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/*
* Code for tracing calls in Linux kernel.
* Copyright (C) 2009 Helge Deller <deller@gmx.de>
*
* based on code for x86 which is:
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
*
* future possible enhancements:
* - add CONFIG_DYNAMIC_FTRACE
* - add CONFIG_STACK_TRACER
*/
#include <linux/init.h>
#include <linux/ftrace.h>
#include <asm/sections.h>
#include <asm/ftrace.h>
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* Add a function return address to the trace stack on thread info.*/
static int push_return_trace(unsigned long ret, unsigned long long time,
unsigned long func, int *depth)
{
int index;
if (!current->ret_stack)
return -EBUSY;
/* The return trace stack is full */
if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
atomic_inc(¤t->trace_overrun);
return -EBUSY;
}
index = ++current->curr_ret_stack;
barrier();
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;
current->ret_stack[index].calltime = time;
*depth = index;
return 0;
}
/* Retrieve a function return address to the trace stack on thread info.*/
static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
{
int index;
index = current->curr_ret_stack;
if (unlikely(index < 0)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic, otherwise we have no where to go */
*ret = (unsigned long)
dereference_function_descriptor(&panic);
return;
}
*ret = current->ret_stack[index].ret;
trace->func = current->ret_stack[index].func;
trace->calltime = current->ret_stack[index].calltime;
trace->overrun = atomic_read(¤t->trace_overrun);
trace->depth = index;
barrier();
current->curr_ret_stack--;
}
/*
* Send the trace to the ring-buffer.
* @return the original return address.
*/
unsigned long ftrace_return_to_handler(unsigned long retval0,
unsigned long retval1)
{
struct ftrace_graph_ret trace;
unsigned long ret;
pop_return_trace(&trace, &ret);
trace.rettime = local_clock();
ftrace_graph_return(&trace);
if (unlikely(!ret)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic. What else to do? */
ret = (unsigned long)
dereference_function_descriptor(&panic);
}
/* HACK: we hand over the old functions' return values
in %r23 and %r24. Assembly in entry.S will take care
and move those to their final registers %ret0 and %ret1 */
asm( "copy %0, %%r23 \n\t"
"copy %1, %%r24 \n" : : "r" (retval0), "r" (retval1) );
return ret;
}
/*
* Hook the return address and push it in the stack of return addrs
* in current thread info.
*/
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
{
unsigned long old;
unsigned long long calltime;
struct ftrace_graph_ent trace;
if (unlikely(ftrace_graph_is_dead()))
return;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
old = *parent;
*parent = (unsigned long)
dereference_function_descriptor(&return_to_handler);
if (unlikely(!__kernel_text_address(old))) {
ftrace_graph_stop();
*parent = old;
WARN_ON(1);
return;
}
calltime = local_clock();
if (push_return_trace(old, calltime,
self_addr, &trace.depth) == -EBUSY) {
*parent = old;
return;
}
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
*parent = old;
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
void ftrace_function_trampoline(unsigned long parent,
unsigned long self_addr,
unsigned long org_sp_gr3)
{
extern ftrace_func_t ftrace_trace_function;
if (function_trace_stop)
return;
if (ftrace_trace_function != ftrace_stub) {
ftrace_trace_function(parent, self_addr);
return;
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (ftrace_graph_entry && ftrace_graph_return) {
unsigned long sp;
unsigned long *parent_rp;
asm volatile ("copy %%r30, %0" : "=r"(sp));
/* sanity check: is stack pointer which we got from
assembler function in entry.S in a reasonable
range compared to current stack pointer? */
if ((sp - org_sp_gr3) > 0x400)
return;
/* calculate pointer to %rp in stack */
parent_rp = (unsigned long *) org_sp_gr3 - 0x10;
/* sanity check: parent_rp should hold parent */
if (*parent_rp != parent)
return;
prepare_ftrace_return(parent_rp, self_addr);
return;
}
#endif
}
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