Commit b99b87f7 authored by Peter Oberparleiter's avatar Peter Oberparleiter Committed by Linus Torvalds

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: default avatarPeter Oberparleiter <oberpar@linux.vnet.ibm.com>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarWANG 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e24aca67
......@@ -14,6 +14,9 @@ extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];
/* Start and end of .ctors section - used for constructor calls. */
extern char __ctors_start[], __ctors_end[];
/* function descriptor handling (if any). Override
* in asm/sections.h */
#ifndef dereference_function_descriptor
......
......@@ -440,12 +440,21 @@
INIT_TASK \
}
#ifdef CONFIG_CONSTRUCTORS
#define KERNEL_CTORS() VMLINUX_SYMBOL(__ctors_start) = .; \
*(.ctors) \
VMLINUX_SYMBOL(__ctors_end) = .;
#else
#define KERNEL_CTORS()
#endif
/* init and exit section handling */
#define INIT_DATA \
*(.init.data) \
DEV_DISCARD(init.data) \
CPU_DISCARD(init.data) \
MEM_DISCARD(init.data) \
KERNEL_CTORS() \
*(.init.rodata) \
DEV_DISCARD(init.rodata) \
CPU_DISCARD(init.rodata) \
......
......@@ -134,6 +134,9 @@ typedef void (*exitcall_t)(void);
extern initcall_t __con_initcall_start[], __con_initcall_end[];
extern initcall_t __security_initcall_start[], __security_initcall_end[];
/* Used for contructor calls. */
typedef void (*ctor_fn_t)(void);
/* Defined in init/main.c */
extern int do_one_initcall(initcall_t fn);
extern char __initdata boot_command_line[];
......
......@@ -363,6 +363,12 @@ struct module
local_t ref;
#endif
#endif
#ifdef CONFIG_CONSTRUCTORS
/* Constructor functions. */
ctor_fn_t *ctors;
unsigned int num_ctors;
#endif
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
......
......@@ -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
......
......@@ -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();
}
......
......@@ -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);
......
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