Re: [PATCH] perf tests: objdump output can contain multi byte chunks

[Arnaldo Carvalho de Melo <acme@redhat.com>]

Em Tue, Jan 12, 2016 at 11:07:44AM +0100, Jan Stancek escreveu:
> objdump's raw insn output can vary across architectures on number of
> bytes per chunk (bpc) displayed and their endian.
> 
> code-reading test relied on reading objdump output as 1 bpc. Kaixu Xia
> reported test failure on ARM64, where objdump displays 4 bpc:
>   70c48:        f90027bf         str        xzr, [x29,#72]
>   70c4c:        91224000         add        x0, x0, #0x890
>   70c50:        f90023a0         str        x0, [x29,#64]
> 
> This patch adds support to read raw insn output for any bpc length.
> In case of 2+ bpc it also guesses objdump's display endian.

Adrian, from a quick read of the patch and problem/solution description,
I think this is ok and Kaixu reports it solves the problem on ARM64, can
I have your reviewed-by/Acked-by?

Thanks,

- Arnaldo
 
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> Reported-and-tested-by: Kaixu Xia <xiakaixu@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
>  tools/perf/tests/code-reading.c | 100 ++++++++++++++++++++++++++++------------
>  1 file changed, 71 insertions(+), 29 deletions(-)
> 
> diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> index a767a6400c5c..0108cb22d1a2 100644
> --- a/tools/perf/tests/code-reading.c
> +++ b/tools/perf/tests/code-reading.c
> @@ -33,44 +33,86 @@ static unsigned int hex(char c)
>  	return c - 'A' + 10;
>  }
>  
> -static size_t read_objdump_line(const char *line, size_t line_len, void *buf,
> -			      size_t len)
> +static size_t read_objdump_chunk(const char **line, unsigned char **buf,
> +				 size_t *buf_len)
> +{
> +	size_t bytes_read = 0;
> +	unsigned char *chunk_start = *buf;
> +
> +	/* Read bytes */
> +	while (*buf_len > 0) {
> +		char c1, c2;
> +
> +		/* Get 2 hex digits */
> +		c1 = *(*line)++;
> +		if (!isxdigit(c1))
> +			break;
> +		c2 = *(*line)++;
> +		if (!isxdigit(c2))
> +			break;
> +
> +		/* Store byte and advance buf */
> +		**buf = (hex(c1) << 4) | hex(c2);
> +		(*buf)++;
> +		(*buf_len)--;
> +		bytes_read++;
> +
> +		/* End of chunk? */
> +		if (isspace(**line))
> +			break;
> +	}
> +
> +	/*
> +	 * objdump will display raw insn as LE if code endian
> +	 * is LE and bytes_per_chunk > 1. In that case reverse
> +	 * the chunk we just read.
> +	 *
> +	 * see disassemble_bytes() at binutils/objdump.c for details
> +	 * how objdump chooses display endian)
> +	 */
> +	if (bytes_read > 1 && !bigendian()) {
> +		unsigned char *chunk_end = chunk_start + bytes_read - 1;
> +		unsigned char tmp;
> +
> +		while (chunk_start < chunk_end) {
> +			tmp = *chunk_start;
> +			*chunk_start = *chunk_end;
> +			*chunk_end = tmp;
> +			chunk_start++;
> +			chunk_end--;
> +		}
> +	}
> +
> +	return bytes_read;
> +}
> +
> +static size_t read_objdump_line(const char *line, unsigned char *buf,
> +				size_t buf_len)
>  {
>  	const char *p;
> -	size_t i, j = 0;
> +	size_t ret, bytes_read = 0;
>  
>  	/* Skip to a colon */
>  	p = strchr(line, ':');
>  	if (!p)
>  		return 0;
> -	i = p + 1 - line;
> +	p++;
>  
> -	/* Read bytes */
> -	while (j < len) {
> -		char c1, c2;
> -
> -		/* Skip spaces */
> -		for (; i < line_len; i++) {
> -			if (!isspace(line[i]))
> -				break;
> -		}
> -		/* Get 2 hex digits */
> -		if (i >= line_len || !isxdigit(line[i]))
> -			break;
> -		c1 = line[i++];
> -		if (i >= line_len || !isxdigit(line[i]))
> -			break;
> -		c2 = line[i++];
> -		/* Followed by a space */
> -		if (i < line_len && line[i] && !isspace(line[i]))
> +	/* Skip initial spaces */
> +	while (*p) {
> +		if (!isspace(*p))
>  			break;
> -		/* Store byte */
> -		*(unsigned char *)buf = (hex(c1) << 4) | hex(c2);
> -		buf += 1;
> -		j++;
> +		p++;
>  	}
> +
> +	do {
> +		ret = read_objdump_chunk(&p, &buf, &buf_len);
> +		bytes_read += ret;
> +		p++;
> +	} while (ret > 0);
> +
>  	/* return number of successfully read bytes */
> -	return j;
> +	return bytes_read;
>  }
>  
>  static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
> @@ -95,7 +137,7 @@ static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
>  		}
>  
>  		/* read objdump data into temporary buffer */
> -		read_bytes = read_objdump_line(line, ret, tmp, sizeof(tmp));
> +		read_bytes = read_objdump_line(line, tmp, sizeof(tmp));
>  		if (!read_bytes)
>  			continue;
>  
> @@ -152,7 +194,7 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
>  
>  	ret = read_objdump_output(f, buf, &len, addr);
>  	if (len) {
> -		pr_debug("objdump read too few bytes\n");
> +		pr_debug("objdump read too few bytes: %lu\n", len);
>  		if (!ret)
>  			ret = len;
>  	}
> -- 
> 1.8.3.1