[PATCH 1/4] kernel: constructor support
From: Peter Oberparleiter
Date: Tue May 19 2009 - 10:26:32 EST
From: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Acked-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Acked-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Jeff Dike <jdike@xxxxxxxxxxx>
---
include/asm-generic/sections.h | 3 +++
include/asm-generic/vmlinux.lds.h | 11 ++++++++++-
include/linux/init.h | 3 +++
include/linux/module.h | 6 ++++++
init/Kconfig | 5 +++++
init/main.c | 12 ++++++++++++
kernel/module.c | 16 ++++++++++++++++
7 files changed, 55 insertions(+), 1 deletion(-)
Index: linux-2.6.30-rc6/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.30-rc6.orig/include/asm-generic/vmlinux.lds.h 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/include/asm-generic/vmlinux.lds.h 2009-05-19 12:41:25.000000000 +0200
@@ -332,6 +332,14 @@
/* Section used for early init (in .S files) */
#define HEAD_TEXT *(HEAD_TEXT_SECTION)
+#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) \
@@ -340,7 +348,8 @@
CPU_DISCARD(init.data) \
CPU_DISCARD(init.rodata) \
MEM_DISCARD(init.data) \
- MEM_DISCARD(init.rodata)
+ MEM_DISCARD(init.rodata) \
+ KERNEL_CTORS()
#define INIT_TEXT \
*(.init.text) \
Index: linux-2.6.30-rc6/include/linux/init.h
===================================================================
--- linux-2.6.30-rc6.orig/include/linux/init.h 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/include/linux/init.h 2009-05-19 12:41:25.000000000 +0200
@@ -136,6 +136,9 @@
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[];
Index: linux-2.6.30-rc6/include/linux/module.h
===================================================================
--- linux-2.6.30-rc6.orig/include/linux/module.h 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/include/linux/module.h 2009-05-19 12:41:25.000000000 +0200
@@ -354,6 +354,12 @@
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 {}
Index: linux-2.6.30-rc6/init/main.c
===================================================================
--- linux-2.6.30-rc6.orig/init/main.c 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/init/main.c 2009-05-19 12:41:25.000000000 +0200
@@ -700,6 +700,17 @@
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);
@@ -780,6 +791,7 @@
usermodehelper_init();
driver_init();
init_irq_proc();
+ do_ctors();
do_initcalls();
}
Index: linux-2.6.30-rc6/kernel/module.c
===================================================================
--- linux-2.6.30-rc6.orig/kernel/module.c 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/kernel/module.c 2009-05-19 12:41:26.000000000 +0200
@@ -2172,6 +2172,10 @@
sizeof(*mod->tracepoints),
&mod->num_tracepoints);
#endif
+#ifdef CONFIG_CONSTRUCTORS
+ mod->ctors = section_objs(hdr, sechdrs, secstrings, ".ctors",
+ sizeof(*mod->ctors), &mod->num_ctors);
+#endif
#ifdef CONFIG_MODVERSIONS
if ((mod->num_syms && !mod->crcs)
@@ -2328,6 +2332,17 @@
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)
@@ -2356,6 +2371,7 @@
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);
Index: linux-2.6.30-rc6/init/Kconfig
===================================================================
--- linux-2.6.30-rc6.orig/init/Kconfig 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/init/Kconfig 2009-05-19 12:41:26.000000000 +0200
@@ -16,6 +16,11 @@
default "$ARCH_DEFCONFIG"
default "arch/$ARCH/defconfig"
+config CONSTRUCTORS
+ bool
+ depends on !UML
+ default y
+
menu "General setup"
config EXPERIMENTAL
Index: linux-2.6.30-rc6/include/asm-generic/sections.h
===================================================================
--- linux-2.6.30-rc6.orig/include/asm-generic/sections.h 2009-05-19 12:27:39.000000000 +0200
+++ linux-2.6.30-rc6/include/asm-generic/sections.h 2009-05-19 12:41:26.000000000 +0200
@@ -14,6 +14,9 @@
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
--
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