1/*
2 * Copyright 2012 Tilera Corporation. All Rights Reserved.
3 *
4 *   This program is free software; you can redistribute it and/or
5 *   modify it under the terms of the GNU General Public License
6 *   as published by the Free Software Foundation, version 2.
7 *
8 *   This program is distributed in the hope that it will be useful, but
9 *   WITHOUT ANY WARRANTY; without even the implied warranty of
10 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 *   NON INFRINGEMENT.  See the GNU General Public License for
12 *   more details.
13 *
14 * TILE-Gx specific ftrace support
15 */
16
17#include <linux/ftrace.h>
18#include <linux/uaccess.h>
19
20#include <asm/cacheflush.h>
21#include <asm/ftrace.h>
22#include <asm/sections.h>
23
24#include <arch/opcode.h>
25
26#ifdef CONFIG_DYNAMIC_FTRACE
27
28static inline tilegx_bundle_bits NOP(void)
29{
30	return create_UnaryOpcodeExtension_X0(FNOP_UNARY_OPCODE_X0) |
31		create_RRROpcodeExtension_X0(UNARY_RRR_0_OPCODE_X0) |
32		create_Opcode_X0(RRR_0_OPCODE_X0) |
33		create_UnaryOpcodeExtension_X1(NOP_UNARY_OPCODE_X1) |
34		create_RRROpcodeExtension_X1(UNARY_RRR_0_OPCODE_X1) |
35		create_Opcode_X1(RRR_0_OPCODE_X1);
36}
37
38static int machine_stopped __read_mostly;
39
40int ftrace_arch_code_modify_prepare(void)
41{
42	machine_stopped = 1;
43	return 0;
44}
45
46int ftrace_arch_code_modify_post_process(void)
47{
48	flush_icache_range(0, CHIP_L1I_CACHE_SIZE());
49	machine_stopped = 0;
50	return 0;
51}
52
53/*
54 * Put { move r10, lr; jal ftrace_caller } in a bundle, this lets dynamic
55 * tracer just add one cycle overhead to every kernel function when disabled.
56 */
57static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
58				       bool link)
59{
60	tilegx_bundle_bits opcode_x0, opcode_x1;
61	long pcrel_by_instr = (addr - pc) >> TILEGX_LOG2_BUNDLE_SIZE_IN_BYTES;
62
63	if (link) {
64		/* opcode: jal addr */
65		opcode_x1 =
66			create_Opcode_X1(JUMP_OPCODE_X1) |
67			create_JumpOpcodeExtension_X1(JAL_JUMP_OPCODE_X1) |
68			create_JumpOff_X1(pcrel_by_instr);
69	} else {
70		/* opcode: j addr */
71		opcode_x1 =
72			create_Opcode_X1(JUMP_OPCODE_X1) |
73			create_JumpOpcodeExtension_X1(J_JUMP_OPCODE_X1) |
74			create_JumpOff_X1(pcrel_by_instr);
75	}
76
77	if (addr == FTRACE_ADDR) {
78		/* opcode: or r10, lr, zero */
79		opcode_x0 =
80			create_Dest_X0(10) |
81			create_SrcA_X0(TREG_LR) |
82			create_SrcB_X0(TREG_ZERO) |
83			create_RRROpcodeExtension_X0(OR_RRR_0_OPCODE_X0) |
84			create_Opcode_X0(RRR_0_OPCODE_X0);
85	} else {
86		/* opcode: fnop */
87		opcode_x0 =
88			create_UnaryOpcodeExtension_X0(FNOP_UNARY_OPCODE_X0) |
89			create_RRROpcodeExtension_X0(UNARY_RRR_0_OPCODE_X0) |
90			create_Opcode_X0(RRR_0_OPCODE_X0);
91	}
92
93	return opcode_x1 | opcode_x0;
94}
95
96static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
97{
98	return NOP();
99}
100
101static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
102{
103	return ftrace_gen_branch(pc, addr, true);
104}
105
106static int ftrace_modify_code(unsigned long pc, unsigned long old,
107			      unsigned long new)
108{
109	unsigned long pc_wr;
110
111	/* Check if the address is in kernel text space and module space. */
112	if (!kernel_text_address(pc))
113		return -EINVAL;
114
115	/* Operate on writable kernel text mapping. */
116	pc_wr = pc - MEM_SV_START + PAGE_OFFSET;
117
118	if (probe_kernel_write((void *)pc_wr, &new, MCOUNT_INSN_SIZE))
119		return -EPERM;
120
121	smp_wmb();
122
123	if (!machine_stopped && num_online_cpus() > 1)
124		flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
125
126	return 0;
127}
128
129int ftrace_update_ftrace_func(ftrace_func_t func)
130{
131	unsigned long pc, old;
132	unsigned long new;
133	int ret;
134
135	pc = (unsigned long)&ftrace_call;
136	memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
137	new = ftrace_call_replace(pc, (unsigned long)func);
138
139	ret = ftrace_modify_code(pc, old, new);
140
141	return ret;
142}
143
144int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
145{
146	unsigned long new, old;
147	unsigned long ip = rec->ip;
148
149	old = ftrace_nop_replace(rec);
150	new = ftrace_call_replace(ip, addr);
151
152	return ftrace_modify_code(rec->ip, old, new);
153}
154
155int ftrace_make_nop(struct module *mod,
156		    struct dyn_ftrace *rec, unsigned long addr)
157{
158	unsigned long ip = rec->ip;
159	unsigned long old;
160	unsigned long new;
161	int ret;
162
163	old = ftrace_call_replace(ip, addr);
164	new = ftrace_nop_replace(rec);
165	ret = ftrace_modify_code(ip, old, new);
166
167	return ret;
168}
169
170int __init ftrace_dyn_arch_init(void)
171{
172	return 0;
173}
174#endif /* CONFIG_DYNAMIC_FTRACE */
175
176#ifdef CONFIG_FUNCTION_GRAPH_TRACER
177void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
178			   unsigned long frame_pointer)
179{
180	unsigned long return_hooker = (unsigned long) &return_to_handler;
181	struct ftrace_graph_ent trace;
182	unsigned long old;
183	int err;
184
185	if (unlikely(atomic_read(&current->tracing_graph_pause)))
186		return;
187
188	old = *parent;
189	*parent = return_hooker;
190
191	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
192				       frame_pointer);
193	if (err == -EBUSY) {
194		*parent = old;
195		return;
196	}
197
198	trace.func = self_addr;
199
200	/* Only trace if the calling function expects to */
201	if (!ftrace_graph_entry(&trace)) {
202		current->curr_ret_stack--;
203		*parent = old;
204	}
205}
206
207#ifdef CONFIG_DYNAMIC_FTRACE
208extern unsigned long ftrace_graph_call;
209
210static int __ftrace_modify_caller(unsigned long *callsite,
211				  void (*func) (void), bool enable)
212{
213	unsigned long caller_fn = (unsigned long) func;
214	unsigned long pc = (unsigned long) callsite;
215	unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);
216	unsigned long nop = NOP();
217	unsigned long old = enable ? nop : branch;
218	unsigned long new = enable ? branch : nop;
219
220	return ftrace_modify_code(pc, old, new);
221}
222
223static int ftrace_modify_graph_caller(bool enable)
224{
225	int ret;
226
227	ret = __ftrace_modify_caller(&ftrace_graph_call,
228				     ftrace_graph_caller,
229				     enable);
230
231	return ret;
232}
233
234int ftrace_enable_ftrace_graph_caller(void)
235{
236	return ftrace_modify_graph_caller(true);
237}
238
239int ftrace_disable_ftrace_graph_caller(void)
240{
241	return ftrace_modify_graph_caller(false);
242}
243#endif /* CONFIG_DYNAMIC_FTRACE */
244#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
245