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fgraph: Create a fgraph.c file to store function graph infrastructure 

As the function graph infrastructure can be used by thing other than
tracing, moving the code to its own file out of the trace_functions_graph.c
code makes more sense.

The fgraph.c file will only contain the infrastructure required to hook into
functions and their return code.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-11-12 15:21:22 -05:00
parent c43ac4a530
commit d864a3ca88
3 changed files with 233 additions and 220 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
kernel/trace/Makefile
View File

@ -57,6 +57,7 @@ obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += trace_functions_graph.o
obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += fgraph.o
ifeq ($(CONFIG_BLOCK),y)
obj-$(CONFIG_EVENT_TRACING) += blktrace.o
endif

232
kernel/trace/fgraph.c Normal file
View File

@ -0,0 +1,232 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Infrastructure to took into function calls and returns.
* Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
* Mostly borrowed from function tracer which
* is Copyright (c) Steven Rostedt <srostedt@redhat.com>
*
* Highly modified by Steven Rostedt (VMware).
*/
#include <linux/ftrace.h>
#include "trace.h"
static bool kill_ftrace_graph;
/**
* ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
*
* ftrace_graph_stop() is called when a severe error is detected in
* the function graph tracing. This function is called by the critical
* paths of function graph to keep those paths from doing any more harm.
*/
bool ftrace_graph_is_dead(void)
{
return kill_ftrace_graph;
}
/**
* ftrace_graph_stop - set to permanently disable function graph tracincg
*
* In case of an error int function graph tracing, this is called
* to try to keep function graph tracing from causing any more harm.
* Usually this is pretty severe and this is called to try to at least
* get a warning out to the user.
*/
void ftrace_graph_stop(void)
{
kill_ftrace_graph = true;
}
/* Add a function return address to the trace stack on thread info.*/
static int
ftrace_push_return_trace(unsigned long ret, unsigned long func,
unsigned long frame_pointer, unsigned long *retp)
{
unsigned long long calltime;
int index;
if (unlikely(ftrace_graph_is_dead()))
return -EBUSY;
if (!current->ret_stack)
return -EBUSY;
/*
* We must make sure the ret_stack is tested before we read
* anything else.
*/
smp_rmb();
/* The return trace stack is full */
if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
atomic_inc(&current->trace_overrun);
return -EBUSY;
}
/*
* The curr_ret_stack is an index to ftrace return stack of
* current task. Its value should be in [0, FTRACE_RETFUNC_
* DEPTH) when the function graph tracer is used. To support
* filtering out specific functions, it makes the index
* negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
* so when it sees a negative index the ftrace will ignore
* the record. And the index gets recovered when returning
* from the filtered function by adding the FTRACE_NOTRACE_
* DEPTH and then it'll continue to record functions normally.
*
* The curr_ret_stack is initialized to -1 and get increased
* in this function. So it can be less than -1 only if it was
* filtered out via ftrace_graph_notrace_addr() which can be
* set from set_graph_notrace file in tracefs by user.
*/
if (current->curr_ret_stack < -1)
return -EBUSY;
calltime = trace_clock_local();
index = ++current->curr_ret_stack;
if (ftrace_graph_notrace_addr(func))
current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
barrier();
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;
current->ret_stack[index].calltime = calltime;
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
current->ret_stack[index].fp = frame_pointer;
#endif
#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
current->ret_stack[index].retp = retp;
#endif
return 0;
}
int function_graph_enter(unsigned long ret, unsigned long func,
unsigned long frame_pointer, unsigned long *retp)
{
struct ftrace_graph_ent trace;
trace.func = func;
trace.depth = ++current->curr_ret_depth;
if (ftrace_push_return_trace(ret, func, frame_pointer, retp))
goto out;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
goto out_ret;
return 0;
out_ret:
current->curr_ret_stack--;
out:
current->curr_ret_depth--;
return -EBUSY;
}
/* Retrieve a function return address to the trace stack on thread info.*/
static void
ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
unsigned long frame_pointer)
{
int index;
index = current->curr_ret_stack;
/*
* A negative index here means that it's just returned from a
* notrace'd function. Recover index to get an original
* return address. See ftrace_push_return_trace().
*
* TODO: Need to check whether the stack gets corrupted.
*/
if (index < 0)
index += FTRACE_NOTRACE_DEPTH;
if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic, otherwise we have no where to go */
*ret = (unsigned long)panic;
return;
}
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
/*
* The arch may choose to record the frame pointer used
* and check it here to make sure that it is what we expect it
* to be. If gcc does not set the place holder of the return
* address in the frame pointer, and does a copy instead, then
* the function graph trace will fail. This test detects this
* case.
*
* Currently, x86_32 with optimize for size (-Os) makes the latest
* gcc do the above.
*
* Note, -mfentry does not use frame pointers, and this test
* is not needed if CC_USING_FENTRY is set.
*/
if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
ftrace_graph_stop();
WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
" from func %ps return to %lx\n",
current->ret_stack[index].fp,
frame_pointer,
(void *)current->ret_stack[index].func,
current->ret_stack[index].ret);
*ret = (unsigned long)panic;
return;
}
#endif
*ret = current->ret_stack[index].ret;
trace->func = current->ret_stack[index].func;
trace->calltime = current->ret_stack[index].calltime;
trace->overrun = atomic_read(&current->trace_overrun);
trace->depth = current->curr_ret_depth--;
/*
* We still want to trace interrupts coming in if
* max_depth is set to 1. Make sure the decrement is
* seen before ftrace_graph_return.
*/
barrier();
}
/*
* Send the trace to the ring-buffer.
* @return the original return address.
*/
unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
{
struct ftrace_graph_ret trace;
unsigned long ret;
ftrace_pop_return_trace(&trace, &ret, frame_pointer);
trace.rettime = trace_clock_local();
ftrace_graph_return(&trace);
/*
* The ftrace_graph_return() may still access the current
* ret_stack structure, we need to make sure the update of
* curr_ret_stack is after that.
*/
barrier();
current->curr_ret_stack--;
/*
* The curr_ret_stack can be less than -1 only if it was
* filtered out and it's about to return from the function.
* Recover the index and continue to trace normal functions.
*/
if (current->curr_ret_stack < -1) {
current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
return ret;
}
if (unlikely(!ret)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic. What else to do? */
ret = (unsigned long)panic;
}
return ret;
}

220
kernel/trace/trace_functions_graph.c
View File

@ -16,33 +16,6 @@
#include "trace.h"
#include "trace_output.h"
static bool kill_ftrace_graph;
/**
* ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
*
* ftrace_graph_stop() is called when a severe error is detected in
* the function graph tracing. This function is called by the critical
* paths of function graph to keep those paths from doing any more harm.
*/
bool ftrace_graph_is_dead(void)
{
return kill_ftrace_graph;
}
/**
* ftrace_graph_stop - set to permanently disable function graph tracincg
*
* In case of an error int function graph tracing, this is called
* to try to keep function graph tracing from causing any more harm.
* Usually this is pretty severe and this is called to try to at least
* get a warning out to the user.
*/
void ftrace_graph_stop(void)
{
kill_ftrace_graph = true;
}
/* When set, irq functions will be ignored */
static int ftrace_graph_skip_irqs;
@ -117,199 +90,6 @@ static void
print_graph_duration(struct trace_array *tr, unsigned long long duration,
struct trace_seq *s, u32 flags);
/* Add a function return address to the trace stack on thread info.*/
static int
ftrace_push_return_trace(unsigned long ret, unsigned long func,
unsigned long frame_pointer, unsigned long *retp)
{
unsigned long long calltime;
int index;
if (unlikely(ftrace_graph_is_dead()))
return -EBUSY;
if (!current->ret_stack)
return -EBUSY;
/*
* We must make sure the ret_stack is tested before we read
* anything else.
*/
smp_rmb();
/* The return trace stack is full */
if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
atomic_inc(&current->trace_overrun);
return -EBUSY;
}
/*
* The curr_ret_stack is an index to ftrace return stack of
* current task. Its value should be in [0, FTRACE_RETFUNC_
* DEPTH) when the function graph tracer is used. To support
* filtering out specific functions, it makes the index
* negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
* so when it sees a negative index the ftrace will ignore
* the record. And the index gets recovered when returning
* from the filtered function by adding the FTRACE_NOTRACE_
* DEPTH and then it'll continue to record functions normally.
*
* The curr_ret_stack is initialized to -1 and get increased
* in this function. So it can be less than -1 only if it was
* filtered out via ftrace_graph_notrace_addr() which can be
* set from set_graph_notrace file in tracefs by user.
*/
if (current->curr_ret_stack < -1)
return -EBUSY;
calltime = trace_clock_local();
index = ++current->curr_ret_stack;
if (ftrace_graph_notrace_addr(func))
current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
barrier();
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;
current->ret_stack[index].calltime = calltime;
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
current->ret_stack[index].fp = frame_pointer;
#endif
#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
current->ret_stack[index].retp = retp;
#endif
return 0;
}
int function_graph_enter(unsigned long ret, unsigned long func,
unsigned long frame_pointer, unsigned long *retp)
{
struct ftrace_graph_ent trace;
trace.func = func;
trace.depth = ++current->curr_ret_depth;
if (ftrace_push_return_trace(ret, func, frame_pointer, retp))
goto out;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
goto out_ret;
return 0;
out_ret:
current->curr_ret_stack--;
out:
current->curr_ret_depth--;
return -EBUSY;
}
/* Retrieve a function return address to the trace stack on thread info.*/
static void
ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
unsigned long frame_pointer)
{
int index;
index = current->curr_ret_stack;
/*
* A negative index here means that it's just returned from a
* notrace'd function. Recover index to get an original
* return address. See ftrace_push_return_trace().
*
* TODO: Need to check whether the stack gets corrupted.
*/
if (index < 0)
index += FTRACE_NOTRACE_DEPTH;
if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic, otherwise we have no where to go */
*ret = (unsigned long)panic;
return;
}
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
/*
* The arch may choose to record the frame pointer used
* and check it here to make sure that it is what we expect it
* to be. If gcc does not set the place holder of the return
* address in the frame pointer, and does a copy instead, then
* the function graph trace will fail. This test detects this
* case.
*
* Currently, x86_32 with optimize for size (-Os) makes the latest
* gcc do the above.
*
* Note, -mfentry does not use frame pointers, and this test
* is not needed if CC_USING_FENTRY is set.
*/
if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
ftrace_graph_stop();
WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
" from func %ps return to %lx\n",
current->ret_stack[index].fp,
frame_pointer,
(void *)current->ret_stack[index].func,
current->ret_stack[index].ret);
*ret = (unsigned long)panic;
return;
}
#endif
*ret = current->ret_stack[index].ret;
trace->func = current->ret_stack[index].func;
trace->calltime = current->ret_stack[index].calltime;
trace->overrun = atomic_read(&current->trace_overrun);
trace->depth = current->curr_ret_depth--;
/*
* We still want to trace interrupts coming in if
* max_depth is set to 1. Make sure the decrement is
* seen before ftrace_graph_return.
*/
barrier();
}
/*
* Send the trace to the ring-buffer.
* @return the original return address.
*/
unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
{
struct ftrace_graph_ret trace;
unsigned long ret;
ftrace_pop_return_trace(&trace, &ret, frame_pointer);
trace.rettime = trace_clock_local();
ftrace_graph_return(&trace);
/*
* The ftrace_graph_return() may still access the current
* ret_stack structure, we need to make sure the update of
* curr_ret_stack is after that.
*/
barrier();
current->curr_ret_stack--;
/*
* The curr_ret_stack can be less than -1 only if it was
* filtered out and it's about to return from the function.
* Recover the index and continue to trace normal functions.
*/
if (current->curr_ret_stack < -1) {
current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
return ret;
}
if (unlikely(!ret)) {
ftrace_graph_stop();
WARN_ON(1);
/* Might as well panic. What else to do? */
ret = (unsigned long)panic;
}
return ret;
}
/**
* ftrace_graph_ret_addr - convert a potentially modified stack return address
* to its original value