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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 #include <asm/insn.h>
 24 
 25 #include <arch/opcode.h>
 26 
 27 #ifdef CONFIG_DYNAMIC_FTRACE
 28 
 29 static int machine_stopped __read_mostly;
 30 
 31 int ftrace_arch_code_modify_prepare(void)
 32 {
 33         machine_stopped = 1;
 34         return 0;
 35 }
 36 
 37 int 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  */
 48 static 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 
 91 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
 92 {
 93         return NOP();
 94 }
 95 
 96 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 97 {
 98         return ftrace_gen_branch(pc, addr, true);
 99 }
100 
101 static 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 
124 int 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 
139 int 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 
150 int 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 
165 int __init ftrace_dyn_arch_init(void)
166 {
167         return 0;
168 }
169 #endif /* CONFIG_DYNAMIC_FTRACE */
170 
171 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
172 void 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
203 extern unsigned long ftrace_graph_call;
204 
205 static 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 
218 static 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 
229 int ftrace_enable_ftrace_graph_caller(void)
230 {
231         return ftrace_modify_graph_caller(true);
232 }
233 
234 int 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 */
240 

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