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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>
#include <asm/asm.h>
#include <asm/asm-offsets.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 */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
unsigned long ftrace_get_parent_addr(unsigned long self_addr,
unsigned long parent,
unsigned long parent_addr,
unsigned long fp)
{
unsigned long sp, ip, ra;
unsigned int code;
/* in module or kernel? */
if (self_addr & 0x40000000) {
/* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
ip = self_addr - 20;
} else {
/* kernel: move to the instruction "move ra, at" */
ip = self_addr - 12;
}
/* search the text until finding the non-store instruction or "s{d,w}
* ra, offset(sp)" instruction */
do {
ip -= 4;
/* get the code at "ip" */
code = *(unsigned int *)ip;
/* If we hit the non-store instruction before finding where the
* ra is stored, then this is a leaf function and it does not
* store the ra on the stack. */
if ((code & S_R_SP) != S_R_SP)
return parent_addr;
} while (((code & S_RA_SP) != S_RA_SP));
sp = fp + (code & OFFSET_MASK);
ra = *(unsigned long *)sp;
if (ra == parent)
return sp;
return 0;
}
/*
* Hook the return address and push it in the stack of return addrs
* in current thread info.
*/
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long fp)
{
unsigned long old;
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
/* "parent" is the stack address saved the return address of the caller
* of _mcount, for a leaf function not save the return address in the
* stack address, so, we "emulate" one in _mcount's stack space, and
* hijack it directly, but for a non-leaf function, it will save the
* return address to the its stack space, so, we can not hijack the
* "parent" directly, but need to find the real stack address,
* ftrace_get_parent_addr() does it!
*/
old = *parent;
parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
(unsigned long)parent,
fp);
/* If fails when getting the stack address of the non-leaf function's
* ra, stop function graph tracer and return */
if (parent == 0) {
ftrace_graph_stop();
WARN_ON(1);
return;
}
*parent = return_hooker;
if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
-EBUSY) {
*parent = old;
return;
}
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
*parent = old;
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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