[PATCH 1/4] kernel: constructor support

From: Peter Oberparleiter
Date: Tue Feb 03 2009 - 07:48:53 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 the host glibc.

Signed-off-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>

---
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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