/*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
* Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
* Author: Wu Zhangjin <wuzhangjin@gmail.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/asm.h>
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/uasm.h>
/*
* If the Instruction Pointer is in module space (0xc0000000), return true;
* otherwise, it is in kernel space (0x80000000), return false.
*
* FIXME: This will not work when the kernel space and module space are the
* same. If they are the same, we need to modify scripts/recordmcount.pl,
* ftrace_make_nop/call() and the other related parts to ensure the
* enabling/disabling of the calling site to _mcount is right for both kernel
* and module.
*/
static inline int in_module(unsigned long ip)
{
return ip & 0x40000000;
}
#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 INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
#define INSN_NOP 0x00000000 /* nop */
#define INSN_JAL(addr) \
((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
static unsigned int insn_jal_ftrace_caller __read_mostly;
static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
static inline void ftrace_dyn_arch_init_insns(void)
{
u32 *buf;
unsigned int v1;
/* lui v1, hi16_mcount */
v1 = 3;
buf = (u32 *)&insn_lui_v1_hi16_mcount;
UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
/* jal (ftrace_caller + 8), jump over the first two instruction */
buf = (u32 *)&insn_jal_ftrace_caller;
uasm_i_jal(&buf, (FTRACE_ADDR + 8));
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* j ftrace_graph_caller */
buf = (u32 *)&insn_j_ftrace_graph_caller;
uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
#endif
}
static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
int faulted;
/* *(unsigned int *)ip = new_code; */
safe_store_code(new_code, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
flush_icache_range(ip, ip + 8);
return 0;
}
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 (in_module(ip)) {
#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
/*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
* addiu v1, v1, low_16bit_of_mcount
* move at, ra
* move $12, ra_address
* jalr v1
* sub sp, sp, 8
* 1: offset = 5 instructions
*/
new = INSN_B_1F_5;
#else
/*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
* addiu v1, v1, low_16bit_of_mcount
* move at, ra
* jalr v1
* nop | move $12, ra_address | sub sp, sp, 8
* 1: offset = 4 instructions
*/
new = INSN_B_1F_4;
#endif
} else {
/*
* move at, ra
* jal _mcount --> nop
*/
new = INSN_NOP;
}
return ftrace_modify_code(ip, new);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
/* ip, module: 0xc0000000, kernel: 0x80000000 */
new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
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 = INSN_JAL((unsigned long)func);
return ftrace_modify_code(FTRACE_CALL_IP, new);
}
int __init ftrace_dyn_arch_init(void *data)
{
/* Encode the instructions when booting */
ftrace_dyn_arch_init_insns();
/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
/* The return code is retured via data */
*(unsigned long *)data = 0;
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
insn_j_ftrace_graph_caller);
}
int ftrace_disable_ftrace_graph_caller(void)
{
return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifndef KBUILD_MCOUNT_RA_ADDRESS
#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;
int faulted;
/*
* For module, move the ip from calling site of mcount to the
* instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
* kernel, move to the instruction "move ra, at"(offset is 12)
*/
ip = self_addr - (in_module(self_addr) ? 20 : 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; */
safe_load_code(code, ip, faulted);
if (unlikely(faulted))
return 0;
/*
* 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; */
safe_load_stack(ra, sp, faulted);
if (unlikely(faulted))
return 0;
if (ra == parent)
return sp;
return 0;
}
#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
/*
* 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;
int faulted;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
/*
* "parent" is the stack address saved the return address of the caller
* of _mcount.
*
* if the gcc < 4.5, a leaf function does 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 save the
* return address to the its own stack space, we can not hijack it
* directly, but need to find the real stack address,
* ftrace_get_parent_addr() does it!
*
* if gcc>= 4.5, with the new -mmcount-ra-address option, for a
* non-leaf function, the location of the return address will be saved
* to $12 for us, and for a leaf function, only put a zero into $12. we
* do it in ftrace_graph_caller of mcount.S.
*/
/* old = *parent; */
safe_load_stack(old, parent, faulted);
if (unlikely(faulted))
goto out;
#ifndef KBUILD_MCOUNT_RA_ADDRESS
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)
goto out;
#endif
/* *parent = return_hooker; */
safe_store_stack(return_hooker, parent, faulted);
if (unlikely(faulted))
goto out;
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;
}
return;
out:
ftrace_graph_stop();
WARN_ON(1);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
