arch/mips/kernel/ftrace.c

   1 /*
   2  * Code for replacing ftrace calls with jumps.
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
   6  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
   7  *
   8  * Thanks goes to Steven Rostedt for writing the original x86 version.
   9  */
  10
  11 #include <linux/uaccess.h>
  12 #include <linux/init.h>
  13 #include <linux/ftrace.h>
  14
  15 #include <asm/asm.h>
  16 #include <asm/asm-offsets.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/uasm.h>
  19
  20 #include <asm-generic/sections.h>
  21
  22 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  23 #define MCOUNT_OFFSET_INSNS 5
  24 #else
  25 #define MCOUNT_OFFSET_INSNS 4
  26 #endif
  27
  28 /*
  29  * Check if the address is in kernel space
  30  *
  31  * Clone core_kernel_text() from kernel/extable.c, but doesn't call
  32  * init_kernel_text() for Ftrace doesn't trace functions in init sections.
  33  */
  34 static inline int in_kernel_space(unsigned long ip)
  35 {
  36         if (ip >= (unsigned long)_stext &&
  37             ip <= (unsigned long)_etext)
  38                 return 1;
  39         return 0;
  40 }
  41
  42 #ifdef CONFIG_DYNAMIC_FTRACE
  43
  44 #define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
  45 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
  46 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
  47
  48 #define INSN_NOP 0x00000000     /* nop */
  49 #define INSN_JAL(addr)  \
  50         ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
  51
  52 static unsigned int insn_jal_ftrace_caller __read_mostly;
  53 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
  54 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
  55
  56 static inline void ftrace_dyn_arch_init_insns(void)
  57 {
  58         u32 *buf;
  59         unsigned int v1;
  60
  61         /* lui v1, hi16_mcount */
  62         v1 = 3;
  63         buf = (u32 *)&insn_lui_v1_hi16_mcount;
  64         UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
  65
  66         /* jal (ftrace_caller + 8), jump over the first two instruction */
  67         buf = (u32 *)&insn_jal_ftrace_caller;
  68         uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
  69
  70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  71         /* j ftrace_graph_caller */
  72         buf = (u32 *)&insn_j_ftrace_graph_caller;
  73         uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
  74 #endif
  75 }
  76
  77 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
  78 {
  79         int faulted;
  80
  81         /* *(unsigned int *)ip = new_code; */
  82         safe_store_code(new_code, ip, faulted);
  83
  84         if (unlikely(faulted))
  85                 return -EFAULT;
  86
  87         flush_icache_range(ip, ip + 8);
  88
  89         return 0;
  90 }
  91
  92 /*
  93  * The details about the calling site of mcount on MIPS
  94  *
  95  * 1. For kernel:
  96  *
  97  * move at, ra
  98  * jal _mcount          --> nop
  99  *
 100  * 2. For modules:
 101  *
 102  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 103  *
 104  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 105  * addiu v1, v1, low_16bit_of_mcount
 106  * move at, ra
 107  * move $12, ra_address
 108  * jalr v1
 109  *  sub sp, sp, 8
 110  *                                  1: offset = 5 instructions
 111  * 2.2 For the Other situations
 112  *
 113  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 114  * addiu v1, v1, low_16bit_of_mcount
 115  * move at, ra
 116  * jalr v1
 117  *  nop | move $12, ra_address | sub sp, sp, 8
 118  *                                  1: offset = 4 instructions
 119  */
 120
 121 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
 122
 123 int ftrace_make_nop(struct module *mod,
 124                     struct dyn_ftrace *rec, unsigned long addr)
 125 {
 126         unsigned int new;
 127         unsigned long ip = rec->ip;
 128
 129         /*
 130          * If ip is in kernel space, no long call, otherwise, long call is
 131          * needed.
 132          */
 133         new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
 134
 135         return ftrace_modify_code(ip, new);
 136 }
 137
 138 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 139 {
 140         unsigned int new;
 141         unsigned long ip = rec->ip;
 142
 143         new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
 144                 insn_lui_v1_hi16_mcount;
 145
 146         return ftrace_modify_code(ip, new);
 147 }
 148
 149 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
 150
 151 int ftrace_update_ftrace_func(ftrace_func_t func)
 152 {
 153         unsigned int new;
 154
 155         new = INSN_JAL((unsigned long)func);
 156
 157         return ftrace_modify_code(FTRACE_CALL_IP, new);
 158 }
 159
 160 int __init ftrace_dyn_arch_init(void *data)
 161 {
 162         /* Encode the instructions when booting */
 163         ftrace_dyn_arch_init_insns();
 164
 165         /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 166         ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
 167
 168         /* The return code is retured via data */
 169         *(unsigned long *)data = 0;
 170
 171         return 0;
 172 }
 173 #endif  /* CONFIG_DYNAMIC_FTRACE */
 174
 175 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 176
 177 #ifdef CONFIG_DYNAMIC_FTRACE
 178
 179 extern void ftrace_graph_call(void);
 180 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
 181
 182 int ftrace_enable_ftrace_graph_caller(void)
 183 {
 184         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 185                         insn_j_ftrace_graph_caller);
 186 }
 187
 188 int ftrace_disable_ftrace_graph_caller(void)
 189 {
 190         return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 191 }
 192
 193 #endif  /* CONFIG_DYNAMIC_FTRACE */
 194
 195 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 196
 197 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
 198 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 199 #define OFFSET_MASK     0xffff  /* stack offset range: 0 ~ PT_SIZE */
 200
 201 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
 202                 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
 203 {
 204         unsigned long sp, ip, tmp;
 205         unsigned int code;
 206         int faulted;
 207
 208         /*
 209          * For module, move the ip from the return address after the
 210          * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
 211          * kernel, move after the instruction "move ra, at"(offset is 16)
 212          */
 213         ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
 214
 215         /*
 216          * search the text until finding the non-store instruction or "s{d,w}
 217          * ra, offset(sp)" instruction
 218          */
 219         do {
 220                 /* get the code at "ip": code = *(unsigned int *)ip; */
 221                 safe_load_code(code, ip, faulted);
 222
 223                 if (unlikely(faulted))
 224                         return 0;
 225                 /*
 226                  * If we hit the non-store instruction before finding where the
 227                  * ra is stored, then this is a leaf function and it does not
 228                  * store the ra on the stack
 229                  */
 230                 if ((code & S_R_SP) != S_R_SP)
 231                         return parent_ra_addr;
 232
 233                 /* Move to the next instruction */
 234                 ip -= 4;
 235         } while ((code & S_RA_SP) != S_RA_SP);
 236
 237         sp = fp + (code & OFFSET_MASK);
 238
 239         /* tmp = *(unsigned long *)sp; */
 240         safe_load_stack(tmp, sp, faulted);
 241         if (unlikely(faulted))
 242                 return 0;
 243
 244         if (tmp == old_parent_ra)
 245                 return sp;
 246         return 0;
 247 }
 248
 249 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
 250
 251 /*
 252  * Hook the return address and push it in the stack of return addrs
 253  * in current thread info.
 254  */
 255 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 256                            unsigned long fp)
 257 {
 258         unsigned long old_parent_ra;
 259         struct ftrace_graph_ent trace;
 260         unsigned long return_hooker = (unsigned long)
 261             &return_to_handler;
 262         int faulted, insns;
 263
 264         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 265                 return;
 266
 267         /*
 268          * "parent_ra_addr" is the stack address saved the return address of
 269          * the caller of _mcount.
 270          *
 271          * if the gcc < 4.5, a leaf function does not save the return address
 272          * in the stack address, so, we "emulate" one in _mcount's stack space,
 273          * and hijack it directly, but for a non-leaf function, it save the
 274          * return address to the its own stack space, we can not hijack it
 275          * directly, but need to find the real stack address,
 276          * ftrace_get_parent_addr() does it!
 277          *
 278          * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 279          * non-leaf function, the location of the return address will be saved
 280          * to $12 for us, and for a leaf function, only put a zero into $12. we
 281          * do it in ftrace_graph_caller of mcount.S.
 282          */
 283
 284         /* old_parent_ra = *parent_ra_addr; */
 285         safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
 286         if (unlikely(faulted))
 287                 goto out;
 288 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 289         parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
 290                         old_parent_ra, (unsigned long)parent_ra_addr, fp);
 291         /*
 292          * If fails when getting the stack address of the non-leaf function's
 293          * ra, stop function graph tracer and return
 294          */
 295         if (parent_ra_addr == 0)
 296                 goto out;
 297 #endif
 298         /* *parent_ra_addr = return_hooker; */
 299         safe_store_stack(return_hooker, parent_ra_addr, faulted);
 300         if (unlikely(faulted))
 301                 goto out;
 302
 303         if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
 304             == -EBUSY) {
 305                 *parent_ra_addr = old_parent_ra;
 306                 return;
 307         }
 308
 309         /*
 310          * Get the recorded ip of the current mcount calling site in the
 311          * __mcount_loc section, which will be used to filter the function
 312          * entries configured through the tracing/set_graph_function interface.
 313          */
 314
 315         insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
 316         trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
 317
 318         /* Only trace if the calling function expects to */
 319         if (!ftrace_graph_entry(&trace)) {
 320                 current->curr_ret_stack--;
 321                 *parent_ra_addr = old_parent_ra;
 322         }
 323         return;
 324 out:
 325         ftrace_graph_stop();
 326         WARN_ON(1);
 327 }
 328 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */