Commit 16444a8a authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo Committed by Thomas Gleixner
Browse files

ftrace: add basic support for gcc profiler instrumentation 



If CONFIG_FTRACE is selected and /proc/sys/kernel/ftrace_enabled is
set to a non-zero value the ftrace routine will be called everytime
we enter a kernel function that is not marked with the "notrace"
attribute.

The ftrace routine will then call a registered function if a function
happens to be registered.

[ This code has been highly hacked by Steven Rostedt and Ingo Molnar,
  so don't blame Arnaldo for all of this ;-) ]

Update:
  It is now possible to register more than one ftrace function.
  If only one ftrace function is registered, that will be the
  function that ftrace calls directly. If more than one function
  is registered, then ftrace will call a function that will loop
  through the functions to call.

Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 6e766410

Makefile

+4 −0
Original line number Diff line number Diff line
@@ -528,6 +528,10 @@ KBUILD_CFLAGS += -g 
KBUILD_AFLAGS	+= -gdwarf-2

endif



ifdef CONFIG_FTRACE

KBUILD_CFLAGS	+= -pg

endif



# We trigger additional mismatches with less inlining

ifdef CONFIG_DEBUG_SECTION_MISMATCH

KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ config X86 
	select HAVE_OPROFILE

	select HAVE_KPROBES

	select HAVE_KRETPROBES

	select HAVE_FTRACE

	select HAVE_KVM if ((X86_32 && !X86_VOYAGER && !X86_VISWS && !X86_NUMAQ) || X86_64)

	select HAVE_ARCH_KGDB if !X86_VOYAGER

arch/x86/kernel/entry_32.S

+27 −0
Original line number Diff line number Diff line
@@ -1109,6 +1109,33 @@ ENDPROC(xen_failsafe_callback) 


#endif	/* CONFIG_XEN */



#ifdef CONFIG_FTRACE

ENTRY(mcount)

	cmpl $ftrace_stub, ftrace_trace_function

	jnz trace



.globl ftrace_stub

ftrace_stub:

	ret



	/* taken from glibc */

trace:

	pushl %eax

	pushl %ecx

	pushl %edx

	movl 0xc(%esp), %eax

	movl 0x4(%ebp), %edx



	call   *ftrace_trace_function



	popl %edx

	popl %ecx

	popl %eax



	jmp ftrace_stub

END(mcount)

#endif



.section .rodata,"a"

#include "syscall_table_32.S"

arch/x86/kernel/entry_64.S

+37 −0
Original line number Diff line number Diff line
@@ -54,6 +54,43 @@ 


	.code64



#ifdef CONFIG_FTRACE

ENTRY(mcount)

	cmpq $ftrace_stub, ftrace_trace_function

	jnz trace

.globl ftrace_stub

ftrace_stub:

	retq



trace:

	/* taken from glibc */

	subq $0x38, %rsp

	movq %rax, (%rsp)

	movq %rcx, 8(%rsp)

	movq %rdx, 16(%rsp)

	movq %rsi, 24(%rsp)

	movq %rdi, 32(%rsp)

	movq %r8, 40(%rsp)

	movq %r9, 48(%rsp)



	movq 0x38(%rsp), %rdi

	movq 8(%rbp), %rsi



	call   *ftrace_trace_function



	movq 48(%rsp), %r9

	movq 40(%rsp), %r8

	movq 32(%rsp), %rdi

	movq 24(%rsp), %rsi

	movq 16(%rsp), %rdx

	movq 8(%rsp), %rcx

	movq (%rsp), %rax

	addq $0x38, %rsp



	jmp ftrace_stub

END(mcount)

#endif



#ifndef CONFIG_PREEMPT

#define retint_kernel retint_restore_args

#endif

include/linux/ftrace.h

0 → 100644
+38 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_FTRACE_H

#define _LINUX_FTRACE_H



#ifdef CONFIG_FTRACE



#include <linux/linkage.h>



#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))

#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))

#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))



typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip);



struct ftrace_ops {

	ftrace_func_t	  func;

	struct ftrace_ops *next;

};



/*

 * The ftrace_ops must be a static and should also

 * be read_mostly.  These functions do modify read_mostly variables

 * so use them sparely. Never free an ftrace_op or modify the

 * next pointer after it has been registered. Even after unregistering

 * it, the next pointer may still be used internally.

 */

int register_ftrace_function(struct ftrace_ops *ops);

int unregister_ftrace_function(struct ftrace_ops *ops);

void clear_ftrace_function(void);



extern void ftrace_stub(unsigned long a0, unsigned long a1);

extern void mcount(void);



#else /* !CONFIG_FTRACE */

# define register_ftrace_function(ops) do { } while (0)

# define unregister_ftrace_function(ops) do { } while (0)

# define clear_ftrace_function(ops) do { } while (0)

#endif /* CONFIG_FTRACE */

#endif /* _LINUX_FTRACE_H */

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