LXR linux/arch/blackfin/kernel/ftrace.c

   1/*
   2 * ftrace graph code
   3 *
   4 * Copyright (C) 2009-2010 Analog Devices Inc.
   5 * Licensed under the GPL-2 or later.
   6 */
   7
   8#include <linux/ftrace.h>
   9#include <linux/kernel.h>
  10#include <linux/sched.h>
  11#include <linux/uaccess.h>
  12#include <linux/atomic.h>
  13#include <asm/cacheflush.h>
  14
  15#ifdef CONFIG_DYNAMIC_FTRACE
  16
  17static const unsigned char mnop[] = {
  18        0x03, 0xc0, 0x00, 0x18, /* MNOP; */
  19        0x03, 0xc0, 0x00, 0x18, /* MNOP; */
  20};
  21
  22static void bfin_make_pcrel24(unsigned char *insn, unsigned long src,
  23                              unsigned long dst)
  24{
  25        uint32_t pcrel = (dst - src) >> 1;
  26        insn[0] = pcrel >> 16;
  27        insn[1] = 0xe3;
  28        insn[2] = pcrel;
  29        insn[3] = pcrel >> 8;
  30}
  31#define bfin_make_pcrel24(insn, src, dst) bfin_make_pcrel24(insn, src, (unsigned long)(dst))
  32
  33static int ftrace_modify_code(unsigned long ip, const unsigned char *code,
  34                              unsigned long len)
  35{
  36        int ret = probe_kernel_write((void *)ip, (void *)code, len);
  37        flush_icache_range(ip, ip + len);
  38        return ret;
  39}
  40
  41int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
  42                    unsigned long addr)
  43{
  44        /* Turn the mcount call site into two MNOPs as those are 32bit insns */
  45        return ftrace_modify_code(rec->ip, mnop, sizeof(mnop));
  46}
  47
  48int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  49{
  50        /* Restore the mcount call site */
  51        unsigned char call[8];
  52        call[0] = 0x67; /* [--SP] = RETS; */
  53        call[1] = 0x01;
  54        bfin_make_pcrel24(&call[2], rec->ip + 2, addr);
  55        call[6] = 0x27; /* RETS = [SP++]; */
  56        call[7] = 0x01;
  57        return ftrace_modify_code(rec->ip, call, sizeof(call));
  58}
  59
  60int ftrace_update_ftrace_func(ftrace_func_t func)
  61{
  62        unsigned char call[4];
  63        unsigned long ip = (unsigned long)&ftrace_call;
  64        bfin_make_pcrel24(call, ip, func);
  65        return ftrace_modify_code(ip, call, sizeof(call));
  66}
  67
  68int __init ftrace_dyn_arch_init(void *data)
  69{
  70        /* return value is done indirectly via data */
  71        *(unsigned long *)data = 0;
  72
  73        return 0;
  74}
  75
  76#endif
  77
  78#ifdef CONFIG_FUNCTION_GRAPH_TRACER
  79
  80# ifdef CONFIG_DYNAMIC_FTRACE
  81
  82extern void ftrace_graph_call(void);
  83
  84int ftrace_enable_ftrace_graph_caller(void)
  85{
  86        unsigned long ip = (unsigned long)&ftrace_graph_call;
  87        uint16_t jump_pcrel12 = ((unsigned long)&ftrace_graph_caller - ip) >> 1;
  88        jump_pcrel12 |= 0x2000;
  89        return ftrace_modify_code(ip, (void *)&jump_pcrel12, sizeof(jump_pcrel12));
  90}
  91
  92int ftrace_disable_ftrace_graph_caller(void)
  93{
  94        return ftrace_modify_code((unsigned long)&ftrace_graph_call, empty_zero_page, 2);
  95}
  96
  97# endif
  98
  99/*
 100 * Hook the return address and push it in the stack of return addrs
 101 * in current thread info.
 102 */
 103void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 104                           unsigned long frame_pointer)
 105{
 106        struct ftrace_graph_ent trace;
 107        unsigned long return_hooker = (unsigned long)&return_to_handler;
 108
 109        if (unlikely(atomic_read(&current->tracing_graph_pause)))
 110                return;
 111
 112        if (ftrace_push_return_trace(*parent, self_addr, &trace.depth,
 113                                     frame_pointer) == -EBUSY)
 114                return;
 115
 116        trace.func = self_addr;
 117
 118        /* Only trace if the calling function expects to */
 119        if (!ftrace_graph_entry(&trace)) {
 120                current->curr_ret_stack--;
 121                return;
 122        }
 123
 124        /* all is well in the world !  hijack RETS ... */
 125        *parent = return_hooker;
 126}
 127
 128#endif
 129