arch/tile/kernel/ftrace.c

   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         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
  96 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
  97 {
  98         return NOP();
  99 }
 100
 101 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 102 {
 103         return ftrace_gen_branch(pc, addr, true);
 104 }
 105
 106 static 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
 129 int 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
 144 int 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
 155 int 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
 170 int __init ftrace_dyn_arch_init(void)
 171 {
 172         return 0;
 173 }
 174 #endif /* CONFIG_DYNAMIC_FTRACE */
 175
 176 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 177 void 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
 208 extern unsigned long ftrace_graph_call;
 209
 210 static 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
 223 static 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
 234 int ftrace_enable_ftrace_graph_caller(void)
 235 {
 236         return ftrace_modify_graph_caller(true);
 237 }
 238
 239 int 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 */