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SubjectRe: [RFC PATCH 4/4] kernel: add support for init_array constructors
On 23.08.2013 10:39, Frantisek Hrbata wrote:
> This adds the .init_array section as yet another section with constructors. This
> is needed because gcc is adding __gcov_init calls to .init_array.
>
> Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
> ---
> include/asm-generic/vmlinux.lds.h | 1 +
> include/linux/module.h | 2 ++
> kernel/module.c | 6 ++++++
> 3 files changed, 9 insertions(+)
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 69732d2..c55d8d9 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -468,6 +468,7 @@
> #define KERNEL_CTORS() . = ALIGN(8); \
> VMLINUX_SYMBOL(__ctors_start) = .; \
> *(.ctors) \
> + *(.init_array) \

This is exactly how I (would) have done it.

> VMLINUX_SYMBOL(__ctors_end) = .;
> #else
> #define KERNEL_CTORS()
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 46f1ea0..89ff829 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -374,6 +374,8 @@ struct module
> /* Constructor functions. */
> ctor_fn_t *ctors;
> unsigned int num_ctors;
> + ctor_fn_t *init_array;
> + unsigned int num_init_array;

I think it would be safe to re-use the ctors-related fields here. Each GCC
version will only ever create either of .ctors or .init_array, but never
both. The only case where separate fields would be required, would be when
linking a kernel module from multiple object files compiled with different
versions of GCC.

> #endif
> };
> #ifndef MODULE_ARCH_INIT
> diff --git a/kernel/module.c b/kernel/module.c
> index 2069158..581ae89 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2760,6 +2760,9 @@ static void find_module_sections(struct module *mod, struct load_info *info)
> #ifdef CONFIG_CONSTRUCTORS
> mod->ctors = section_objs(info, ".ctors",
> sizeof(*mod->ctors), &mod->num_ctors);

When reusing mod->ctors, you could check for mod->ctors == NULL here and
fill in the values from section_objs(".init_array").

> + mod->init_array = section_objs(info, ".init_array",
> + sizeof(*mod->init_array),
> + &mod->num_init_array);
> #endif
>
> #ifdef CONFIG_TRACEPOINTS
> @@ -3024,6 +3027,9 @@ static void do_mod_ctors(struct module *mod)
>
> for (i = 0; i < mod->num_ctors; i++)
> mod->ctors[i]();
> +
> + for (i = 0; i < mod->num_init_array; i++)
> + mod->init_array[i]();
> #endif
> }
>

--
Peter Oberparleiter
Linux on System z Development - IBM Germany



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