Re: [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext

[Anton Blanchard <anton@samba.org>]

Hi,

> In our linker script we open code the list of text sections, because
> we need to include the __ftr_alt sections, which are arch-specific.
> 
> This means we can't use TEXT_TEXT as defined in vmlinux.lds.h, and so
> we don't have the MEM_KEEP() logic for memory hotplug sections.
> 
> If we build the kernel with the gold linker, and with
> CONFIG_MEMORY_HOTPLUG=y, we see that functions marked __meminit can
> end up outside of the _stext/_etext range, and also outside of
> _sinittext/_einittext, eg:
> 
>     c000000000000000 T _stext
>     c0000000009e0000 A _etext
>     c0000000009e3f18 T hash__vmemmap_create_mapping
>     c000000000ca0000 T _sinittext
>     c000000000d00844 T _einittext
> 
> This causes them to not be recognised as text by is_kernel_text(), and
> prevents them being patched by jump_label (and presumably
> ftrace/kprobes etc.).
> 
> Fix it by adding MEM_KEEP() directives, mirroring what TEXT_TEXT does.
> 
> This isn't a problem when CONFIG_MEMORY_HOTPLUG=n, because we use the
> standard INIT_TEXT_SECTION() and EXIT_TEXT macros from vmlinux.lds.h.

Thanks Michael, looks good:

Tested-by: Anton Blanchard <anton@samba.org>

Anton
--
 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>  arch/powerpc/kernel/vmlinux.lds.S | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S
> b/arch/powerpc/kernel/vmlinux.lds.S index b5fba689fca6..b59d75e194a5
> 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -56,6 +56,8 @@ SECTIONS
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
>  		SOFTIRQENTRY_TEXT
> +		MEM_KEEP(init.text)
> +		MEM_KEEP(exit.text)
>  
>  #ifdef CONFIG_PPC32
>  		*(.got1)