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SubjectRe: [PATCH] [GIT PULL] tracing: allow to change permissions for text with dynamic ftrace enabled

* Steven Rostedt <rostedt@goodmis.org> wrote:

>
> Ingo,
>
> The cause of the ftrace bug you saw in tip/master was caused by a change
> in tip's x86/mm branch.
>
> Please pull the latest tip/x86/mm tree, which can be found at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
> tip/x86/mm
>
>
> Steven Rostedt (1):
> tracing: allow to change permissions for text with dynamic ftrace enabled
>
> ----
> arch/x86/mm/pageattr.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
> ---------------------------
> commit 883242dd0e5faaba041528a9a99f483f2a656c83
> Author: Steven Rostedt <srostedt@redhat.com>
> Date: Tue Oct 27 13:15:11 2009 -0400
>
> tracing: allow to change permissions for text with dynamic ftrace enabled
>
> The commit 74e081797bd9d2a7d8005fe519e719df343a2ba8
> x86-64: align RODATA kernel section to 2MB with CONFIG_DEBUG_RODATA
> prevents text sections from becoming read/write using set_memory_rw.
>
> The dynamic ftrace changes all text pages to read/write just before
> converting the calls to tracing to nops, and vice versa.
>
> I orginally just added a flag to allow this transaction when ftrace
> did the change, but I also found that when the CPA testing was running
> it would remove the read/write as well, and ftrace does not do the text
> conversion on boot up, and the CPA changes caused the dynamic tracer
> to fail on self tests.
>
> The current solution I have is to simply not to prevent
> change_page_attr from setting the RW bit for kernel text pages.
>
> Reported-by: Ingo Molnar <mingo@elte.hu>
> Cc: Suresh Siddha <suresh.b.siddha@intel.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> index b494fc4..78d3168 100644
> --- a/arch/x86/mm/pageattr.c
> +++ b/arch/x86/mm/pageattr.c
> @@ -279,7 +279,8 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
> __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
> pgprot_val(forbidden) |= _PAGE_RW;
>
> -#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
> +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) && \
> + !defined(CONFIG_DYNAMIC_FTRACE)
> /*
> * Kernel text mappings for the large page aligned .rodata section
> * will be read-only. For the kernel identity mappings covering

Pulled, thanks Steve!

Ingo


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