Commit 8b96f011 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

tracing/function-graph-tracer: introduce __notrace_funcgraph to filter special functions 



Impact: trace more functions

When the function graph tracer is configured, three more files are not
traced to prevent only four functions to be traced. And this impacts the
normal function tracer too.

arch/x86/kernel/process_64/32.c:

I had crashes when I let this file traced. After some debugging, I saw
that the "current" task point was changed inside__swtich_to(), ie:
"write_pda(pcurrent, next_p);" inside process_64.c Since the tracer store
the original return address of the function inside current, we had
crashes. Only __switch_to() has to be excluded from tracing.

kernel/module.c and kernel/extable.c:

Because of a function used internally by the function graph tracer:
__kernel_text_address()

To let the other functions inside these files to be traced, this patch
introduces the __notrace_funcgraph function prefix which is __notrace if
function graph tracer is configured and nothing if not.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent decbec38

arch/x86/kernel/Makefile

+0 −6
Original line number Diff line number Diff line
@@ -14,12 +14,6 @@ CFLAGS_REMOVE_paravirt-spinlocks.o = -pg 
CFLAGS_REMOVE_ftrace.o = -pg

endif



ifdef CONFIG_FUNCTION_GRAPH_TRACER

# Don't trace __switch_to() but let it for function tracer

CFLAGS_REMOVE_process_32.o = -pg

CFLAGS_REMOVE_process_64.o = -pg

endif



#

# vsyscalls (which work on the user stack) should have

# no stack-protector checks:

arch/x86/kernel/process_32.c

+3 −1
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <linux/percpu.h>

#include <linux/prctl.h>

#include <linux/dmi.h>

#include <linux/ftrace.h>



#include <asm/uaccess.h>

#include <asm/pgtable.h>
@@ -548,7 +549,8 @@ __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, 
 * the task-switch, and shows up in ret_from_fork in entry.S,

 * for example.

 */

struct task_struct * __switch_to(struct task_struct *prev_p, struct task_struct *next_p)

__notrace_funcgraph struct task_struct *

__switch_to(struct task_struct *prev_p, struct task_struct *next_p)

{

	struct thread_struct *prev = &prev_p->thread,

				 *next = &next_p->thread;

arch/x86/kernel/process_64.c

+3 −1
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include <linux/prctl.h>

#include <linux/uaccess.h>

#include <linux/io.h>

#include <linux/ftrace.h>



#include <asm/pgtable.h>

#include <asm/system.h>
@@ -551,8 +552,9 @@ static inline void __switch_to_xtra(struct task_struct *prev_p, 
 * - could test fs/gs bitsliced

 *

 * Kprobes not supported here. Set the probe on schedule instead.

 * Function graph tracer not supported too.

 */

struct task_struct *

__notrace_funcgraph struct task_struct *

__switch_to(struct task_struct *prev_p, struct task_struct *next_p)

{

	struct thread_struct *prev = &prev_p->thread;

include/linux/ftrace.h

+11 −0
Original line number Diff line number Diff line
@@ -369,6 +369,14 @@ struct ftrace_graph_ret { 
};



#ifdef CONFIG_FUNCTION_GRAPH_TRACER



/*

 * Sometimes we don't want to trace a function with the function

 * graph tracer but we want them to keep traced by the usual function

 * tracer if the function graph tracer is not configured.

 */

#define __notrace_funcgraph		notrace



#define FTRACE_RETFUNC_DEPTH 50

#define FTRACE_RETSTACK_ALLOC_SIZE 32

/* Type of the callback handlers for tracing function graph*/
@@ -394,6 +402,9 @@ static inline int task_curr_ret_stack(struct task_struct *t) 
	return t->curr_ret_stack;

}

#else



#define __notrace_funcgraph



static inline void ftrace_graph_init_task(struct task_struct *t) { }

static inline void ftrace_graph_exit_task(struct task_struct *t) { }

kernel/Makefile

+0 −4
Original line number Diff line number Diff line
@@ -21,10 +21,6 @@ CFLAGS_REMOVE_cgroup-debug.o = -pg 
CFLAGS_REMOVE_sched_clock.o = -pg

CFLAGS_REMOVE_sched.o = -pg

endif

ifdef CONFIG_FUNCTION_GRAPH_TRACER

CFLAGS_REMOVE_extable.o = -pg # For __kernel_text_address()

CFLAGS_REMOVE_module.o = -pg # For __module_text_address()

endif



obj-$(CONFIG_FREEZER) += freezer.o

obj-$(CONFIG_PROFILING) += profile.o

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