LXR linux/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
  19static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
  20static unsigned long movt_and_call_insn[2];
  21
  22static unsigned char *ftrace_nop_replace(void)
  23{
  24        return (char *)&NOP[0];
  25}
  26
  27static 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
  51static 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
  81int 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
  95int 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
 107int 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/* run from kstop_machine */
 119int __init ftrace_dyn_arch_init(void)
 120{
 121        return 0;
 122}
 123