linux-kernel - [PATCH v3 1/4] perf tests: take into account address of each objdump line

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Message-Id: <786600d67e80b0b0229a4eb16134244b23783c43.1441275982.git.jstancek@redhat.com>
Date:	Thu,  3 Sep 2015 13:23:31 +0200
From:	Jan Stancek <jstancek@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	acme@...nel.org, jolsa@...nel.org, adrian.hunter@...el.com,
	dsahern@...il.com, cjashfor@...ux.vnet.ibm.com, fweisbec@...il.com,
	mingo@...nel.org, namhyung@...nel.org, paulus@...ba.org,
	a.p.zijlstra@...llo.nl, jstancek@...hat.com
Subject: [PATCH v3 1/4] perf tests: take into account address of each objdump line

objdump output can contain repeated bytes. At the moment test reads
all output sequentially, assuming each address is represented in
output only once:

  ffffffff8164efb3 <retint_swapgs+0x9>:
  ffffffff8164efb3:  c1 5d 00 eb        rcrl   $0xeb,0x0(%rbp)
  ffffffff8164efb7:  00 4c 8b 5c        add    %cl,0x5c(%rbx,%rcx,4)

  ffffffff8164efb8 <restore_c_regs_and_iret>:
  ffffffff8164efb8:  4c 8b 5c 24 30     mov    0x30(%rsp),%r11
  ffffffff8164efbd:  4c 8b 54 24 38     mov    0x38(%rsp),%r10

Store objdump output to buffer according to offset calculated
from address on each line.

Signed-off-by: Jan Stancek <jstancek@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 tools/perf/tests/code-reading.c | 53 +++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 13 deletions(-)

Changes in v3:
  align read_objdump_line parameters on 2nd line
  fix multiline comment
  replace MIN with min

diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 39c784a100a9..7fd7ebc0b692 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -33,20 +33,20 @@ static unsigned int hex(char c)
 	return c - 'A' + 10;
 }
 
-static void read_objdump_line(const char *line, size_t line_len, void **buf,
-			      size_t *len)
+static size_t read_objdump_line(const char *line, size_t line_len, void *buf,
+				size_t len)
 {
 	const char *p;
-	size_t i;
+	size_t i, j = 0;
 
 	/* Skip to a colon */
 	p = strchr(line, ':');
 	if (!p)
-		return;
+		return 0;
 	i = p + 1 - line;
 
 	/* Read bytes */
-	while (*len) {
+	while (j < len) {
 		char c1, c2;
 
 		/* Skip spaces */
@@ -65,20 +65,26 @@ static void read_objdump_line(const char *line, size_t line_len, void **buf,
 		if (i < line_len && line[i] && !isspace(line[i]))
 			break;
 		/* Store byte */
-		*(unsigned char *)*buf = (hex(c1) << 4) | hex(c2);
-		*buf += 1;
-		*len -= 1;
+		*(unsigned char *)buf = (hex(c1) << 4) | hex(c2);
+		buf += 1;
+		j++;
 	}
+	/* return number of successfully read bytes */
+	return j;
 }
 
-static int read_objdump_output(FILE *f, void **buf, size_t *len)
+static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
 {
 	char *line = NULL;
-	size_t line_len;
+	size_t line_len, off_last = 0;
 	ssize_t ret;
 	int err = 0;
+	u64 addr;
+
+	while (off_last < *len) {
+		size_t off, read_bytes, written_bytes;
+		unsigned char tmp[BUFSZ];
 
-	while (1) {
 		ret = getline(&line, &line_len, f);
 		if (feof(f))
 			break;
@@ -87,9 +93,30 @@ static int read_objdump_output(FILE *f, void **buf, size_t *len)
 			err = -1;
 			break;
 		}
-		read_objdump_line(line, ret, buf, len);
+
+		/* read objdump data into temporary buffer */
+		read_bytes = read_objdump_line(line, ret, tmp, sizeof(tmp));
+		if (!read_bytes)
+			continue;
+
+		if (sscanf(line, "%"PRIx64, &addr) != 1)
+			continue;
+
+		/*
+		 * Copy it from temporary buffer to 'buf' according
+		 * to address on current objdump line.
+		 */
+		off = addr - start_addr;
+		if (off >= *len)
+			break;
+		written_bytes = min(read_bytes, *len - off);
+		memcpy(buf + off, tmp, written_bytes);
+		off_last = off + written_bytes;
 	}
 
+	/* len returns number of bytes that could not be read */
+	*len -= off_last;
+
 	free(line);
 
 	return err;
@@ -120,7 +147,7 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
 		return -1;
 	}
 
-	ret = read_objdump_output(f, &buf, &len);
+	ret = read_objdump_output(f, buf, &len, addr);
 	if (len) {
 		pr_debug("objdump read too few bytes\n");
 		if (!ret)
-- 
1.8.3.1

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