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         /*
  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 */