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Commit caf4b323 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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tracing, x86: add low level support for ftrace return tracing 



Impact: add infrastructure for function-return tracing

Add low level support for ftrace return tracing.

This plug-in stores return addresses on the thread_info structure of
the current task.

The index of the current return address is initialized when the task
is the first one (init) and when a process forks (the child). It is
not needed when a task does a sys_execve because after this syscall,
it still needs to return on the kernel functions it called.

Note that the code of return_to_handler has been suggested by Steven
Rostedt as almost all of the ideas of improvements in this V3.

For purpose of security, arch/x86/kernel/process_32.c is not traced
because __switch_to() changes the current task during its execution.
That could cause inconsistency in the stored return address of this
function even if I didn't have any crash after testing with tracing on
this function enabled.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d844222a

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ config 64BIT 


config X86_32

	def_bool !64BIT

	select HAVE_FUNCTION_RET_TRACER



config X86_64

	def_bool 64BIT

arch/x86/include/asm/ftrace.h

+26 −0
Original line number Diff line number Diff line
@@ -20,4 +20,30 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 
#endif /* __ASSEMBLY__ */

#endif /* CONFIG_FUNCTION_TRACER */



#ifdef CONFIG_FUNCTION_RET_TRACER

#define FTRACE_RET_STACK_SIZE 20



#ifndef __ASSEMBLY__



/*

 * Stack of return addresses for functions

 * of a thread.

 * Used in struct thread_info

 */

struct ftrace_ret_stack {

	unsigned long ret;

	unsigned long func;

	unsigned long long calltime;

};



/*

 * Primary handler of a function return.

 * It relays on ftrace_return_to_handler.

 * Defined in entry32.S

 */

extern void return_to_handler(void);



#endif /* __ASSEMBLY__ */

#endif /* CONFIG_FUNCTION_RET_TRACER */



#endif /* _ASM_X86_FTRACE_H */

arch/x86/include/asm/thread_info.h

+24 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
struct task_struct;

struct exec_domain;

#include <asm/processor.h>

#include <asm/ftrace.h>



struct thread_info {

	struct task_struct	*task;		/* main task structure */
@@ -38,8 +39,30 @@ struct thread_info { 
						*/

	__u8			supervisor_stack[0];

#endif



#ifdef CONFIG_FUNCTION_RET_TRACER

	/* Index of current stored adress in ret_stack */

	int		curr_ret_stack;

	/* Stack of return addresses for return function tracing */

	struct ftrace_ret_stack	ret_stack[FTRACE_RET_STACK_SIZE];

#endif

};



#ifdef CONFIG_FUNCTION_RET_TRACER

#define INIT_THREAD_INFO(tsk)			\

{						\

	.task		= &tsk,			\

	.exec_domain	= &default_exec_domain,	\

	.flags		= 0,			\

	.cpu		= 0,			\

	.preempt_count	= 1,			\

	.addr_limit	= KERNEL_DS,		\

	.restart_block = {			\

		.fn = do_no_restart_syscall,	\

	},					\

	.curr_ret_stack = -1,\

}

#else

#define INIT_THREAD_INFO(tsk)			\

{						\

	.task		= &tsk,			\
@@ -52,6 +75,7 @@ struct thread_info { 
		.fn = do_no_restart_syscall,	\

	},					\

}

#endif



#define init_thread_info	(init_thread_union.thread_info)

#define init_stack		(init_thread_union.stack)

arch/x86/kernel/Makefile

+6 −0
Original line number Diff line number Diff line
@@ -14,6 +14,11 @@ CFLAGS_REMOVE_paravirt-spinlocks.o = -pg 
CFLAGS_REMOVE_ftrace.o = -pg

endif



ifdef CONFIG_FUNCTION_RET_TRACER

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

CFLAGS_REMOVE_process_32.o = -pg

endif



#

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

# no stack-protector checks:
@@ -65,6 +70,7 @@ obj-$(CONFIG_X86_LOCAL_APIC) += apic.o nmi.o 
obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o

obj-$(CONFIG_X86_REBOOTFIXUPS)	+= reboot_fixups_32.o

obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o

obj-$(CONFIG_FUNCTION_RET_TRACER)	+= ftrace.o

obj-$(CONFIG_KEXEC)		+= machine_kexec_$(BITS).o

obj-$(CONFIG_KEXEC)		+= relocate_kernel_$(BITS).o crash.o

obj-$(CONFIG_CRASH_DUMP)	+= crash_dump_$(BITS).o

arch/x86/kernel/entry_32.S

+33 −0
Original line number Diff line number Diff line
@@ -1188,6 +1188,10 @@ ENTRY(mcount) 


	cmpl $ftrace_stub, ftrace_trace_function

	jnz trace

#ifdef CONFIG_FUNCTION_RET_TRACER

	cmpl $ftrace_stub, ftrace_function_return

	jnz trace_return

#endif

.globl ftrace_stub

ftrace_stub:

	ret
@@ -1206,8 +1210,37 @@ trace: 
	popl %edx

	popl %ecx

	popl %eax

	jmp ftrace_stub



#ifdef CONFIG_FUNCTION_RET_TRACER

trace_return:

	pushl %eax

	pushl %ecx

	pushl %edx

	movl 0xc(%esp), %eax

	pushl %eax

	lea 0x4(%ebp), %eax

	pushl %eax

	call prepare_ftrace_return

	addl $8, %esp

	popl %edx

	popl %ecx

	popl %eax

	jmp ftrace_stub



.globl return_to_handler

return_to_handler:

	pushl $0

	pushl %eax

	pushl %ecx

	pushl %edx

	call ftrace_return_to_handler

	movl %eax, 0xc(%esp)

	popl %edx

	popl %ecx

	popl %eax

	ret

#endif /* CONFIG_FUNCTION_RET_TRACER */

END(mcount)

#endif /* CONFIG_DYNAMIC_FTRACE */

#endif /* CONFIG_FUNCTION_TRACER */