid),
+ };
+
+ size_t k;
+
+ for (k = 0; k < LTTNG_ARRAY_SIZE(libc_pointers); ++k) {
+ void *procedure = dlsym(RTLD_NEXT, libc_pointers[k].symbol);
+
+ if (NULL == procedure) {
+ fprintf(stderr,
+ "libustfork: unable to find \"%s\" symbol\n",
+ libc_pointers[k].symbol);
+ continue;
+ }
+
+ uatomic_set(libc_pointers[k].procedure, procedure);
+ }
+}
+
+/*
+ * Lazy initialization is required because it is possible for a shared library
+ * to have a constructor that is executed before our constructor, which could
+ * call some libc functions that we are wrapping.
+ *
+ * It is also possible for this library constructor to create a thread using the
+ * raw system call. Therefore, the lazy initialization must be multi-thread safe.
+ */
+static void *lazy_initialize(void **pfunc)
+{
+ void *func = uatomic_read(pfunc);
+
+ /*
+ * If *pfunc != NULL, then it is assumed that some thread has already
+ * called the initialization routine.
+ */
+ if (caa_likely(func)) {
+ goto out;
+ }
+
+ pthread_mutex_lock(&initialization_guard);
+ if (!was_initialized) {
+ initialize();
+ was_initialized = true;
+ }
+ func = *pfunc;
+ pthread_mutex_unlock(&initialization_guard);
+out:
+ return func;
+}
+
+#define LAZY_INITIALIZE_OR_NOSYS(ptr) \
+ ({ \
+ void *ret; \
+ \
+ ret = lazy_initialize((void**)&(ptr)); \
+ if (NULL == ret) { \
+ errno = ENOSYS; \
+ return -1; \
+ } \
+ \
+ ret; \
+ })
+
+static void lttng_ust_fork_wrapper_ctor(void)
+{
+ /*
+ * Using fork here because it is defined on all supported OS.
+ */
+ (void) lazy_initialize((void**)&plibc_fork);
+}
+
pid_t fork(void)
{
- static pid_t (*plibc_func)(void) = NULL;
- pid_t (*func)(void);
sigset_t sigset;
pid_t retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "fork");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"fork\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ pid_t (*func)(void) = LAZY_INITIALIZE_OR_NOSYS(plibc_fork);
lttng_ust_before_fork(&sigset);
/* Do the real fork */
int daemon(int nochdir, int noclose)
{
- static int (*plibc_func)(int nochdir, int noclose) = NULL;
- int (*func)(int nochdir, int noclose);
sigset_t sigset;
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "daemon");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"daemon\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(int, int) = LAZY_INITIALIZE_OR_NOSYS(plibc_daemon);
lttng_ust_before_fork(&sigset);
/* Do the real daemon call */
int setuid(uid_t uid)
{
- static int (*plibc_func)(uid_t uid) = NULL;
- int (*func)(uid_t uid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setuid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setuid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(uid_t) = LAZY_INITIALIZE_OR_NOSYS(plibc_setuid);
/* Do the real setuid */
retval = func(uid);
int setgid(gid_t gid)
{
- static int (*plibc_func)(gid_t gid) = NULL;
- int (*func)(gid_t gid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setgid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setgid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(gid_t) = LAZY_INITIALIZE_OR_NOSYS(plibc_setgid);
/* Do the real setgid */
retval = func(gid);
int seteuid(uid_t euid)
{
- static int (*plibc_func)(uid_t euid) = NULL;
- int (*func)(uid_t euid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "seteuid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"seteuid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(uid_t) = LAZY_INITIALIZE_OR_NOSYS(plibc_seteuid);
/* Do the real seteuid */
retval = func(euid);
int setegid(gid_t egid)
{
- static int (*plibc_func)(gid_t egid) = NULL;
- int (*func)(gid_t egid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setegid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setegid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(gid_t) = LAZY_INITIALIZE_OR_NOSYS(plibc_setegid);
/* Do the real setegid */
retval = func(egid);
int setreuid(uid_t ruid, uid_t euid)
{
- static int (*plibc_func)(uid_t ruid, uid_t euid) = NULL;
- int (*func)(uid_t ruid, uid_t euid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setreuid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setreuid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(uid_t, uid_t) =
+ LAZY_INITIALIZE_OR_NOSYS(plibc_setreuid);
/* Do the real setreuid */
retval = func(ruid, euid);
int setregid(gid_t rgid, gid_t egid)
{
- static int (*plibc_func)(gid_t rgid, gid_t egid) = NULL;
- int (*func)(gid_t rgid, gid_t egid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setregid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setregid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(gid_t, gid_t) = LAZY_INITIALIZE_OR_NOSYS(plibc_setregid);
/* Do the real setregid */
retval = func(rgid, egid);
#ifdef __linux__
-struct user_desc;
-
struct ustfork_clone_info {
int (*fn)(void *);
void *arg;
int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...)
{
- static int (*plibc_func)(int (*fn)(void *), void *child_stack,
- int flags, void *arg, pid_t *ptid,
- struct user_desc *tls, pid_t *ctid) = NULL;
- int (*func)(int (*fn)(void *), void *child_stack,
- int flags, void *arg, pid_t *ptid,
- struct user_desc *tls, pid_t *ctid);
/* var args */
pid_t *ptid;
struct user_desc *tls;
ctid = va_arg(ap, pid_t *);
va_end(ap);
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "clone");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"clone\" symbol.\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(int (*)(void *), void *, int , void *, pid_t *,
+ struct user_desc *, pid_t *) =
+ LAZY_INITIALIZE_OR_NOSYS(plibc_clone);
if (flags & CLONE_VM) {
/*
int setns(int fd, int nstype)
{
- static int (*plibc_func)(int fd, int nstype) = NULL;
- int (*func)(int fd, int nstype);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setns");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setns\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(int, int) = LAZY_INITIALIZE_OR_NOSYS(plibc_setns);
/* Do the real setns */
retval = func(fd, nstype);
int unshare(int flags)
{
- static int (*plibc_func)(int flags) = NULL;
- int (*func)(int flags);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "unshare");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"unshare\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(int) = LAZY_INITIALIZE_OR_NOSYS(plibc_unshare);
/* Do the real setns */
retval = func(flags);
int setresuid(uid_t ruid, uid_t euid, uid_t suid)
{
- static int (*plibc_func)(uid_t ruid, uid_t euid, uid_t suid) = NULL;
- int (*func)(uid_t ruid, uid_t euid, uid_t suid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setresuid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setresuid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(uid_t, uid_t, uid_t) =
+ LAZY_INITIALIZE_OR_NOSYS(plibc_setresuid);
/* Do the real setresuid */
retval = func(ruid, euid, suid);
int setresgid(gid_t rgid, gid_t egid, gid_t sgid)
{
- static int (*plibc_func)(gid_t rgid, gid_t egid, gid_t sgid) = NULL;
- int (*func)(gid_t rgid, gid_t egid, gid_t sgid);
int retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "setresgid");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"setresgid\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ int (*func)(gid_t, gid_t, gid_t) =
+ LAZY_INITIALIZE_OR_NOSYS(plibc_setresgid);
/* Do the real setresgid */
retval = func(rgid, egid, sgid);
pid_t rfork(int flags)
{
- static pid_t (*plibc_func)(int flags) = NULL;
- pid_t (*func)(int flags);
sigset_t sigset;
pid_t retval;
int saved_errno;
- func = uatomic_read(&plibc_func);
- if (func == NULL) {
- func = dlsym(RTLD_NEXT, "rfork");
- if (func == NULL) {
- fprintf(stderr, "libustfork: unable to find \"rfork\" symbol\n");
- errno = ENOSYS;
- return -1;
- }
- uatomic_set(&plibc_func, func);
- }
+ pid_t (*func)(int) = LAZY_INITIALIZE_OR_NOSYS(plibc_rfork);
lttng_ust_before_fork(&sigset);
/* Do the real rfork */
projects / lttng-ust.git / commitdiff
