kernel: constructor support

Call constructors (gcc-generated initcall-like functions) during kernel
start and module load.  Constructors are e.g.  used for gcov data
initialization.

Disable constructor support for usermode Linux to prevent conflicts with
host glibc.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Li Wei <W.Li@Sun.COM>
Cc: Michael Ellerman <michaele@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heicars2@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <mschwid2@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/init/Kconfig b/init/Kconfig
index c4b3c6d51a72..1ce05a4cb5f6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -16,6 +16,11 @@ config DEFCONFIG_LIST
         default "$ARCH_DEFCONFIG"
         default "arch/$ARCH/defconfig"
 
+config CONSTRUCTORS
+        bool
+        depends on !UML
+        default y
+
 menu "General setup"
 
 config EXPERIMENTAL
diff --git a/init/main.c b/init/main.c
index 0e7aedeaa05f..1a65fdd06318 100644
--- a/init/main.c
+++ b/init/main.c
@@ -720,6 +720,17 @@ asmlinkage void __init start_kernel(void)
         rest_init();
 }
 
+/* Call all constructor functions linked into the kernel. */
+static void __init do_ctors(void)
+{
+#ifdef CONFIG_CONSTRUCTORS
+        ctor_fn_t *call = (ctor_fn_t *) __ctors_start;
+
+        for (; call < (ctor_fn_t *) __ctors_end; call++)
+                (*call)();
+#endif
+}
+
 int initcall_debug;
 core_param(initcall_debug, initcall_debug, bool, 0644);
 
@@ -800,6 +811,7 @@ static void __init do_basic_setup(void)
         usermodehelper_init();
         driver_init();
         init_irq_proc();
+        do_ctors();
         do_initcalls();
 }