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
  17 static const unsigned char mnop[] = {
  18         0x03, 0xc0, 0x00, 0x18, /* MNOP; */
  19         0x03, 0xc0, 0x00, 0x18, /* MNOP; */
  20 };
  21
  22 static 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
  33 static 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
  41 int 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
  48 int 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
  60 int 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
  68 int __init ftrace_dyn_arch_init(void)
  69 {
  70         return 0;
  71 }
  72
  73 #endif
  74
  75 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  76
  77 # ifdef CONFIG_DYNAMIC_FTRACE
  78
  79 extern void ftrace_graph_call(void);
  80
  81 int ftrace_enable_ftrace_graph_caller(void)
  82 {
  83         unsigned long ip = (unsigned long)&ftrace_graph_call;
  84         uint16_t jump_pcrel12 = ((unsigned long)&ftrace_graph_caller - ip) >> 1;
  85         jump_pcrel12 |= 0x2000;
  86         return ftrace_modify_code(ip, (void *)&jump_pcrel12, sizeof(jump_pcrel12));
  87 }
  88
  89 int ftrace_disable_ftrace_graph_caller(void)
  90 {
  91         return ftrace_modify_code((unsigned long)&ftrace_graph_call, empty_zero_page, 2);
  92 }
  93
  94 # endif
  95
  96 /*
  97  * Hook the return address and push it in the stack of return addrs
  98  * in current thread info.
  99  */
 100 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 101                            unsigned long frame_pointer)
 102 {
 103         struct ftrace_graph_ent trace;
 104         unsigned long return_hooker = (unsigned long)&return_to_handler;
 105
 106         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 107                 return;
 108
 109         if (ftrace_push_return_trace(*parent, self_addr, &trace.depth,
 110                                      frame_pointer) == -EBUSY)
 111                 return;
 112
 113         trace.func = self_addr;
 114
 115         /* Only trace if the calling function expects to */
 116         if (!ftrace_graph_entry(&trace)) {
 117                 current->curr_ret_stack--;
 118                 return;
 119         }
 120
 121         /* all is well in the world !  hijack RETS ... */
 122         *parent = return_hooker;
 123 }
 124
 125 #endif