Fix: ustfork: save and restore errno in syscall wrappers

[lttng-ust.git] / liblttng-ust-fork / ustfork.c

diff --git a/liblttng-ust-fork/ustfork.c b/liblttng-ust-fork/ustfork.c
index cc6963b344419beaec236b24bc0831847e29103d..71c4b86c1189ff7f89e1f7edba541c5d69d98df5 100644 (file)
--- a/liblttng-ust-fork/ustfork.c
+++ b/liblttng-ust-fork/ustfork.c
@@ -18,13 +18,13 @@
  */
 
 #define _GNU_SOURCE
-#include <dlfcn.h>
+#include <lttng/ust-dlfcn.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <signal.h>
 #include <sched.h>
 #include <stdarg.h>
-#include "usterr.h"
+#include <errno.h>
 
 #include <lttng/ust.h>
 
@@ -33,6 +33,7 @@ pid_t fork(void)
        static pid_t (*plibc_func)(void) = NULL;
        sigset_t sigset;
        pid_t retval;
+       int saved_errno;
 
        if (plibc_func == NULL) {
                plibc_func = dlsym(RTLD_NEXT, "fork");
@@ -46,12 +47,45 @@ pid_t fork(void)
        ust_before_fork(&sigset);
        /* Do the real fork */
        retval = plibc_func();
+       saved_errno = errno;
        if (retval == 0) {
                /* child */
                ust_after_fork_child(&sigset);
        } else {
                ust_after_fork_parent(&sigset);
        }
+       errno = saved_errno;
+       return retval;
+}
+
+int daemon(int nochdir, int noclose)
+{
+       static int (*plibc_func)(int nochdir, int noclose) = NULL;
+       sigset_t sigset;
+       int retval;
+       int saved_errno;
+
+       if (plibc_func == NULL) {
+               plibc_func = dlsym(RTLD_NEXT, "daemon");
+               if (plibc_func == NULL) {
+                       fprintf(stderr, "libustfork: unable to find \"daemon\" symbol\n");
+                       errno = ENOSYS;
+                       return -1;
+               }
+       }
+
+       ust_before_fork(&sigset);
+       /* Do the real daemon call */
+       retval = plibc_func(nochdir, noclose);
+       saved_errno = errno;
+       if (retval == 0) {
+               /* child, parent called _exit() directly */
+               ust_after_fork_child(&sigset);
+       } else {
+               /* on error in the parent */
+               ust_after_fork_parent(&sigset);
+       }
+       errno = saved_errno;
        return retval;
 }
 
@@ -86,6 +120,7 @@ int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...)
        /* end of var args */
        va_list ap;
        int retval;
+       int saved_errno;
 
        va_start(ap, arg);
        ptid = va_arg(ap, pid_t *);
@@ -109,16 +144,19 @@ int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...)
                 */
                retval = plibc_func(fn, child_stack, flags, arg, ptid,
                                tls, ctid);
+               saved_errno = errno;
        } else {
                /* Creating a real process, we need to intervene. */
-               struct ustfork_clone_info info = { fn = fn, arg = arg };
+               struct ustfork_clone_info info = { .fn = fn, .arg = arg };
 
                ust_before_fork(&info.sigset);
                retval = plibc_func(clone_fn, child_stack, flags, &info,
                                ptid, tls, ctid);
+               saved_errno = errno;
                /* The child doesn't get here. */
                ust_after_fork_parent(&info.sigset);
        }
+       errno = saved_errno;
        return retval;
 }
 
@@ -129,6 +167,7 @@ pid_t rfork(int flags)
        static pid_t (*plibc_func)(void) = NULL;
        sigset_t sigset;
        pid_t retval;
+       int saved_errno;
 
        if (plibc_func == NULL) {
                plibc_func = dlsym(RTLD_NEXT, "rfork");
@@ -142,12 +181,14 @@ pid_t rfork(int flags)
        ust_before_fork(&sigset);
        /* Do the real rfork */
        retval = plibc_func();
+       saved_errno = errno;
        if (retval == 0) {
                /* child */
                ust_after_fork_child(&sigset);
        } else {
                ust_after_fork_parent(&sigset);
        }
+       errno = saved_errno;
        return retval;
 }