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tracing: allow to change permissions for text with dynamic ftrace enabled 

The commit 74e081797b
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>
This commit is contained in:
Steven Rostedt 2009-10-27 13:15:11 -04:00 committed by Steven Rostedt
parent 4868402d95
commit 883242dd0e
1 changed files with 2 additions and 1 deletions
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3
arch/x86/mm/pageattr.c
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@ -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