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 #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 */