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

[Michael Ellerman]

On Thu, 2016-15-09 at 05:11:59 UTC, Michael Ellerman wrote:
> 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.
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> Tested-by: Anton Blanchard <anton at samba.org>

Applied to powerpc next.

https://git.kernel.org/powerpc/c/7de3b27bac47da9de08409df1d

cheers