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Commit 6f93fc07 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: x86 use copy to and from user functions 



The modification of code is performed either by kstop_machine, before
SMP starts, or on module code before the module is executed. There is
no reason to do the modifications from assembly. The copy to and from
user functions are sufficient and produces cleaner and easier to read
code.

Thanks to Benjamin Herrenschmidt for suggesting the idea.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8feff1ca

arch/x86/kernel/ftrace.c

+13 −25
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 


#include <linux/spinlock.h>

#include <linux/hardirq.h>

#include <linux/uaccess.h>

#include <linux/ftrace.h>

#include <linux/percpu.h>

#include <linux/init.h>
@@ -60,11 +61,7 @@ notrace int 
ftrace_modify_code(unsigned long ip, unsigned char *old_code,

		   unsigned char *new_code)

{

	unsigned replaced;

	unsigned old = *(unsigned *)old_code; /* 4 bytes */

	unsigned new = *(unsigned *)new_code; /* 4 bytes */

	unsigned char newch = new_code[4];

	int faulted = 0;

	unsigned char replaced[MCOUNT_INSN_SIZE];



	/*

	 * Note: Due to modules and __init, code can
@@ -72,29 +69,20 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code, 
	 *  as well as code changing.

	 *

	 * No real locking needed, this code is run through

	 * kstop_machine.

	 * kstop_machine, or before SMP starts.

	 */

	asm volatile (

		"1: lock\n"

		"   cmpxchg %3, (%2)\n"

		"   jnz 2f\n"

		"   movb %b4, 4(%2)\n"

		"2:\n"

		".section .fixup, \"ax\"\n"

		"3:	movl $1, %0\n"

		"	jmp 2b\n"

		".previous\n"

		_ASM_EXTABLE(1b, 3b)

		: "=r"(faulted), "=a"(replaced)

		: "r"(ip), "r"(new), "c"(newch),

		  "0"(faulted), "a"(old)

		: "memory");

	sync_core();

	if (__copy_from_user(replaced, (char __user *)ip, MCOUNT_INSN_SIZE))

		return 1;



	if (replaced != old && replaced != new)

		faulted = 2;

	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)

		return 2;



	return faulted;

	WARN_ON_ONCE(__copy_to_user((char __user *)ip, new_code,

				    MCOUNT_INSN_SIZE));



	sync_core();



	return 0;

}



notrace int ftrace_update_ftrace_func(ftrace_func_t func)