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Commit e4486fe3 authored by Steven Rostedt's avatar Steven Rostedt
Browse files

powerpc: ftrace, use probe_kernel API to modify code 



Impact: use cleaner probe_kernel API over assembly

Using probe_kernel_read/write interface is a much cleaner approach
than the current assembly version.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 8fd6e5a8

arch/powerpc/kernel/ftrace.c

+21 −32
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 


#include <linux/spinlock.h>

#include <linux/hardirq.h>

#include <linux/uaccess.h>

#include <linux/ftrace.h>

#include <linux/percpu.h>

#include <linux/init.h>
@@ -72,45 +73,33 @@ static int 
ftrace_modify_code(unsigned long ip, unsigned char *old_code,

		   unsigned char *new_code)

{

	unsigned replaced;

	unsigned old = *(unsigned *)old_code;

	unsigned new = *(unsigned *)new_code;

	int faulted = 0;

	unsigned char replaced[MCOUNT_INSN_SIZE];



	/*

	 * Note: Due to modules and __init, code can

	 *  disappear and change, we need to protect against faulting

	 *  as well as code changing.

	 *  as well as code changing. We do this by using the

	 *  probe_kernel_* functions.

	 *

	 * No real locking needed, this code is run through

	 * kstop_machine.

	 * kstop_machine, or before SMP starts.

	 */

	asm volatile (

		"1: lwz		%1, 0(%2)\n"

		"   cmpw	%1, %5\n"

		"   bne		2f\n"

		"   stwu	%3, 0(%2)\n"

		"2:\n"

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

		"3:	li %0, 1\n"

		"	b 2b\n"

		".previous\n"

		".section __ex_table,\"a\"\n"

		_ASM_ALIGN "\n"

		_ASM_PTR "1b, 3b\n"

		".previous"

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

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

		  "0"(faulted), "r"(old)

		: "memory");



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

		faulted = 2;



	if (!faulted)



	/* read the text we want to modify */

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))

		return -EFAULT;



	/* Make sure it is what we expect it to be */

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

		return -EINVAL;



	/* replace the text with the new text */

	if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))

		return -EPERM;



	flush_icache_range(ip, ip + 8);



	return faulted;

	return 0;

}



static int test_24bit_addr(unsigned long ip, unsigned long addr)