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 */