uwrap: Optimalization of uid_wrapper_enabled() function.

Check only bool variable inside uwrap structure instead
of calling whole uid_init().

In the best case only one mutex lock is need when check.

NOTES:
 * This patch uses __atomic_load gcc builtin function.
 * uid_init() were moved outside uid_wrapper_enabled() function.

Signed-off-by: Robin Hack <hack.robin@gmail.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

diff --git a/ConfigureChecks.cmake b/ConfigureChecks.cmake
index 30f89fc983ddd00221137ca53122e3c68b3391db..26c2238256cff24b25acfb3732120fdba94e0787 100644 (file)
--- a/ConfigureChecks.cmake
+++ b/ConfigureChecks.cmake
@@ -124,6 +124,15 @@ int main(void) {
     set(CMAKE_REQUIRED_DEFINITIONS)
 endif (LINUX)
 
+check_c_source_compiles("
+#include <stdbool.h>
+int main(void) {
+    bool x;
+    bool *p_x = &x;
+    __atomic_load(p_x, &x, __ATOMIC_RELAXED);
+    return 0;
+}" HAVE_GCC_ATOMIC_BUILTINS)
+
 check_c_source_compiles("
 __thread int tls;
 

diff --git a/config.h.cmake b/config.h.cmake
index ac1d33179f5dc627f23ff2a9dd8db21b57a073ef..b2a03b28a3cc9596dab9ecde2ce9847bd7eb0e96 100644 (file)
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -57,6 +57,7 @@
 #cmakedefine HAVE_LINUX_32BIT_SYSCALLS 1
 
 #cmakedefine HAVE_GCC_THREAD_LOCAL_STORAGE 1
+#cmakedefine HAVE_GCC_ATOMIC_BUILTINS 1
 #cmakedefine HAVE_CONSTRUCTOR_ATTRIBUTE 1
 #cmakedefine HAVE_DESTRUCTOR_ATTRIBUTE 1
 #cmakedefine HAVE_FUNCTION_ATTRIBUTE_FORMAT 1

diff --git a/src/uid_wrapper.c b/src/uid_wrapper.c
index 578977dadc1c14bc67a2490f6b569946b12ef676..aa3f30212a843a4db272d28aed2a86a5689c204b 100644 (file)
--- a/src/uid_wrapper.c
+++ b/src/uid_wrapper.c
@@ -639,10 +639,15 @@ static void uwrap_init(void)
 
 bool uid_wrapper_enabled(void)
 {
-       uwrap_init();
-
-       return uwrap.enabled ? true : false;
-       UWRAP_UNLOCK(uwrap_id);
+       bool enabled = false;
+       #ifdef HAVE_GCC_ATOMIC_BUILTINS
+               __atomic_load(&uwrap.enabled, &enabled, __ATOMIC_RELAXED);
+       #else
+               UWRAP_LOCK(uwrap_id);
+               enabled = uwrap.enabled;
+               UWRAP_UNLOCK(uwrap_id);
+       #endif
+       return enabled;
 }
 
 static int uwrap_setresuid_thread(uid_t ruid, uid_t euid, uid_t suid)
@@ -712,6 +717,7 @@ int setuid(uid_t uid)
                return libc_setuid(uid);
        }
 
+       uwrap_init();
        return uwrap_setresuid(uid, -1, -1);
 }
 
@@ -727,6 +733,7 @@ int seteuid(uid_t euid)
                return libc_seteuid(euid);
        }
 
+       uwrap_init();
        return uwrap_setresuid(-1, euid, -1);
 }
 #endif
@@ -743,6 +750,7 @@ int setreuid(uid_t ruid, uid_t euid)
                return libc_setreuid(ruid, euid);
        }
 
+       uwrap_init();
        return uwrap_setresuid(ruid, euid, -1);
 }
 #endif
@@ -754,6 +762,7 @@ int setresuid(uid_t ruid, uid_t euid, uid_t suid)
                return libc_setresuid(ruid, euid, suid);
        }
 
+       uwrap_init();
        return uwrap_setresuid(ruid, euid, suid);
 }
 #endif
@@ -779,6 +788,7 @@ uid_t getuid(void)
                return libc_getuid();
        }
 
+       uwrap_init();
        return uwrap_getuid();
 }
 
@@ -809,6 +819,7 @@ uid_t geteuid(void)
                return libc_geteuid();
        }
 
+       uwrap_init();
        return uwrap_geteuid();
 }
 
@@ -879,6 +890,7 @@ int setgid(gid_t gid)
                return libc_setgid(gid);
        }
 
+       uwrap_init();
        return uwrap_setresgid(gid, -1, -1);
 }
 
@@ -889,6 +901,7 @@ int setegid(gid_t egid)
                return libc_setegid(egid);
        }
 
+       uwrap_init();
        return uwrap_setresgid(-1, egid, -1);
 }
 #endif
@@ -900,6 +913,7 @@ int setregid(gid_t rgid, gid_t egid)
                return libc_setregid(rgid, egid);
        }
 
+       uwrap_init();
        return uwrap_setresgid(rgid, egid, -1);
 }
 #endif
@@ -911,6 +925,7 @@ int setresgid(gid_t rgid, gid_t egid, gid_t sgid)
                return libc_setresgid(rgid, egid, sgid);
        }
 
+       uwrap_init();
        return uwrap_setresgid(rgid, egid, sgid);
 }
 #endif
@@ -936,6 +951,7 @@ gid_t getgid(void)
                return libc_getgid();
        }
 
+       uwrap_init();
        return uwrap_getgid();
 }
 
@@ -960,6 +976,7 @@ uid_t getegid(void)
                return libc_getegid();
        }
 
+       uwrap_init();
        return uwrap_getegid();
 }
 
@@ -1041,6 +1058,7 @@ int setgroups(size_t size, const gid_t *list)
                return libc_setgroups(size, list);
        }
 
+       uwrap_init();
        return uwrap_setgroups(size, list);
 }
 
@@ -1076,6 +1094,7 @@ int getgroups(int size, gid_t *list)
                return libc_getgroups(size, list);
        }
 
+       uwrap_init();
        return uwrap_getgroups(size, list);
 }
 
@@ -1242,6 +1261,7 @@ long int syscall (long int sysno, ...)
                return rc;
        }
 
+       uwrap_init();
        rc = uwrap_syscall(sysno, va);
        va_end(va);
 
@@ -1263,6 +1283,11 @@ void uwrap_constructor(void)
        pthread_atfork(&uwrap_thread_prepare,
                       &uwrap_thread_parent,
                       &uwrap_thread_child);
+
+       /* Here is safe place to call uwrap_init() and initialize data
+        * for main process.
+        */
+       uwrap_init();
 }
 
 /****************************