arch/metag/kernel/ftrace.c

   1 /*
   2  * Copyright (C) 2008 Imagination Technologies Ltd.
   3  * Licensed under the GPL
   4  *
   5  * Dynamic ftrace support.
   6  */
   7
   8 #include <linux/ftrace.h>
   9 #include <linux/io.h>
  10 #include <linux/uaccess.h>
  11
  12 #include <asm/cacheflush.h>
  13
  14 #define D04_MOVT_TEMPLATE       0x02200005
  15 #define D04_CALL_TEMPLATE       0xAC200005
  16 #define D1RTP_MOVT_TEMPLATE     0x03200005
  17 #define D1RTP_CALL_TEMPLATE     0xAC200006
  18
  19 static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
  20 static unsigned long movt_and_call_insn[2];
  21
  22 static unsigned char *ftrace_nop_replace(void)
  23 {
  24         return (char *)&NOP[0];
  25 }
  26
  27 static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
  28 {
  29         unsigned long hi16, low16;
  30
  31         hi16 = (addr & 0xffff0000) >> 13;
  32         low16 = (addr & 0x0000ffff) << 3;
  33
  34         /*
  35          * The compiler makes the call to mcount_wrapper()
  36          * (Meta's wrapper around mcount()) through the register
  37          * D0.4. So whenever we're patching one of those compiler-generated
  38          * calls we also need to go through D0.4. Otherwise use D1RtP.
  39          */
  40         if (pc == (unsigned long)&ftrace_call) {
  41                 writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
  42                 writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
  43         } else {
  44                 writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
  45                 writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
  46         }
  47
  48         return (unsigned char *)&movt_and_call_insn[0];
  49 }
  50
  51 static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
  52                               unsigned char *new_code)
  53 {
  54         unsigned char replaced[MCOUNT_INSN_SIZE];
  55
  56         /*
  57          * Note:
  58          * We are paranoid about modifying text, as if a bug was to happen, it
  59          * could cause us to read or write to someplace that could cause harm.
  60          * Carefully read and modify the code with probe_kernel_*(), and make
  61          * sure what we read is what we expected it to be before modifying it.
  62          */
  63
  64         /* read the text we want to modify */
  65         if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE))
  66                 return -EFAULT;
  67
  68         /* Make sure it is what we expect it to be */
  69         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
  70                 return -EINVAL;
  71
  72         /* replace the text with the new text */
  73         if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE))
  74                 return -EPERM;
  75
  76         flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
  77
  78         return 0;
  79 }
  80
  81 int ftrace_update_ftrace_func(ftrace_func_t func)
  82 {
  83         int ret;
  84         unsigned long pc;
  85         unsigned char old[MCOUNT_INSN_SIZE], *new;
  86
  87         pc = (unsigned long)&ftrace_call;
  88         memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
  89         new = ftrace_call_replace(pc, (unsigned long)func);
  90         ret = ftrace_modify_code(pc, old, new);
  91
  92         return ret;
  93 }
  94
  95 int ftrace_make_nop(struct module *mod,
  96                     struct dyn_ftrace *rec, unsigned long addr)
  97 {
  98         unsigned char *new, *old;
  99         unsigned long ip = rec->ip;
 100
 101         old = ftrace_call_replace(ip, addr);
 102         new = ftrace_nop_replace();
 103
 104         return ftrace_modify_code(ip, old, new);
 105 }
 106
 107 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 108 {
 109         unsigned char *new, *old;
 110         unsigned long ip = rec->ip;
 111
 112         old = ftrace_nop_replace();
 113         new = ftrace_call_replace(ip, addr);
 114
 115         return ftrace_modify_code(ip, old, new);
 116 }
 117
 118 int __init ftrace_dyn_arch_init(void)
 119 {
 120         return 0;
 121 }