Em Wed, Jul 01, 2020 at 08:44:21AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Jul 01, 2020 at 08:25:34AM -0300, Arnaldo Carvalho de Melo escreveu:
> > The latest changeset shows what this is about, see its example
> > below, please help testing and suggesting whatever needs you have
> > regarding pretty printing.
> >
> > Now to implement --skip.
> Now to implement --seek, this time in bytes, so that we can, for
> instance, pretty print perf.data records, looking at 'perf report -D'
> and getting the offset of the start of a series of 'struct
> perf_event_attr' or 'struct perf_event_header'.
Here it is with more complex examples dissecting perf.data file data
structures, including BPF related structs:
commit fe284221448c950d2ba17bce91d19c484d6580a0
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Date: Wed Jul 1 09:17:38 2020 -0300
pahole: Introduce --seek_bytes
Works with stdio, will work with files where we'll use plain lseek and
allow for pretty printing trailer structs.
E.g.:
$ objcopy -O binary --only-section=__versions drivers/scsi/sg.ko versions
$ pahole -C modversion_info drivers/scsi/sg.ko
struct modversion_info {
long unsigned int crc; /* 0 8 */
char name[56]; /* 8 56 */
/* size: 64, cachelines: 1, members: 2 */
};
$ pahole --count 2 -C modversion_info drivers/scsi/sg.ko < versions
{
.crc = 0x8dabd84,
.name = "module_layout",
},
{
.crc = 0x45e4617b,
.name = "no_llseek",
},
$ pahole --skip 1 --count 1 -C modversion_info drivers/scsi/sg.ko < versions
{
.crc = 0x45e4617b,
.name = "no_llseek",
},
Then the equivalent, skipping sizeof(modversion_info) explicitely:
$ pahole --seek_bytes 64 --count 1 -C modversion_info drivers/scsi/sg.ko < versions
{
.crc = 0x45e4617b,
.name = "no_llseek",
},
$
Using a perf.data file generated by 'perf record':
$ perf report -D | head -18
# To display the perf.data header info, please use --header/--header-only options.
#
0x130 [0x20]: event: 79
.
. ... raw event: size 32 bytes
. 0000: 4f 00 00 00 00 00 20 00 1f 00 00 00 00 00 00 00 O..... .........
. 0010: 31 30 9b 3c 00 00 00 00 2e 53 f8 0c 52 8c 01 00 10.<.....S�.R...
0 0x130 [0x20]: PERF_RECORD_TIME_CONV: unhandled!
0x150 [0x28]: event: 73
.
. ... raw event: size 40 bytes
. 0000: 49 00 00 00 00 00 28 00 01 00 00 00 00 00 00 00 I.....(.........
. 0010: 50 7e 00 00 00 00 00 00 00 00 00 00 00 00 00 00 P~..............
. 0020: 00 00 00 00 00 00 00 00 ........
$ pahole --seek_bytes 0x130 --count 1 -C perf_event_header < perf.data
{
.type = 0x4f,
.misc = 0,
.size = 0x20,
},
$ printf "0x%x\n" 79
0x4f
$ pahole --seek_bytes 0x150 --count 1 -C perf_event_header < perf.data
{
.type = 0x49,
.misc = 0,
.size = 0x28,
},
$ printf "0x%x\n" 73
0x49
$
Now to use more complex types, again using perf.data files.
# perf record -a sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 3.834 MB perf.data (31853 samples) ]
# perf report -D | grep -m1 -B20 PERF_RECORD_BPF
0x6aa0 [0x58]: event: 17
.
. ... raw event: size 88 bytes
. 0020: 5f 37 62 65 34 39 65 33 39 33 34 61 31 32 35 62 _7be49e3934a125b
. 0030: 61 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a...............
. 0040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
. 0050: 00 00 00 00 00 00 00 00 ........
0 0 0x6aa0 [0x58]: PERF_RECORD_KSYMBOL addr ffffffffc03e0e90 len 203 type 1 flags 0x0 name bpf_prog_7be49e3934a125ba
0x6af8 [0x38]: event: 18
.
. ... raw event: size 56 bytes
. 0000: 12 00 00 00 00 00 38 00 01 00 00 00 11 00 00 00 ......8.........
. 0020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
. 0030: 00 00 00 00 00 00 00 00 ........
0 0 0x6af8 [0x38]: PERF_RECORD_BPF_EVENT type 1, flags 0, id 17
Binary file (standard input) matches
# pahole -C perf_record_bpf_event ~/bin/perf
struct perf_record_bpf_event {
struct perf_event_header header; /* 0 8 */
__u16 type; /* 8 2 */
__u16 flags; /* 10 2 */
__u32 id; /* 12 4 */
__u8 tag[8]; /* 16 8 */
/* size: 24, cachelines: 1, members: 5 */
/* last cacheline: 24 bytes */
};
# pahole -C perf_record_bpf_event --seek_bytes 0x6af8 --count 1 ~/bin/perf < perf.data
{
.header = 0x12 0x00 0x00 0x00 0x00 0x00 0x38 0x00,
.type = 0x1,
.flags = 0,
.id = 0x11,
.tag = { 0, 0, 0, 0, 0, 0, 0, 0},
},
# printf "0x%x\n" 18
0x12
# pahole -C perf_record_ksymbol ~/bin/perf
struct perf_record_ksymbol {
struct perf_event_header header; /* 0 8 */
__u64 addr; /* 8 8 */
__u32 len; /* 16 4 */
__u16 ksym_type; /* 20 2 */
__u16 flags; /* 22 2 */
char name[256]; /* 24 256 */
/* size: 280, cachelines: 5, members: 6 */
/* last cacheline: 24 bytes */
};
# pahole -C perf_record_ksymbol --seek_bytes 0x6aa0 --count 1 ~/bin/perf < perf.data
{
.header = 0x11 0x00 0x00 0x00 0x00 0x00 0x58 0x00,
.addr = 0xffffffffc03e0e90,
.len = 0xcb,
.ksym_type = 0x1,
.flags = 0,
.name = "bpf_prog_7be49e3934a125ba",
},
# printf "0x%x\n" 17
0x11
#
Need to recursively pretty print substructs, but all seems to work with
the simple hexdump.
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
diff --git a/dwarves.h b/dwarves.h
index 24f9c7c37843..1b118d03ec15 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -13,6 +13,7 @@
#include <obstack.h>
#include <dwarf.h>
#include <elfutils/libdwfl.h>
+#include <sys/types.h>
#include "dutil.h"
#include "list.h"
@@ -56,6 +57,7 @@ struct conf_load {
*
* @count - Just like 'dd', stop pretty printing input after 'count' records
* @skip - Just like 'dd', skip 'count' records when pretty printing input
+ * @seek_bytes - Number of bytes to seek, if stdin only from start, when we have --pretty FILE, then from the end as well with negative numbers
* @flat_arrays - a->foo[10][2] becomes a->foo[20]
* @classes_as_structs - class f becomes struct f, CTF doesn't have a "class"
* @cachelinep - pointer to current cacheline, so that when expanding types we keep track of it,
@@ -72,6 +74,7 @@ struct conf_fprintf {
uint32_t base_offset;
uint32_t count;
uint32_t *cachelinep;
+ off_t seek_bytes;
uint32_t skip;
uint8_t indent;
uint8_t expand_types:1;
diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
index db820cca323f..ad4e92d716cf 100644
--- a/man-pages/pahole.1
+++ b/man-pages/pahole.1
@@ -516,6 +516,14 @@ $ pahole --skip 1 --count 2 -C modversion_info drivers/scsi/sg.ko < versions
.name = "param_ops_int",
},
$
+This is equivalent to:
+
+$ pahole --seek_bytes 64 --count 1 -C modversion_info drivers/scsi/sg.ko < versions
+{
+ .crc = 0x45e4617b,
+ .name = "no_llseek",
+},
+$
.fi
.P
diff --git a/pahole.c b/pahole.c
index 7d8431c64423..245a3f2f14f7 100644
--- a/pahole.c
+++ b/pahole.c
@@ -3,7 +3,7 @@
Copyright (C) 2006 Mandriva Conectiva S.A.
Copyright (C) 2006 Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxx>
- Copyright (C) 2007-2008 Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
+ Copyright (C) 2007- Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
*/
#include <argp.h>
@@ -804,6 +804,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_just_structs 310
#define ARGP_count 311
#define ARGP_skip 312
+#define ARGP_seek_bytes 313
static const struct argp_option pahole__options[] = {
{
@@ -836,6 +837,12 @@ static const struct argp_option pahole__options[] = {
.arg = "COUNT",
.doc = "Skip COUNT input records"
},
+ {
+ .name = "seek_bytes",
+ .key = ARGP_seek_bytes,
+ .arg = "BYTES",
+ .doc = "Seek COUNT input records"
+ },
{
.name = "find_pointers_to",
.key = 'f',
@@ -1163,6 +1170,8 @@ static error_t pahole__options_parser(int key, char *arg,
conf.count = atoi(arg); break;
case ARGP_skip:
conf.skip = atoi(arg); break;
+ case ARGP_seek_bytes:
+ conf.seek_bytes = strtol(arg, NULL, 0); break;
default:
return ARGP_ERR_UNKNOWN;
}
@@ -1329,6 +1338,25 @@ static int tag__fprintf_value(struct tag *type, struct cu *cu, void *instance, i
return tag__fprintf_hexdump_value(type, cu, instance, _sizeof, fp);
}
+static int pipe_seek(FILE *fp, off_t offset)
+{
+ char bf[4096];
+ int chunk = sizeof(bf);
+
+ if (chunk > offset)
+ chunk = offset;
+
+ while (fread(bf, chunk, 1, stdin) == 1) {
+ offset -= chunk;
+ if (offset == 0)
+ return 0;
+ if (chunk > offset)
+ chunk = offset;
+ }
+
+ return offset == 0 ? 0 : -1;
+}
+
static int tag__stdio_fprintf_value(struct tag *type, struct cu *cu, FILE *fp)
{
int _sizeof = tag__size(type, cu), printed = 0;
@@ -1339,6 +1367,12 @@ static int tag__stdio_fprintf_value(struct tag *type, struct cu *cu, FILE *fp)
if (instance == NULL)
return -ENOMEM;
+ if (conf.seek_bytes && pipe_seek(stdin, conf.seek_bytes) < 0) {
+ int err = --errno;
+ fprintf(stderr, "Couldn't --seek_bytes %ld\n", conf.seek_bytes);
+ return err;
+ }
+
while (fread(instance, _sizeof, 1, stdin) == 1) {
if (skip) {
--skip;
