Commit 819e50e2 authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Will Deacon
Browse files

arm64: Add ftrace support 



This patch implements arm64 specific part to support function tracers,
such as function (CONFIG_FUNCTION_TRACER), function_graph
(CONFIG_FUNCTION_GRAPH_TRACER) and function profiler
(CONFIG_FUNCTION_PROFILER).

With 'function' tracer, all the functions in the kernel are traced with
timestamps in ${sysfs}/tracing/trace. If function_graph tracer is
specified, call graph is generated.

The kernel must be compiled with -pg option so that _mcount() is inserted
at the beginning of functions. This function is called on every function's
entry as long as tracing is enabled.
In addition, function_graph tracer also needs to be able to probe function's
exit. ftrace_graph_caller() & return_to_handler do this by faking link
register's value to intercept function's return path.

More details on architecture specific requirements are described in
Documentation/trace/ftrace-design.txt.

Reviewed-by: default avatarGanapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent af64d2aa

arch/arm64/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -38,6 +38,8 @@ config ARM64 
	select HAVE_DMA_CONTIGUOUS

	select HAVE_EFFICIENT_UNALIGNED_ACCESS

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FUNCTION_TRACER

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_GENERIC_DMA_COHERENT

	select HAVE_HW_BREAKPOINT if PERF_EVENTS

	select HAVE_MEMBLOCK

arch/arm64/include/asm/ftrace.h

0 → 100644
+23 −0
Original line number Diff line number Diff line 
/*

 * arch/arm64/include/asm/ftrace.h

 *

 * Copyright (C) 2013 Linaro Limited

 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#ifndef __ASM_FTRACE_H

#define __ASM_FTRACE_H



#include <asm/insn.h>



#define MCOUNT_ADDR		((unsigned long)_mcount)

#define MCOUNT_INSN_SIZE	AARCH64_INSN_SIZE



#ifndef __ASSEMBLY__

extern void _mcount(unsigned long);

#endif /* __ASSEMBLY__ */



#endif /* __ASM_FTRACE_H */

arch/arm64/kernel/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -5,6 +5,9 @@ 
CPPFLAGS_vmlinux.lds	:= -DTEXT_OFFSET=$(TEXT_OFFSET)

AFLAGS_head.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)



CFLAGS_REMOVE_ftrace.o = -pg

CFLAGS_REMOVE_insn.o = -pg



# Object file lists.

arm64-obj-y		:= cputable.o debug-monitors.o entry.o irq.o fpsimd.o	\

			   entry-fpsimd.o process.o ptrace.o setup.o signal.o	\
@@ -13,6 +16,7 @@ arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \ 


arm64-obj-$(CONFIG_COMPAT)		+= sys32.o kuser32.o signal32.o 	\

					   sys_compat.o

arm64-obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o entry-ftrace.o

arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o

arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o topology.o

arm64-obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o

arch/arm64/kernel/arm64ksyms.c

+4 −0
Original line number Diff line number Diff line
@@ -61,3 +61,7 @@ EXPORT_SYMBOL(clear_bit); 
EXPORT_SYMBOL(test_and_clear_bit);

EXPORT_SYMBOL(change_bit);

EXPORT_SYMBOL(test_and_change_bit);



#ifdef CONFIG_FUNCTION_TRACER

EXPORT_SYMBOL(_mcount);

#endif

arch/arm64/kernel/entry-ftrace.S

0 → 100644
+175 −0
Original line number Diff line number Diff line 
/*

 * arch/arm64/kernel/entry-ftrace.S

 *

 * Copyright (C) 2013 Linaro Limited

 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#include <linux/linkage.h>

#include <asm/ftrace.h>

#include <asm/insn.h>



/*

 * Gcc with -pg will put the following code in the beginning of each function:

 *      mov x0, x30

 *      bl _mcount

 *	[function's body ...]

 * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic

 * ftrace is enabled.

 *

 * Please note that x0 as an argument will not be used here because we can

 * get lr(x30) of instrumented function at any time by winding up call stack

 * as long as the kernel is compiled without -fomit-frame-pointer.

 * (or CONFIG_FRAME_POINTER, this is forced on arm64)

 *

 * stack layout after mcount_enter in _mcount():

 *

 * current sp/fp =>  0:+-----+

 * in _mcount()        | x29 | -> instrumented function's fp

 *                     +-----+

 *                     | x30 | -> _mcount()'s lr (= instrumented function's pc)

 * old sp       => +16:+-----+

 * when instrumented   |     |

 * function calls      | ... |

 * _mcount()           |     |

 *                     |     |

 * instrumented => +xx:+-----+

 * function's fp       | x29 | -> parent's fp

 *                     +-----+

 *                     | x30 | -> instrumented function's lr (= parent's pc)

 *                     +-----+

 *                     | ... |

 */



	.macro mcount_enter

	stp	x29, x30, [sp, #-16]!

	mov	x29, sp

	.endm



	.macro mcount_exit

	ldp	x29, x30, [sp], #16

	ret

	.endm



	.macro mcount_adjust_addr rd, rn

	sub	\rd, \rn, #AARCH64_INSN_SIZE

	.endm



	/* for instrumented function's parent */

	.macro mcount_get_parent_fp reg

	ldr	\reg, [x29]

	ldr	\reg, [\reg]

	.endm



	/* for instrumented function */

	.macro mcount_get_pc0 reg

	mcount_adjust_addr	\reg, x30

	.endm



	.macro mcount_get_pc reg

	ldr	\reg, [x29, #8]

	mcount_adjust_addr	\reg, \reg

	.endm



	.macro mcount_get_lr reg

	ldr	\reg, [x29]

	ldr	\reg, [\reg, #8]

	mcount_adjust_addr	\reg, \reg

	.endm



	.macro mcount_get_lr_addr reg

	ldr	\reg, [x29]

	add	\reg, \reg, #8

	.endm



/*

 * void _mcount(unsigned long return_address)

 * @return_address: return address to instrumented function

 *

 * This function makes calls, if enabled, to:

 *     - tracer function to probe instrumented function's entry,

 *     - ftrace_graph_caller to set up an exit hook

 */

ENTRY(_mcount)

#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST

	ldr	x0, =ftrace_trace_stop

	ldr	x0, [x0]		// if ftrace_trace_stop

	ret				//   return;

#endif

	mcount_enter



	ldr	x0, =ftrace_trace_function

	ldr	x2, [x0]

	adr	x0, ftrace_stub

	cmp	x0, x2			// if (ftrace_trace_function

	b.eq	skip_ftrace_call	//     != ftrace_stub) {



	mcount_get_pc	x0		//       function's pc

	mcount_get_lr	x1		//       function's lr (= parent's pc)

	blr	x2			//   (*ftrace_trace_function)(pc, lr);



#ifndef CONFIG_FUNCTION_GRAPH_TRACER

skip_ftrace_call:			//   return;

	mcount_exit			// }

#else

	mcount_exit			//   return;

					// }

skip_ftrace_call:

	ldr	x1, =ftrace_graph_return

	ldr	x2, [x1]		//   if ((ftrace_graph_return

	cmp	x0, x2			//        != ftrace_stub)

	b.ne	ftrace_graph_caller



	ldr	x1, =ftrace_graph_entry	//     || (ftrace_graph_entry

	ldr	x2, [x1]		//        != ftrace_graph_entry_stub))

	ldr	x0, =ftrace_graph_entry_stub

	cmp	x0, x2

	b.ne	ftrace_graph_caller	//     ftrace_graph_caller();



	mcount_exit

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

ENDPROC(_mcount)



ENTRY(ftrace_stub)

	ret

ENDPROC(ftrace_stub)



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

/*

 * void ftrace_graph_caller(void)

 *

 * Called from _mcount() or ftrace_caller() when function_graph tracer is

 * selected.

 * This function w/ prepare_ftrace_return() fakes link register's value on

 * the call stack in order to intercept instrumented function's return path

 * and run return_to_handler() later on its exit.

 */

ENTRY(ftrace_graph_caller)

	mcount_get_lr_addr	  x0	//     pointer to function's saved lr

	mcount_get_pc		  x1	//     function's pc

	mcount_get_parent_fp	  x2	//     parent's fp

	bl	prepare_ftrace_return	// prepare_ftrace_return(&lr, pc, fp)



	mcount_exit

ENDPROC(ftrace_graph_caller)



/*

 * void return_to_handler(void)

 *

 * Run ftrace_return_to_handler() before going back to parent.

 * @fp is checked against the value passed by ftrace_graph_caller()

 * only when CONFIG_FUNCTION_GRAPH_FP_TEST is enabled.

 */

ENTRY(return_to_handler)

	str	x0, [sp, #-16]!

	mov	x0, x29			//     parent's fp

	bl	ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);

	mov	x30, x0			// restore the original return address

	ldr	x0, [sp], #16

	ret

END(return_to_handler)

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

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