* [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext
@ 2016-09-15 5:11 Michael Ellerman
2016-09-15 5:28 ` Anton Blanchard
2016-09-20 13:07 ` Michael Ellerman
0 siblings, 2 replies; 3+ messages in thread
From: Michael Ellerman @ 2016-09-15 5:11 UTC (permalink / raw)
To: linuxppc-dev; +Cc: anton
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@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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext
2016-09-15 5:11 [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext Michael Ellerman
@ 2016-09-15 5:28 ` Anton Blanchard
2016-09-20 13:07 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Anton Blanchard @ 2016-09-15 5:28 UTC (permalink / raw)
To: Michael Ellerman; +Cc: linuxppc-dev
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)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: powerpc: Ensure .mem(init|exit).text are within _stext/_etext
2016-09-15 5:11 [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext Michael Ellerman
2016-09-15 5:28 ` Anton Blanchard
@ 2016-09-20 13:07 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2016-09-20 13:07 UTC (permalink / raw)
To: Michael Ellerman, linuxppc-dev; +Cc: anton
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@ellerman.id.au>
> Tested-by: Anton Blanchard <anton@samba.org>
Applied to powerpc next.
https://git.kernel.org/powerpc/c/7de3b27bac47da9de08409df1d
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-09-15 5:11 [PATCH] powerpc: Ensure .mem(init|exit).text are within _stext/_etext Michael Ellerman
2016-09-15 5:28 ` Anton Blanchard
2016-09-20 13:07 ` Michael Ellerman
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