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Linux/arch/tile/kernel/ftrace.c

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  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 
 28 static 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 
 38 static int machine_stopped __read_mostly;
 39 
 40 int ftrace_arch_code_modify_prepare(void)
 41 {
 42         machine_stopped = 1;
 43         return 0;
 44 }
 45 
 46 int 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  */
 57 static 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 
100 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
101 {
102         return NOP();
103 }
104 
105 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
106 {
107         return ftrace_gen_branch(pc, addr, true);
108 }
109 
110 static 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 
133 int 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 
148 int 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 
159 int 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 
174 int __init ftrace_dyn_arch_init(void)
175 {
176         return 0;
177 }
178 #endif /* CONFIG_DYNAMIC_FTRACE */
179 
180 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
181 void 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
212 extern unsigned long ftrace_graph_call;
213 
214 static 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 
227 static 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 
238 int ftrace_enable_ftrace_graph_caller(void)
239 {
240         return ftrace_modify_graph_caller(true);
241 }
242 
243 int 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 

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