[linux-2.6-block.git] / arch / arm64 / kernel / ftrace.c

/*
 * arch/arm64/kernel/ftrace.c
 *
 * Copyright (C) 2013 Linaro Limited
 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/ftrace.h>
#include <linux/swab.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>
#include <asm/ftrace.h>
#include <asm/insn.h>

#ifdef CONFIG_DYNAMIC_FTRACE
/*
 * Replace a single instruction, which may be a branch or NOP.
 * If @validate == true, a replaced instruction is checked against 'old'.
 */
static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
			      bool validate)
{
	u32 replaced;

	/*
	 * Note:
	 * Due to modules and __init, code can disappear and change,
	 * we need to protect against faulting as well as code changing.
	 * We do this by aarch64_insn_*() which use the probe_kernel_*().
	 *
	 * No lock is held here because all the modifications are run
	 * through stop_machine().
	 */
	if (validate) {
		if (aarch64_insn_read((void *)pc, &replaced))
			return -EFAULT;

		if (replaced != old)
			return -EINVAL;
	}
	if (aarch64_insn_patch_text_nosync((void *)pc, new))
		return -EPERM;

	return 0;
}

/*
 * Replace tracer function in ftrace_caller()
 */
int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned long pc;
	u32 new;

	pc = (unsigned long)&ftrace_call;
	new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
					  AARCH64_INSN_BRANCH_LINK);

	return ftrace_modify_code(pc, 0, new, false);
}

/*
 * Turn on the call to ftrace_caller() in instrumented function
 */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned long pc = rec->ip;
	u32 old, new;

	old = aarch64_insn_gen_nop();
	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);

	return ftrace_modify_code(pc, old, new, true);
}

/*
 * Turn off the call to ftrace_caller() in instrumented function
 */
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
		    unsigned long addr)
{
	unsigned long pc = rec->ip;
	u32 old, new;

	old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
	new = aarch64_insn_gen_nop();

	return ftrace_modify_code(pc, old, new, true);
}

int __init ftrace_dyn_arch_init(void)
{
	return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
 * function_graph tracer expects ftrace_return_to_handler() to be called
 * on the way back to parent. For this purpose, this function is called
 * in _mcount() or ftrace_caller() to replace return address (*parent) on
 * the call stack to return_to_handler.
 *
 * Note that @frame_pointer is used only for sanity check later.
 */
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
			   unsigned long frame_pointer)
{
	unsigned long return_hooker = (unsigned long)&return_to_handler;
	unsigned long old;
	struct ftrace_graph_ent trace;
	int err;

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

	/*
	 * Note:
	 * No protection against faulting at *parent, which may be seen
	 * on other archs. It's unlikely on AArch64.
	 */
	old = *parent;
	*parent = return_hooker;

	trace.func = self_addr;
	trace.depth = current->curr_ret_stack + 1;

	/* Only trace if the calling function expects to */
	if (!ftrace_graph_entry(&trace)) {
		*parent = old;
		return;
	}

	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
				       frame_pointer);
	if (err == -EBUSY) {
		*parent = old;
		return;
	}
}

#ifdef CONFIG_DYNAMIC_FTRACE
/*
 * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
 * depending on @enable.
 */
static int ftrace_modify_graph_caller(bool enable)
{
	unsigned long pc = (unsigned long)&ftrace_graph_call;
	u32 branch, nop;

	branch = aarch64_insn_gen_branch_imm(pc,
					     (unsigned long)ftrace_graph_caller,
					     AARCH64_INSN_BRANCH_NOLINK);
	nop = aarch64_insn_gen_nop();

	if (enable)
		return ftrace_modify_code(pc, nop, branch, true);
	else
		return ftrace_modify_code(pc, branch, nop, true);
}

int ftrace_enable_ftrace_graph_caller(void)
{
	return ftrace_modify_graph_caller(true);
}

int ftrace_disable_ftrace_graph_caller(void)
{
	return ftrace_modify_graph_caller(false);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
Commit	Line	Data
819e50e2 AT	1	/*
	2	* arch/arm64/kernel/ftrace.c
	3	*
	4	* Copyright (C) 2013 Linaro Limited
	5	* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*/
	11
	12	#include <linux/ftrace.h>
	13	#include <linux/swab.h>
	14	#include <linux/uaccess.h>
	15
	16	#include <asm/cacheflush.h>
	17	#include <asm/ftrace.h>
	18	#include <asm/insn.h>
	19
bd7d38db AT	20	#ifdef CONFIG_DYNAMIC_FTRACE
	21	/*
	22	* Replace a single instruction, which may be a branch or NOP.
	23	* If @validate == true, a replaced instruction is checked against 'old'.
	24	*/
	25	static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
	26	bool validate)
	27	{
	28	u32 replaced;
	29
	30	/*
	31	* Note:
	32	* Due to modules and __init, code can disappear and change,
	33	* we need to protect against faulting as well as code changing.
	34	* We do this by aarch64_insn_() which use the probe_kernel_().
	35	*
	36	* No lock is held here because all the modifications are run
	37	* through stop_machine().
	38	*/
	39	if (validate) {
	40	if (aarch64_insn_read((void *)pc, &replaced))
	41	return -EFAULT;
	42
	43	if (replaced != old)
	44	return -EINVAL;
	45	}
	46	if (aarch64_insn_patch_text_nosync((void *)pc, new))
	47	return -EPERM;
	48
	49	return 0;
	50	}
	51
	52	/*
	53	* Replace tracer function in ftrace_caller()
	54	*/
	55	int ftrace_update_ftrace_func(ftrace_func_t func)
	56	{
	57	unsigned long pc;
	58	u32 new;
	59
	60	pc = (unsigned long)&ftrace_call;
9f1ae759 CM	61	new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
9f1ae759 CM	62	AARCH64_INSN_BRANCH_LINK);
bd7d38db AT	63
	64	return ftrace_modify_code(pc, 0, new, false);
	65	}
	66
	67	/*
	68	* Turn on the call to ftrace_caller() in instrumented function
	69	*/
	70	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	71	{
	72	unsigned long pc = rec->ip;
	73	u32 old, new;
	74
	75	old = aarch64_insn_gen_nop();
9f1ae759	76	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
bd7d38db AT	77
	78	return ftrace_modify_code(pc, old, new, true);
	79	}
	80
	81	/*
	82	* Turn off the call to ftrace_caller() in instrumented function
	83	*/
	84	int ftrace_make_nop(struct module mod, struct dyn_ftrace rec,
	85	unsigned long addr)
	86	{
	87	unsigned long pc = rec->ip;
	88	u32 old, new;
	89
9f1ae759	90	old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
bd7d38db AT	91	new = aarch64_insn_gen_nop();
	92
	93	return ftrace_modify_code(pc, old, new, true);
	94	}
	95
	96	int __init ftrace_dyn_arch_init(void)
	97	{
	98	return 0;
	99	}
	100	#endif /* CONFIG_DYNAMIC_FTRACE */
	101
819e50e2 AT	102	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	103	/*
	104	* function_graph tracer expects ftrace_return_to_handler() to be called
	105	* on the way back to parent. For this purpose, this function is called
	106	* in _mcount() or ftrace_caller() to replace return address (*parent) on
	107	* the call stack to return_to_handler.
	108	*
	109	* Note that @frame_pointer is used only for sanity check later.
	110	*/
	111	void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
	112	unsigned long frame_pointer)
	113	{
	114	unsigned long return_hooker = (unsigned long)&return_to_handler;
	115	unsigned long old;
	116	struct ftrace_graph_ent trace;
	117	int err;
	118
	119	if (unlikely(atomic_read(&current->tracing_graph_pause)))
	120	return;
	121
	122	/*
	123	* Note:
	124	* No protection against faulting at *parent, which may be seen
	125	* on other archs. It's unlikely on AArch64.
	126	*/
	127	old = *parent;
	128	*parent = return_hooker;
	129
	130	trace.func = self_addr;
	131	trace.depth = current->curr_ret_stack + 1;
	132
	133	/* Only trace if the calling function expects to */
	134	if (!ftrace_graph_entry(&trace)) {
	135	*parent = old;
	136	return;
	137	}
	138
	139	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
	140	frame_pointer);
	141	if (err == -EBUSY) {
	142	*parent = old;
	143	return;
	144	}
	145	}
bd7d38db AT	146
	147	#ifdef CONFIG_DYNAMIC_FTRACE
	148	/*
	149	* Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
	150	* depending on @enable.
	151	*/
	152	static int ftrace_modify_graph_caller(bool enable)
	153	{
	154	unsigned long pc = (unsigned long)&ftrace_graph_call;
	155	u32 branch, nop;
	156
	157	branch = aarch64_insn_gen_branch_imm(pc,
9f1ae759	158	(unsigned long)ftrace_graph_caller,
d0d62230	159	AARCH64_INSN_BRANCH_NOLINK);
bd7d38db AT	160	nop = aarch64_insn_gen_nop();
	161
	162	if (enable)
	163	return ftrace_modify_code(pc, nop, branch, true);
	164	else
	165	return ftrace_modify_code(pc, branch, nop, true);
	166	}
	167
	168	int ftrace_enable_ftrace_graph_caller(void)
	169	{
	170	return ftrace_modify_graph_caller(true);
	171	}
	172
	173	int ftrace_disable_ftrace_graph_caller(void)
	174	{
	175	return ftrace_modify_graph_caller(false);
	176	}
	177	#endif /* CONFIG_DYNAMIC_FTRACE */
819e50e2	178	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */