linux-kernel - Re: [PATCH 09/10] ARM: ftrace: add Thumb-2 support to dynamic ftrace

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Message-Id: <1266932100.19540.12.camel@frodo>
Date:	Tue, 23 Feb 2010 08:35:00 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rabin Vincent <rabin@....in>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Abhishek Sagar <sagar.abhishek@...il.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH 09/10] ARM: ftrace: add Thumb-2 support to dynamic
 ftrace

On Sun, 2010-02-14 at 01:18 +0530, Rabin Vincent wrote:
> Handle the different nop and call instructions for Thumb-2.  Also, we
> need to adjust the recorded mcount_loc addresses because they have the
> lsb set.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Rabin Vincent <rabin@....in>
> ---
>  arch/arm/include/asm/ftrace.h |    4 ++++
>  arch/arm/kernel/ftrace.c      |   33 +++++++++++++++++++++++++++++++++
>  scripts/recordmcount.pl       |    2 +-
>  3 files changed, 38 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
> index 4a56a2e..0845f2d 100644
> --- a/arch/arm/include/asm/ftrace.h
> +++ b/arch/arm/include/asm/ftrace.h
> @@ -18,7 +18,11 @@ struct dyn_arch_ftrace {
>  
>  static inline unsigned long ftrace_call_adjust(unsigned long addr)
>  {
> +#ifdef CONFIG_THUMB2_KERNEL
> +	return addr & ~1;

Would it be safe to do that for all arm archs? Instead of adding a
config option around it. Or do some arm archs need the lsb set.

I'm just saying a comment here would look better than #ifdef #else.

> +#else
>  	return addr;
> +#endif
>  }
>  
>  extern void ftrace_caller_old(void);
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index f09014c..971ac8c 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -18,7 +18,11 @@
>  #include <asm/cacheflush.h>
>  #include <asm/ftrace.h>
>  
> +#ifdef CONFIG_THUMB2_KERNEL
> +#define	NOP		0xeb04f85d	/* pop.w {lr} */
> +#else
>  #define	NOP		0xe8bd4000	/* pop {lr} */
> +#endif
>  
>  #ifdef CONFIG_OLD_MCOUNT
>  #define OLD_MCOUNT_ADDR	((unsigned long) mcount)
> @@ -56,6 +60,34 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
>  #endif
>  
>  /* construct a branch (BL) instruction to addr */
> +#ifdef CONFIG_THUMB2_KERNEL
> +static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
> +{
> +	unsigned long s, j1, j2, i1, i2, imm10, imm11;
> +	unsigned long first, second;
> +	long offset;
> +
> +	offset = (long)addr - (long)(pc + 4);
> +	if (offset < -16777216 || offset > 16777214) {
> +		WARN_ON_ONCE(1);
> +		return 0;
> +	}
> +
> +	s	= (offset >> 24) & 0x1;
> +	i1	= (offset >> 23) & 0x1;
> +	i2	= (offset >> 22) & 0x1;
> +	imm10	= (offset >> 12) & 0x3ff;
> +	imm11	= (offset >>  1) & 0x7ff;
> +
> +	j1 = (!i1) ^ s;
> +	j2 = (!i2) ^ s;
> +
> +	first = 0xf000 | (s << 10) | imm10;
> +	second = 0xd000 | (j1 << 13) | (j2 << 11) | imm11;
> +
> +	return (second << 16) | first;
> +}
> +#else
>  static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
>  {
>  	long offset;
> @@ -73,6 +105,7 @@ static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
>  
>  	return 0xeb000000 | offset;
>  }
> +#endif
>  
>  static int ftrace_modify_code(unsigned long pc, unsigned long old,
>  			      unsigned long new)
> diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> index 66c1c4b..88b083b 100755
> --- a/scripts/recordmcount.pl
> +++ b/scripts/recordmcount.pl

For the recordmcount.pl change;

Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> @@ -267,7 +267,7 @@ if ($arch eq "x86_64") {
>  } elsif ($arch eq "arm") {
>      $alignment = 2;
>      $section_type = '%progbits';
> -    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24)" .
> +    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
>  			"\\s+(__gnu_mcount_nc|mcount)\$";
>  
>  } elsif ($arch eq "ia64") {

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