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Commit 55ca3cc1 authored by Suresh Siddha's avatar Suresh Siddha Committed by Ingo Molnar
Browse files

x86_64, ftrace: Make ftrace use kernel identity mapping to modify code 



On x86_64, kernel text mappings are mapped read-only with
CONFIG_DEBUG_RODATA. So use the kernel identity mapping instead
of the kernel text mapping to modify the kernel text.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Tested-by: default avatarSteven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20091029024821.080941108@sbs-t61.sc.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 502f6604

arch/x86/kernel/ftrace.c

+17 −0
Original line number Diff line number Diff line
@@ -187,9 +187,26 @@ static void wait_for_nmi(void) 
	nmi_wait_count++;

}



static inline int

within(unsigned long addr, unsigned long start, unsigned long end)

{

	return addr >= start && addr < end;

}



static int

do_ftrace_mod_code(unsigned long ip, void *new_code)

{

	/*

	 * On x86_64, kernel text mappings are mapped read-only with

	 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead

	 * of the kernel text mapping to modify the kernel text.

	 *

	 * For 32bit kernels, these mappings are same and we can use

	 * kernel identity mapping to modify code.

	 */

	if (within(ip, (unsigned long)_text, (unsigned long)_etext))

		ip = (unsigned long)__va(__pa(ip));



	mod_code_ip = (void *)ip;

	mod_code_newcode = new_code;

arch/x86/mm/pageattr.c

+1 −2
Original line number Diff line number Diff line
@@ -279,8 +279,7 @@ 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) && \

	!defined(CONFIG_DYNAMIC_FTRACE)

#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)

	/*

	 * Once the kernel maps the text as RO (kernel_set_to_readonly is set),

	 * kernel text mappings for the large page aligned text, rodata sections