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pahole: Introduce --prettify option

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The use of isatty(0) to switch into pretty printing is problematic as
reported by Bernd Buschinski, that ran into problems with his scripts:

========================================================================
  I am using pahole 1.21 and I recently noticed that I no longer have
  any pahole output in several scripts.

  Using (on the command line):

    $ pahole -V -E -C my_struct /path/to/my/debug.o

  works fine and gives the expected output.

  But:

    $ parallel -j 1 pahole -V -E -C my_struct ::: /path/to/my/debug.o

  gives nothing, no stderr, no stdout and ret code 0.

  After testing some versions, it works fine in 1.17 and no longer works in 1.18.
========================================================================

Since the pretty printer broke existing scripts, and its a relatively
new feature, lets switch to using a explicit command line option to
activate the pretty printer, i.e. where we used:

  $ pahole --header elf64_hdr < /bin/bash

We now use one of:

  ⬢[acme@toolbox pahole]$ pahole --header elf64_hdr --prettify=/bin/bash
  {
  	.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
  	.e_type = 3,
  	.e_machine = 62,
  	.e_version = 1,
  	.e_entry = 204016,
  	.e_phoff = 64,
  	.e_shoff = 1388096,
  	.e_flags = 0,
  	.e_ehsize = 64,
  	.e_phentsize = 56,
  	.e_phnum = 13,
  	.e_shentsize = 64,
  	.e_shnum = 31,
  	.e_shstrndx = 30,
  },
  ⬢[acme@toolbox pahole]$ pahole --header elf64_hdr --prettify /bin/bash
  {
  	.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
  	.e_type = 3,
  	.e_machine = 62,
  	.e_version = 1,
  	.e_entry = 204016,
  	.e_phoff = 64,
  	.e_shoff = 1388096,
  	.e_flags = 0,
  	.e_ehsize = 64,
  	.e_phentsize = 56,
  	.e_phnum = 13,
  	.e_shentsize = 64,
  	.e_shnum = 31,
  	.e_shstrndx = 30,
  },
  ⬢[acme@toolbox pahole]$ pahole --header elf64_hdr --prettify - < /bin/bash
  {
  	.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
  	.e_type = 3,
  	.e_machine = 62,
  	.e_version = 1,
  	.e_entry = 204016,
  	.e_phoff = 64,
  	.e_shoff = 1388096,
  	.e_flags = 0,
  	.e_ehsize = 64,
  	.e_phentsize = 56,
  	.e_phnum = 13,
  	.e_shentsize = 64,
  	.e_shnum = 31,
  	.e_shstrndx = 30,
  },
  ⬢[acme@toolbox pahole]$ pahole --header elf64_hdr --prettify=- < /bin/bash
  {
  	.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
  	.e_type = 3,
  	.e_machine = 62,
  	.e_version = 1,
  	.e_entry = 204016,
  	.e_phoff = 64,
  	.e_shoff = 1388096,
  	.e_flags = 0,
  	.e_ehsize = 64,
  	.e_phentsize = 56,
  	.e_phnum = 13,
  	.e_shentsize = 64,
  	.e_shnum = 31,
  	.e_shstrndx = 30,
  },
  ⬢[acme@toolbox pahole]$

Reported-by: Bernd Buschinski <b.buschinski@googlemail.com>
Report-Link: https://lore.kernel.org/dwarves/CACN-hLVoz2tWrtgDLabOv6S1-H_8RD2fh8SV6EnADF1ikMxrmw@mail.gmail.com/
Tested-by-by: Bernd Buschinski <b.buschinski@googlemail.com>
Test-Link: https://lore.kernel.org/dwarves/CACN-hLXgHWdBkyMz+w58qX8DaV+WJ1mj1qheGBHbPv4fqozi5w@mail.gmail.com/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2021-06-29 13:22:00 -03:00
parent bc36e94f32
commit 33e0d5f874
2 changed files with 48 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
man-pages/pahole.1
View File

@ -21,7 +21,7 @@ It also uses these structure layouts to pretty print data feed to its standard
input, e.g.:
.PP
.nf
$ pahole --header elf64_hdr < /lib/modules/5.8.0-rc6+/build/vmlinux
$ pahole --header elf64_hdr --prettify /lib/modules/5.8.0-rc6+/build/vmlinux
{
.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
.e_type = 2,
@ -566,8 +566,8 @@ $
.SH PRETTY PRINTING
.P
pahole can also use the data structure types to pretty print raw data coming
from its standard input.
pahole can also use the data structure types to pretty print raw data specified via --prettify.
To consume raw data from the standard input, just use '--prettify -'
.P
It can also pretty print raw data from stdin according to the type specified:
.PP
@ -585,7 +585,7 @@ $
$ ls -la versions
-rw-rw-r--. 1 acme acme 7616 Jun 25 11:33 versions
$
$ pahole --count 3 -C modversion_info drivers/scsi/sg.ko < versions
$ pahole --count 3 -C modversion_info drivers/scsi/sg.ko --prettify versions
{
.crc = 0x8dabd84,
.name = "module_layout",
@ -599,7 +599,7 @@ $ pahole --count 3 -C modversion_info drivers/scsi/sg.ko < versions
.name = "param_ops_int",
},
$
$ pahole --skip 1 --count 2 -C modversion_info drivers/scsi/sg.ko < versions
$ pahole --skip 1 --count 2 -C modversion_info drivers/scsi/sg.ko --prettify - < versions
{
.crc = 0x45e4617b,
.name = "no_llseek",
@ -611,7 +611,7 @@ $ pahole --skip 1 --count 2 -C modversion_info drivers/scsi/sg.ko < versions
$
This is equivalent to:
$ pahole --seek_bytes 64 --count 1 -C modversion_info drivers/scsi/sg.ko < versions
$ pahole --seek_bytes 64 --count 1 -C modversion_info drivers/scsi/sg.ko --prettify versions
{
.crc = 0x45e4617b,
.name = "no_llseek",
@ -662,7 +662,7 @@ $
Now we can use this to show the first record from offset zero:
.PP
.nf
$ pahole -C elf64_hdr --count 1 < /lib/modules/5.8.0-rc3+/build/vmlinux
$ pahole -C elf64_hdr --count 1 --prettify /lib/modules/5.8.0-rc3+/build/vmlinux
{
.e_ident = { 127, 69, 76, 70, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
.e_type = 2,
@ -685,7 +685,7 @@ $
This is equivalent to:
.PP
.nf
$ pahole --header elf64_hdr < /lib/modules/5.8.0-rc3+/build/vmlinux
$ pahole --header elf64_hdr --prettify /lib/modules/5.8.0-rc3+/build/vmlinux
.fi
.P
The --header option also allows reference in other command line options to fields in the header.
@ -693,7 +693,7 @@ This is useful when one wants to show multiple records in a file and the range w
are located is specified in header fields, such as for perf.data files:
.PP
.nf
$ pahole --hex ~/bin/perf --header perf_file_header < perf.data
$ pahole --hex ~/bin/perf --header perf_file_header --prettify perf.data
{
.magic = 0x32454c4946524550,
.size = 0x68,
@ -718,7 +718,7 @@ $
So to display the cgroups records in the perf_file_header.data section we can use:
.PP
.nf
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type,filter=type==PERF_RECORD_CGROUP)' < perf.data
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type,filter=type==PERF_RECORD_CGROUP)' --prettify perf.data
{
.header = {
.type = PERF_RECORD_CGROUP,
@ -770,7 +770,7 @@ $
For the common case of the header having a member that has the 'offset' and 'size' members, it is possible to use this more compact form:
.PP
.nf
$ pahole ~/bin/perf --header=perf_file_header --range=data -C 'perf_event_header(sizeof,type,type_enum=perf_event_type,filter=type==PERF_RECORD_CGROUP)' < perf.data
$ pahole ~/bin/perf --header=perf_file_header --range=data -C 'perf_event_header(sizeof,type,type_enum=perf_event_type,filter=type==PERF_RECORD_CGROUP)' --prettify perf.data
.fi
.P
This uses ~/bin/perf to get the type definitions, the defines 'struct perf_file_header' as the header,
@ -844,7 +844,7 @@ If we remove that type_enum=perf_event_type, we will lose the conversion of 'str
more descriptive 'struct perf_record_cgroup', and also the beautification of the header.type field:
.PP
.nf
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,filter=type==19)' < perf.data
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,filter=type==19)' --prettify perf.data
{
.type = 19,
.misc = 0,
@ -876,7 +876,7 @@ $
Some of the records are not found in 'type_enum=perf_event_type' so some of the records don't get converted to a type that fully shows its contents. For perf we know that those are in another enumeration, 'enum perf_user_event_type', so, for these cases, we can create a 'virtual enum', i.e. the sum of two enums and then get all those entries decoded and properly casted, first few records with just 'enum perf_event_type':
.PP
.nf
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type)' --count 4 < perf.data
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type)' --count 4 --prettify perf.data
{
.type = 79,
.misc = 0,
@ -907,7 +907,7 @@ $
Now with both enumerations, i.e. with 'type_enum=perf_event_type+perf_user_event_type':
.PP
.nf
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type+perf_user_event_type)' --count 5 < perf.data
$ pahole ~/bin/perf --header=perf_file_header --seek_bytes '$header.data.offset' --size_bytes='$header.data.size' -C 'perf_event_header(sizeof,type,type_enum=perf_event_type+perf_user_event_type)' --count 5 --prettify perf.data
{
.header = {
.type = PERF_RECORD_TIME_CONV,
@ -966,7 +966,7 @@ data range with the following command:
.PP
.nf
pahole ~/bin/perf --header=perf_file_header \
-C 'perf_file_attr(range=attrs),perf_event_header(range=data,sizeof,type,type_enum=perf_event_type+perf_user_event_type)' < perf.data
-C 'perf_file_attr(range=attrs),perf_event_header(range=data,sizeof,type,type_enum=perf_event_type+perf_user_event_type)' --prettify perf.data
.fi
.SH SEE ALSO

40
pahole.c
View File

@ -35,6 +35,9 @@ static bool skip_encoding_btf_vars;
static bool btf_encode_force;
static const char *base_btf_file;
static const char *prettify_input_filename;
static FILE *prettify_input;
static uint8_t class__include_anonymous;
static uint8_t class__include_nested_anonymous;
static uint8_t word_size, original_word_size;
@ -854,6 +857,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_with_flexible_array 324
#define ARGP_kabi_prefix 325
#define ARGP_btf_encode_detached 326
#define ARGP_prettify_input_filename 327
static const struct argp_option pahole__options[] = {
{
@ -1202,6 +1206,12 @@ static const struct argp_option pahole__options[] = {
.key = ARGP_numeric_version,
.doc = "Print a numeric version, i.e. 119 instead of v1.19"
},
{
.name = "prettify",
.key = ARGP_prettify_input_filename,
.arg = "PATH",
.doc = "Path to the raw data to pretty print",
},
{
.name = NULL,
}
@ -1332,6 +1342,8 @@ static error_t pahole__options_parser(int key, char *arg,
btf_gen_floats = true; break;
case ARGP_with_flexible_array:
show_with_flexible_array = true; break;
case ARGP_prettify_input_filename:
prettify_input_filename = arg; break;
default:
return ARGP_ERR_UNKNOWN;
}
@ -2586,7 +2598,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
class_id = 0;
}
if (!isatty(0)) {
if (prettify_input) {
prototype->class = class;
prototype->cu = cu;
continue;
@ -2624,7 +2636,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
// If we got here with pretty printing is because we have everything solved except for type_enum or --header
if (!isatty(0)) {
if (prettify_input) {
// Check if we need to continue loading CUs to get those type_enum= and --header resolved
if (header == NULL && conf.header_type)
return LSK__KEEPIT;
@ -2637,7 +2649,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
// All set, pretty print it!
list_for_each_entry_safe(prototype, n, &class_names, node) {
list_del_init(&prototype->node);
if (prototype__stdio_fprintf_value(prototype, header, stdin, stdout) < 0)
if (prototype__stdio_fprintf_value(prototype, header, prettify_input, stdout) < 0)
break;
}
@ -2783,9 +2795,6 @@ int main(int argc, char *argv[])
{
int err, remaining, rc = EXIT_FAILURE;
if (!isatty(0))
conf.hex_fmt = 0;
if (argp_parse(&pahole__argp, argc, argv, 0, &remaining, NULL)) {
argp_help(&pahole__argp, stderr, ARGP_HELP_SEE, argv[0]);
goto out;
@ -2801,6 +2810,19 @@ int main(int argc, char *argv[])
goto out;
}
if (prettify_input_filename) {
if (strcmp(prettify_input_filename, "-") == 0) {
prettify_input = stdin;
} else {
prettify_input = fopen(prettify_input_filename, "r");
if (prettify_input == NULL) {
fprintf(stderr, "Failed to read input '%s': %s\n",
prettify_input_filename, strerror(errno));
goto out_dwarves_exit;
}
}
}
if (base_btf_file) {
conf_load.base_btf = btf__parse(base_btf_file, NULL);
if (libbpf_get_error(conf_load.base_btf)) {
@ -2825,7 +2847,7 @@ int main(int argc, char *argv[])
conf_load.steal = pahole_stealer;
// Make 'pahole --header type < file' a shorter form of 'pahole -C type --count 1 < file'
if (conf.header_type && !class_name && !isatty(0)) {
if (conf.header_type && !class_name && prettify_input) {
conf.count = 1;
class_name = conf.header_type;
conf.header_type = 0; // so that we don't read it and then try to read the -C type
@ -2923,6 +2945,10 @@ out_cus_delete:
conf_load.base_btf = NULL;
#endif
out_dwarves_exit:
if (prettify_input && prettify_input != stdin) {
fclose(prettify_input);
prettify_input = NULL;
}
#ifdef DEBUG_CHECK_LEAKS
dwarves__exit();
#endif