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>

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 215aaab09e91..38928fcaff2b 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2216,6 +2216,10 @@ static noinline struct module *load_module(void __user *umod,
         mod->unused_gpl_crcs = section_addr(hdr, sechdrs, secstrings,
                                             "__kcrctab_unused_gpl");
 #endif
+#ifdef CONFIG_CONSTRUCTORS
+        mod->ctors = section_objs(hdr, sechdrs, secstrings, ".ctors",
+                                  sizeof(*mod->ctors), &mod->num_ctors);
+#endif
 
 #ifdef CONFIG_MARKERS
         mod->markers = section_objs(hdr, sechdrs, secstrings, "__markers",
@@ -2389,6 +2393,17 @@ static noinline struct module *load_module(void __user *umod,
         goto free_hdr;
 }
 
+/* Call module constructors. */
+static void do_mod_ctors(struct module *mod)
+{
+#ifdef CONFIG_CONSTRUCTORS
+        unsigned long i;
+
+        for (i = 0; i < mod->num_ctors; i++)
+                mod->ctors[i]();
+#endif
+}
+
 /* This is where the real work happens */
 SYSCALL_DEFINE3(init_module, void __user *, umod,
                 unsigned long, len, const char __user *, uargs)
@@ -2417,6 +2432,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
         blocking_notifier_call_chain(&module_notify_list,
                         MODULE_STATE_COMING, mod);
 
+        do_mod_ctors(mod);
         /* Start the module */
         if (mod->init != NULL)
                 ret = do_one_initcall(mod->init);