Commit 5a45cfe1 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: use code patching for ftrace graph tracer 



Impact: more efficient code for ftrace graph tracer

This patch uses the dynamic patching, when available, to patch
the function graph code into the kernel.

This patch will ease the way for letting both function tracing
and function graph tracing run together.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent df4fc315

arch/x86/kernel/entry_32.S

+5 −0
Original line number Diff line number Diff line
@@ -1174,6 +1174,11 @@ ftrace_call: 
	popl %edx

	popl %ecx

	popl %eax

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

.globl ftrace_graph_call

ftrace_graph_call:

	jmp ftrace_stub

#endif



.globl ftrace_stub

ftrace_stub:

arch/x86/kernel/ftrace.c

+46 −2
Original line number Diff line number Diff line
@@ -111,7 +111,6 @@ static void ftrace_mod_code(void) 
	 */

	mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,

					     MCOUNT_INSN_SIZE);



}



void ftrace_nmi_enter(void)
@@ -325,7 +324,51 @@ int __init ftrace_dyn_arch_init(void *data) 


#ifdef CONFIG_FUNCTION_GRAPH_TRACER



#ifndef CONFIG_DYNAMIC_FTRACE

#ifdef CONFIG_DYNAMIC_FTRACE

extern void ftrace_graph_call(void);



static int ftrace_mod_jmp(unsigned long ip,

			  int old_offset, int new_offset)

{

	unsigned char code[MCOUNT_INSN_SIZE];



	if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))

		return -EFAULT;



	if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))

		return -EINVAL;



	*(int *)(&code[1]) = new_offset;



	if (do_ftrace_mod_code(ip, &code))

		return -EPERM;



	return 0;

}



int ftrace_enable_ftrace_graph_caller(void)

{

	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	int old_offset, new_offset;



	old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);

	new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);



	return ftrace_mod_jmp(ip, old_offset, new_offset);

}



int ftrace_disable_ftrace_graph_caller(void)

{

	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	int old_offset, new_offset;



	old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);

	new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);



	return ftrace_mod_jmp(ip, old_offset, new_offset);

}



#else /* CONFIG_DYNAMIC_FTRACE */



/*

 * These functions are picked from those used on
@@ -343,6 +386,7 @@ void ftrace_nmi_exit(void) 
{

	atomic_dec(&in_nmi);

}



#endif /* !CONFIG_DYNAMIC_FTRACE */



/* Add a function return address to the trace stack on thread info.*/

include/linux/ftrace.h

+5 −0
Original line number Diff line number Diff line
@@ -117,6 +117,11 @@ extern void ftrace_call(void); 
extern void mcount_call(void);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

extern void ftrace_graph_caller(void);

extern int ftrace_enable_ftrace_graph_caller(void);

extern int ftrace_disable_ftrace_graph_caller(void);

#else

static inline int ftrace_enable_ftrace_graph_caller(void) { return 0; }

static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; }

#endif



/**

kernel/trace/ftrace.c

+16 −19
Original line number Diff line number Diff line
@@ -281,6 +281,8 @@ enum { 
	FTRACE_UPDATE_TRACE_FUNC	= (1 << 2),

	FTRACE_ENABLE_MCOUNT		= (1 << 3),

	FTRACE_DISABLE_MCOUNT		= (1 << 4),

	FTRACE_START_FUNC_RET		= (1 << 5),

	FTRACE_STOP_FUNC_RET		= (1 << 6),

};



static int ftrace_filtered;
@@ -465,14 +467,7 @@ __ftrace_replace_code(struct dyn_ftrace *rec, int enable) 
	unsigned long ip, fl;

	unsigned long ftrace_addr;



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	if (ftrace_tracing_type == FTRACE_TYPE_ENTER)

		ftrace_addr = (unsigned long)ftrace_caller;

	else

		ftrace_addr = (unsigned long)ftrace_graph_caller;

#else

	ftrace_addr = (unsigned long)ftrace_caller;

#endif



	ip = rec->ip;
@@ -605,6 +600,11 @@ static int __ftrace_modify_code(void *data) 
	if (*command & FTRACE_UPDATE_TRACE_FUNC)

		ftrace_update_ftrace_func(ftrace_trace_function);



	if (*command & FTRACE_START_FUNC_RET)

		ftrace_enable_ftrace_graph_caller();

	else if (*command & FTRACE_STOP_FUNC_RET)

		ftrace_disable_ftrace_graph_caller();



	return 0;

}
@@ -629,10 +629,8 @@ static void ftrace_startup_enable(int command) 
	ftrace_run_update_code(command);

}



static void ftrace_startup(void)

static void ftrace_startup(int command)

{

	int command = 0;



	if (unlikely(ftrace_disabled))

		return;
@@ -645,10 +643,8 @@ static void ftrace_startup(void) 
	mutex_unlock(&ftrace_start_lock);

}



static void ftrace_shutdown(void)

static void ftrace_shutdown(int command)

{

	int command = 0;



	if (unlikely(ftrace_disabled))

		return;
@@ -1453,8 +1449,9 @@ device_initcall(ftrace_nodyn_init); 


static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }

static inline void ftrace_startup_enable(int command) { }

# define ftrace_startup()		do { } while (0)

# define ftrace_shutdown()		do { } while (0)

/* Keep as macros so we do not need to define the commands */

# define ftrace_startup(command)	do { } while (0)

# define ftrace_shutdown(command)	do { } while (0)

# define ftrace_startup_sysctl()	do { } while (0)

# define ftrace_shutdown_sysctl()	do { } while (0)

#endif /* CONFIG_DYNAMIC_FTRACE */
@@ -1585,7 +1582,7 @@ int register_ftrace_function(struct ftrace_ops *ops) 
	}



	ret = __register_ftrace_function(ops);

	ftrace_startup();

	ftrace_startup(0);



out:

	mutex_unlock(&ftrace_sysctl_lock);
@@ -1604,7 +1601,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops) 


	mutex_lock(&ftrace_sysctl_lock);

	ret = __unregister_ftrace_function(ops);

	ftrace_shutdown();

	ftrace_shutdown(0);

	mutex_unlock(&ftrace_sysctl_lock);



	return ret;
@@ -1751,7 +1748,7 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc, 
	ftrace_tracing_type = FTRACE_TYPE_RETURN;

	ftrace_graph_return = retfunc;

	ftrace_graph_entry = entryfunc;

	ftrace_startup();

	ftrace_startup(FTRACE_START_FUNC_RET);



out:

	mutex_unlock(&ftrace_sysctl_lock);
@@ -1765,7 +1762,7 @@ void unregister_ftrace_graph(void) 
	atomic_dec(&ftrace_graph_active);

	ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;

	ftrace_graph_entry = (trace_func_graph_ent_t)ftrace_stub;

	ftrace_shutdown();

	ftrace_shutdown(FTRACE_STOP_FUNC_RET);

	/* Restore normal tracing type */

	ftrace_tracing_type = FTRACE_TYPE_ENTER;

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