[PATCH] perf tests: improve reading of objdump output
From: Jan Stancek
Date: Mon Aug 31 2015 - 03:18:48 EST
There are couple of situations, where objdump output doesn't
match "code reading" test expectations:
1. gaps in output, objdump skips zero blocks by default
ffffffff816704fe <sysret_check+0x4b>:
ffffffff816704fe: 7b 34 jnp ffffffff81670534 <sysret_signal+0x1c>
...
ffffffff81670501 <sysret_careful>:
ffffffff81670501: 0f ba e2 03 bt $0x3,%edx
ffffffff81670505: 73 11 jae ffffffff81670518 <sysret_signal>
This patch adds "-z" to objdump parameters.
2. bytes can be repeated in objdump output, test reads it all 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
This patch stores objdump output to buffer according to address
on each line.
3. 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
This patch aborts further reading if address starts going backwards,
assuming we crossed sections.
Signed-off-by: Jan Stancek <jstancek@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
tools/perf/tests/code-reading.c | 74 +++++++++++++++++++++++++++++++++--------
1 file changed, 60 insertions(+), 14 deletions(-)
diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 39c784a100a9..2d21183bd661 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, last_addr = start_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 +93,33 @@ 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;
+ 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 */
+ 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;
@@ -103,7 +133,7 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
FILE *f;
int ret;
- fmt = "%s -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
+ fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
ret = snprintf(cmd, sizeof(cmd), fmt, "objdump", addr, addr + len,
filename);
if (ret <= 0 || (size_t)ret >= sizeof(cmd))
@@ -120,7 +150,7 @@ 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)
@@ -132,6 +162,18 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
return ret;
}
+static void dump_buf(unsigned char *buf, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len; i++) {
+ pr_debug("0x%02x ", buf[i]);
+ if (i % 16 == 15)
+ pr_debug("\n");
+ }
+ pr_debug("\n");
+}
+
static int read_object_code(u64 addr, size_t len, u8 cpumode,
struct thread *thread, struct state *state)
{
@@ -234,6 +276,10 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
/* The results should be identical */
if (memcmp(buf1, buf2, len)) {
pr_debug("Bytes read differ from those read by objdump\n");
+ pr_debug("buf1 (dso):\n");
+ dump_buf(buf1, len);
+ pr_debug("buf2 (objdump):\n");
+ dump_buf(buf2, len);
return -1;
}
pr_debug("Bytes read match those read by objdump\n");
--
1.8.3.1
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