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ftrace: x86 use copy to and from user functions

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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>
This commit is contained in:
Steven Rostedt 2008-08-20 12:55:07 -04:00 committed by Ingo Molnar
parent 8feff1cacc
commit 6f93fc076a
1 changed files with 13 additions and 25 deletions
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38
arch/x86/kernel/ftrace.c
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@ -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");
if (__copy_from_user(replaced, (char __user *)ip, MCOUNT_INSN_SIZE))
return 1;
if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
return 2;
WARN_ON_ONCE(__copy_to_user((char __user *)ip, new_code,
MCOUNT_INSN_SIZE));
sync_core();
if (replaced != old && replaced != new)
faulted = 2;
return faulted;
return 0;
}
notrace int ftrace_update_ftrace_func(ftrace_func_t func)