Date:	Thu, 28 May 2009 10:21:30 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	wuzhangjin@...il.com
cc:	linux-mips@...ux-mips.org, LKML <linux-kernel@...r.kernel.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nicholas Mc Guire <der.herr@...r.at>, wuzj@...ote.com
Subject: Re: [PATCH] mips-specific ftrace support



On Thu, 28 May 2009, wuzhangjin@...il.com wrote:

> From: Wu Zhangjin <wuzj@...ote.com>
> 
> ftrace is a mcount based kernel tracing tool/framework, which is
> originally from RT_PREEMPT(http://rt.wiki.kernel.org).
> 
> ftrace is short for function tracer, this is its original name, but now,
> it becomes a kernel tracing framework, lots of kernel tracers are built
> on it, such as irqoff tracer, wakeup tracer and so forth.  these tracers
> are arch-independent(?), but some of them are arch-dependent, such as
> the original ftrace: function tracer, and dynamic function tracer,
> function graph tracer, and also, system call tracer.
> 
> here is the mips porting of the front three arch-dependent tracers,
> currently, the porting of system call tracer is not stable, so, not
> included in this patch.
> 
> here is the new available kernel config options added by this patch.
> 
> kernel hacking --->
>            Tracers -->
>                 [*] Kernel Function Tracer
>                 [*]   Kernel Function Graph Tracer
>                 ...
>                 [*] enable/disable ftrace tracepoints dynamically
> 
> in reality, because the high-precision time information getting function
> are arch-dependent, lots of the tracers are arch-dependent. the
> arch-dependent part is that: sched_clock, or we say
> ring_buffer_time_stamp or trace_clock_local function. to get
> high-precision time, we can read the MIPS clock counter, but for it only
> have 32bit, so, overflow should be handled carefully.
> 
> read the following document, and play with it:
> 	Documentation/trace/ftrace.txt

Very nice!

Could you possibly break this patch up into porting the tracers one by 
one. That is:

First patch: make function tracing work.
Second patch: make dynamic tracing work.
Third patch: add Function graph tracing.
Forth patch: the time stamp updates

This would make things a lot easier to review, and if one of the changes 
breaks something, it will be easier to bisect.

Thanks,

-- Steve

> 
> Signed-off-by: Wu Zhangjin <wuzj@...ote.com>
> ---
>  arch/mips/Kconfig              |    6 +
>  arch/mips/Makefile             |    2 +
>  arch/mips/include/asm/ftrace.h |   37 ++++-
>  arch/mips/kernel/Makefile      |   11 ++
>  arch/mips/kernel/csrc-r4k.c    |    2 +-
>  arch/mips/kernel/ftrace.c      |  366 ++++++++++++++++++++++++++++++++++++++++
>  arch/mips/kernel/mcount.S      |  239 ++++++++++++++++++++++++++
>  arch/mips/kernel/mips_ksyms.c  |    5 +
>  arch/mips/kernel/vmlinux.lds.S |    1 +
>  include/linux/clocksource.h    |    4 +-
>  kernel/sched_clock.c           |    2 +-
>  kernel/trace/ring_buffer.c     |    3 +-
>  kernel/trace/trace_clock.c     |    2 +-
>  scripts/Makefile.build         |    1 +
>  scripts/recordmcount.pl        |   31 +++-
>  15 files changed, 699 insertions(+), 13 deletions(-)
>  create mode 100644 arch/mips/kernel/ftrace.c
>  create mode 100644 arch/mips/kernel/mcount.S
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 09b1287..b588f74 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -3,6 +3,12 @@ config MIPS
>  	default y
>  	select HAVE_IDE
>  	select HAVE_OPROFILE
> +	select HAVE_FTRACE_MCOUNT_RECORD
> +	select HAVE_DYNAMIC_FTRACE
> +	select HAVE_FUNCTION_GRAPH_TRACER
> +	select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
> +	select HAVE_FUNCTION_TRACER
> +	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
>  	select HAVE_ARCH_KGDB
>  	# Horrible source of confusion.  Die, die, die ...
>  	select EMBEDDED
> 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 += $(call cc-option, -mno-check-zero-division)
>  
>  ifdef CONFIG_32BIT
> diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
> index 40a8c17..1501f2c 100644
> --- a/arch/mips/include/asm/ftrace.h
> +++ b/arch/mips/include/asm/ftrace.h
> @@ -1 +1,36 @@
> -/* empty */
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *
> + * Copyright (C) 2009 DSLab, Lanzhou University, China
> + * Author: Wu Zhangjin <wuzj@...ote.com>
> + */
> +
> +
> +#ifndef _ASM_MIPS_FTRACE_H
> +#define _ASM_MIPS_FTRACE_H
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +
> +#define MCOUNT_ADDR ((unsigned long)(_mcount))
> +#define MCOUNT_INSN_SIZE 4	/* sizeof mcount call */
> +
> +#ifndef __ASSEMBLY__
> +extern void _mcount(void);
> +#define mcount _mcount
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +
> +static inline unsigned long ftrace_call_adjust(unsigned long addr)
> +{
> +    /* reloction of mcount call site is the same as the address */
> +    return addr;
> +}
> +
> +struct dyn_arch_ftrace {
> +};
> +#endif				/* CONFIG_DYNAMIC_FTRACE */
> +#endif				/* __ASSEMBLY__ */
> +#endif				/* CONFIG_FUNCTION_TRACER */
> +#endif				/* _ASM_MIPS_FTRACE_H */
> diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
> index e961221..3a3621b 100644
> --- a/arch/mips/kernel/Makefile
> +++ b/arch/mips/kernel/Makefile
> @@ -8,6 +8,13 @@ obj-y		+= cpu-probe.o branch.o entry.o genex.o irq.o process.o \
>  		   ptrace.o reset.o setup.o signal.o syscall.o \
>  		   time.o topology.o traps.o unaligned.o watch.o
>  
> +ifdef CONFIG_FUNCTION_TRACER
> +# Do not profile debug and lowlevel utilities
> +CFLAGS_REMOVE_mcount.o = -pg
> +CFLAGS_REMOVE_ftrace.o = -pg
> +CFLAGS_REMOVE_early_printk.o = -pg
> +endif
> +
>  obj-$(CONFIG_CEVT_BCM1480)	+= cevt-bcm1480.o
>  obj-$(CONFIG_CEVT_R4K_LIB)	+= cevt-r4k.o
>  obj-$(CONFIG_MIPS_MT_SMTC)	+= cevt-smtc.o
> @@ -20,6 +27,8 @@ obj-$(CONFIG_CSRC_IOASIC)	+= csrc-ioasic.o
>  obj-$(CONFIG_CSRC_R4K_LIB)	+= csrc-r4k.o
>  obj-$(CONFIG_CSRC_SB1250)	+= csrc-sb1250.o
>  obj-$(CONFIG_SYNC_R4K)		+= sync-r4k.o
> +obj-$(CONFIG_FUNCTION_TRACER)		+= mcount.o
> +obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= mcount.o
>  
>  obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
>  obj-$(CONFIG_MODULES)		+= mips_ksyms.o module.o
> @@ -83,6 +92,8 @@ obj-$(CONFIG_I8253)		+= i8253.o
>  
>  obj-$(CONFIG_GPIO_TXX9)		+= gpio_txx9.o
>  
> +obj-$(CONFIG_NOP_TRACER)	+= ftrace.o
> +
>  obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
>  obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
>  
> diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
> index e95a3cd..3da1c7a 100644
> --- a/arch/mips/kernel/csrc-r4k.c
> +++ b/arch/mips/kernel/csrc-r4k.c
> @@ -10,7 +10,7 @@
>  
>  #include <asm/time.h>
>  
> -static cycle_t c0_hpt_read(struct clocksource *cs)
> +static cycle_t notrace c0_hpt_read(struct clocksource *cs)
>  {
>  	return read_c0_count();
>  }
> diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
> new file mode 100644
> index 0000000..d421ce0
> --- /dev/null
> +++ b/arch/mips/kernel/ftrace.c
> @@ -0,0 +1,366 @@
> +/*
> + * Code for replacing ftrace calls with jumps.
> + *
> + * Copyright (C) 2007-2008 Steven Rostedt <srostedt@...hat.com>
> + * Copyright (C) 2009 DSLab, Lanzhou University, China
> + * Author: Wu Zhangjin <wuzj@...ote.com>
> + *
> + * Thanks goes to Steven Rostedt for writing the original x86 version.
> + */
> +
> +#include <linux/clocksource.h>
> +#include <linux/ring_buffer.h>
> +#include <linux/spinlock.h>
> +#include <linux/jiffies.h>
> +#include <linux/hardirq.h>
> +#include <linux/uaccess.h>
> +#include <linux/ftrace.h>
> +#include <linux/percpu.h>
> +#include <linux/sched.h>
> +#include <linux/init.h>
> +#include <linux/list.h>
> +#include <linux/ftrace.h>
> +
> +#include <asm/cacheflush.h>
> +#include <asm/ftrace.h>
> +#include <asm/asm.h>
> +
> +#ifndef DEBUG_SHIFT
> +#define DEBUG_SHIFT 0
> +#endif
> +
> +u64 native_ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
> +{
> +	u64 current_cycles;
> +	static unsigned long old_jiffies;
> +	static u64 time, old_cycles;
> +
> +	preempt_disable_notrace();
> +	/* update timestamp to avoid missing the timer interrupt */
> +	if (time_before(jiffies, old_jiffies)) {
> +		old_jiffies = jiffies;
> +		time = sched_clock();
> +		old_cycles = clock->cycle_last;
> +	}
> +	current_cycles = clock->read(clock);
> +
> +	time = (time + cyc2ns(clock, (current_cycles - old_cycles) \
> +				& clock->mask)) << DEBUG_SHIFT;
> +
> +	old_cycles = current_cycles;
> +	preempt_enable_no_resched_notrace();
> +
> +	return time;
> +}
> +
> +u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
> +		__attribute__((alias("native_ring_buffer_time_stamp")));
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +
> +#define JMP	0x08000000	/* jump to target directly */
> +#define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */
> +#define ADDR_MASK 0x03ffffff	/*  op_code|addr : 31...26|25 ....0 */
> +
> +static unsigned int ftrace_nop = 0x00000000;
> +
> +static unsigned char *ftrace_call_replace(unsigned long op_code,
> +					  unsigned long addr)
> +{
> +    static unsigned int op;
> +
> +    op = op_code | ((addr >> 2) & ADDR_MASK);
> +
> +    return (unsigned char *) &op;
> +}
> +
> +static atomic_t in_nmi = ATOMIC_INIT(0);
> +static int mod_code_status;	/* holds return value of text write */
> +static int mod_code_write;	/* set when NMI should do the write */
> +static void *mod_code_ip;	/* holds the IP to write to */
> +static void *mod_code_newcode;	/* holds the text to write to the IP */
> +
> +static unsigned nmi_wait_count;
> +static atomic_t nmi_update_count = ATOMIC_INIT(0);
> +
> +int ftrace_arch_read_dyn_info(char *buf, int size)
> +{
> +    int r;
> +
> +    r = snprintf(buf, size, "%u %u",
> +		 nmi_wait_count, atomic_read(&nmi_update_count));
> +    return r;
> +}
> +
> +static void ftrace_mod_code(void)
> +{
> +    /*
> +     * Yes, more than one CPU process can be writing to mod_code_status.
> +     *    (and the code itself)
> +     * But if one were to fail, then they all should, and if one were
> +     * to succeed, then they all should.
> +     */
> +    mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
> +					 MCOUNT_INSN_SIZE);
> +
> +    /* if we fail, then kill any new writers */
> +    if (mod_code_status)
> +		mod_code_write = 0;
> +}
> +
> +void ftrace_nmi_enter(void)
> +{
> +    atomic_inc(&in_nmi);
> +    /* Must have in_nmi seen before reading write flag */
> +    smp_mb();
> +    if (mod_code_write) {
> +		ftrace_mod_code();
> +		atomic_inc(&nmi_update_count);
> +    }
> +}
> +
> +void ftrace_nmi_exit(void)
> +{
> +    /* Finish all executions before clearing in_nmi */
> +    smp_wmb();
> +    atomic_dec(&in_nmi);
> +}
> +
> +static void wait_for_nmi(void)
> +{
> +    int waited = 0;
> +
> +    while (atomic_read(&in_nmi)) {
> +		waited = 1;
> +		cpu_relax();
> +    }
> +
> +    if (waited)
> +		nmi_wait_count++;
> +}
> +
> +static int do_ftrace_mod_code(unsigned long ip, void *new_code)
> +{
> +    mod_code_ip = (void *) ip;
> +    mod_code_newcode = new_code;
> +
> +    /* The buffers need to be visible before we let NMIs write them */
> +    smp_wmb();
> +
> +    mod_code_write = 1;
> +
> +    /* Make sure write bit is visible before we wait on NMIs */
> +    smp_mb();
> +
> +    wait_for_nmi();
> +
> +    /* Make sure all running NMIs have finished before we write the code */
> +    smp_mb();
> +
> +    ftrace_mod_code();
> +
> +    /* Make sure the write happens before clearing the bit */
> +    smp_wmb();
> +
> +    mod_code_write = 0;
> +
> +    /* make sure NMIs see the cleared bit */
> +    smp_mb();
> +
> +    wait_for_nmi();
> +
> +    return mod_code_status;
> +}
> +
> +static unsigned char *ftrace_nop_replace(void)
> +{
> +    return (unsigned char *) &ftrace_nop;
> +}
> +
> +static int
> +ftrace_modify_code(unsigned long ip, unsigned char *old_code,
> +		   unsigned char *new_code)
> +{
> +    unsigned char replaced[MCOUNT_INSN_SIZE];
> +
> +    /*
> +     * Note: Due to modules and __init, code can
> +     *  disappear and change, we need to protect against faulting
> +     *  as well as code changing. We do this by using the
> +     *  probe_kernel_* functions.
> +     *
> +     * No real locking needed, this code is run through
> +     * kstop_machine, or before SMP starts.
> +     */
> +
> +    /* read the text we want to modify */
> +    if (probe_kernel_read(replaced, (void *) ip, MCOUNT_INSN_SIZE))
> +		return -EFAULT;
> +
> +    /* Make sure it is what we expect it to be */
> +    if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
> +		return -EINVAL;
> +
> +    /* replace the text with the new text */
> +    if (do_ftrace_mod_code(ip, new_code))
> +		return -EPERM;
> +
> +    return 0;
> +}
> +
> +int ftrace_make_nop(struct module *mod,
> +		    struct dyn_ftrace *rec, unsigned long addr)
> +{
> +    unsigned char *new, *old;
> +
> +    old = ftrace_call_replace(JAL, addr);
> +    new = ftrace_nop_replace();
> +
> +    return ftrace_modify_code(rec->ip, old, new);
> +}
> +
> +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> +{
> +    unsigned char *new, *old;
> +
> +    old = ftrace_nop_replace();
> +    new = ftrace_call_replace(JAL, addr);
> +
> +    return ftrace_modify_code(rec->ip, old, new);
> +}
> +
> +int ftrace_update_ftrace_func(ftrace_func_t func)
> +{
> +    unsigned long ip = (unsigned long) (&ftrace_call);
> +    unsigned char old[MCOUNT_INSN_SIZE], *new;
> +    int ret;
> +
> +    memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
> +    new = ftrace_call_replace(JAL, (unsigned long) func);
> +    ret = ftrace_modify_code(ip, old, new);
> +
> +    return ret;
> +}
> +
> +int __init ftrace_dyn_arch_init(void *data)
> +{
> +    /* The return code is retured via data */
> +    *(unsigned long *) data = 0;
> +
> +    return 0;
> +}
> +#endif				/* CONFIG_DYNAMIC_FTRACE */
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +
> +/*
> + * trace_clock_local(): the simplest and least coherent tracing clock.
> + *
> + * Useful for tracing that does not cross to other CPUs nor
> + * does it go through idle events.
> + */
> +u64 notrace native_trace_clock_local(void)
> +{
> +	unsigned long flags;
> +	u64 clock;
> +
> +	/*
> +	 * sched_clock() is an architecture implemented, fast, scalable,
> +	 * lockless clock. It is not guaranteed to be coherent across
> +	 * CPUs, nor across CPU idle events.
> +	 */
> +	raw_local_irq_save(flags);
> +	clock = ring_buffer_time_stamp(NULL, raw_smp_processor_id());
> +	raw_local_irq_restore(flags);
> +
> +	return clock;
> +}
> +
> +u64 trace_clock_local(void)
> +		__attribute__((alias("native_trace_clock_local")));
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +extern void ftrace_graph_call(void);
> +
> +int ftrace_enable_ftrace_graph_caller(void)
> +{
> +    unsigned long ip = (unsigned long) (&ftrace_graph_call);
> +    unsigned char old[MCOUNT_INSN_SIZE], *new;
> +    int ret;
> +
> +	/* j ftrace_stub */
> +    memcpy(old, (unsigned long *) ip, MCOUNT_INSN_SIZE);
> +    new = ftrace_call_replace(JMP, (unsigned long) ftrace_graph_caller);
> +
> +    ret = ftrace_modify_code(ip, old, new);
> +
> +    return ret;
> +}
> +
> +int ftrace_disable_ftrace_graph_caller(void)
> +{
> +    unsigned long ip = (unsigned long) (&ftrace_graph_call);
> +    unsigned char old[MCOUNT_INSN_SIZE], *new;
> +    int ret;
> +
> +	/* j ftrace_graph_caller */
> +    memcpy(old, (unsigned long *) ip, MCOUNT_INSN_SIZE);
> +    new = ftrace_call_replace(JMP, (unsigned long) ftrace_stub);
> +
> +    ret = ftrace_modify_code(ip, old, new);
> +
> +    return ret;
> +}
> +
> +#else				/* CONFIG_DYNAMIC_FTRACE */
> +
> +/*
> + * These functions are picked from those used on
> + * this page for dynamic ftrace. They have been
> + * simplified to ignore all traces in NMI context.
> + */
> +static atomic_t in_nmi;
> +
> +void ftrace_nmi_enter(void)
> +{
> +    atomic_inc(&in_nmi);
> +    /* Must have in_nmi seen before reading write flag */
> +    smp_mb();
> +}
> +
> +void ftrace_nmi_exit(void)
> +{
> +    /* Finish all executions before clearing in_nmi */
> +    smp_wmb();
> +    atomic_dec(&in_nmi);
> +}
> +
> +#endif				/* !CONFIG_DYNAMIC_FTRACE */
> +
> +unsigned long prepare_ftrace_return(unsigned long ip,
> +				    unsigned long parent_ip)
> +{
> +    struct ftrace_graph_ent trace;
> +
> +    /* Nmi's are currently unsupported */
> +    if (unlikely(atomic_read(&in_nmi)))
> +		goto out;
> +
> +    if (unlikely(atomic_read(&current->tracing_graph_pause)))
> +		goto out;
> +
> +    if (ftrace_push_return_trace(parent_ip, ip, &trace.depth) == -EBUSY)
> +		goto out;
> +
> +    trace.func = ip;
> +
> +    /* Only trace if the calling function expects to */
> +    if (!ftrace_graph_entry(&trace)) {
> +		current->curr_ret_stack--;
> +		goto out;
> +    }
> +    return (unsigned long) &return_to_handler;
> +out:
> +    return parent_ip;
> +}
> +#endif				/* CONFIG_FUNCTION_GRAPH_TRACER */
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> new file mode 100644
> index 0000000..0c73105
> --- /dev/null
> +++ b/arch/mips/kernel/mcount.S
> @@ -0,0 +1,239 @@
> +/*
> + * the mips-specific _mcount implementation of ftrace
> + *
> + * 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@...ote.com>
> + */
> +
> +#include <asm/regdef.h>
> +#include <asm/stackframe.h>
> +#include <asm/ftrace.h>
> +
> +#ifdef CONFIG_32BIT
> +
> +		#define FTRACE_FRMSZ	32
> +		#define RA_REG	4
> +
> +		/* there is a "addiu sp,sp,-8" before "jal _mcount" in 32bit */
> +		.macro RESTORE_SP_FOR_32BIT
> +		addiu sp, sp, 8
> +		.endm
> +
> +		.macro MCOUNT_SAVE_REGS
> +		addiu	sp, sp, -FTRACE_FRMSZ
> +#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
> +		sw	v0,	28(sp)
> +		sw	v1,	24(sp)
> +#endif
> +		sw	a0, 20(sp)
> +		sw	a1, 16(sp)
> +		sw	a2, 12(sp)
> +		sw	a3, 8(sp)
> +		sw	ra, RA_REG(sp)
> +		.set	noat
> +		sw	$1, 0(sp)
> +		.set	at
> +		.endm
> +
> +		.macro MCOUNT_RESTORE_REGS
> +#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
> +		lw	v0,	28(sp)
> +		lw	v1,	24(sp)
> +#endif
> +		lw	a0, 20(sp)
> +		lw	a1, 16(sp)
> +		lw	a2, 12(sp)
> +		lw	a3, 8(sp)
> +		lw	ra, RA_REG(sp)
> +		.set	noat
> +		lw	$1, 0(sp)
> +		.set	at
> +		addiu	sp, sp, FTRACE_FRMSZ
> +		.endm
> +
> +#else	/* CONFIG_64BIT */
> +
> +		#define FTRACE_FRMSZ	96
> +		#define RA_REG 8
> +
> +		.macro RESTORE_SP_FOR_32BIT
> +		/* no need for 64bit */
> +		.endm
> +
> +		.macro MCOUNT_SAVE_REGS
> +		daddiu	sp, sp, -FTRACE_FRMSZ
> +#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
> +		sd	v0, 88(sp)
> +		sd	v1,	80(sp)
> +#endif
> +		sd	a0, 72(sp)
> +		sd	a1, 64(sp)
> +		sd	a2, 56(sp)
> +		sd	a3, 48(sp)
> +		sd	a4, 40(sp)
> +		sd	a5, 32(sp)
> +		sd	a6, 24(sp)
> +		sd	a7, 16(sp)
> +		sd	ra, RA_REG(sp)
> +		.set	noat
> +		sd	$1, 0(sp)
> +		.set	at
> +		.endm
> +
> +		.macro MCOUNT_RESTORE_REGS
> +#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
> +		ld	v0, 88(sp)
> +		ld	v1,	80(sp)
> +#endif
> +		ld	a0, 72(sp)
> +		ld	a1, 64(sp)
> +		ld	a2, 56(sp)
> +		ld	a3, 48(sp)
> +		ld	a4, 40(sp)
> +		ld	a5, 32(sp)
> +		ld	a6, 24(sp)
> +		ld	a7, 16(sp)
> +		ld	ra, RA_REG(sp)
> +		.set	noat
> +		ld	$1, 0(sp)
> +		.set	at
> +		daddiu	sp, sp, FTRACE_FRMSZ
> +		.endm
> +#endif
> +
> +		.macro MCOUNT_SET_ARGS
> +		move	a0, ra	/* arg1: next ip, selfaddr */
> +		.set	noat
> +		move	a1, $1	/* arg2: the caller's next ip, parent */
> +		.set	at
> +		LONG_SUB	a0, a0, MCOUNT_INSN_SIZE
> +		.endm
> +
> +		.macro RETURN_BACK
> +		/* fix for loongson2f */
> +#ifdef	CONFIG_LOONGSON2F
> +		.set	noat
> +		move	t0,	$1
> +		.set	at
> +		jr	ra
> +		move	ra,	t0
> +#else
> +		jr	ra
> +		.set	noat
> +		move	ra, $1
> +		.set	at
> +#endif
> +		.endm
> +
> +.set noreorder
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +
> +LEAF(_mcount)
> +	RESTORE_SP_FOR_32BIT
> +	RETURN_BACK
> +	END(_mcount)
> +
> +NESTED(ftrace_caller, FTRACE_FRMSZ, ra)
> +	RESTORE_SP_FOR_32BIT
> +	lw	t0, function_trace_stop
> +	bnez	t0, ftrace_stub
> +	nop
> +
> +	MCOUNT_SAVE_REGS
> +
> +	MCOUNT_SET_ARGS
> +	.globl ftrace_call
> +ftrace_call:
> +	jal	ftrace_stub
> +	nop
> +
> +	MCOUNT_RESTORE_REGS
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +	.globl ftrace_graph_call
> +ftrace_graph_call:
> +	j	ftrace_stub
> +	nop
> +#endif
> +	.globl ftrace_stub
> +ftrace_stub:
> +	RETURN_BACK
> +	END(ftrace_caller)
> +
> +#else	/* ! CONFIG_DYNAMIC_FTRACE */
> +
> +NESTED(_mcount, FTRACE_FRMSZ, ra)
> +	RESTORE_SP_FOR_32BIT
> +	lw	t0, function_trace_stop
> +	bnez	t0, ftrace_stub
> +	nop
> +
> +	PTR_LA	t0, ftrace_stub
> +	/* *ftrace_trace_function -> t1, please don't use t1 later, safe? */
> +	LONG_L	t1, ftrace_trace_function
> +	bne	t0, t1, static_trace
> +	nop
> +
> +#ifdef	CONFIG_FUNCTION_GRAPH_TRACER
> +	LONG_L	t2, ftrace_graph_return
> +	bne	t0,	t2, ftrace_graph_caller
> +	nop
> +	PTR_LA	t0, ftrace_graph_entry_stub
> +	LONG_L	t2, ftrace_graph_entry
> +	bne	t0,	t2, ftrace_graph_caller
> +	nop
> +#endif
> +	j	ftrace_stub
> +	nop
> +
> +static_trace:
> +	MCOUNT_SAVE_REGS
> +	MCOUNT_SET_ARGS
> +
> +	/* t1 hold *ftrace_trace_function */
> +	jalr	t1
> +	nop
> +
> +	MCOUNT_RESTORE_REGS
> +#	.globl ftrace_stub
> +FEXPORT(ftrace_stub)
> +	RETURN_BACK
> +	END(_mcount)
> +
> +#endif 		/* !CONFIG_FUNCTION_TRACER */
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +
> +NESTED(ftrace_graph_caller, FTRACE_FRMSZ, ra)
> +	MCOUNT_SAVE_REGS
> +	MCOUNT_SET_ARGS
> +
> +	jal	prepare_ftrace_return
> +	nop
> +	/* overwrite the parent as &return_to_handler, safe or not?? */
> +	LONG_S	v0, 0(sp)
> +
> +	MCOUNT_RESTORE_REGS
> +	RETURN_BACK
> +	END(ftrace_graph_caller)
> +
> +	.align	2
> +	.globl	return_to_handler
> +return_to_handler:
> +	MCOUNT_SAVE_REGS
> +
> +	/* restore the real parent address */
> +	jal	ftrace_return_to_handler
> +	nop
> +	LONG_S	v0, RA_REG(sp)
> +
> +	MCOUNT_RESTORE_REGS
> +	RETURN_BACK
> +
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> +.set reorder
> diff --git a/arch/mips/kernel/mips_ksyms.c b/arch/mips/kernel/mips_ksyms.c
> index 225755d..30833fe 100644
> --- a/arch/mips/kernel/mips_ksyms.c
> +++ b/arch/mips/kernel/mips_ksyms.c
> @@ -13,6 +13,7 @@
>  #include <asm/checksum.h>
>  #include <asm/pgtable.h>
>  #include <asm/uaccess.h>
> +#include <asm/ftrace.h>
>  
>  extern void *__bzero(void *__s, size_t __count);
>  extern long __strncpy_from_user_nocheck_asm(char *__to,
> @@ -51,3 +52,7 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
>  EXPORT_SYMBOL(__csum_partial_copy_user);
>  
>  EXPORT_SYMBOL(invalid_pte_table);
> +#ifdef CONFIG_FUNCTION_TRACER
> +/* mcount is defined in assembly */
> +EXPORT_SYMBOL(_mcount);
> +#endif
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index 58738c8..67435e5 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -36,6 +36,7 @@ SECTIONS
>  		SCHED_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
> +		IRQENTRY_TEXT
>  		*(.text.*)
>  		*(.fixup)
>  		*(.gnu.warning)
> diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
> index 5a40d14..93066c8 100644
> --- a/include/linux/clocksource.h
> +++ b/include/linux/clocksource.h
> @@ -273,7 +273,7 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
>   *
>   * Uses the clocksource to return the current cycle_t value
>   */
> -static inline cycle_t clocksource_read(struct clocksource *cs)
> +static inline notrace cycle_t clocksource_read(struct clocksource *cs)
>  {
>  	return cs->read(cs);
>  }
> @@ -314,7 +314,7 @@ static inline void clocksource_disable(struct clocksource *cs)
>   *
>   * XXX - This could use some mult_lxl_ll() asm optimization
>   */
> -static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
> +static inline notrace s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
>  {
>  	u64 ret = (u64)cycles;
>  	ret = (ret * cs->mult) >> cs->shift;
> diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
> index e1d16c9..c809677 100644
> --- a/kernel/sched_clock.c
> +++ b/kernel/sched_clock.c
> @@ -36,7 +36,7 @@
>   * This is default implementation.
>   * Architectures and sub-architectures can override this.
>   */
> -unsigned long long __attribute__((weak)) sched_clock(void)
> +unsigned long long notrace __attribute__((weak)) sched_clock(void)
>  {
>  	return (unsigned long long)(jiffies - INITIAL_JIFFIES)
>  					* (NSEC_PER_SEC / HZ);
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 960cbf4..717bd8e 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -420,7 +420,8 @@ struct ring_buffer_iter {
>  /* Up this if you want to test the TIME_EXTENTS and normalization */
>  #define DEBUG_SHIFT 0
>  
> -u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
> +u64 __attribute__((weak)) ring_buffer_time_stamp(struct ring_buffer *buffer,
> +				int cpu)
>  {
>  	u64 time;
>  
> diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
> index b588fd8..78c98c8 100644
> --- a/kernel/trace/trace_clock.c
> +++ b/kernel/trace/trace_clock.c
> @@ -26,7 +26,7 @@
>   * Useful for tracing that does not cross to other CPUs nor
>   * does it go through idle events.
>   */
> -u64 notrace trace_clock_local(void)
> +u64 __attribute__((weak)) notrace trace_clock_local(void)
>  {
>  	unsigned long flags;
>  	u64 clock;
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 5c4b7a4..548d575 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -207,6 +207,7 @@ endif
>  
>  ifdef CONFIG_FTRACE_MCOUNT_RECORD
>  cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
> +	"$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
>  	"$(if $(CONFIG_64BIT),64,32)" \
>  	"$(OBJDUMP)" "$(OBJCOPY)" "$(CC)" "$(LD)" "$(NM)" "$(RM)" "$(MV)" \
>  	"$(if $(part-of-module),1,0)" "$(@)";
> diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> index 409596e..8c1b218 100755
> --- a/scripts/recordmcount.pl
> +++ b/scripts/recordmcount.pl
> @@ -1,5 +1,6 @@
>  #!/usr/bin/perl -w
>  # (c) 2008, Steven Rostedt <srostedt@...hat.com>
> +# (c) 2009, Wu Zhangjin <wuzj@...ote.com>, DSLab,Lanzhou University,China
>  # Licensed under the terms of the GNU GPL License version 2
>  #
>  # recordmcount.pl - makes a section called __mcount_loc that holds
> @@ -100,13 +101,13 @@ $P =~ s@.*/@@g;
>  
>  my $V = '0.1';
>  
> -if ($#ARGV < 7) {
> -	print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
> +if ($#ARGV < 8) {
> +	print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
>  	print "version: $V\n";
>  	exit(1);
>  }
>  
> -my ($arch, $bits, $objdump, $objcopy, $cc,
> +my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
>      $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
>  
>  # This file refers to mcount and shouldn't be ftraced, so lets' ignore it
> @@ -213,6 +214,24 @@ if ($arch eq "x86_64") {
>      if ($is_module eq "0") {
>          $cc .= " -mconstant-gp";
>      }
> +
> +} elsif ($arch eq "mips") {
> +	$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
> +	$objdump .= " -Melf-trad".$endian."mips ";
> +	if ($endian eq "big") {
> +		$endian = " -EB ";
> +		$ld .= " -melf".$bits."btsmip";
> +	} else {
> +		$endian = " -EL ";
> +		$ld .= " -melf".$bits."ltsmip";
> +	}
> +	$cc .= " -mno-abicalls -mabi=" . $bits . $endian;
> +	$ld .= $endian;
> +
> +	if ($bits == 64) {
> +		$type = ".dword";
> +	}
> +
>  } else {
>      die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
>  }
> @@ -441,12 +460,12 @@ if ($#converts >= 0) {
>      #
>      # Step 5: set up each local function as a global
>      #
> -    `$objcopy $globallist $inputfile $globalobj`;
> +    `$objcopy $globallist $inputfile $globalobj 2>&1 >/dev/null`;
>  
>      #
>      # Step 6: Link the global version to our list.
>      #
> -    `$ld -r $globalobj $mcount_o -o $globalmix`;
> +    `$ld -r $globalobj $mcount_o -o $globalmix 2>&1 >/dev/null`;
>  
>      #
>      # Step 7: Convert the local functions back into local symbols
> @@ -454,7 +473,7 @@ if ($#converts >= 0) {
>      `$objcopy $locallist $globalmix $inputfile`;
>  
>      # Remove the temp files
> -    `$rm $globalobj $globalmix`;
> +    `$rm $globalobj $globalmix 2>&1 >/dev/null`;
>  
>  } else {
>  
> -- 
> 1.6.0.4
> 
> 
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