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	/*
78	 * Also put { move r10, lr; jal ftrace_stub } in a bundle, which
79	 * is used to replace the instruction in address ftrace_call.
80	 */
81	if (addr == FTRACE_ADDR || addr == (unsigned long)ftrace_stub) {
82		/* opcode: or r10, lr, zero */
83		opcode_x0 =
84			create_Dest_X0(10) |
85			create_SrcA_X0(TREG_LR) |
86			create_SrcB_X0(TREG_ZERO) |
87			create_RRROpcodeExtension_X0(OR_RRR_0_OPCODE_X0) |
88			create_Opcode_X0(RRR_0_OPCODE_X0);
89	} else {
90		/* opcode: fnop */
91		opcode_x0 =
92			create_UnaryOpcodeExtension_X0(FNOP_UNARY_OPCODE_X0) |
93			create_RRROpcodeExtension_X0(UNARY_RRR_0_OPCODE_X0) |
94			create_Opcode_X0(RRR_0_OPCODE_X0);
95	}
96
97	return opcode_x1 | opcode_x0;
98}
99
100static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
101{
102	return NOP();
103}
104
105static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
106{
107	return ftrace_gen_branch(pc, addr, true);
108}
109
110static int ftrace_modify_code(unsigned long pc, unsigned long old,
111			      unsigned long new)
112{
113	unsigned long pc_wr;
114
115	/* Check if the address is in kernel text space and module space. */
116	if (!kernel_text_address(pc))
117		return -EINVAL;
118
119	/* Operate on writable kernel text mapping. */
120	pc_wr = pc - MEM_SV_START + PAGE_OFFSET;
121
122	if (probe_kernel_write((void *)pc_wr, &new, MCOUNT_INSN_SIZE))
123		return -EPERM;
124
125	smp_wmb();
126
127	if (!machine_stopped && num_online_cpus() > 1)
128		flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
129
130	return 0;
131}
132
133int ftrace_update_ftrace_func(ftrace_func_t func)
134{
135	unsigned long pc, old;
136	unsigned long new;
137	int ret;
138
139	pc = (unsigned long)&ftrace_call;
140	memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
141	new = ftrace_call_replace(pc, (unsigned long)func);
142
143	ret = ftrace_modify_code(pc, old, new);
144
145	return ret;
146}
147
148int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
149{
150	unsigned long new, old;
151	unsigned long ip = rec->ip;
152
153	old = ftrace_nop_replace(rec);
154	new = ftrace_call_replace(ip, addr);
155
156	return ftrace_modify_code(rec->ip, old, new);
157}
158
159int ftrace_make_nop(struct module *mod,
160		    struct dyn_ftrace *rec, unsigned long addr)
161{
162	unsigned long ip = rec->ip;
163	unsigned long old;
164	unsigned long new;
165	int ret;
166
167	old = ftrace_call_replace(ip, addr);
168	new = ftrace_nop_replace(rec);
169	ret = ftrace_modify_code(ip, old, new);
170
171	return ret;
172}
173
174int __init ftrace_dyn_arch_init(void)
175{
176	return 0;
177}
178#endif /* CONFIG_DYNAMIC_FTRACE */
179
180#ifdef CONFIG_FUNCTION_GRAPH_TRACER
181void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
182			   unsigned long frame_pointer)
183{
184	unsigned long return_hooker = (unsigned long) &return_to_handler;
185	struct ftrace_graph_ent trace;
186	unsigned long old;
187	int err;
188
189	if (unlikely(atomic_read(&current->tracing_graph_pause)))
190		return;
191
192	old = *parent;
193	*parent = return_hooker;
194
195	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
196				       frame_pointer);
197	if (err == -EBUSY) {
198		*parent = old;
199		return;
200	}
201
202	trace.func = self_addr;
203
204	/* Only trace if the calling function expects to */
205	if (!ftrace_graph_entry(&trace)) {
206		current->curr_ret_stack--;
207		*parent = old;
208	}
209}
210
211#ifdef CONFIG_DYNAMIC_FTRACE
212extern unsigned long ftrace_graph_call;
213
214static int __ftrace_modify_caller(unsigned long *callsite,
215				  void (*func) (void), bool enable)
216{
217	unsigned long caller_fn = (unsigned long) func;
218	unsigned long pc = (unsigned long) callsite;
219	unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);
220	unsigned long nop = NOP();
221	unsigned long old = enable ? nop : branch;
222	unsigned long new = enable ? branch : nop;
223
224	return ftrace_modify_code(pc, old, new);
225}
226
227static int ftrace_modify_graph_caller(bool enable)
228{
229	int ret;
230
231	ret = __ftrace_modify_caller(&ftrace_graph_call,
232				     ftrace_graph_caller,
233				     enable);
234
235	return ret;
236}
237
238int ftrace_enable_ftrace_graph_caller(void)
239{
240	return ftrace_modify_graph_caller(true);
241}
242
243int ftrace_disable_ftrace_graph_caller(void)
244{
245	return ftrace_modify_graph_caller(false);
246}
247#endif /* CONFIG_DYNAMIC_FTRACE */
248#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
249