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#include <asm/insn.h>
 24
 25#include <arch/opcode.h>
 26
 27#ifdef CONFIG_DYNAMIC_FTRACE
 28
 29static int machine_stopped __read_mostly;
 30
 31int ftrace_arch_code_modify_prepare(void)
 32{
 33	machine_stopped = 1;
 34	return 0;
 35}
 36
 37int ftrace_arch_code_modify_post_process(void)
 38{
 39	flush_icache_range(0, CHIP_L1I_CACHE_SIZE());
 40	machine_stopped = 0;
 41	return 0;
 42}
 43
 44/*
 45 * Put { move r10, lr; jal ftrace_caller } in a bundle, this lets dynamic
 46 * tracer just add one cycle overhead to every kernel function when disabled.
 47 */
 48static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
 49				       bool link)
 50{
 51	tilegx_bundle_bits opcode_x0, opcode_x1;
 52	long pcrel_by_instr = (addr - pc) >> TILEGX_LOG2_BUNDLE_SIZE_IN_BYTES;
 53
 54	if (link) {
 55		/* opcode: jal addr */
 56		opcode_x1 =
 57			create_Opcode_X1(JUMP_OPCODE_X1) |
 58			create_JumpOpcodeExtension_X1(JAL_JUMP_OPCODE_X1) |
 59			create_JumpOff_X1(pcrel_by_instr);
 60	} else {
 61		/* opcode: j addr */
 62		opcode_x1 =
 63			create_Opcode_X1(JUMP_OPCODE_X1) |
 64			create_JumpOpcodeExtension_X1(J_JUMP_OPCODE_X1) |
 65			create_JumpOff_X1(pcrel_by_instr);
 66	}
 67
 68	/*
 69	 * Also put { move r10, lr; jal ftrace_stub } in a bundle, which
 70	 * is used to replace the instruction in address ftrace_call.
 71	 */
 72	if (addr == FTRACE_ADDR || addr == (unsigned long)ftrace_stub) {
 73		/* opcode: or r10, lr, zero */
 74		opcode_x0 =
 75			create_Dest_X0(10) |
 76			create_SrcA_X0(TREG_LR) |
 77			create_SrcB_X0(TREG_ZERO) |
 78			create_RRROpcodeExtension_X0(OR_RRR_0_OPCODE_X0) |
 79			create_Opcode_X0(RRR_0_OPCODE_X0);
 80	} else {
 81		/* opcode: fnop */
 82		opcode_x0 =
 83			create_UnaryOpcodeExtension_X0(FNOP_UNARY_OPCODE_X0) |
 84			create_RRROpcodeExtension_X0(UNARY_RRR_0_OPCODE_X0) |
 85			create_Opcode_X0(RRR_0_OPCODE_X0);
 86	}
 87
 88	return opcode_x1 | opcode_x0;
 89}
 90
 91static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
 92{
 93	return NOP();
 94}
 95
 96static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 97{
 98	return ftrace_gen_branch(pc, addr, true);
 99}
100
101static int ftrace_modify_code(unsigned long pc, unsigned long old,
102			      unsigned long new)
103{
104	unsigned long pc_wr;
105
106	/* Check if the address is in kernel text space and module space. */
107	if (!kernel_text_address(pc))
108		return -EINVAL;
109
110	/* Operate on writable kernel text mapping. */
111	pc_wr = ktext_writable_addr(pc);
112
113	if (probe_kernel_write((void *)pc_wr, &new, MCOUNT_INSN_SIZE))
114		return -EPERM;
115
116	smp_wmb();
117
118	if (!machine_stopped && num_online_cpus() > 1)
119		flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
120
121	return 0;
122}
123
124int ftrace_update_ftrace_func(ftrace_func_t func)
125{
126	unsigned long pc, old;
127	unsigned long new;
128	int ret;
129
130	pc = (unsigned long)&ftrace_call;
131	memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
132	new = ftrace_call_replace(pc, (unsigned long)func);
133
134	ret = ftrace_modify_code(pc, old, new);
135
136	return ret;
137}
138
139int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
140{
141	unsigned long new, old;
142	unsigned long ip = rec->ip;
143
144	old = ftrace_nop_replace(rec);
145	new = ftrace_call_replace(ip, addr);
146
147	return ftrace_modify_code(rec->ip, old, new);
148}
149
150int ftrace_make_nop(struct module *mod,
151		    struct dyn_ftrace *rec, unsigned long addr)
152{
153	unsigned long ip = rec->ip;
154	unsigned long old;
155	unsigned long new;
156	int ret;
157
158	old = ftrace_call_replace(ip, addr);
159	new = ftrace_nop_replace(rec);
160	ret = ftrace_modify_code(ip, old, new);
161
162	return ret;
163}
164
165int __init ftrace_dyn_arch_init(void)
166{
167	return 0;
168}
169#endif /* CONFIG_DYNAMIC_FTRACE */
170
171#ifdef CONFIG_FUNCTION_GRAPH_TRACER
172void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
173			   unsigned long frame_pointer)
174{
175	unsigned long return_hooker = (unsigned long) &return_to_handler;
176	struct ftrace_graph_ent trace;
177	unsigned long old;
178	int err;
179
180	if (unlikely(atomic_read(&current->tracing_graph_pause)))
181		return;
182
183	old = *parent;
184	*parent = return_hooker;
185
186	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
187				       frame_pointer, NULL);
188	if (err == -EBUSY) {
189		*parent = old;
190		return;
191	}
192
193	trace.func = self_addr;
194
195	/* Only trace if the calling function expects to */
196	if (!ftrace_graph_entry(&trace)) {
197		current->curr_ret_stack--;
198		*parent = old;
199	}
200}
201
202#ifdef CONFIG_DYNAMIC_FTRACE
203extern unsigned long ftrace_graph_call;
204
205static int __ftrace_modify_caller(unsigned long *callsite,
206				  void (*func) (void), bool enable)
207{
208	unsigned long caller_fn = (unsigned long) func;
209	unsigned long pc = (unsigned long) callsite;
210	unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);
211	unsigned long nop = NOP();
212	unsigned long old = enable ? nop : branch;
213	unsigned long new = enable ? branch : nop;
214
215	return ftrace_modify_code(pc, old, new);
216}
217
218static int ftrace_modify_graph_caller(bool enable)
219{
220	int ret;
221
222	ret = __ftrace_modify_caller(&ftrace_graph_call,
223				     ftrace_graph_caller,
224				     enable);
225
226	return ret;
227}
228
229int ftrace_enable_ftrace_graph_caller(void)
230{
231	return ftrace_modify_graph_caller(true);
232}
233
234int ftrace_disable_ftrace_graph_caller(void)
235{
236	return ftrace_modify_graph_caller(false);
237}
238#endif /* CONFIG_DYNAMIC_FTRACE */
239#endif /* CONFIG_FUNCTION_GRAPH_TRACER */