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

[Michael Ellerman]

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>
---
 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)
-- 
2.7.4