Message-ID: <20140115104741.2d78cee4@gandalf.local.home>
Date:	Wed, 15 Jan 2014 10:47:41 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v6 7/8] x86: patch all traced function calls using the
 int3-based framework

On Tue, 10 Dec 2013 16:42:19 +0100
Petr Mladek <pmladek@...e.cz> wrote:

> 
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 03abf9abf681..e5c02af3a8cc 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -613,7 +613,7 @@ void __kprobes text_poke_or_die(void *addr, const void *opcode, size_t len)
>   * responsible for setting the patched code read-write. This is more effective
>   * only when you patch many addresses at the same time.
>   */
> -static int text_poke_part(void *addr, const void *opcode, size_t len)
> +static int notrace text_poke_part(void *addr, const void *opcode, size_t len)

I can understand why you want to not trace any of these, but again, I
hate using notrace unless it is absolutely necessary. That's what the
set_ftrace_notrace is for. If you don't want to trace it, simply tell
the kernel not to.

>  {
>  	int ret;
>  
> @@ -662,7 +662,7 @@ static void *bp_int3_handler, *bp_int3_addr;
>  static size_t bp_int3_len;
>  static void *(*bp_int3_is_handled)(const unsigned long ip);
>  
> -int poke_int3_handler(struct pt_regs *regs)
> +int notrace poke_int3_handler(struct pt_regs *regs)
>  {
>  	/* bp_patching_in_progress */
>  	smp_rmb();
> @@ -771,7 +771,7 @@ void text_poke_bp_or_die(void *addr, const void *opcode, size_t len,
>  	BUG_ON(err);
>  }
>  
> -static int text_poke_check(void *addr, const void *opcode, size_t len)
> +static int notrace text_poke_check(void *addr, const void *opcode, size_t len)
>  {
>  	unsigned char actual[MAX_PATCH_LEN];
>  	int ret;
> @@ -787,7 +787,7 @@ static int text_poke_check(void *addr, const void *opcode, size_t len)
>  	return 0;
>  }
>  
> -static int add_iter_breakpoint(struct text_poke_bp_iter *iterator,
> +static int notrace add_iter_breakpoint(struct text_poke_bp_iter *iterator,
>  				       void *iter)
>  {
>  	void *addr;
> @@ -809,7 +809,7 @@ static int add_iter_breakpoint(struct text_poke_bp_iter *iterator,
>  	return ret;
>  }
>  
> -static int update_iter_code(struct text_poke_bp_iter *iterator,
> +static int notrace update_iter_code(struct text_poke_bp_iter *iterator,
>  				   void *iter)
>  {
>  	void *addr;
> @@ -827,7 +827,7 @@ static int update_iter_code(struct text_poke_bp_iter *iterator,
>  			      bp_int3_len - sizeof(bp_int3));
>  }
>  
> -static int finish_iter_update(struct text_poke_bp_iter *iterator,
> +static int notrace finish_iter_update(struct text_poke_bp_iter *iterator,
>  				      void *iter)
>  {
>  	void *addr;
> @@ -848,7 +848,7 @@ static int finish_iter_update(struct text_poke_bp_iter *iterator,
>  	return ret;
>  }
>  
> -static void recover_iter(struct text_poke_bp_iter *iterator,
> +static void notrace recover_iter(struct text_poke_bp_iter *iterator,
>  				void *iter)
>  {
>  	void *addr;
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 5ade40e4a175..92fe8cac0802 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -127,23 +127,6 @@ static const unsigned char *ftrace_nop_replace(void)
>  }
>  
>  static int
> -ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
> -		   unsigned const char *new_code)
> -{
> -	int ret;
> -
> -	ret = ftrace_check_code(ip, old_code);
> -
> -	/* replace the text with the new text */
> -	if (!ret && do_ftrace_mod_code(ip, new_code))
> -		return -EPERM;
> -
> -	sync_core();
> -
> -	return 0;
> -}
> -
> -static int
>  ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
>  		   unsigned const char *new_code)
>  {
> @@ -168,20 +151,7 @@ int ftrace_make_nop(struct module *mod,
>  	old = ftrace_call_replace(ip, addr);
>  	new = ftrace_nop_replace();
>  
> -	/*
> -	 * On boot up, and when modules are loaded, the MCOUNT_ADDR
> -	 * is converted to a nop, and will never become MCOUNT_ADDR
> -	 * again. This code is either running before SMP (on boot up)
> -	 * or before the code will ever be executed (module load).
> -	 * We do not want to use the breakpoint version in this case,
> -	 * just modify the code directly.
> -	 */
> -	if (addr == MCOUNT_ADDR)
> -		return ftrace_modify_code_direct(rec->ip, old, new);
> -
> -	/* Normal cases use add_brk_on_nop */
> -	WARN_ONCE(1, "invalid use of ftrace_make_nop");
> -	return -EINVAL;
> +	return ftrace_modify_code(ip, old, new);
>  }
>  
>  int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> @@ -192,44 +162,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
>  	old = ftrace_nop_replace();
>  	new = ftrace_call_replace(ip, addr);
>  
> -	/* Should only be called when module is loaded */
> -	return ftrace_modify_code_direct(rec->ip, old, new);
> +	return ftrace_modify_code(ip, old, new);
>  }
>  
>  /*
> - * The modifying_ftrace_code is used to tell the breakpoint
> - * handler to call ftrace_int3_handler(). If it fails to
> - * call this handler for a breakpoint added by ftrace, then
> - * the kernel may crash.
> - *
> - * As atomic_writes on x86 do not need a barrier, we do not
> - * need to add smp_mb()s for this to work. It is also considered
> - * that we can not read the modifying_ftrace_code before
> - * executing the breakpoint. That would be quite remarkable if
> - * it could do that. Here's the flow that is required:
> - *
> - *   CPU-0                          CPU-1
> - *
> - * atomic_inc(mfc);
> - * write int3s
> - *				<trap-int3> // implicit (r)mb
> - *				if (atomic_read(mfc))
> - *					call ftrace_int3_handler()
> - *
> - * Then when we are finished:
> - *
> - * atomic_dec(mfc);
> - *
> - * If we hit a breakpoint that was not set by ftrace, it does not
> - * matter if ftrace_int3_handler() is called or not. It will
> - * simply be ignored. But it is crucial that a ftrace nop/caller
> - * breakpoint is handled. No other user should ever place a
> - * breakpoint on an ftrace nop/caller location. It must only
> - * be done by this code.
> - */

The above is a nice comment. It should be copied over to the
alternative.c file for the explanation of bp_patching_in_progress.

> -atomic_t modifying_ftrace_code __read_mostly;
> -
> -/*
>   * Should never be called:
>   *  As it is only called by __ftrace_replace_code() which is called by
>   *  ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
> @@ -267,80 +203,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>  }
>  
>  /*
> - * A breakpoint was added to the code address we are about to
> - * modify, and this is the handle that will just skip over it.
> - * We are either changing a nop into a trace call, or a trace
> - * call to a nop. While the change is taking place, we treat
> - * it just like it was a nop.
> - */
> -int ftrace_int3_handler(struct pt_regs *regs)
> -{
> -	if (WARN_ON_ONCE(!regs))
> -		return 0;
> -
> -	if (!ftrace_location(regs->ip - 1))
> -		return 0;
> -
> -	regs->ip += MCOUNT_INSN_SIZE - 1;
> -
> -	return 1;
> -}
> -
> -static int ftrace_write(unsigned long ip, const char *val, int size)
> -{
> -	/*
> -	 * On x86_64, kernel text mappings are mapped read-only with
> -	 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
> -	 * of the kernel text mapping to modify the kernel text.
> -	 *
> -	 * For 32bit kernels, these mappings are same and we can use
> -	 * kernel identity mapping to modify code.
> -	 */
> -	if (within(ip, (unsigned long)_text, (unsigned long)_etext))
> -		ip = (unsigned long)__va(__pa_symbol(ip));
> -
> -	return probe_kernel_write((void *)ip, val, size);
> -}
> -
> -static int add_break(unsigned long ip, const char *old)
> -{
> -	unsigned char replaced[MCOUNT_INSN_SIZE];
> -	unsigned char brk = BREAKPOINT_INSTRUCTION;
> -
> -	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, MCOUNT_INSN_SIZE) != 0)
> -		return -EINVAL;
> -
> -	if (ftrace_write(ip, &brk, 1))
> -		return -EPERM;
> -
> -	return 0;
> -}
> -
> -static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
> -{
> -	unsigned const char *old;
> -	unsigned long ip = rec->ip;
> -
> -	old = ftrace_call_replace(ip, addr);
> -
> -	return add_break(rec->ip, old);
> -}
> -
> -
> -static int add_brk_on_nop(struct dyn_ftrace *rec)
> -{
> -	unsigned const char *old;
> -
> -	old = ftrace_nop_replace();
> -
> -	return add_break(rec->ip, old);
> -}
> -
> -/*
>   * If the record has the FTRACE_FL_REGS set, that means that it
>   * wants to convert to a callback that saves all regs. If FTRACE_FL_REGS
>   * is not not set, then it wants to convert to the normal callback.
> @@ -366,275 +228,131 @@ static unsigned long get_ftrace_old_addr(struct dyn_ftrace *rec)
>  		return (unsigned long)FTRACE_ADDR;
>  }
>  
> -static int add_breakpoints(struct dyn_ftrace *rec, int enable)
> -{
> -	unsigned long ftrace_addr;
> -	int ret;
> -
> -	ret = ftrace_test_record(rec, enable);
> -
> -	ftrace_addr = get_ftrace_addr(rec);
> -
> -	switch (ret) {
> -	case FTRACE_UPDATE_IGNORE:
> -		return 0;
> -
> -	case FTRACE_UPDATE_MAKE_CALL:
> -		/* converting nop to call */
> -		return add_brk_on_nop(rec);
> -
> -	case FTRACE_UPDATE_MODIFY_CALL_REGS:
> -	case FTRACE_UPDATE_MODIFY_CALL:
> -		ftrace_addr = get_ftrace_old_addr(rec);
> -		/* fall through */
> -	case FTRACE_UPDATE_MAKE_NOP:
> -		/* converting a call to a nop */
> -		return add_brk_on_call(rec, ftrace_addr);
> -	}
> -	return 0;
> -}
> +struct ftrace_tp_iter {
> +	struct ftrace_rec_iter *rec_iter;
> +	struct dyn_ftrace *rec;
> +	int enable;
> +};
>  
> -/*
> - * On error, we need to remove breakpoints. This needs to
> - * be done caefully. If the address does not currently have a
> - * breakpoint, we know we are done. Otherwise, we look at the
> - * remaining 4 bytes of the instruction. If it matches a nop
> - * we replace the breakpoint with the nop. Otherwise we replace
> - * it with the call instruction.
> - */
> -static int remove_breakpoint(struct dyn_ftrace *rec)
> +static struct ftrace_tp_iter *ftrace_tp_set_record(struct ftrace_tp_iter *tp_iter)
>  {
> -	unsigned char ins[MCOUNT_INSN_SIZE];
> -	unsigned char brk = BREAKPOINT_INSTRUCTION;
> -	const unsigned char *nop;
> -	unsigned long ftrace_addr;
> -	unsigned long ip = rec->ip;
> -
> -	/* If we fail the read, just give up */
> -	if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
> -		return -EFAULT;
> +	if (!tp_iter->rec_iter)
> +		return NULL;
>  
> -	/* If this does not have a breakpoint, we are done */
> -	if (ins[0] != brk)
> -		return -1;
> -
> -	nop = ftrace_nop_replace();
> -
> -	/*
> -	 * If the last 4 bytes of the instruction do not match
> -	 * a nop, then we assume that this is a call to ftrace_addr.
> -	 */
> -	if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
> -		/*
> -		 * For extra paranoidism, we check if the breakpoint is on
> -		 * a call that would actually jump to the ftrace_addr.
> -		 * If not, don't touch the breakpoint, we make just create
> -		 * a disaster.
> -		 */
> -		ftrace_addr = get_ftrace_addr(rec);
> -		nop = ftrace_call_replace(ip, ftrace_addr);
> -
> -		if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
> -			goto update;
> -
> -		/* Check both ftrace_addr and ftrace_old_addr */
> -		ftrace_addr = get_ftrace_old_addr(rec);
> -		nop = ftrace_call_replace(ip, ftrace_addr);
> -
> -		if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
> -			return -EINVAL;
> -	}
> -
> - update:
> -	return probe_kernel_write((void *)ip, &nop[0], 1);
> +	tp_iter->rec = ftrace_rec_iter_record(tp_iter->rec_iter);
> +	return tp_iter;
>  }
>  
> -static int add_update_code(unsigned long ip, unsigned const char *new)
> +void *ftrace_tp_iter_start(void *init)
>  {
> -	/* skip breakpoint */
> -	ip++;
> -	new++;
> -	if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1))
> -		return -EPERM;
> -	return 0;
> +	struct ftrace_tp_iter *tp_iter = init;
> +
> +	tp_iter->rec_iter = ftrace_rec_iter_start();
> +	return ftrace_tp_set_record(tp_iter);
>  }
>  
> -static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
> +void *ftrace_tp_iter_next(void *cur)
>  {
> -	unsigned long ip = rec->ip;
> -	unsigned const char *new;
> +	struct ftrace_tp_iter *tp_iter = cur;
>  
> -	new = ftrace_call_replace(ip, addr);
> -	return add_update_code(ip, new);
> +	tp_iter->rec_iter = ftrace_rec_iter_next(tp_iter->rec_iter);
> +	return ftrace_tp_set_record(tp_iter);
>  }
>  
> -static int add_update_nop(struct dyn_ftrace *rec)
> +void *ftrace_tp_iter_get_addr(void *cur)
>  {
> -	unsigned long ip = rec->ip;
> -	unsigned const char *new;
> +	struct ftrace_tp_iter *tp_iter = cur;
>  
> -	new = ftrace_nop_replace();
> -	return add_update_code(ip, new);
> +	return (void *)(tp_iter->rec->ip);
>  }
>  
> -static int add_update(struct dyn_ftrace *rec, int enable)
> +const void *ftrace_tp_iter_get_opcode(void *cur)
>  {
> -	unsigned long ftrace_addr;
> +	struct ftrace_tp_iter *tp_iter = cur;
> +	unsigned long addr;
>  	int ret;
>  
> -	ret = ftrace_test_record(rec, enable);
> -
> -	ftrace_addr  = get_ftrace_addr(rec);
> +	ret = ftrace_test_record(tp_iter->rec, tp_iter->enable);
>  
>  	switch (ret) {
> -	case FTRACE_UPDATE_IGNORE:
> -		return 0;
> +	case FTRACE_UPDATE_MAKE_NOP:
> +		return ftrace_nop_replace();
>  
> -	case FTRACE_UPDATE_MODIFY_CALL_REGS:
> -	case FTRACE_UPDATE_MODIFY_CALL:
>  	case FTRACE_UPDATE_MAKE_CALL:
> -		/* converting nop to call */
> -		return add_update_call(rec, ftrace_addr);
> +	case FTRACE_UPDATE_MODIFY_CALL:
> +	case FTRACE_UPDATE_MODIFY_CALL_REGS:
> +		addr = get_ftrace_addr(tp_iter->rec);
> +		return ftrace_call_replace(tp_iter->rec->ip, addr);
>  
> -	case FTRACE_UPDATE_MAKE_NOP:
> -		/* converting a call to a nop */
> -		return add_update_nop(rec);
> +	case FTRACE_UPDATE_IGNORE:
> +	default:			/* unknown ftrace bug */
> +		return NULL;
>  	}
> -
> -	return 0;
> -}
> -
> -static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
> -{
> -	unsigned long ip = rec->ip;
> -	unsigned const char *new;
> -
> -	new = ftrace_call_replace(ip, addr);
> -
> -	if (ftrace_write(ip, new, 1))
> -		return -EPERM;
> -
> -	return 0;
> -}
> -
> -static int finish_update_nop(struct dyn_ftrace *rec)
> -{
> -	unsigned long ip = rec->ip;
> -	unsigned const char *new;
> -
> -	new = ftrace_nop_replace();
> -
> -	if (ftrace_write(ip, new, 1))
> -		return -EPERM;
> -	return 0;
>  }
>  
> -static int finish_update(struct dyn_ftrace *rec, int enable)
> +const void *ftrace_tp_iter_get_old_opcode(void *cur)
>  {
> -	unsigned long ftrace_addr;
> +	struct ftrace_tp_iter *tp_iter = cur;
> +	unsigned long old_addr;
>  	int ret;
>  
> -	ret = ftrace_update_record(rec, enable);
> -
> -	ftrace_addr = get_ftrace_addr(rec);
> +	ret = ftrace_test_record(tp_iter->rec, tp_iter->enable);
>  
>  	switch (ret) {
> -	case FTRACE_UPDATE_IGNORE:
> -		return 0;
> -
> -	case FTRACE_UPDATE_MODIFY_CALL_REGS:
> -	case FTRACE_UPDATE_MODIFY_CALL:
>  	case FTRACE_UPDATE_MAKE_CALL:
> -		/* converting nop to call */
> -		return finish_update_call(rec, ftrace_addr);
> +		return ftrace_nop_replace();
>  
>  	case FTRACE_UPDATE_MAKE_NOP:
> -		/* converting a call to a nop */
> -		return finish_update_nop(rec);
> -	}
> +	case FTRACE_UPDATE_MODIFY_CALL:
> +	case FTRACE_UPDATE_MODIFY_CALL_REGS:
> +		old_addr = get_ftrace_old_addr(tp_iter->rec);
> +		return ftrace_call_replace(tp_iter->rec->ip, old_addr);
>  
> -	return 0;
> +	case FTRACE_UPDATE_IGNORE:
> +	default:			/* unknown ftrace bug */
> +		return NULL;
> +	}
>  }
>  
> -static void do_sync_core(void *data)
> +int ftrace_tp_iter_finish(void *cur)
>  {
> -	sync_core();
> -}
> +	struct ftrace_tp_iter *tp_iter = cur;
>  
> -static void run_sync(void)
> -{
> -	int enable_irqs = irqs_disabled();
> -
> -	/* We may be called with interrupts disbled (on bootup). */
> -	if (enable_irqs)
> -		local_irq_enable();
> -	on_each_cpu(do_sync_core, NULL, 1);
> -	if (enable_irqs)
> -		local_irq_disable();
> +	ftrace_update_record(tp_iter->rec, tp_iter->enable);
> +	return 0;
>  }
>  
>  void ftrace_replace_code(int enable)
>  {
> -	struct ftrace_rec_iter *iter;
> -	struct dyn_ftrace *rec;
> -	const char *report = "adding breakpoints";
> -	int count = 0;
> +	struct text_poke_bp_iter tp_bp_iter;
> +	struct ftrace_tp_iter tp_iter;
>  	int ret;
>  
> -	for_ftrace_rec_iter(iter) {
> -		rec = ftrace_rec_iter_record(iter);
> -
> -		ret = add_breakpoints(rec, enable);
> -		if (ret)
> -			goto remove_breakpoints;
> -		count++;
> -	}
> -
> -	run_sync();
> -
> -	report = "updating code";
> -
> -	for_ftrace_rec_iter(iter) {
> -		rec = ftrace_rec_iter_record(iter);
> -
> -		ret = add_update(rec, enable);
> -		if (ret)
> -			goto remove_breakpoints;
> -	}
> +	tp_iter.enable = enable;
>  
> -	run_sync();
> +	tp_bp_iter.init = (void *)&tp_iter;
> +	tp_bp_iter.len = MCOUNT_INSN_SIZE;
> +	tp_bp_iter.start = ftrace_tp_iter_start;
> +	tp_bp_iter.next = ftrace_tp_iter_next;
> +	tp_bp_iter.get_addr = ftrace_tp_iter_get_addr;
> +	tp_bp_iter.get_opcode = ftrace_tp_iter_get_opcode;
> +	tp_bp_iter.get_old_opcode = ftrace_tp_iter_get_old_opcode;
> +	tp_bp_iter.finish = ftrace_tp_iter_finish;
> +	tp_bp_iter.is_handled = (void *(*)(const unsigned long))ftrace_location;
>  
> -	report = "removing breakpoints";
> +	ret = text_poke_bp_list(&tp_bp_iter);
>  
> -	for_ftrace_rec_iter(iter) {
> -		rec = ftrace_rec_iter_record(iter);
> -
> -		ret = finish_update(rec, enable);
> -		if (ret)
> -			goto remove_breakpoints;
> -	}
> -
> -	run_sync();
> -
> -	return;
> -
> - remove_breakpoints:
> -	ftrace_bug(ret, rec ? rec->ip : 0);
> -	printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
> -	for_ftrace_rec_iter(iter) {
> -		rec = ftrace_rec_iter_record(iter);
> -		remove_breakpoint(rec);
> -	}
> +	if (ret)
> +		ftrace_bug(ret, (unsigned long)(tp_bp_iter.fail_addr));
>  }
>  
> +/*
> + * The code is modified using Int3 guard,
> + * so we do not need to call the stop machine
> + */
>  void arch_ftrace_update_code(int command)
>  {
> -	/* See comment above by declaration of modifying_ftrace_code */
> -	atomic_inc(&modifying_ftrace_code);
> -
>  	ftrace_modify_all_code(command);
> -
> -	atomic_dec(&modifying_ftrace_code);
>  }
>  
>  int __init ftrace_dyn_arch_init(void *data)
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index b857ed890b4c..69ad8cf8b7f0 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -50,7 +50,6 @@
>  #include <asm/processor.h>
>  #include <asm/debugreg.h>
>  #include <linux/atomic.h>
> -#include <asm/ftrace.h>
>  #include <asm/traps.h>
>  #include <asm/desc.h>
>  #include <asm/i387.h>
> @@ -319,15 +318,6 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
>  {
>  	enum ctx_state prev_state;
>  
> -#ifdef CONFIG_DYNAMIC_FTRACE
> -	/*
> -	 * ftrace must be first, everything else may cause a recursive crash.
> -	 * See note by declaration of modifying_ftrace_code in ftrace.c
> -	 */
> -	if (unlikely(atomic_read(&modifying_ftrace_code)) &&
> -	    ftrace_int3_handler(regs))
> -		return;
> -#endif
>  	if (poke_int3_handler(regs))
>  		return;
>  
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 31ea4b428360..fe50347cf18e 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -383,12 +383,6 @@ struct ftrace_rec_iter *ftrace_rec_iter_start(void);
>  struct ftrace_rec_iter *ftrace_rec_iter_next(struct ftrace_rec_iter *iter);
>  struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter);
>  
> -#define for_ftrace_rec_iter(iter)		\
> -	for (iter = ftrace_rec_iter_start();	\
> -	     iter;				\
> -	     iter = ftrace_rec_iter_next(iter))
> -
> -

Leave this, it's good for other archs. Which reminds me, I need to
update them.

-- Steve

>  int ftrace_update_record(struct dyn_ftrace *rec, int enable);
>  int ftrace_test_record(struct dyn_ftrace *rec, int enable);
>  void ftrace_run_stop_machine(int command);

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