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/*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
* Copyright (C) 2009 DSLab, Lanzhou University, China
* Author: Wu Zhangjin <wuzj@lemote.com>
*
* Thanks goes to Steven Rostedt for writing the original x86 version.
*/
#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/ftrace.h>
#include <asm/cacheflush.h>
#ifdef CONFIG_DYNAMIC_FTRACE
#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
#define jump_insn_encode(op_code, addr) \
((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
static unsigned int ftrace_nop = 0x00000000;
static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
*(unsigned int *)ip = new_code;
flush_icache_range(ip, ip + 8);
return 0;
}
static int lui_v1;
static int jal_mcount;
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
/* We have compiled module with -mlong-calls, but compiled the kernel
* without it, we need to cope with them respectively. */
if (ip & 0x40000000) {
/* record it for ftrace_make_call */
if (lui_v1 == 0)
lui_v1 = *(unsigned int *)ip;
/* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
* addiu v1, v1, low_16bit_of_mcount
* move at, ra
* jalr v1
* nop
* 1f: (ip + 12)
*/
new = 0x10000004;
} else {
/* record/calculate it for ftrace_make_call */
if (jal_mcount == 0) {
/* We can record it directly like this:
* jal_mcount = *(unsigned int *)ip;
* Herein, jump over the first two nop instructions */
jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
}
/* move at, ra
* jalr v1 --> nop
*/
new = ftrace_nop;
}
return ftrace_modify_code(ip, new);
}
static int modified; /* initialized as 0 by default */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
/* We just need to remove the "b ftrace_stub" at the fist time! */
if (modified == 0) {
modified = 1;
ftrace_modify_code(addr, ftrace_nop);
}
/* ip, module: 0xc0000000, kernel: 0x80000000 */
new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
return ftrace_modify_code(ip, new);
}
#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned int new;
new = jump_insn_encode(JAL, (unsigned long)func);
return ftrace_modify_code(FTRACE_CALL_IP, new);
}
int __init ftrace_dyn_arch_init(void *data)
{
/* The return code is retured via data */
*(unsigned long *)data = 0;
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
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