[RFC PATCH 1/8] kernel: call constructors

From: Peter Oberparleiter
Date: Mon Apr 21 2008 - 08:34:37 EST


From: Peter Oberparleiter <peter.oberparleiter@xxxxxxxxxx>

Call constructors during kernel init and module load. Required by the
gcov profiling infrastructure: gcc's profiling code uses constructors
to register profiling data structures.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@xxxxxxxxxx>
---
arch/powerpc/kernel/vmlinux.lds.S | 3 +++
include/asm-generic/sections.h | 1 +
include/asm-generic/vmlinux.lds.h | 8 ++++++++
include/linux/module.h | 5 +++++
init/main.c | 10 ++++++++++
kernel/module.c | 13 +++++++++++++
6 files changed, 40 insertions(+)

Index: linux-2.6.25/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.25.orig/include/asm-generic/vmlinux.lds.h
+++ linux-2.6.25/include/asm-generic/vmlinux.lds.h
@@ -352,3 +352,11 @@
*(.data.percpu.shared_aligned) \
} \
__per_cpu_end = .;
+
+#define CONSTRUCTORS \
+ __CTOR_LIST__ = .; \
+ *(.ctors) \
+ __CTOR_END__ = .; \
+ __DTOR_LIST__ = .; \
+ *(.dtors) \
+ __DTOR_END__ = .;
Index: linux-2.6.25/arch/powerpc/kernel/vmlinux.lds.S
===================================================================
--- linux-2.6.25.orig/arch/powerpc/kernel/vmlinux.lds.S
+++ linux-2.6.25/arch/powerpc/kernel/vmlinux.lds.S
@@ -196,6 +196,9 @@ SECTIONS
*(.toc)
}
#endif
+ .data.gcov : {
+ CONSTRUCTORS
+ }

. = ALIGN(PAGE_SIZE);
_edata = .;
Index: linux-2.6.25/include/asm-generic/sections.h
===================================================================
--- linux-2.6.25.orig/include/asm-generic/sections.h
+++ linux-2.6.25/include/asm-generic/sections.h
@@ -13,5 +13,6 @@ extern char __per_cpu_start[], __per_cpu
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];
+extern char __CTOR_LIST__[], __CTOR_END__[];

#endif /* _ASM_GENERIC_SECTIONS_H_ */
Index: linux-2.6.25/include/linux/module.h
===================================================================
--- linux-2.6.25.orig/include/linux/module.h
+++ linux-2.6.25/include/linux/module.h
@@ -246,6 +246,8 @@ struct module_sect_attrs

struct module_param_attrs;

+typedef void (*ctorcall_t)(void);
+
struct module
{
enum module_state state;
@@ -359,6 +361,9 @@ struct module
struct marker *markers;
unsigned int num_markers;
#endif
+ /* Constructor calls. */
+ ctorcall_t *ctors;
+ unsigned long num_ctors;
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
Index: linux-2.6.25/kernel/module.c
===================================================================
--- linux-2.6.25.orig/kernel/module.c
+++ linux-2.6.25/kernel/module.c
@@ -1718,6 +1718,7 @@ static struct module *load_module(void _
unsigned int unusedgplcrcindex;
unsigned int markersindex;
unsigned int markersstringsindex;
+ unsigned int ctorsindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -1814,6 +1815,7 @@ static struct module *load_module(void _
#ifdef ARCH_UNWIND_SECTION_NAME
unwindex = find_sec(hdr, sechdrs, secstrings, ARCH_UNWIND_SECTION_NAME);
#endif
+ ctorsindex = find_sec(hdr, sechdrs, secstrings, ".ctors");

/* Don't keep modinfo section */
sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
@@ -2021,6 +2023,8 @@ static struct module *load_module(void _
mod->num_markers =
sechdrs[markersindex].sh_size / sizeof(*mod->markers);
#endif
+ mod->ctors = (void *) sechdrs[ctorsindex].sh_addr;
+ mod->num_ctors = sechdrs[ctorsindex].sh_size / sizeof(*mod->ctors);

/* Find duplicate symbols */
err = verify_export_symbols(mod);
@@ -2133,6 +2137,14 @@ static struct module *load_module(void _
goto free_hdr;
}

+static void do_mod_ctors(struct module *mod)
+{
+ unsigned long i;
+
+ for (i = 0; i < mod->num_ctors; i++)
+ mod->ctors[i]();
+}
+
/* This is where the real work happens */
asmlinkage long
sys_init_module(void __user *umod,
@@ -2163,6 +2175,7 @@ sys_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 = mod->init();
Index: linux-2.6.25/init/main.c
===================================================================
--- linux-2.6.25.orig/init/main.c
+++ linux-2.6.25/init/main.c
@@ -650,6 +650,15 @@ asmlinkage void __init start_kernel(void
rest_init();
}

+static void __init do_ctors(void)
+{
+ ctorcall_t *call;
+
+ for (call = (ctorcall_t *) __CTOR_LIST__;
+ call < (ctorcall_t *) __CTOR_END__; call++)
+ (*call)();
+}
+
static int __initdata initcall_debug;

static int __init initcall_debug_setup(char *str)
@@ -735,6 +744,7 @@ static void __init do_basic_setup(void)
usermodehelper_init();
driver_init();
init_irq_proc();
+ do_ctors();
do_initcalls();
}






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