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Message-ID: <4989AECD.6030009@linux.vnet.ibm.com>
Date: Wed, 04 Feb 2009 16:05:49 +0100
From: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
To: Rusty Russell <rusty@...tcorp.com.au>
CC: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Andi Kleen <andi@...stfloor.org>,
Huang Ying <ying.huang@...el.com>,
Sam Ravnborg <sam@...nborg.org>, Jeff Dike <jdike@...toit.com>
Subject: Re: [PATCH 1/4] kernel: constructor support
Rusty Russell wrote:
> On Tuesday 03 February 2009 23:16:33 Peter Oberparleiter wrote:
>> +#ifdef CONFIG_CONSTRUCTORS
>> + mod->ctors = section_objs(hdr, sechdrs, secstrings, "ctors",
>> + sizeof(*mod->ctors), &mod->num_ctors);
>> +#endif
>
> This looks horribly like untested code: shouldn't that be ".ctors"?
You're right - this must have slipped in with last minute changes.
Sorry about that. See fixed patch below (tested successfully with
modules on s390).
From: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
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@...ux.vnet.ibm.com>
---
include/asm-generic/vmlinux.lds.h | 11 ++++++++++-
include/linux/init.h | 2 ++
include/linux/module.h | 6 ++++++
init/Kconfig | 5 +++++
init/main.c | 13 +++++++++++++
kernel/module.c | 16 ++++++++++++++++
6 files changed, 52 insertions(+), 1 deletion(-)
Index: linux-2.6.29-rc3/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.29-rc3.orig/include/asm-generic/vmlinux.lds.h
+++ linux-2.6.29-rc3/include/asm-generic/vmlinux.lds.h
@@ -301,6 +301,14 @@
/* Section used for early init (in .S files) */
#define HEAD_TEXT *(.head.text)
+#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) \
@@ -317,7 +325,8 @@
. = ALIGN(8); \
VMLINUX_SYMBOL(__start___verbose) = .; \
*(__verbose) \
- VMLINUX_SYMBOL(__stop___verbose) = .;
+ VMLINUX_SYMBOL(__stop___verbose) = .; \
+ KERNEL_CTORS()
#define INIT_TEXT \
*(.init.text) \
Index: linux-2.6.29-rc3/include/linux/init.h
===================================================================
--- linux-2.6.29-rc3.orig/include/linux/init.h
+++ linux-2.6.29-rc3/include/linux/init.h
@@ -142,6 +142,8 @@ typedef void (*exitcall_t)(void);
extern initcall_t __con_initcall_start[], __con_initcall_end[];
extern initcall_t __security_initcall_start[], __security_initcall_end[];
+typedef void (*ctorcall_t)(void);
+
/* Defined in init/main.c */
extern int do_one_initcall(initcall_t fn);
extern char __initdata boot_command_line[];
Index: linux-2.6.29-rc3/include/linux/module.h
===================================================================
--- linux-2.6.29-rc3.orig/include/linux/module.h
+++ linux-2.6.29-rc3/include/linux/module.h
@@ -347,6 +347,12 @@ struct module
/* Reference counts */
struct module_ref ref[NR_CPUS];
#endif
+
+#ifdef CONFIG_CONSTRUCTORS
+ /* Constructor functions. */
+ ctorcall_t *ctors;
+ unsigned int num_ctors;
+#endif
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
Index: linux-2.6.29-rc3/init/main.c
===================================================================
--- linux-2.6.29-rc3.orig/init/main.c
+++ linux-2.6.29-rc3/init/main.c
@@ -686,6 +686,18 @@ 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
+ extern ctorcall_t __ctors_start[], __ctors_end[];
+ ctorcall_t *call;
+
+ for (call = __ctors_start; call < __ctors_end; call++)
+ (*call)();
+#endif
+}
+
int initcall_debug;
core_param(initcall_debug, initcall_debug, bool, 0644);
@@ -765,6 +777,7 @@ static void __init do_basic_setup(void)
usermodehelper_init();
driver_init();
init_irq_proc();
+ do_ctors();
do_initcalls();
}
Index: linux-2.6.29-rc3/kernel/module.c
===================================================================
--- linux-2.6.29-rc3.orig/kernel/module.c
+++ linux-2.6.29-rc3/kernel/module.c
@@ -2145,6 +2145,10 @@ static noinline struct module *load_modu
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)
@@ -2295,6 +2299,17 @@ static noinline struct module *load_modu
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)
@@ -2323,6 +2338,7 @@ SYSCALL_DEFINE3(init_module, void __user
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-2.6.29-rc3/init/Kconfig
===================================================================
--- linux-2.6.29-rc3.orig/init/Kconfig
+++ linux-2.6.29-rc3/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
--
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