linux-kernel - Re: [PATCH] scripts/faddr2line: show the code context

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Date:   Tue, 29 May 2018 12:07:10 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     changbin.du@...el.com, akpm@...ux-foundation.org,
        tglx@...utronix.de, pombredanne@...b.com, neilb@...e.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/faddr2line: show the code context

On Tue, May 29, 2018 at 06:26:36PM +0200, Peter Zijlstra wrote:
> On Tue, May 29, 2018 at 06:03:32PM +0200, Peter Zijlstra wrote:
> > On Mon, Mar 19, 2018 at 03:23:25PM +0800, changbin.du@...el.com wrote:
> > > From: Changbin Du <changbin.du@...el.com>
> > > 
> > > Inspired by gdb command 'list', show the code context of target lines.
> > > Here is a example:
> > > 
> > > $ scripts/faddr2line vmlinux native_write_msr+0x6
> > > native_write_msr+0x6/0x20:
> > > arch_static_branch at arch/x86/include/asm/msr.h:105
> > > 100             return EAX_EDX_VAL(val, low, high);
> > > 101     }
> > > 102
> > > 103     static inline void notrace __wrmsr(unsigned int msr, u32 low, u32 high)
> > > 104     {
> > > 105             asm volatile("1: wrmsr\n"
> > > 106                          "2:\n"
> > > 107                          _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
> > > 108                          : : "c" (msr), "a"(low), "d" (high) : "memory");
> > > 109     }
> > > 110
> > > (inlined by) static_key_false at include/linux/jump_label.h:142
> > > 137     #define JUMP_TYPE_LINKED        2UL
> > > 138     #define JUMP_TYPE_MASK          3UL
> > > 139
> > > 140     static __always_inline bool static_key_false(struct static_key *key)
> > > 141     {
> > > 142             return arch_static_branch(key, false);
> > > 143     }
> > > 144
> > > 145     static __always_inline bool static_key_true(struct static_key *key)
> > > 146     {
> > > 147             return !arch_static_branch(key, true);
> > > (inlined by) native_write_msr at arch/x86/include/asm/msr.h:150
> > > 145     static inline void notrace
> > > 146     native_write_msr(unsigned int msr, u32 low, u32 high)
> > > 147     {
> > > 148             __wrmsr(msr, low, high);
> > > 149
> > > 150             if (msr_tracepoint_active(__tracepoint_write_msr))
> > > 151                     do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
> > > 152     }
> > > 153
> > > 154     /* Can be uninlined because referenced by paravirt */
> > > 155     static inline int notrace
> > 
> > Not a fan of this :-/ And you didn't even make it optional. Nor did you
> > Cc the original author of the tool.
> 
> Something like so fixes it up and attempts to make the --list version
> more readable.
> 
> ---
>  scripts/faddr2line | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/faddr2line b/scripts/faddr2line
> index 1876a741087c..a0149db00be7 100755
> --- a/scripts/faddr2line
> +++ b/scripts/faddr2line
> @@ -56,7 +56,7 @@ command -v ${SIZE} >/dev/null 2>&1 || die "size isn't installed"
>  command -v ${NM} >/dev/null 2>&1 || die "nm isn't installed"
>  
>  usage() {
> -	echo "usage: faddr2line <object file> <func+offset> <func+offset>..." >&2
> +	echo "usage: faddr2line [--list] <object file> <func+offset> <func+offset>..." >&2
>  	exit 1
>  }
>  
> @@ -166,15 +166,25 @@ __faddr2line() {
>  		local file_lines=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
>  		[[ -z $file_lines ]] && return
>  
> +		if [[ $LIST = 0 ]]; then
> +			echo "$file_lines" | while read -r line
> +			do
> +				echo $line
> +			done
> +			DONE=1;
> +			return
> +		fi
> +
>  		# show each line with context
>  		echo "$file_lines" | while read -r line
>  		do
> +			echo
>  			echo $line
>  			n=$(echo $line | sed 's/.*:\([0-9]\+\).*/\1/g')
>  			n1=$[$n-5]
>  			n2=$[$n+5]
>  			f=$(echo $line | sed 's/.*at \(.\+\):.*/\1/g')
> -			awk 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") {printf("%d\t%s\n", NR, $0)}' $f
> +			awk 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
>  		done
>  
>  		DONE=1
> @@ -185,6 +195,10 @@ __faddr2line() {
>  [[ $# -lt 2 ]] && usage
>  
>  objfile=$1
> +
> +LIST=0
> +[[ "$objfile" == "--list" ]] && LIST=1 && shift && objfile=$1
> +
>  [[ ! -f $objfile ]] && die "can't find objfile $objfile"
>  shift

Yeah, this change really should have been an optional arg.  It hurt the
readability and compactness of the output.  The above looks good to me.

Care to send a proper patch?  If you send it to Linus he might apply it
directly as he did with my original patches.

-- 
Josh