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Date: Mon, 5 May 2008 21:19:42 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Peter Oberparleiter <peter.oberparleiter@...ibm.com>
Cc: linux-kernel@...r.kernel.org, ltp-list@...ts.sourceforge.net,
ltp-coverage@...ts.sourceforge.net, sam@...nborg.org,
Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [RFC PATCH 1/6] kernel: call constructors
On Mon, 05 May 2008 17:24:04 +0200 Peter Oberparleiter <peter.oberparleiter@...ibm.com> wrote:
> From: Peter Oberparleiter <peter.oberparleiter@...ibm.com>
>
> 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.
>
Looks sane.
> ---
> 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-2.6.26-rc1/include/asm-generic/vmlinux.lds.h
> ===================================================================
> --- linux-2.6.26-rc1.orig/include/asm-generic/vmlinux.lds.h
> +++ linux-2.6.26-rc1/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-2.6.26-rc1/arch/powerpc/kernel/vmlinux.lds.S
> ===================================================================
> --- linux-2.6.26-rc1.orig/arch/powerpc/kernel/vmlinux.lds.S
> +++ linux-2.6.26-rc1/arch/powerpc/kernel/vmlinux.lds.S
> @@ -193,6 +193,9 @@ SECTIONS
> *(.toc)
> }
> #endif
> + .data.gcov : {
> + CONSTRUCTORS
> + }
Why did powerpc (and only powerpc) need this touchup? It already includes
asm-generic/vmlinux.lds.h?
> . = ALIGN(PAGE_SIZE);
> _edata = .;
> Index: linux-2.6.26-rc1/include/asm-generic/sections.h
> ===================================================================
> --- linux-2.6.26-rc1.orig/include/asm-generic/sections.h
> +++ linux-2.6.26-rc1/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-2.6.26-rc1/include/linux/module.h
> ===================================================================
> --- linux-2.6.26-rc1.orig/include/linux/module.h
> +++ linux-2.6.26-rc1/include/linux/module.h
> @@ -229,6 +229,8 @@ enum module_state
> MODULE_STATE_GOING,
> };
>
> +typedef void (*ctorcall_t)(void);
> +
> struct module
> {
> enum module_state state;
> @@ -342,6 +344,9 @@ 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-2.6.26-rc1/kernel/module.c
> ===================================================================
> --- linux-2.6.26-rc1.orig/kernel/module.c
> +++ linux-2.6.26-rc1/kernel/module.c
> @@ -1736,6 +1736,7 @@ 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 */
> @@ -1832,6 +1833,7 @@ 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 and version sections. */
> sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
> @@ -2041,6 +2043,8 @@ 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);
> @@ -2153,6 +2157,14 @@ 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,
> @@ -2183,6 +2195,7 @@ 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-2.6.26-rc1/init/main.c
> ===================================================================
> --- linux-2.6.26-rc1.orig/init/main.c
> +++ linux-2.6.26-rc1/init/main.c
> @@ -683,6 +683,15 @@ 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)
> @@ -760,6 +769,7 @@ static void __init do_basic_setup(void)
> usermodehelper_init();
> driver_init();
> init_irq_proc();
> + do_ctors();
> do_initcalls();
> }
>
>
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