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

[Adrian Hunter]

On 12/01/16 17:30, Arnaldo Carvalho de Melo wrote:
> 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?

Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

> 
> Thanks,
> 
> - Arnaldo
>  
>> Signed-off-by: Jan Stancek <jstancek@xxxxxxxxxx>
>> Reported-and-tested-by: Kaixu Xia <xiakaixu@xxxxxxxxxx>
>> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
>> Cc: David Ahern <dsahern@xxxxxxxxx>
>> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
>> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
>> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
>> Cc: Paul Mackerras <paulus@xxxxxxxxx>
>> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
>> ---
>>  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
>