linux-kernel - [PATCH v2 3/4] perf tests: stop reading if objdump output crossed sections

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Message-Id: <9d1ea95e5f9884fdff1be6f761a2feabef37412c.1441181335.git.jstancek@redhat.com>
Date:	Wed,  2 Sep 2015 10:19:16 +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 v2 3/4] perf tests: stop reading if objdump output crossed sections

objdump output can span across multiple sections:

  Disassembly of section .text:
    0000000000000008 <crc32c+0x8>:
       8:       48 89 e5                mov    %rsp,%rbp
       b:       53                      push   %rbx
       c:       8b 01                   mov    (%rcx),%eax
    <snip>
      6b:       90                      nop

  Disassembly of section .init.text:
    0000000000000008 <init_module+0x8>:
       8:       00 00                   add    %al,(%rax)
       a:       00 00                   add    %al,(%rax)
       c:       48 89 e5

Stop further reading if address starts going backwards,
assuming we crossed sections.

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 | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 375ba30e4ed0..e6bf47ff7e91 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -79,7 +79,7 @@ static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
 	size_t line_len, off_last = 0;
 	ssize_t ret;
 	int err = 0;
-	u64 addr;
+	u64 addr, last_addr = start_addr;
 
 	while (off_last < *len) {
 		size_t off, read_bytes, written_bytes;
@@ -101,6 +101,11 @@ static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
 
 		if (sscanf(line, "%"PRIx64, &addr) != 1)
 			continue;
+		if (addr < last_addr) {
+			pr_debug("addr going backwards, read beyond section?\n");
+			break;
+		}
+		last_addr = addr;
 
 		/* copy it from temporary buffer to 'buf' according
 		 * to address on current objdump line */
-- 
1.8.3.1

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