arch/parisc/kernel/ftrace.c

   1 /*
   2  * Code for tracing calls in Linux kernel.
   3  * Copyright (C) 2009 Helge Deller <deller@gmx.de>
   4  *
   5  * based on code for x86 which is:
   6  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   7  *
   8  * future possible enhancements:
   9  *      - add CONFIG_DYNAMIC_FTRACE
  10  *      - add CONFIG_STACK_TRACER
  11  */
  12
  13 #include <linux/init.h>
  14 #include <linux/ftrace.h>
  15
  16 #include <asm/sections.h>
  17 #include <asm/ftrace.h>
  18
  19
  20
  21 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  22
  23 /* Add a function return address to the trace stack on thread info.*/
  24 static int push_return_trace(unsigned long ret, unsigned long long time,
  25                                 unsigned long func, int *depth)
  26 {
  27         int index;
  28
  29         if (!current->ret_stack)
  30                 return -EBUSY;
  31
  32         /* The return trace stack is full */
  33         if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
  34                 atomic_inc(&current->trace_overrun);
  35                 return -EBUSY;
  36         }
  37
  38         index = ++current->curr_ret_stack;
  39         barrier();
  40         current->ret_stack[index].ret = ret;
  41         current->ret_stack[index].func = func;
  42         current->ret_stack[index].calltime = time;
  43         *depth = index;
  44
  45         return 0;
  46 }
  47
  48 /* Retrieve a function return address to the trace stack on thread info.*/
  49 static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
  50 {
  51         int index;
  52
  53         index = current->curr_ret_stack;
  54
  55         if (unlikely(index < 0)) {
  56                 ftrace_graph_stop();
  57                 WARN_ON(1);
  58                 /* Might as well panic, otherwise we have no where to go */
  59                 *ret = (unsigned long)
  60                         dereference_function_descriptor(&panic);
  61                 return;
  62         }
  63
  64         *ret = current->ret_stack[index].ret;
  65         trace->func = current->ret_stack[index].func;
  66         trace->calltime = current->ret_stack[index].calltime;
  67         trace->overrun = atomic_read(&current->trace_overrun);
  68         trace->depth = index;
  69         barrier();
  70         current->curr_ret_stack--;
  71
  72 }
  73
  74 /*
  75  * Send the trace to the ring-buffer.
  76  * @return the original return address.
  77  */
  78 unsigned long ftrace_return_to_handler(unsigned long retval0,
  79                                        unsigned long retval1)
  80 {
  81         struct ftrace_graph_ret trace;
  82         unsigned long ret;
  83
  84         pop_return_trace(&trace, &ret);
  85         trace.rettime = cpu_clock(raw_smp_processor_id());
  86         ftrace_graph_return(&trace);
  87
  88         if (unlikely(!ret)) {
  89                 ftrace_graph_stop();
  90                 WARN_ON(1);
  91                 /* Might as well panic. What else to do? */
  92                 ret = (unsigned long)
  93                         dereference_function_descriptor(&panic);
  94         }
  95
  96         /* HACK: we hand over the old functions' return values
  97            in %r23 and %r24. Assembly in entry.S will take care
  98            and move those to their final registers %ret0 and %ret1 */
  99         asm( "copy %0, %%r23 \n\t"
 100              "copy %1, %%r24 \n" : : "r" (retval0), "r" (retval1) );
 101
 102         return ret;
 103 }
 104
 105 /*
 106  * Hook the return address and push it in the stack of return addrs
 107  * in current thread info.
 108  */
 109 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 110 {
 111         unsigned long old;
 112         unsigned long long calltime;
 113         struct ftrace_graph_ent trace;
 114
 115         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 116                 return;
 117
 118         old = *parent;
 119         *parent = (unsigned long)
 120                   dereference_function_descriptor(&return_to_handler);
 121
 122         if (unlikely(!__kernel_text_address(old))) {
 123                 ftrace_graph_stop();
 124                 *parent = old;
 125                 WARN_ON(1);
 126                 return;
 127         }
 128
 129         calltime = cpu_clock(raw_smp_processor_id());
 130
 131         if (push_return_trace(old, calltime,
 132                                 self_addr, &trace.depth) == -EBUSY) {
 133                 *parent = old;
 134                 return;
 135         }
 136
 137         trace.func = self_addr;
 138
 139         /* Only trace if the calling function expects to */
 140         if (!ftrace_graph_entry(&trace)) {
 141                 current->curr_ret_stack--;
 142                 *parent = old;
 143         }
 144 }
 145
 146 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 147
 148
 149 void ftrace_function_trampoline(unsigned long parent,
 150                                 unsigned long self_addr,
 151                                 unsigned long org_sp_gr3)
 152 {
 153         extern ftrace_func_t ftrace_trace_function;
 154
 155         if (function_trace_stop)
 156                 return;
 157
 158         if (ftrace_trace_function != ftrace_stub) {
 159                 ftrace_trace_function(parent, self_addr);
 160                 return;
 161         }
 162 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 163         if (ftrace_graph_entry && ftrace_graph_return) {
 164                 unsigned long sp;
 165                 unsigned long *parent_rp;
 166
 167                 asm volatile ("copy %%r30, %0" : "=r"(sp));
 168                 /* sanity check: is stack pointer which we got from
 169                    assembler function in entry.S in a reasonable
 170                    range compared to current stack pointer? */
 171                 if ((sp - org_sp_gr3) > 0x400)
 172                         return;
 173
 174                 /* calculate pointer to %rp in stack */
 175                 parent_rp = (unsigned long *) org_sp_gr3 - 0x10;
 176                 /* sanity check: parent_rp should hold parent */
 177                 if (*parent_rp != parent)
 178                         return;
 179
 180                 prepare_ftrace_return(parent_rp, self_addr);
 181                 return;
 182         }
 183 #endif
 184 }
 185