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

Arnaldo Carvalho de Melo
2016-01-12T15:31:00Z

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