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: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a3049da61985f777bbbcc0c2eedb9b3820b4d63b..1cad9318d2172f16e3269dda122b093a54ef4107 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -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:

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 0a1302fe6d45307ffa880ed9e355050a194518af..24c2276aa453dfbfe4ffabec3e05cd30d93db1e0 100644 (file)
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -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;

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index c958120fb1b6f549f853a79a26864abeb38ceb24..fbb321d53d3495990c946ecbfa51f2ddfdc2ad19 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -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;

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index b9b4d0a22d10b6209a5f4dd0b0b3f1c44ea26278..449fa8e9e34f574602183ca647f179bf4deb7d1e 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -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) { }
 

diff --git a/kernel/Makefile b/kernel/Makefile
index 703cf3b7389cefa72d7dbb311d069a5a90cb5e17..19fad003b19d6ac0752597f5a23e18341d1d579a 100644 (file)
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -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

diff --git a/kernel/extable.c b/kernel/extable.c
index a26cb2e170237d849c9f87038a6def48ee948dd6..feb0317cf09ab5960d0288a31ec00d03ae5a6335 100644 (file)
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -17,6 +17,7 @@
 */
 #include <linux/module.h>
 #include <linux/init.h>
+#include <linux/ftrace.h>
 #include <asm/uaccess.h>
 #include <asm/sections.h>
 
@@ -40,7 +41,7 @@ const struct exception_table_entry *search_exception_tables(unsigned long addr)
        return e;
 }
 
-int core_kernel_text(unsigned long addr)
+__notrace_funcgraph int core_kernel_text(unsigned long addr)
 {
        if (addr >= (unsigned long)_stext &&
            addr <= (unsigned long)_etext)
@@ -53,7 +54,7 @@ int core_kernel_text(unsigned long addr)
        return 0;
 }
 
-int __kernel_text_address(unsigned long addr)
+__notrace_funcgraph int __kernel_text_address(unsigned long addr)
 {
        if (core_kernel_text(addr))
                return 1;

diff --git a/kernel/module.c b/kernel/module.c
index 89bcf7c1327d7dc0ffd0f9fbb365bd67f9109767..dd2a54155b54ab45df7ac5a9e7e13344e4611b1e 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2704,7 +2704,7 @@ int is_module_address(unsigned long addr)
 
 
 /* Is this a valid kernel address? */
-struct module *__module_text_address(unsigned long addr)
+__notrace_funcgraph struct module *__module_text_address(unsigned long addr)
 {
        struct module *mod;