From: christophe leroy <christophe.leroy@c-s.fr>
To: Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>, Scott Wood <oss@buserror.net>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] powerpc/mm: Implement CONFIG_DEBUG_RODATA on PPC32
Date: Wed, 19 Apr 2017 20:36:43 +0200 [thread overview]
Message-ID: <694d02a4-d2bd-a276-928f-0dd5189a936a@c-s.fr> (raw)
In-Reply-To: <d3713d6a-28b6-fb8f-ce32-c0d37958b59f@c-s.fr>
Le 19/04/2017 à 16:22, Christophe LEROY a écrit :
>
>
> Le 19/04/2017 à 16:01, Michael Ellerman a écrit :
>> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>>
>>> diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
>>> index 32509de6ce4c..4af81fb23653 100644
>>> --- a/arch/powerpc/kernel/ftrace.c
>>> +++ b/arch/powerpc/kernel/ftrace.c
>>> @@ -526,7 +526,9 @@ void ftrace_replace_code(int enable)
>>> */
>>> void arch_ftrace_update_code(int command)
>>> {
>>> + set_kernel_text_rw();
>>> ftrace_modify_all_code(command);
>>> + set_kernel_text_ro();
>>> }
>>
>> I'm not sure that's the right place for that.
>
>
> I took arch/arm/ as model. It does the following. Is that wrong ?
>
>
> static int __ftrace_modify_code(void *data)
> {
> int *command = data;
>
> set_kernel_text_rw();
> ftrace_modify_all_code(*command);
> set_kernel_text_ro();
>
> return 0;
> }
>
> void arch_ftrace_update_code(int command)
> {
> stop_machine(__ftrace_modify_code, &command, NULL);
> }
>
>
>
>> If you look at other arches they hook into ftrace_modify_code(), where
>> you have the address that's being modified.
>>
>
> Ok, I will look at other arches.
Could you provide more details on what you have seen on other arches ? I
didn't notice anything related in any other arches' ftrace_modify_code()
What I could find however is, in x86, the use of
ftrace_arch_code_modify_prepare() and
ftrace_arch_code_modify_post_process ():
int ftrace_arch_code_modify_prepare(void)
{
set_kernel_text_rw();
set_all_modules_text_rw();
return 0;
}
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
set_kernel_text_ro();
return 0;
}
Those functions are also used on arm but only for modules:
int ftrace_arch_code_modify_prepare(void)
{
set_all_modules_text_rw();
return 0;
}
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
/* Make sure any TLB misses during machine stop are cleared. */
flush_tlb_all();
return 0;
}
Should I apply the x86 approach, or something else ?
Christophe
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next prev parent reply other threads:[~2017-04-19 18:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 10:59 [PATCH 0/3] powerpc/mm: Fix kernel protection and implement CONFIG_DEBUG_RODATA on PPC32 Christophe Leroy
2017-04-19 10:59 ` [PATCH 1/3] powerpc/mm: Ensure change_page_attr() doesn't invalidate pinned TLBs Christophe Leroy
2017-04-19 11:00 ` [PATCH 2/3] powerpc/mm: Fix kernel RAM protection after freeing unused memory on PPC32 Christophe Leroy
2017-04-19 11:00 ` [PATCH 3/3] powerpc/mm: Implement CONFIG_DEBUG_RODATA " Christophe Leroy
2017-04-19 14:01 ` Michael Ellerman
2017-04-19 14:22 ` Christophe LEROY
2017-04-19 18:36 ` christophe leroy [this message]
2017-04-20 6:04 ` Michael Ellerman
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