[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / mips / kernel / ftrace.c

/*
 * 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>

#include <asm-generic/sections.h>

#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
#define MCOUNT_OFFSET_INSNS 5
#else
#define MCOUNT_OFFSET_INSNS 4
#endif

/* Arch override because MIPS doesn't need to run this from stop_machine() */
void arch_ftrace_update_code(int command)
{
	ftrace_modify_all_code(command);
}

/*
 * Check if the address is in kernel space
 *
 * Clone core_kernel_text() from kernel/extable.c, but doesn't call
 * init_kernel_text() for Ftrace doesn't trace functions in init sections.
 */
static inline int in_kernel_space(unsigned long ip)
{
	if (ip >= (unsigned long)_stext &&
	    ip <= (unsigned long)_etext)
		return 1;
	return 0;
}

#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_RANGE_MASK ((1UL << 28) - 1)

#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) & JUMP_RANGE_MASK);

#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 & JUMP_RANGE_MASK);
#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;
}

#ifndef CONFIG_64BIT
static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
				unsigned int new_code2)
{
	int faulted;

	safe_store_code(new_code1, ip, faulted);
	if (unlikely(faulted))
		return -EFAULT;
	ip += 4;
	safe_store_code(new_code2, ip, faulted);
	if (unlikely(faulted))
		return -EFAULT;
	flush_icache_range(ip, ip + 8); /* original ip + 12 */
	return 0;
}
#endif

/*
 * The details about the calling site of mcount on MIPS
 *
 * 1. For kernel:
 *
 * move at, ra
 * jal _mcount		--> nop
 *
 * 2. For modules:
 *
 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and 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
 * 2.2 For the Other situations
 *
 * 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
 */

#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)

int ftrace_make_nop(struct module *mod,
		    struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned int new;
	unsigned long ip = rec->ip;

	/*
	 * If ip is in kernel space, no long call, otherwise, long call is
	 * needed.
	 */
	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
#ifdef CONFIG_64BIT
	return ftrace_modify_code(ip, new);
#else
	/*
	 * On 32 bit MIPS platforms, gcc adds a stack adjust
	 * instruction in the delay slot after the branch to
	 * mcount and expects mcount to restore the sp on return.
	 * This is based on a legacy API and does nothing but
	 * waste instructions so it's being removed at runtime.
	 */
	return ftrace_modify_code_2(ip, new, INSN_NOP);
#endif
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned int new;
	unsigned long ip = rec->ip;

	new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
		insn_lui_v1_hi16_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 = 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_ra_addr(unsigned long self_ra, unsigned long
		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
{
	unsigned long sp, ip, tmp;
	unsigned int code;
	int faulted;

	/*
	 * For module, move the ip from the return address after the
	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
	 * kernel, move after the instruction "move ra, at"(offset is 16)
	 */
	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);

	/*
	 * search the text until finding the non-store instruction or "s{d,w}
	 * ra, offset(sp)" instruction
	 */
	do {
		/* 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_ra_addr;

		/* Move to the next instruction */
		ip -= 4;
	} while ((code & S_RA_SP) != S_RA_SP);

	sp = fp + (code & OFFSET_MASK);

	/* tmp = *(unsigned long *)sp; */
	safe_load_stack(tmp, sp, faulted);
	if (unlikely(faulted))
		return 0;

	if (tmp == old_parent_ra)
		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_ra_addr, unsigned long self_ra,
			   unsigned long fp)
{
	unsigned long old_parent_ra;
	struct ftrace_graph_ent trace;
	unsigned long return_hooker = (unsigned long)
	    &return_to_handler;
	int faulted, insns;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
		return;

	/*
	 * "parent_ra_addr" 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_ra = *parent_ra_addr; */
	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
	if (unlikely(faulted))
		goto out;
#ifndef KBUILD_MCOUNT_RA_ADDRESS
	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
			old_parent_ra, (unsigned long)parent_ra_addr, fp);
	/*
	 * If fails when getting the stack address of the non-leaf function's
	 * ra, stop function graph tracer and return
	 */
	if (parent_ra_addr == 0)
		goto out;
#endif
	/* *parent_ra_addr = return_hooker; */
	safe_store_stack(return_hooker, parent_ra_addr, faulted);
	if (unlikely(faulted))
		goto out;

	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
	    == -EBUSY) {
		*parent_ra_addr = old_parent_ra;
		return;
	}

	/*
	 * Get the recorded ip of the current mcount calling site in the
	 * __mcount_loc section, which will be used to filter the function
	 * entries configured through the tracing/set_graph_function interface.
	 */

	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);

	/* Only trace if the calling function expects to */
	if (!ftrace_graph_entry(&trace)) {
		current->curr_ret_stack--;
		*parent_ra_addr = old_parent_ra;
	}
	return;
out:
	ftrace_graph_stop();
	WARN_ON(1);
}
#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */
Commit	Line	Data
538f1952 WZ	1	/*
	2	* Code for replacing ftrace calls with jumps.
	3	*
	4	* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
e4240540	5	* Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
f7a904df	6	* Author: Wu Zhangjin <wuzhangjin@gmail.com>
538f1952 WZ	7	*
	8	* Thanks goes to Steven Rostedt for writing the original x86 version.
	9	*/
	10
	11	#include <linux/uaccess.h>
	12	#include <linux/init.h>
	13	#include <linux/ftrace.h>
	14
29c5d346 WZ	15	#include <asm/asm.h>
29c5d346 WZ	16	#include <asm/asm-offsets.h>
e4240540 WZ	17	#include <asm/cacheflush.h>
e4240540 WZ	18	#include <asm/uasm.h>
538f1952	19
d9cdb2f1	20	#include <asm-generic/sections.h>
c9f84873	21
49de830a TG	22	#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
	23	#define MCOUNT_OFFSET_INSNS 5
	24	#else
	25	#define MCOUNT_OFFSET_INSNS 4
	26	#endif
	27
58b69401 AC	28	/* Arch override because MIPS doesn't need to run this from stop_machine() */
	29	void arch_ftrace_update_code(int command)
	30	{
	31	ftrace_modify_all_code(command);
	32	}
	33
49de830a TG	34	/*
	35	* Check if the address is in kernel space
	36	*
	37	* Clone core_kernel_text() from kernel/extable.c, but doesn't call
	38	* init_kernel_text() for Ftrace doesn't trace functions in init sections.
	39	*/
	40	static inline int in_kernel_space(unsigned long ip)
	41	{
	42	if (ip >= (unsigned long)_stext &&
	43	ip <= (unsigned long)_etext)
	44	return 1;
	45	return 0;
	46	}
	47
538f1952 WZ	48	#ifdef CONFIG_DYNAMIC_FTRACE
	49
	50	#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
	51	#define ADDR_MASK 0x03ffffff /* op_code\|addr : 31...26\|25 ....0 */
c54794d1	52	#define JUMP_RANGE_MASK ((1UL << 28) - 1)
538f1952	53
4d6829f9	54	#define INSN_NOP 0x00000000 /* nop */
e4240540 WZ	55	#define INSN_JAL(addr) \
	56	((unsigned int)(JAL \| (((addr) >> 2) & ADDR_MASK)))
	57
	58	static unsigned int insn_jal_ftrace_caller __read_mostly;
	59	static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
	60	static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
	61
	62	static inline void ftrace_dyn_arch_init_insns(void)
	63	{
	64	u32 *buf;
	65	unsigned int v1;
	66
	67	/* lui v1, hi16_mcount */
	68	v1 = 3;
	69	buf = (u32 *)&insn_lui_v1_hi16_mcount;
	70	UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
	71
	72	/* jal (ftrace_caller + 8), jump over the first two instruction */
	73	buf = (u32 *)&insn_jal_ftrace_caller;
c54794d1	74	uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
e4240540 WZ	75
	76	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	77	/* j ftrace_graph_caller */
	78	buf = (u32 *)&insn_j_ftrace_graph_caller;
c54794d1	79	uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
e4240540 WZ	80	#endif
e4240540 WZ	81	}
538f1952 WZ	82
	83	static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
	84	{
046199ca WZ	85	int faulted;
	86
	87	/* (unsigned int )ip = new_code; */
	88	safe_store_code(new_code, ip, faulted);
	89
	90	if (unlikely(faulted))
	91	return -EFAULT;
538f1952 WZ	92
	93	flush_icache_range(ip, ip + 8);
	94
	95	return 0;
	96	}
	97
58b69401 AC	98	#ifndef CONFIG_64BIT
	99	static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
	100	unsigned int new_code2)
	101	{
	102	int faulted;
	103
	104	safe_store_code(new_code1, ip, faulted);
	105	if (unlikely(faulted))
	106	return -EFAULT;
	107	ip += 4;
	108	safe_store_code(new_code2, ip, faulted);
	109	if (unlikely(faulted))
	110	return -EFAULT;
	111	flush_icache_range(ip, ip + 8); /* original ip + 12 */
	112	return 0;
	113	}
	114	#endif
	115
7f21a609 WZ	116	/*
	117	* The details about the calling site of mcount on MIPS
	118	*
	119	* 1. For kernel:
	120	*
	121	* move at, ra
	122	* jal _mcount --> nop
	123	*
	124	* 2. For modules:
	125	*
	126	* 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
	127	*
70342287	128	* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
7f21a609 WZ	129	* addiu v1, v1, low_16bit_of_mcount
	130	* move at, ra
	131	* move $12, ra_address
	132	* jalr v1
	133	* sub sp, sp, 8
70342287	134	* 1: offset = 5 instructions
7f21a609 WZ	135	* 2.2 For the Other situations
7f21a609 WZ	136	*
70342287	137	* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
7f21a609 WZ	138	* addiu v1, v1, low_16bit_of_mcount
	139	* move at, ra
	140	* jalr v1
	141	* nop \| move $12, ra_address \| sub sp, sp, 8
70342287	142	* 1: offset = 4 instructions
7f21a609 WZ	143	*/
7f21a609 WZ	144
7f21a609 WZ	145	#define INSN_B_1F (0x10000000 \| MCOUNT_OFFSET_INSNS)
7f21a609 WZ	146
538f1952 WZ	147	int ftrace_make_nop(struct module *mod,
	148	struct dyn_ftrace *rec, unsigned long addr)
	149	{
	150	unsigned int new;
	151	unsigned long ip = rec->ip;
	152
e4240540	153	/*
d9cdb2f1 WZ	154	* If ip is in kernel space, no long call, otherwise, long call is
d9cdb2f1 WZ	155	* needed.
e4240540	156	*/
7f21a609	157	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
58b69401	158	#ifdef CONFIG_64BIT
538f1952	159	return ftrace_modify_code(ip, new);
58b69401 AC	160	#else
	161	/*
	162	* On 32 bit MIPS platforms, gcc adds a stack adjust
	163	* instruction in the delay slot after the branch to
	164	* mcount and expects mcount to restore the sp on return.
	165	* This is based on a legacy API and does nothing but
	166	* waste instructions so it's being removed at runtime.
	167	*/
	168	return ftrace_modify_code_2(ip, new, INSN_NOP);
	169	#endif
538f1952 WZ	170	}
538f1952 WZ	171
538f1952 WZ	172	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	173	{
	174	unsigned int new;
	175	unsigned long ip = rec->ip;
	176
d9cdb2f1 WZ	177	new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
d9cdb2f1 WZ	178	insn_lui_v1_hi16_mcount;
538f1952 WZ	179
	180	return ftrace_modify_code(ip, new);
	181	}
	182
	183	#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
	184
	185	int ftrace_update_ftrace_func(ftrace_func_t func)
	186	{
	187	unsigned int new;
	188
4d6829f9	189	new = INSN_JAL((unsigned long)func);
538f1952 WZ	190
	191	return ftrace_modify_code(FTRACE_CALL_IP, new);
	192	}
	193
	194	int __init ftrace_dyn_arch_init(void *data)
	195	{
e4240540 WZ	196	/* Encode the instructions when booting */
	197	ftrace_dyn_arch_init_insns();
	198
	199	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
	200	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
	201
538f1952 WZ	202	/* The return code is retured via data */
	203	(unsigned long )data = 0;
	204
	205	return 0;
	206	}
68ccf752	207	#endif /* CONFIG_DYNAMIC_FTRACE */
29c5d346 WZ	208
	209	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	210
e17ff5fe WZ	211	#ifdef CONFIG_DYNAMIC_FTRACE
	212
	213	extern void ftrace_graph_call(void);
e17ff5fe WZ	214	#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
	215
	216	int ftrace_enable_ftrace_graph_caller(void)
	217	{
	218	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
e4240540	219	insn_j_ftrace_graph_caller);
e17ff5fe WZ	220	}
	221
	222	int ftrace_disable_ftrace_graph_caller(void)
	223	{
4d6829f9	224	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
e17ff5fe WZ	225	}
e17ff5fe WZ	226
68ccf752	227	#endif /* CONFIG_DYNAMIC_FTRACE */
e17ff5fe	228
7326c4e5	229	#ifndef KBUILD_MCOUNT_RA_ADDRESS
68ccf752	230
70342287 RB	231	#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
70342287 RB	232	#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
29c5d346 WZ	233	#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
29c5d346 WZ	234
2816e325 WZ	235	unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
2816e325 WZ	236	old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
29c5d346	237	{
2816e325	238	unsigned long sp, ip, tmp;
29c5d346	239	unsigned int code;
046199ca	240	int faulted;
29c5d346	241
68ccf752	242	/*
2816e325	243	* For module, move the ip from the return address after the
9a620a55 WZ	244	* instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
9a620a55 WZ	245	* kernel, move after the instruction "move ra, at"(offset is 16)
68ccf752	246	*/
2816e325	247	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
29c5d346	248
68ccf752 WZ	249	/*
	250	* search the text until finding the non-store instruction or "s{d,w}
	251	* ra, offset(sp)" instruction
	252	*/
29c5d346	253	do {
046199ca WZ	254	/* get the code at "ip": code = (unsigned int )ip; */
	255	safe_load_code(code, ip, faulted);
	256
	257	if (unlikely(faulted))
	258	return 0;
68ccf752 WZ	259	/*
68ccf752 WZ	260	* If we hit the non-store instruction before finding where the
29c5d346	261	* ra is stored, then this is a leaf function and it does not
68ccf752 WZ	262	* store the ra on the stack
68ccf752 WZ	263	*/
29c5d346	264	if ((code & S_R_SP) != S_R_SP)
2816e325	265	return parent_ra_addr;
29c5d346	266
9a620a55 WZ	267	/* Move to the next instruction */
	268	ip -= 4;
	269	} while ((code & S_RA_SP) != S_RA_SP);
29c5d346 WZ	270
29c5d346 WZ	271	sp = fp + (code & OFFSET_MASK);
046199ca	272
2816e325 WZ	273	/* tmp = (unsigned long )sp; */
2816e325 WZ	274	safe_load_stack(tmp, sp, faulted);
046199ca WZ	275	if (unlikely(faulted))
046199ca WZ	276	return 0;
29c5d346	277
2816e325	278	if (tmp == old_parent_ra)
29c5d346	279	return sp;
29c5d346 WZ	280	return 0;
	281	}
	282
68ccf752	283	#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
7326c4e5	284
29c5d346 WZ	285	/*
	286	* Hook the return address and push it in the stack of return addrs
	287	* in current thread info.
	288	*/
2816e325	289	void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
29c5d346 WZ	290	unsigned long fp)
29c5d346 WZ	291	{
2816e325	292	unsigned long old_parent_ra;
29c5d346 WZ	293	struct ftrace_graph_ent trace;
	294	unsigned long return_hooker = (unsigned long)
	295	&return_to_handler;
b9f07eb2	296	int faulted, insns;
29c5d346 WZ	297
	298	if (unlikely(atomic_read(&current->tracing_graph_pause)))
	299	return;
	300
68ccf752	301	/*
2816e325 WZ	302	* "parent_ra_addr" is the stack address saved the return address of
2816e325 WZ	303	* the caller of _mcount.
7326c4e5 WZ	304	*
	305	* if the gcc < 4.5, a leaf function does not save the return address
	306	* in the stack address, so, we "emulate" one in _mcount's stack space,
	307	* and hijack it directly, but for a non-leaf function, it save the
	308	* return address to the its own stack space, we can not hijack it
	309	* directly, but need to find the real stack address,
29c5d346	310	* ftrace_get_parent_addr() does it!
7326c4e5 WZ	311	*
	312	* if gcc>= 4.5, with the new -mmcount-ra-address option, for a
	313	* non-leaf function, the location of the return address will be saved
	314	* to $12 for us, and for a leaf function, only put a zero into $12. we
	315	* do it in ftrace_graph_caller of mcount.S.
29c5d346 WZ	316	*/
29c5d346 WZ	317
2816e325 WZ	318	/* old_parent_ra = parent_ra_addr; /
2816e325 WZ	319	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
046199ca WZ	320	if (unlikely(faulted))
046199ca WZ	321	goto out;
7326c4e5	322	#ifndef KBUILD_MCOUNT_RA_ADDRESS
2816e325 WZ	323	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
2816e325 WZ	324	old_parent_ra, (unsigned long)parent_ra_addr, fp);
68ccf752 WZ	325	/*
	326	* If fails when getting the stack address of the non-leaf function's
	327	* ra, stop function graph tracer and return
	328	*/
2816e325	329	if (parent_ra_addr == 0)
046199ca	330	goto out;
7326c4e5	331	#endif
2816e325 WZ	332	/* parent_ra_addr = return_hooker; /
2816e325 WZ	333	safe_store_stack(return_hooker, parent_ra_addr, faulted);
046199ca WZ	334	if (unlikely(faulted))
046199ca WZ	335	goto out;
29c5d346	336
2816e325 WZ	337	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
	338	== -EBUSY) {
	339	*parent_ra_addr = old_parent_ra;
29c5d346 WZ	340	return;
	341	}
	342
b9f07eb2 WZ	343	/*
	344	* Get the recorded ip of the current mcount calling site in the
	345	* __mcount_loc section, which will be used to filter the function
	346	* entries configured through the tracing/set_graph_function interface.
	347	*/
	348
	349	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
	350	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
29c5d346 WZ	351
	352	/* Only trace if the calling function expects to */
	353	if (!ftrace_graph_entry(&trace)) {
	354	current->curr_ret_stack--;
2816e325	355	*parent_ra_addr = old_parent_ra;
29c5d346	356	}
046199ca WZ	357	return;
	358	out:
	359	ftrace_graph_stop();
	360	WARN_ON(1);
29c5d346	361	}
68ccf752	362	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */