[tip:perf/urgent] perf tests: objdump output can contain multi byte chunks

tip-bot for Jan Stancek
2016-08-04T09:15:01Z

Commit-ID: b2d0dbf09772d091368261ce95db3afce45d994d
Gitweb: http://git.kernel.org/tip/b2d0dbf09772d091368261ce95db3afce45d994d
Author: Jan Stancek <jstancek@redhat.com>
AuthorDate: Tue, 12 Jan 2016 11:07:44 +0100
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 2 Aug 2016 16:42:51 -0300

perf tests: objdump output can contain multi byte chunks

objdump's raw insn output can vary across architectures on the number of
bytes per chunk (bpc) displayed and their endianness.

The 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.

Reported-and-Tested-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
Acked-by: 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>
Link: http://lkml.kernel.org/r/07f0f7bcbda78deb423298708ef9b6a54d6b92bd.1452592712.git.jstancek@redhat.com
[ Fix up pr_fmt() call to use %zd for size_t variables, fixing the build on Ubuntu cross-compiling to armhf and ppc64 ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
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 68a69a1..2af156a 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)
{
- const char *p;
- size_t i, j = 0;
-
- /* Skip to a colon */
- p = strchr(line, ':');
- if (!p)
- return 0;
- i = p + 1 - line;
+ size_t bytes_read = 0;
+ unsigned char *chunk_start = *buf;

/* Read bytes */
- while (j < len) {
+ while (*buf_len > 0) {
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]))
+ c1 = *(*line)++;
+ if (!isxdigit(c1))
break;
- c1 = line[i++];
- if (i >= line_len || !isxdigit(line[i]))
+ c2 = *(*line)++;
+ if (!isxdigit(c2))
break;
- c2 = line[i++];
- /* Followed by a space */
- if (i < line_len && line[i] && !isspace(line[i]))
+
+ /* Store byte and advance buf */
+ **buf = (hex(c1) << 4) | hex(c2);
+ (*buf)++;
+ (*buf_len)--;
+ bytes_read++;
+
+ /* End of chunk? */
+ if (isspace(**line))
break;
- /* Store byte */
- *(unsigned char *)buf = (hex(c1) << 4) | hex(c2);
- buf += 1;
- j++;
}
+
+ /*
+ * 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 ret, bytes_read = 0;
+
+ /* Skip to a colon */
+ p = strchr(line, ':');
+ if (!p)
+ return 0;
+ p++;
+
+ /* Skip initial spaces */
+ while (*p) {
+ if (!isspace(*p))
+ break;
+ 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: %zd\n", len);
if (!ret)
ret = len;
}