From 6f93fc076a464bfe24e8d4c5fea3f6ca5bdb264d Mon Sep 17 00:00:00 2001
From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 20 Aug 2008 12:55:07 -0400
Subject: [PATCH] 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: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/ftrace.c | 38 +++++++++++++-------------------------
1 file changed, 13 insertions(+), 25 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 4151c91254e8..082d99642622 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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)
--
2.20.1