Em Thu, May 27, 2021 at 01:41:13PM -0700, Andrii Nakryiko escreveu:
> On Thu, May 27, 2021 at 12:57 PM Arnaldo <arnaldo.melo@xxxxxxxxx> wrote:
> > On May 27, 2021 4:14:17 PM GMT-03:00, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
> > >If we make 1.22 mandatory there will be no good reason to make 1.23
> > >mandatory again. So I will have absolutely no inclination to work on
> > >this, for example. So we are just wasting a chance to clean up the
> > >Kbuild story w.r.t. pahole. And we are talking about just a few days
> > >at most, while we do have a reasonable work around on the kernel side.
> > So there were patches for stop using objcopy, which we thought could
> > uncover some can of worms, were there patches for the detached BTF
> > file?
> No, there weren't, if I remember correctly. What's the concern,
> though? That detached BTF file isn't even an ELF, so it's
> btf__get_raw_data() and write it to the file. Done.
See patch below, lightly tested, now working on making pahole accept raw
BTF files out of /sys/kernel/btf/
Please test, and if works as expected, try to bolt this into the kbuild
process, as intended.
- Arnaldo
commit b579a18a1ea0ee84b90b5302f597dda2edf2f61b
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Date: Fri May 28 16:41:30 2021 -0300
pahole: Allow encoding BTF into a detached file
Previously the newly encoded BTF info was stored into a ELF section in
the file where the DWARF info was obtained, but it is useful to just
dump it into a separate file, do it.
Requested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
diff --git a/btf_encoder.c b/btf_encoder.c
index 033c927b537dad1e..bc3ac72968cea826 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -21,6 +21,14 @@
#include <stdlib.h> /* for qsort() and bsearch() */
#include <inttypes.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <unistd.h>
+
+#include <errno.h>
+
/*
* This corresponds to the same macro defined in
* include/linux/kallsyms.h
@@ -267,14 +275,62 @@ static struct btf_elf *btfe;
static uint32_t array_index_id;
static bool has_index_type;
-int btf_encoder__encode()
+static int btf_encoder__dump(struct btf *btf, const char *filename)
+{
+ uint32_t raw_btf_size;
+ const void *raw_btf_data;
+ int fd, err;
+
+ /* Empty file, nothing to do, so... done! */
+ if (btf__get_nr_types(btf) == 0)
+ return 0;
+
+ if (btf__dedup(btf, NULL, NULL)) {
+ fprintf(stderr, "%s: btf__dedup failed!\n", __func__);
+ return -1;
+ }
+
+ raw_btf_data = btf__get_raw_data(btf, &raw_btf_size);
+ if (raw_btf_data == NULL) {
+ fprintf(stderr, "%s: btf__get_raw_data failed!\n", __func__);
+ return -1;
+ }
+
+ fd = open(filename, O_WRONLY | O_CREAT);
+ if (fd < 0) {
+ fprintf(stderr, "%s: Couldn't open %s for writing the raw BTF info: %s\n", __func__, filename, strerror(errno));
+ return -1;
+ }
+ err = write(fd, raw_btf_data, raw_btf_size);
+ if (err < 0)
+ fprintf(stderr, "%s: Couldn't open %s for writing the raw BTF info: %s\n", __func__, filename, strerror(errno));
+
+ close(fd);
+
+ if (err != raw_btf_size) {
+ fprintf(stderr, "%s: Could only write %d bytes to %s of raw BTF info out of %d, aborting\n", __func__, err, filename, raw_btf_size);
+ unlink(filename);
+ err = -1;
+ } else {
+ /* go from bytes written == raw_btf_size to an indication that all went fine */
+ err = 0;
+ }
+
+ return err;
+}
+
+int btf_encoder__encode(const char *filename)
{
int err;
if (gobuffer__size(&btfe->percpu_secinfo) != 0)
btf_elf__add_datasec_type(btfe, PERCPU_SECTION, &btfe->percpu_secinfo);
- err = btf_elf__encode(btfe, 0);
+ if (filename == NULL)
+ err = btf_elf__encode(btfe, 0);
+ else
+ err = btf_encoder__dump(btfe->btf, filename);
+
delete_functions();
btf_elf__delete(btfe);
btfe = NULL;
@@ -412,7 +468,7 @@ static bool has_arg_names(struct cu *cu, struct ftype *ftype)
}
int cu__encode_btf(struct cu *cu, int verbose, bool force,
- bool skip_encoding_vars)
+ bool skip_encoding_vars, const char *detached_btf_filename)
{
uint32_t type_id_off;
uint32_t core_id;
@@ -425,7 +481,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
btf_elf__force = force;
if (btfe && strcmp(btfe->filename, cu->filename)) {
- err = btf_encoder__encode();
+ err = btf_encoder__encode(detached_btf_filename);
if (err)
goto out;
diff --git a/btf_encoder.h b/btf_encoder.h
index 46fb2312fc0eea9b..bfc6085092028adc 100644
--- a/btf_encoder.h
+++ b/btf_encoder.h
@@ -11,9 +11,9 @@
struct cu;
-int btf_encoder__encode();
+int btf_encoder__encode(const char *filename);
int cu__encode_btf(struct cu *cu, int verbose, bool force,
- bool skip_encoding_vars);
+ bool skip_encoding_vars, const char *detached_btf_filename);
#endif /* _BTF_ENCODER_H_ */
diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
index 2659fe6f231405d8..6e7ded59595f5ea7 100644
--- a/man-pages/pahole.1
+++ b/man-pages/pahole.1
@@ -189,6 +189,10 @@ features such as BPF CO-RE (Compile Once - Run Everywhere).
See \fIhttps://nakryiko.com/posts/bpf-portability-and-co-re/\fR.
+.TP
+.B \-j, \-\-btf_encode_detached=FILENAME
+Same thing as -J/--btf_encode, but storing the raw BTF info into a separate file.
+
.TP
.B \-\-btf_encode_force
Ignore those symbols found invalid when encoding BTF.
diff --git a/pahole.c b/pahole.c
index 24659e2969c8fb85..1cbff6175b60af51 100644
--- a/pahole.c
+++ b/pahole.c
@@ -26,6 +26,7 @@
#include "lib/bpf/src/libbpf.h"
#include "pahole_strings.h"
+static char *detached_btf_filename;
static bool btf_encode;
static bool ctf_encode;
static bool first_obj_only;
@@ -1152,6 +1153,12 @@ static const struct argp_option pahole__options[] = {
.key = 'J',
.doc = "Encode as BTF",
},
+ {
+ .name = "btf_encode_detached",
+ .key = 'j',
+ .arg = "FILENAME",
+ .doc = "Encode as BTF in a detached file",
+ },
{
.name = "skip_encoding_btf_vars",
.key = ARGP_skip_encoding_btf_vars,
@@ -1223,6 +1230,7 @@ static error_t pahole__options_parser(int key, char *arg,
conf_load.extra_dbg_info = 1; break;
case 'i': find_containers = 1;
class_name = arg; break;
+ case 'j': detached_btf_filename = arg; // fallthru
case 'J': btf_encode = 1;
conf_load.get_addr_info = true;
no_bitfield_type_recode = true; break;
@@ -2458,7 +2466,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
if (btf_encode) {
if (cu__encode_btf(cu, global_verbose, btf_encode_force,
- skip_encoding_btf_vars)) {
+ skip_encoding_btf_vars, detached_btf_filename)) {
fprintf(stderr, "Encountered error while encoding BTF.\n");
exit(1);
}
@@ -2872,7 +2880,7 @@ try_sole_arg_as_class_names:
header = NULL;
if (btf_encode) {
- err = btf_encoder__encode();
+ err = btf_encoder__encode(detached_btf_filename);
if (err) {
fputs("Failed to encode BTF\n", stderr);
goto out_cus_delete;
