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Re: [PATCH v1 1/5] mips static function tracer support

To: wuzhangjin@gmail.com
Subject: Re: [PATCH v1 1/5] mips static function tracer support
From: Steven Rostedt <rostedt@goodmis.org>
Date: Thu, 28 May 2009 21:13:50 -0400 (EDT)
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Wu Zhangjin <wuzj@lemote.com>, Ralf Baechle <ralf@linux-mips.org>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, Nicholas Mc Guire <der.herr@hofr.at>
In-reply-to: <4c501e9dec76ac317021c9d7dd62a8a5ed13812c.1243543471.git.wuzj@lemote.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1243543471.git.wuzj@lemote.com> <4c501e9dec76ac317021c9d7dd62a8a5ed13812c.1243543471.git.wuzj@lemote.com>
Sender: linux-mips-bounce@linux-mips.org
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On Fri, 29 May 2009, wuzhangjin@gmail.com wrote:

> From: Wu Zhangjin <wuzj@lemote.com>
> 
> if -pg of gcc is enabled. a calling to _mcount will be inserted to each
> kernel function. so, there is a possibility to trace the functions in
> _mcount.
> 
> here is the implementation of mips specific _mcount for static function
> tracer.
> 
> -ffunction-sections option not works with -pg, so disable it if enables
> FUNCTION_TRACER.
> 
> Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
> ---
>  arch/mips/Kconfig              |    2 +
>  arch/mips/Makefile             |    2 +
>  arch/mips/include/asm/ftrace.h |   25 ++++++++++-
>  arch/mips/kernel/Makefile      |    8 +++
>  arch/mips/kernel/mcount.S      |   98 
> ++++++++++++++++++++++++++++++++++++++++
>  arch/mips/kernel/mips_ksyms.c  |    5 ++
>  6 files changed, 139 insertions(+), 1 deletions(-)
>  create mode 100644 arch/mips/kernel/mcount.S
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 09b1287..d5c01ca 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -4,6 +4,8 @@ config MIPS
>       select HAVE_IDE
>       select HAVE_OPROFILE
>       select HAVE_ARCH_KGDB
> +     select HAVE_FUNCTION_TRACER
> +     select HAVE_FUNCTION_TRACE_MCOUNT_TEST
>       # Horrible source of confusion.  Die, die, die ...
>       select EMBEDDED
>       select RTC_LIB
> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> index c4cae9e..f86fb15 100644
> --- a/arch/mips/Makefile
> +++ b/arch/mips/Makefile
> @@ -48,7 +48,9 @@ ifneq ($(SUBARCH),$(ARCH))
>    endif
>  endif
>  
> +ifndef CONFIG_FUNCTION_TRACER
>  cflags-y := -ffunction-sections
> +endif
>  cflags-y += $(call cc-option, -mno-check-zero-division)
>  
>  ifdef CONFIG_32BIT
> diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
> index 40a8c17..5f8ebcf 100644
> --- a/arch/mips/include/asm/ftrace.h
> +++ b/arch/mips/include/asm/ftrace.h
> @@ -1 +1,24 @@
> -/* empty */
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive for
> + * more details.
> + *
> + * Copyright (C) 2009 DSLab, Lanzhou University, China
> + * Author: Wu Zhangjin <wuzj@lemote.com>
> + */
> +
> +#ifndef _ASM_MIPS_FTRACE_H
> +#define _ASM_MIPS_FTRACE_H
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +
> +#define MCOUNT_ADDR ((unsigned long)(_mcount))
> +#define MCOUNT_INSN_SIZE 4           /* sizeof mcount call */
> +
> +#ifndef __ASSEMBLY__
> +extern void _mcount(void);
> +#define mcount _mcount
> +
> +#endif /* __ASSEMBLY__ */
> +#endif /* CONFIG_FUNCTION_TRACER */
> +#endif /* _ASM_MIPS_FTRACE_H */
> diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
> index e961221..d167dde 100644
> --- a/arch/mips/kernel/Makefile
> +++ b/arch/mips/kernel/Makefile
> @@ -8,6 +8,12 @@ obj-y                += cpu-probe.o branch.o entry.o genex.o 
> irq.o process.o \
>                  ptrace.o reset.o setup.o signal.o syscall.o \
>                  time.o topology.o traps.o unaligned.o watch.o
>  
> +ifdef CONFIG_FUNCTION_TRACER
> +# Do not profile debug and lowlevel utilities
> +CFLAGS_REMOVE_mcount.o = -pg

mcount.S is an assembly file, the above is for C files. So it is not 
needed.

-- Steve

> +CFLAGS_REMOVE_early_printk.o = -pg
> +endif
> +
>  obj-$(CONFIG_CEVT_BCM1480)   += cevt-bcm1480.o
>  obj-$(CONFIG_CEVT_R4K_LIB)   += cevt-r4k.o
>  obj-$(CONFIG_MIPS_MT_SMTC)   += cevt-smtc.o
> @@ -24,6 +30,8 @@ obj-$(CONFIG_SYNC_R4K)              += sync-r4k.o
>  obj-$(CONFIG_STACKTRACE)     += stacktrace.o
>  obj-$(CONFIG_MODULES)                += mips_ksyms.o module.o
>  
> +obj-$(CONFIG_FUNCTION_TRACER)        += mcount.o
> +
>  obj-$(CONFIG_CPU_LOONGSON2)  += r4k_fpu.o r4k_switch.o
>  obj-$(CONFIG_CPU_MIPS32)     += r4k_fpu.o r4k_switch.o
>  obj-$(CONFIG_CPU_MIPS64)     += r4k_fpu.o r4k_switch.o
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> new file mode 100644
> index 0000000..268724e
> --- /dev/null

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