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

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Date:	Tue, 27 Oct 2009 13:53:43 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH] [GIT PULL] tracing: allow to change permissions for text
 with dynamic ftrace enabled


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@...hat.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@...e.hu>
    Cc: Suresh Siddha <suresh.b.siddha@...el.com>
    Cc: H. Peter Anvin <hpa@...or.com>
    Signed-off-by: Steven Rostedt <rostedt@...dmis.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


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